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Manila Water Company, Inc. Manila, Philippines Environmental Impact Statement (EIS) for Manila Third Sewerage Project Volume 5: Bio Solids Management Strategy February 11, 2005 (Revised Draft) Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized

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Page 1: Environmental Impact Statement (EIS) · – Dewatering. Optimisation of dewatering processes to minimise haulage costs. Long-term (2010 onwards) ?? Biosolids markets – Lahar application

Manila Water Company, Inc. Manila, Philippines

Environmental Impact Statement (EIS)

for

Manila Third Sewerage Project

Volume 5: Bio Solids Management Strategy

February 11, 2005 (Revised Draft)

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Administrator
E1073 v5
Page 2: Environmental Impact Statement (EIS) · – Dewatering. Optimisation of dewatering processes to minimise haulage costs. Long-term (2010 onwards) ?? Biosolids markets – Lahar application

August 2004

Manila Water Company, Inc.

Biosolids Management Strategy Options Study

Report

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Contents

Executive Summary 1

Technical Acronyms and Abbreviations 4

1. Introduction 6

1.1 General 6 1.2 Project Objectives 6 1.3 Definition of Terms 6

2. Available Information 8

2.1 Data Sources 8 2.2 Required Data from Additional Testing and Monitoring 8 2.3 Assumptions 9

3. MWCI Operations 10

3.1 MWCI Service Area 10 3.2 Existing Facilities Related to Biosolids Generation and

Management 10 3.3 Certifications and Licenses 10 3.4 On Going and Planned Projects 10 3.5 Key Issues in Establishing the MWCI Biosolids Strategy 10

4. Biosolids Quantity and Quality 10

4.1 General 10 4.2 Dried Sludge from Magallanes WWTP 10 4.3 Liquid Sludge from Operating WWTPs 10 4.4 Dewatered Sludge from MSSP Facilities 10 4.5 Sludge from MTSP Facilities 10 4.6 Liquid Sludge Generation from MSSP WWTPs 10 4.7 Septage 10 4.8 Filter Cakes from Proposed Septage Treatment Plants 10 4.9 Summary of the Expected Biosolids Quantity 10 4.10 Biosolids Quality 10

5. Planning Considerations 10

5.1 General 10 5.2 Review of Local Guidelines on Biosolids Management 10

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5.3 Review of International Guidelines on Biosolids Management 10 5.4 Review of US EPA Guidelines on Land Application of Domestic

Septage 10 5.5 Global Trends 10 5.6 Carbon Credit Opportunities 10 5.7 Transport Alternatives 10 5.8 Planning Issues 10 5.9 Social Issues 10

6. Biosolids Reuse and Disposal Assessment 10

6.1 Potential Reuse 10 6.2 Disposal Options 10 6.3 Short-listing of Options 10

7. Biosolids Treatment Unit Processes 10

7.1 Introduction 10 7.2 Technology Options Overview 10 7.3 MWCI Technology Requirements 10 7.4 Short-listed Technologies 10

8. Enhancement of Existing Operations 10

8.1 Magallanes WWTP 10 8.2 Valle Verde Homes WWTP 10 8.3 Existing Karangalan Village WWTP 10 8.4 Diego Sillang WWTP Infrastructure 10 8.5 Lahar Application Practices 10

9. Proposed Strategy 10

9.1 Short-term (Current to 2005) 10 9.2 Medium-term (2005 to 2010) 10 9.3 Long-term (2010 onwards) 10

10. Risk Assessment 10

10.1 General 10 10.2 Project Risk Assessment 10 10.3 Discussion of the High and Extreme Risks 10

11. Preliminary Costing of Preferred Options 10

11.1 Basis of Cost Estimates 10 11.2 Short Term (Current to 2005) 10

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11.3 Medium Term (2005 to 2010) 10 11.4 Long Term (2010 onwards) 10

12. Conclusions and Recommendations 10

12.1 Conclusions 10 12.2 Recommendations 10

13. References 10

Table Index Table 1 MWCI Concession Area Forecasted Population1 10 Table 2 MWCI Sewerage Service Coverage Targets (% of

total population in area)1 10 Table 3 MWCI Sanitation Service Coverage Targets (% of

total population in area)1 10 Table 4 Existing Communal Septic Tanks 10 Table 5 Septic Tank Desludging Data (Number of individual

tanks serviced)1 10 Table 6 On Going and Planned Wastewater Projects under

the MSSP (Bio-contact Activated Sludge Process) 10 Table 7 On Going and Planned Wastewater Projects under

the MTSP 10 Table 8 Estimated Biosolids Generation Rate for Existing

WWTPs* 10 Table 9 Biosolids Generation from MSSP Projects 10 Table 10 Biosolids Generation of Wastewater Projects under

the MTSP 10 Table 11 Biosolids Generation Rates of MSSP WWTPs 10 Table 12 STP Solids Generation Growth Rate in m3/day 10 Table 13 Summary of Biosolids Generation in Terms of

Source 10 Table 14 Summary of Biosolids Generation in Terms of

Biosolids Type 10 Table 15 List of Controlled Contaminants 10 Table 16 Typical Properties and Composition of Various

Sludge Types* 10 Table 17 Typical Septage Constituent Concentrations and

Unit Loading Factors* 10 Table 18 Metro Manila Septage Characteristics 10

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Table 19 Maximum Average Concentration of Heavy Metals for Land Application (mg/kg) 10

Table 20 Allowed Annual Loading Rates (kg/ha/yr) 10 Table 21 Comparison of US EPA Guidelines with MWCI

Practices 10 Table 22 Comparison of Annual Greenhouse Gas Emissions

for Management Options* 10 Table 23 Potential Biosolids Reuse Market Sectors 10 Table 24 Short-listed Biosolids Market Options 10 Table 25 Sludge Treatment Overview 10 Table 26 Qualitative Measures of Consequence or Impact of

Any Single Incident 10 Table 27 Qualitative Measures of Likelihood 10 Table 28 Qualitative Risk Analysis Matrix 10 Table 29 Qualitative Risk Assessment – Identified Risks 10 Table 30 Classification Requirements for Biosolids Reuse 10 Table 31 Comparison of Various Composting Methods 10 Table 32 Short-term Storage Characterisations for Various

Sludge Types 10

Appendices A Environmental Management Bureau Classification of Domestic

Sludge and Septage B Review of International Guidelines on Biosolids Management C Processing Technology Review

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Executive Summary

GHD was commissioned by Manila Water Company, Inc. (MWCI) to undertake the planning and development of a robust and sustainable Biosolids Management Strategy to deliver efficient solutions and enhance MWCI’s reputation as a company with strong environmental values.

MWCI operates a number of wastewater treatment and septage collection facilities that currently generate a significant volume of biosolids requiring treatment and disposal/reuse. Biosolids are the organic sludge produced from physical and biological treatment of wastewater and include treated septage, secondary sludge, and processed/stabilized sludge.

Significant increases in the rate of biosolids generation are anticipated (from 95 m3/day to around 400 m3/day of dry solids), in line with a number of wastewater treatment plants and septage collection initiatives currently underway. This increased biosolids generation (to around 180 dry tonnes/day) will result in significant increases in operational costs for MWCI, unless the current management practices are improved and streamlined, particularly the transport and disposal/reuse options.

The objectives of this project are to:

??Develop a long-term Biosolids Management Strategy to provide a cost effective and environmentally sustainable solution for MWCI’s anticipated increase in septage and wastewater sludge generation.

??Within this strategy, investigate measures to improve the efficiency and operability of the current biosolids management systems particularly:

– Reducing the current operational costs of the system.

– Identifying low capital cost improvement options with short payback periods (less than 3 years).

– Reducing health and safety risks to operational staff.

??Ensure that the septage treatment process selected for the Manila Third Sewerage Project (MTSP), Pasig River Rehabilitation Commission (PRRC) projects and other wastewater treatment plants is compatible with the downstream biosolids processing, reuse and final disposal options selected under the strategy.

??Ensure that environmental performance in biosolids management promotes a positive corporate image for MWCI at an appropriate cost.

The study concludes the following:

??Biosolids produced from MWCI plants are unstabilised. The use of biosolids should be restricted and applied to land adapting internationally recognised practices.

??Current viable markets include the rehabilitation of the lahar fields, and in extensive agriculture in Pampanga, Tarlac, and other nearby provinces.

?? In the short term, management of the application of biosolids in these markets needs to be improved for health and safety reasons, and to avoid potential environmental harm in the long term. This should include reviewing current practice of distributing dried sludge to third parties.

?? The production of higher quality biosolids will create alternative markets. These markets are likely to be closer to Manila and transportation costs will be lower. Having a range of viable markets will reduce risks for MWCI in case the current options are restricted.

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??Pilot scale evaluation of alternative stabilisation technologies will provide MWCI with an understanding of the technology and minimise the risks of a full-scale operation.

??Storm events have the potential to limit the ability to continuously apply biosolids to land. Sufficient biosolids storage facilities are required to balance the production rates with practical application rates.

?? A landfill disposal option would play a significant role in contingency planning. This is a risk management option to protect against a potential disruption of operations due to climactic conditions and other unforseen circumstances.

Based on the outcomes of this study, the following strategy is proposed:

Short-term (Current to 2005)

??Biosolids markets

– Lahar application needs to be fully investigated. Lahar application dependent on surface and ground water monitoring, adsorptive capacity of lahar, and computed agronomic rates for application.

– Extensive Agriculture. Improvements to the current practice of septage application on agricultural sites in accordance with the guidance of the US EPA Part 503 rule (Biosolids to be injected below the surface, or incorporated within 6 hours of application to the land).

– Other markets. Commence discussions with fertiliser retailers to identify potentially higher value markets and other market opportunities for biosolids products. Assess interest with relevant parties in preparing a feasibility study for a landfill bioreactor.

– Transport/Management. Improvements to the septage haulage practices as identified in this report. Formalize waste exchange agreements with Manila Fertilizer, farmers, etc. Commence development of a tracking system to ensure that biosolids despatched are handled and transported correctly with all appropriate checks and balances confirmed and documented. Commence preparation of educational material and stakeholder consultation processes and identify key stakeholders.

– Disposal. As a contingency plan, suitable disposal site(s) need to be identified. These sites will need to accept biosolids that are unsuitable/unable to be reused.

?? Technology

– Stabilisation. No stabilisation required provided biosolids are applied to extensive agriculture and land rehabilitation (lahar) in accordance with acceptable practices.

– Dewatering. Dewatering progressively implemented to minimise haulage costs.

Medium-term (2005 – 2010)

??Biosolids markets

– Lahar application optimised and sustainable. The recommendations of the Environmental Risk Assessment being conducted by EDCOP for the lahar application of biosolids are adopted and implemented. Possible collaboration with other agencies (Department of Agriculture) to achieve this goal.

– Extensive Agriculture. Reuse practices monitored for compliance with local and appropriate requirements.

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– Other markets. Test the market acceptance and economics (cost/revenue) of alternative biosolids products in pilot trial quantities.

– Transport/Management. Tracking, handling and identification system fully implemented. Promote and seek expressions of interest from third parties to undertake biosolids management contracts with MWCI. Review international guidelines for advancements in biosolids management approaches. Distribution of educational material and continue stakeholder consultation processes.

– Disposal. Agreement with relevant regulatory bodies on the use of disposal sites.

?? Technology

– Stabilisation. Plan and implement a pilot scale trial (~5m3/d) on an alternative stabilisation process (eg. vermiculture) at one of the WWTPs. If stabilisation is required as a contingency plan on full-scale plants, lime processes can be adopted.

– Dewatering. Optimisation of dewatering processes to minimise haulage costs.

Long-term (2010 onwards)

??Biosolids markets

– Lahar application. Volume of product used in this market is reduced as markets closer to Manila are developed.

– Intensive agriculture and landscaping. Higher quality biosolids product (vermicast/compost or equivalent) is used extensively in these markets.

– Transport/Management. Paperless tracking systems investigated and adopted. Engagement with local regulatory bodies to ensure development of guidelines is viable and aligns with MWCI practice. Distribution of educational material and continue stakeholder consultation processes in intensive agricultural and landscaping markets. Third parties undertake biosolids management contracts for MWCI on a competitive basis.

?? Technology

– Stabilisation. Lime facilities decommissioned, or kept as a back up (if installed). Vermiculture, composting or other alternative process is adopted to generate high quality biosolids product suitable for intensive agriculture and landscaping markets.

– Dewatering. Review technology advances in dewatering (electro dewatering, microwave etc.) to further minimise haulage costs. Drying beds likely to be phased out due to increased concerns over odour issues.

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Technical Acronyms and Abbreviations

Abbreviations and acronyms used in the report are as follows:

ALI Ayala Land, Inc.

AS Activated sludge

ASP Active sludge pasteurisation

ATAD Autoheated thermophilic aerobic digestion

BNR Biological nutrient removal

BOD Biological oxygen demand

CAS Conventional activated sludge

CST Communal septic tank

DAF Dissolved air flotation

DAF+F or DAFF Dissolved air flotation and filtration

DENR Department of Environment and Natural Resources

ds or DS Dry solids

EDCOP Engineering Development Corporation

ep or EP Equivalent population

FPA Fertilizers and Pesticides Authority

HCB Hexachlorobenzene

IDEA Intermittently decanted extended aeration

LGU Local Government Unit

MSSP Manila Second Sewerage Project

MTSP Manila Third Sewerage Project

MWCI Manila Water Company, Inc.

MWSS Manila Waterworks and Sewerage System

NJS Nippon Jogesuido Sekkei Co., Ltd.

NSO National Statistics Office

OFS Oil from sludge

PRRC Pasig River Rehabilitation Commission

SKM Sinclair Knight Merz Phils.

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SRA Sugar Regulatory Administration

SS Suspended solids

STP Septage treatment plant

TS Total solids

VSS Volatile suspended solids

WAS Waste activated sludge

wt Tonnes (wet)

WWTP Wastewater treatment plant

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1. Introduction

1.1 General

GHD was commissioned by Manila Water Company, Inc. (MWCI) to undertake the planning and development of a robust and sustainable Biosolids Management Strategy to deliver efficient solutions and enhance MWCI’s reputation as a company with strong environmental values.

MWCI operates a number of wastewater treatment and septage collection facilities that currently generate a significant volume of biosolids requiring treatment and disposal/reuse. Biosolids are the organic sludge produced from physical and biological treatment of wastewater and include treated septage, secondary sludge, and processed/stabilized sludge.

Significant increases in the rate of biosolids generation are anticipated in line with a number of wastewater treatment plants and septage collection initiatives currently underway. This increased biosolids generation will result in significant increases in operational costs for MWCI, unless the current management practices are improved and streamlined, particularly the transport and disposal/reuse options. Effective planning and the preparation and implementation of a Biosolids Management Strategy is the first and most important step in developing an efficient and cost effective sanitation program.

1.2 Project Objectives

The project aims to:

??Develop a long-term Biosolids Management Strategy to provide a cost effective and environmentally sustainable solution for MWCI’s anticipated increase in septage and wastewater sludge generation.

??Within this strategy, investigate measures to improve the efficiency and operability of the current biosolids management systems particularly:

– Reducing the current operational costs of the system.

– Identifying low capital cost improvement options with short payback periods (less than 3 years).

– Reducing health and safety risks to operational staff.

??Ensure that the septage treatment process selected for the Manila Third Sewerage Project (MTSP), Pasig River Rehabilitation Commission (PRRC) projects and other wastewater treatment plants is compatible with the downstream biosolids processing, reuse and final disposal options selected under the strategy.

??Ensure that environmental performance in biosolids management promotes a positive corporate image for MWCI at an appropriate cost.

1.3 Definition of Terms

Biosolids are the organic solids produced by wastewater treatment processes due to the conversion of liquid organic matter into biological mass. Biosolids and sewage sludge have been used interchangeably, however preference for using biosolids in developed countries is prevalent due to the reuse potential for the solids. The term biosolids does not include untreated raw wastewater, industrial sludges that cannot be used beneficially without further processing, or the product produced from the

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high temperature incineration of sewage sludge. It should also be noted that other solid waste materials are not classified as biosolids e.g., animal manures, food processing or abattoir wastes.

Domestic wastewater treatment plants produce solid materials as by-products of the treatment process. These are typically:

??Screenings - materials trapped by screens that filter the raw sewage as it enters the plants.

??Grit - sand and grit trapped in tanks that treat the raw sewage.

??Primary sludge - material that is settled from the raw sewage as it passes through primary settling tanks.

??Secondary sludge - solid material separated from sewage after it has undergone biological treatment termed humus for the trickling filter process and waste activated sludge (WAS) for the activated sludge or BNR processes.

?? Tertiary sludge - solid material separated from effluent following tertiary treatment, typically filtration or dissolved air flotation.

Solids collected from screens and grit collection facilities are not included in this report as they are primarily inorganic in nature and not biological solids. However, handling and disposal for these materials should comply with environmental regulations, and occupational safety and health regulations. As a minimum screenings are to be dripped dried and bagged whilst grit should be washed and classified prior to on site storage. Screenings and grit can then be collected by the municipal solid waste contractor and disposed to an approved landfill facility.

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2. Available Information

2.1 Data Sources

Information cited in this report has been provided or sourced from MWCI and includes:

??Operational data.

??Planning data.

?? Listing of current and proposed projects.

??Environmental licensing status.

Information on international regulatory requirements and best practice guidelines has been sourced directly via the Internet.

Parallel projects on biosolids management, i.e. lahar application, septage treatment plant design, etc., are currently being undertaken by other consultants and these projects are targeted for completion prior to finalisation of this study. The information from these projects has been incorporated into this report to ensure the overall strategy is consistent and complete. The project details are as follows:

?? The Pasig River Rehabilitation Commission (PRRC) Feasibility Study for the Treatment, Handling and Disposal of Sludge prepared by Sinclair Knight Merz Phils. (SKM).

?? The Metropolitan Waterworks and Sewerage System (MWSS) Water Supply and Sewerage Master Plan of Metro Manila prepared by Nippon Jogesuido Sekkei Co., Ltd. (NJS)

?? The Manila Third Sewerage Project (MTSP) Feasibility Study and Detailed Design undertaken by NJS.

?? The lahar application Environmental Assessment being undertaken by Engineering Development Corporation (EDCOP).

GHD also visited several MWCI WWTP and septage holding tanks to provide additional operational information and identify potential improvement opportunities. Sites visited include:

??Magallanes WWTP.

??Pabahay Village WWTP.

??Diego Silang WWTP (currently under rehabilitation with a temporary septage holding tank added into the infrastructure).

??Valle Verde WWTP.

??Karangalan Village WWTP.

??West Ave. (Philam) septage holding tank (a WWTP is currently being constructed in the site).

?? Lahar fields in Concepcion, Tarlac and San Fernando, Pampanga.

2.2 Required Data from Additional Testing and Monitoring

Testing data on sludge and septage samples for the following are recommended for confirming biosolids quality and monitoring purposes:

??Heavy metals (arsenic, cadmium, chromium, copper, nickel, lead, selenium, zinc, mercury).

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??Organochlorine pesticides (Aldrin, BHC (alpha, beta, delta), DDD, DDE, DDT, DDT total, dieldrin, heptachlor, heptachlor epoxide, hexachlorobenzene (HCB), lindane (BHC-gamma), chlordane (cis), chlordane (trans), total chlordane).

2.3 Assumptions

The following were assumed in establishing the MWCI biosolids management strategy:

??Population growth in the service area is as per National Statistics Office (NSO) assumed growth rates and forecasted population.

??Connectivity rates for population in the service area is as per MWCI rates rebasing data.

??Given the domestic nature of biosolids produced within the MWCI service area and lack of information on biosolids characteristics, heavy metal, organochlorine, and other organic and inorganic contaminant concentration levels would be within the limits set by international standards. Additional testing and monitoring are required to confirm this assumption (particularly for copper, mercury and cadmium).

??Agronomic rates for potential land application reuse options would be within the limits provided by international guidelines. Confirmation of this assumption needs to be undertaken for each identified area for biosolids application.

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3. MWCI Operations

3.1 MWCI Service Area

The Manila Waterworks and Sewerage System (MWSS) was privatised in 1997 with MWCI assuming control over the eastern concession area. The privatisation involved a 25-year concession agreement for both water supply and sewerage services.

The east concession covers approximately 1,400 square kilometers in area. The MWCI service area includes, in part or in whole, 24 cities and municipalities in Metro Manila and the nearby Rizal province, including:

??Mandaluyong ??Binangonan

??Marikina ??Cainta

??Pasig ??Cardona

??Pateros ?? Jala-Jala

??San Juan ??Morong

?? Taguig ??Pililia

??Makati ??Rodriguez

??Parts of Quezon City ??San Mateo

??Parts of Manila ?? Tanay

??Angono ?? Taytay

??Antipolo ?? Teresa

??Baras ??Montalban

3.1.1 Population Forecast

From MWCI provided information based on the NSO population growth rates and data, forecasted population levels in the concession area are given in Table 1.

Table 1 MWCI Concession Area Forecasted Population1

Location 2004 2006 2011 2016 2021

Mandaluyong 280,000 281,000 283,000 285,000 287,000

Makati2 411,000 424,000 457,000 492,000 530,000

Marikina 418,000 436,000 471,000 507,000 530,000

Quezon City3 835,000 852,000 874,000 955,000 959,000

Pasig 536,000 557,000 596,000 624,000 642,000

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Location 2004 2006 2011 2016 2021

Pateros 57,400 57,400 56,000 58,100 56,000

San Juan 112,000 108,000 97,800 94,300 82,900

Taguig 539,000 587,000 712,000 846,000 992,000

Angono 83,100 88,700 103,000 130,000 149,000

Antipolo 604,000 693,000 986,000 1,250,000 1,690,000

Baras 26,200 27,300 30,000 38,100 43,600

Binangonan 200,000 208,000 227,000 316,000 354,000

Cainta 299,000 337,000 454,000 499,000 503,000

Cardona 40,300 41,200 42,900 45,600 45,600

Jala-jala 24,600 25,500 27,500 31,900 33,000

Morong 43,500 44,200 45,400 53,100 54,200

Pililia 47,700 49,300 52,800 63,600 67,000

Rodriguez 123,000 142,000 181,000 207,000 231,000

San Mateo 149,000 158,000 181,000 222,000 241,000

Tanay 85,000 89,300 100,000 109,000 117,000

Taytay 215,000 227,000 255,000 359,000 414,000

Teresa 31,500 32,600 35,200 45,100 49,600

Manila4 128,000 124,100 113,000 110,000 97,500

Total 5,290,000 5,590,000 6,380,000 7,340,000 8,160,000 1Using the National Statistics Office growth rates for the specified area as estimated by MWCI. 2MWCI coverage in Makati City is 87% of the total land area and population is based on this percentage of total population. 3MWCI coverage in Quezon City is 41% of the total land area and population is based on this percentage of total population. 4MWCI coverage in Manila is 13% of the total land area and population is based on this percentage of total population.

3.1.2 Sanitation and Sewer Services

MWCI has separate target coverage for sanitation, i.e. maintenance of individual septic tanks through periodic desludging, and sewerage, i.e. provision of communal septic tanks and wastewater treatment plants. Table 2 and Table 3 provide the target connectivity rates for proposed MWCI infrastructure.

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Table 2 MWCI Sewerage Service Coverage Targets (% of total population in area)1

Location 2001 2006 2011 2016 2021

Mandaluyong 0.5 4 10 15

Makati 22 40 38 28 23

Quezon City 13 20 16 17

Pasig 9 10 12 14

San Juan 18 41

Taguig 5 25 26 20 1 From MWCI rates rebasing data.

Note: Blank cells indicate no specified target for the area. Other cities and municipalities within the MWCI concession are not planned for connection to a sewer system.

Table 3 MWCI Sanitation Service Coverage Targets (% of total population in area)1

Location 2001 2006 2011 2016 2021

Mandaluyong 99.5 96 90 85

Makati 60 62 72 77

Marikina 0 100 100 100 100

Quezon City 3.2 87 80 84 83

Pasig 1.2 91 90 88 86

Pateros 100 100 100 100

San Juan 100 100 82 59

Taguig 95 75 74 80

Angono 0 100 100 100 100

Antipolo 0.5 100 100 100 100

Baras 0.5 0 0 100 100

Binangonan 0 0 100 100

Cainta 0.2 100 100 100 100

Cardona 0 0 100 100

Jala-jala 0.2 0 0 100 100

Morong 0.7 0 0 100 100

Pililia 0 0 100 100

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Location 2001 2006 2011 2016 2021

Rodriguez 100 100 100 100

San Mateo 0.7 100 100 100 100

Tanay 0 0 100 100

Taytay 0 100 100 100 100

Teresa 0 0 100 100

Manila 100 100 100 100 1 From MWCI rates rebasing data.

Note: Blank cells indicate no specified target for the area.

Population within the service area not connected to the MWCI full sewerage infrastructure or provided with sanitation services are expected to have:

?? Individual septic tanks collecting wastewater and providing minimal treatment prior to discharge to receiving bodies of water without the periodic desludging services; or

??Direct discharge of wastewater to receiving bodies of water especially for illegal settlers residing on riverbanks.

It was estimated that the number of individual septic tanks in Metro Manila would be over one million (based on 1996 data referenced from the SKM Septage Feasibility Study report). However, actual count of individual septic tanks and unconnected population were not sighted during the course of this study.

3.2 Existing Facilities Related to Biosolids Generation and Management

3.2.1 Wastewater Treatment Plants

Among the current facilities being operated by MWCI, only the Magallanes WWTP produces digested and dried sludge. Primary sludge and wasted activated sludge is currently being conveyed to two anaerobic digesters for stabilisation prior to dewatering in drying beds. These are bagged and stored under covered areas within the WWTP site.

MWCI trucks the dried sludge in 25 kg sacks to Porac, Pampanga and Nueva Ecija for distribution to farmers. The farmers use these as soil conditioner for agricultural lands. No information on application practices was available during the study. Average disposal rate to Porac and Nueva Ecija is 350 and 500 bags respectively per 3 months. MWCI has direct operational control only on the trucking of the sludge to the site.

According to the WWTP operators, dried sludge is also being collected by various entities for land application. However, there are no formal agreements with any of the entities for the hauling and reuse of the dried sludge. Third party collector of Magallanes dried sludge includes:

??Manila Fertilizer. It is understood that the sludge is being mixed with fertilizer products and sold. Manila Fertilizer sludge collection is on a seasonal basis.

?? Farmers from Tarlac province haul dried sludge for application to agricultural lands.

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??Makati City and other nearby local government units (LGUs). It is assumed that the sludge is used for urban amenities, i.e. landscaping purposes.

??Ayala Land, Inc. (ALI) land development projects. Assumed to reuse the sludge for landscaping.

MWCI provided copies of certificates issued by the Fertilizers and Pesticides Authority (FPA) accrediting MWCI as a fertilizer manufacturer and distributor. It is uncertain if any soil and groundwater monitoring is being undertaken within the application sites of the dried sludge.

An observation during the Magallanes WWTP visit was the uncertainty in the anaerobic digester condition and the level of stabilisation being achieved. There is a potential that the dried sludge maybe poorly stabilised (if not fully dried) and unsuitable for direct land application, i.e. vector attraction maybe significant after the sludge has been applied and re-wetted via rainfall or irrigation. Therefore it is necessary to review the distribution of dried sludge to third parties as MWCI may be exposed to liabilities arising from this practice.

There are 3 other WWTPs operating within the MWCI concession area. These are the:

??Pabahay Village WWTP based on a bio-contact activated sludge process with a capacity of 600 m3/d. Excess liquid sludge produced from the plant is currently being pumped out and trucked to the Diego Silang septage holding tank prior to disposal to lahar fields in Pampanga.

??Valle Verde WWTP based on a bio-contact activated sludge process with a capacity of 115 m3/d. Excess liquid sludge produced from the plant is currently being pumped out on an infrequent basis and trucked to the Diego Silang septage holding tank prior to disposal to lahar fields in Pampanga.

??Karangalan Village WWTP based on a bio-contact activated sludge process with a capacity of 484 m3/d. Excess liquid sludge produced from the plant is currently being pumped out on an infrequent basis and trucked to the West Avenue septage holding tank prior to disposal to lahar fields in Pampanga.

Information from operators of the Valle Verde and Karangalan WWTPs indicates very little sludge is currently produced from the plants. Potential causes for this are discussed in Section 8.

3.2.2 Communal Septic Tanks

MWCI has implemented several communal septic tank (CST) facilities to help improve the Pasig River conditions (Refer to section 5.8 for details). Septage from CSTs is collected by MWCI and conveyed to one of the septage holding facilities. CST pump out is being done by MWCI on a routine basis of once every five years. Ten of these CSTs are programmed for conversion as wastewater treatment plants in the future. Current operational CSTs and capacities are shown in Table 4.

Table 4 Existing Communal Septic Tanks

Location Tank Capacity (m3)

Violeta St., Roxas District, QC 113

Umbel St., Roxas District, QC 53

Gumamela St., Roxas District, QC 114

Gumamela St., Roxas District, QC 121

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Location Tank Capacity (m3)

Waling Waling St., Roxas District, QC 192

Waling Waling St., Roxas District, QC 153

Everlasting St., Roxas District, QC 230

Azucena St., Roxas District, QC 191

Azucena St., Roxas District, QC 90

Azucena St., Roxas District, QC 70

Champaca St., Roxas District, QC 143

Camia St., Roxas District, QC 84

Everlasting St., Roxas District, QC 79

Alley nr. Rimas St., Project 2, QC 338

J. Zobel St., Project 4, QC 252

near Sangchio St., Kamuning, QC 410

Matiwasay St., U.P. Village, QC 829

Mapagmahal St., U.P. Village, QC 432

3.2.3 Septage Management

Areas within the concession not connected to sewerage are assumed to have individual septic tanks as required by the National Plumbing Code of the Philippines. Normal design practices in the Philippines assume a minimum of 24-hour detention period for septic tanks with a per capita water consumption of 150-200 liters per day. Wastewater generation is usually taken as 90% of the water consumption rate. Various studies on Metro Manila sanitation requirements indicate a 6-year period between septage pump outs for individual septic tanks is ideal and this is programmed for implementation by MWCI.

Septage Collection

Vacuum desludging trucks collect septage from individual and communal septic tanks. MWCI currently has 7 units of 10 cubic meter capacity vacuum trucks undertaking the septage collection. Historical data on septic tanks desludged is presented in Table 5.

Table 5 Septic Tank Desludging Data (Number of individual tanks serviced)1

Location 1997 1998 1999 2000 2001 2002 2003 Waiver

Mandaluyong 11 11 9 21 160 1,966 277

Makati 3 11 11 11 58 940 1,449 1

Marikina 19 78 83 119 440 709 2,216 445

Quezon City 17 111 117 136 369 1,974 6,183 1,385

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Location 1997 1998 1999 2000 2001 2002 2003 Waiver

Pasig 2 14 16 30 426 420 1,482 347

Pateros 3 1 452 3 0

San Juan 2 11 11 12 8 15 17 0

Taguig 136 244 0

Antipolo 6 6 7 4 8 213 0

Cainta 3 3 3 13 3 1,544 195

San Mateo 7 7 10 1 4 10 0

Manila 3 9 9 7 21 58 2,451 113

Montalban 4 8 8 4 6 36 43

Total 50 269 282 351 1368 4915 17821 2763 1 From MWCI provided monitoring data.

Note: Waiver column indicates the cumulative number of households from the start of the privatisation of the water service who opted not to avail of the free desludging services offered by MWCI. Blank spaces means no desludging services were offered in the area for the given year. Areas not included in the table were not included in the septage management program of MWCI for the years listed.

Each truck collects an average of 3 septic tanks per trip. Septage collection and transport to the septage holding facilities is under direct management of MWCI.

Septage Holding Facilities

Currently, septage collected within the MWCI service area is conveyed to either one of two septage-holding facilities. Locations and capacities of the holding tanks are:

??Philam, West Ave., West Triangle, Quezon City with a tank volume of 250 m3. A WWTP is being constructed on the site and this is expected to be commissioned in mid 2004.

??Diego Silang WWTP site with an estimated tank volume of 200 m3. We were unable to confirm the tank volume from as -built drawings of the facility. The existing WWTP is currently not operating. However, there is a plan to rehabilitate the plant and once operational, this is expected to treat on average 2,700 m3/d of wastewater. MWCI currently anticipates commissioning of the rehabilitated WWTP by middle of 2005.

Septage Transport and Disposal to Pampanga and Tarlac

Private hauling contractors collect and transport the septage from the Philam and Diego Silang holding tanks to Pampanga and Tarlac. Each truck makes 1 to 2 round trips per day with truck capacities ranging from 16 to 25 m3.

A site visit to the Philam septage holding facility was conducted on 23 March 2004 and it was observed that:

?? Transport vehicles are water or fuel tankers converted to serve as septage transport vehicles.

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??Drain valves were not secured and have a significant potential for accidental discharge due to inadvertent opening of valves or leakage.

Although GHD was not able to observe private contractors collecting septage from the Diego Silang facility, MWCI informed that the Philam and Diego Silang contractors are the same, i.e. contractors for Philam also collects the sludge from Diego Silang. Therefore, the observations for the Philam site may be applicable to the Diego Silang operations.

GHD requested for confirmation from the DENR-EMB on the requirements for the transport, handling, and management of septage and domestic wastewater sludges. It was confirmed that septage and domestic wastewater sludge are not substances under the jurisdiction of RA 6969. A copy of the DENR-EMB correspondence is presented in Appendix A.

MWCI is currently disposing wet septage to lahar fields in Tarlac and Pampanga as land rehabilitation and broad acre agriculture reuse options. Lahar is the term given to pyroclastic flows caused by the Mt. Pinatubo eruption in 1991. The lahar application is being done in collaboration with the Sugar Regulatory Administration (SRA) and is on a trial basis to assess the effect of liquid septage application on the growth and yield of sugarcane. Lahar depths on the Tarlac application area are reportedly from 5 to 15 meters and the fields were not previously used for agricultural purposes, i.e. prior to the Mt. Pinatubo eruption. The San Fernando, Pampanga application area was agricultural land prior to the lahar deposit and lahar depths were estimated to be between 1.5 to 5.0 meters.

It is understood that the majority of the lahar fields being applied with septage are owned or leased by the septage-hauling contractor. Application rate is in the order of 200 m3 of septage per hectare over a 2-month period during the early part of the planting season. This gives an average septage application of 20 mm over the 2-month period. Septage is applied via:

??Hoses and allowed to flow through furrows between planted sugarcane.

??Direct spray application using transportable tanks on areas not yet planted with sugarcane.

According to the septage haulers, the farmers would turn the soil over upon completion of the septage application for areas yet to be planted with sugarcane, however this was not observed during the site visit. Areas already planted with sugarcane however were observed to have dried septage solids on the ground surface.

Allocation of septage is programmed on a rotation basis as trucks come in. However, in most instances other farmers not currently being supplied with septage, specially the barangay captains and those with land along the access route to the application area, request that the haulers apply septage to their land as well. The septage hauling contractors are not charging any fees to farmers who request the septage.

Application of liquid septage to lahar carries with it certain risks because of the adsorption capacity of lahar and its erosion characteristics. There are some concerns in terms of potential nutrient leaching to the groundwater due to the perceived low adsorption capacity of lahar. Contaminant transport via surface runoff is also a concern due to the perceived high erodability of lahar.

The lahar application environmental assessment being undertaken by EDCOP needs to consider the following items:

?? Lahar adsorption rates for nutrients from the septage to provide information on potential nutrient transport to surface and ground water resources.

??Erosion potential for lahar to provide a check on septage transport with surface runoff.

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??Agronomic rates, i.e. maximum allowable septage application rates on lahar considering soil characteristics, irrigation practices, and plant uptake, to provide an upper limit on the septage applied per square meter of lahar area.

??An assessment of topsoil or binder addition (sourced from nearby regions) to lahar-laden areas to prevent potential runoff of septage due to erosion. Optimisation of the biosolids/binder/lahar mix.

??A comparison of the unstabilised septage, dewatered septage (20% w/w) and lime stabilised dewatered septage (comprising 0.5 kg lime added per kg dry solids) to determine any benefits and disadvantages in achieving the above goals. Note that lime could also contribute to groundwater contamination.

Further details on these items are provided in Section 6.1.3.

This assessment should take into consideration the carbon/nitrogen ratio (C/N). Literature (Walmsley & Dougherty, 1995) suggests that the C/N ratio could be manipulated to reduce the rate of mineralisation and hence nitrogen movement and pH reduction. The authors successfully applied biosolids to a sandy/silty soil (which had a low nutrient level and low cation exchange capacity) using woodchips to increase the C/N ratio.

Associated Costs for the Current Septage Management System

According to MWCI information, the following are the costs for the current septage management system:

??Cost of hauling and disposal to Pampanga per cu. m. Php 330.00

(Average from Philam and Diego Silang holding tanks)

?? Labor cost for septage collection per shift (2 shifts) Php 1,363.00

Note that the maintenance cost for collection vehicles is already included in the overall OPEX of MWCI. Maintenance is done in-house at the MWCI motorpool and this includes vehicles for the water and wastewater operations of the company. Labor costs for the Diego Silang holding tank is not separate from the Diego Silang WWTP OPEX and as such is not considered as a separate expense.

MWCI collects fees for septage collection services in the amount of Php 803.00 and Php 5,000.00 per truckload for residential and commercial areas. Residential charges are applicable only for services provided when requested by the resident. Regular septic tank maintenance is provided for free for residents by MWCI.

3.3 Certifications and Licenses

The Fertilizer and Pesticides Authority (FPA) have approved MWCI domestic liquid sludge application on sugarcane and other similar crops, and domestic dried sludge application for corn and similar crops. Additionally, the FPA also licensed MWCI to operate as “Manufacturer-Distributor” of fertilizers. It is assumed that the fertilizers manufactured by MWCI would be the residuals from WWTP operations and septage collection practices.

3.4 On Going and Planned Projects

MWCI is currently undertaking significant expansion works for sewerage and sanitation as required by their concession agreement with the government. They are currently constructing or planning a number of WWTP and communal septic tanks to achieve the level of service as contained in their rates rebasing

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data. Sanitation coverage is also programmed for expansion during the concession period. These projects are being undertaken as part of the Manila Second Sewerage Project (MSSP) and the MTSP.

General descriptions of the projects are presented in Section 5.8.

Table 6 On Going and Planned Wastewater Projects under the MSSP (Bio-contact Activated Sludge Process)

Location Capacity (m3/day)

Expected Commissioning

Philam Village, West Ave., QC 2,069 July 2004

Kalayaan Ave. near Kamias Rd., QC 4,414 July 2004

Pag-asa BLISS, QC 785 July 2004

Sikatuna BLISS, QC 609 July 2004

Belarmino St., Project 4, QC 1,640 October 2004

Visayas Ave. near Fisheries St., Project 6, QC 400 December 2004

U.P. Campus, Diliman, QC 7,027 July 2004

Karangalan Village1, Pasig City 861 October 2004

Karangalan Village1, Pasig City 792 October 2004

Karangalan Village1, Pasig City 961 October 2004

Karangalan Village1, Pasig City 945 October 2004

Karangalan Village1, Pasig City 435 October 2004

Karangalan Village1, Pasig City 318 October 2004

Karangalan Village1, Pasig City 357 December 2004

Karangalan Village1, Pasig City 742 October 2004

Karangalan Village1, Pasig City 588 October 2004

Mandaluyong MRH, Mandaluyong City 287 July 2004

Guadalupe BLISS, Makati City 851 October 2004

A. Luna St., Project 4, QC 1,800 December 2004

Palosapis St., Project 2, QC 2,500 December 2004

Heroes Hill, QC 2,000 December 2004

Balara, QC 250 December 2004

Lakeview Manors, Taguig 513 December 2004

Maharlika MRH, Taguig 470 July 2004

Centennial Village, Taguig 1,277 July 2004

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Location Capacity (m3/day)

Expected Commissioning

Fortville, Taguig 1,142 December 2004

Bagong Lipunan, Taguig 1,359 December 2004 1 Individual capacity sourced from the Environmental Compliance Certificate (ECC) listing 9 separate projects with a total capacity of 6,000 m3/day. Other documents from MWCI show capacity for the Karangalan WWTPs to be 7,463 m3/day.

Table 7 On Going and Planned Wastewater Projects under the MTSP

Type of Project Location Capacity

Sequencing Batch Reactor Road 5, Project 6, QC (upgrade of CST) 3,537 m3/day

Sequencing Batch Reactor Anonas St., QC (upgrade of CST) 1,858 m3/day

Sequencing Batch Reactor Option 2 – covering 3 barangays in QC (upgrade of CST)

11,477 m3/day

Sequencing Batch Reactor Camp Atienza, QC – serving villages near the camp including Blue Ridge, St. Ignatius, Libis and Cinco Hermanos

5,339 m3/day

Sequencing Batch Reactor Taguig – serving 4 communities in Bicutan 3,766 m3/day

Oxidation Ditch Manggahan – serving 7 communities 8,964 m3/day

Sequencing Batch Reactor Capitolyo, Pasig City 3,946 m3/day

Sequencing Batch Reactor Ilaya, Mandaluyong City 1,059 m3/day

Sequencing Batch Reactor Poblacion, Pasig City 659 m3/day

Oxidation Ditch Labasan and Taguig

Oxidation Ditch Tapayan and Taytay

Oxidation Ditch Hagonoy and Taguig

375,000 m3

Aside from the above wastewater projects, sludge and septage management projects proposed within the east concession area includes the following:

?? 600 m3/day Septage Treatment Plant (STP) under the PRRC programs to be located in Pinugay, Antipolo.

?? 586 m3/day STP under the MTSP to be located in Payatas, QC.

?? 815 m3/day STP under the MTSP to be located in FTI Complex, Taguig.

A brief description of the STP projects is presented in Section 5.8.

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3.5 Key Issues in Establishing the MWCI Biosolids Strategy

The key factors in the establishment of the MWCI biosolids strategy will be economics and environmental protection. Issues that would need to be addressed by the biosolids strategy include:

?? The current transport and hauling of septage to Pampanga entails significant operating costs, primarily due to the excessive amount of liquid in the septage being transported. There is an opportunity to minimise hauling costs if excess liquid is removed prior to disposal thereby reducing the volume of septage required for transport.

?? The initiation and/or formalization of any agreements with waste exchange partners, i.e. Manila Fertilizer, Makati City LGU, etc. The agreements should include liability issues in terms of the proper handling, application to land, and disposal of biosolids produced from MWCI infrastructure. This will reduce operating requirements from MWCI and at the same time ensure potential liabilities due to waste partner operations are not passed on to MWCI.

??Maximise reuse potential for biosolids. Global focus on biosolids management is geared towards minimising disposal. Economics play a part in identifying the potential options for managing biosolids including capital expenditures for proposed equipment, operations and maintenance costs, and potential reuse revenues and/or disposal costs.

??Recommend standards for biosolids management. This will allow the adoption of stricter performance requirements for biosolids treatment to reflect international trends. Using more stringent standards will also ensure long-term compliance with any regulation that may be enacted by the Philippine government.

?? Identify and implement improvement opportunities in the operation of the facilities. This might include occupational health and safety issues, risk management, compliance issues and the like.

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4. Biosolids Quantity and Quality

4.1 General

Ultimately, MWCI sanitation services and sewer infrastructure will generate biosolids from the following sources:

??Magallanes WWTP producing dried sludge using drying beds.

??MSSP facilities producing liquid sludge and dewatered sludge using filter presses.

??MTSP facilities producing liquid sludge and dewatered sludge using filter presses.

??PRRC STP producing dewatered and stabilised cakes using a combination of screw press and lime stabilisation.

??MTSP STPs (2 no.) producing dewatered cakes using screw presses.

From discussions with design consultants of the proposed facilities (i.e. MSSP communal septic tanks, MSSP WWTPs, and MTSP WWTPs) and existing bio-contact activated sludge WWTPs, septage and liquid sludge produced from these facilities will be treated in one of the proposed STPs within the MWCI service area. All septage pumped out from individual septic tanks will also be conveyed to the STPs prior to ultimate disposal.

4.2 Dried Sludge from Magallanes WWTP

The Magallanes WWTP historical data shows biosolids generation of approximately 400 kg per day of dry solids. This is significantly less than the expected generation rates based on the design capacity of the plant.

Based on design parameters for the proposed MSSP WWTPs, the expected dry solids generation at the Magallanes WWTP would be approximately 1,500 to 2,000 kg per day (4 to 7 m3 per day assuming 30-40% dry solids).

Based on independent calculations for similar plants (capacity and process) as Magallanes and using the influent and effluent BOD5, suspended solids, and dissolved solids data provided by MWCI for Magallanes, the dry solids generation is expected to be between 3,000 to 6,000 kg per day (10 to 20 m3 per day assuming 40% dry solids). These values were estimated from sludge ages of 10 to 40 days and an HRT of 4.3 hours as advised by MWCI. This is significantly higher than the observed generation rates and the equivalent MSSP rates.

The MSSP values and GHD calculations indicate that solids capture may be an issue at the Magallanes WWTP. Poor solids capture is the most likely explanation for the lower sludge generation being observed. It is recommended that a more detailed review of the Magallanes WWTP operation be undertaken to ascertain the discrepancy between expected and actual solids generation rates.

4.3 Liquid Sludge from Operating WWTPs

In addition to Magallanes, MWCI currently operates three other WWTPs. As discussed in Section 3.2.1, these plants produce liquid sludge that is transferred to the Philam and Diego Silang septage holding tanks.

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Design parameters for the existing WWTPs were not sighted during the study (except for the plant capacities). However, an estimate of the biosolids generation rates has been made based on similar process and plant capacities for on-going WWTP projects under the MSSP as designed by JFE. JFE provided information on the expected liquid sludge volume generation for their plants as shown in Section 4.6. The following table presents the expected generation rates from the existing WWTPs.

Table 8 Estimated Biosolids Generation Rate for Existing WWTPs*

Location Dry Solids (kg/day)

Transport Volume (m3/day)

Pabahay Village 8 1

Valle Verde 1.5 0.15

Karangalan Village 7 0.4

Total 16.5 1.55 *Estimates based on JFE provided dry solids generation rates for on-going WWTP projects.

4.4 Dewatered Sludge from MSSP Facilities

Information from the MSSP contractor (Chemitreat) involved with the following projects indicated that sludge from these facilities would be dewatered on site via belt filter press. The MSSP design biosolids generation rates, assuming 25% solids content in the filter cakes, are presented in Table 9.

Table 9 Biosolids Generation from MSSP Projects

Location Dry Solids (kg/day)

Transport Volume (m3/day)

U.P. Campus, Diliman, QC 365 1.5

Lakeview Manors, Taguig 20 0.08

Maharlika MRH, Taguig 18 0.07

Centennial Village, Taguig 50 0.2

Fortville, Taguig 43 0.17

Bagong Lipunan, Taguig 52 0.21

TOTAL 550 2.2

Note: WWTP contractor provided generation rate in terms of kg dry solids per day. GHD converted this data to a transport volume requirement assuming 25% dry solids content and a sludge density of 1,000 kg/m3.

4.5 Sludge from MTSP Facilities

There are 12 WWTPs proposed to be built under the MTSP. According to data provided by NJS (the MTSP consultant), secondary treated sludge from the WWTPs will be thickened to 2.5% prior to dewatering. Dewatered sludge is estimated to have 25% dry solids content and the total generation rate

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is expected to be around 32,100 kg/d dry solids (equivalent to 157 m3/d). Digestion processes are currently not proposed for the new facilities. A summary of the projected sludge generation rates is given in Table 10.

Table 10 Biosolids Generation of Wastewater Projects under the MTSP

Location Thickening Dewatering Dry Solids (kg/day)

Transport Volume (m3/day)

Road 5, Project 6, QC 2.5% 25% 420 1.68

Anonas St., QC 2.5% 25% 221 0.88

Option 2 –3 barangays in QC 2.5% 25% 1,611 6.44

Camp Atienza, QC 2.5% 25% 2,011 8.05

Taguig 2.5% 25% 1,156 4.62

Manggahan 2.5% 25% 1,466 5.86

Capitolyo, Pasig City 2.5% None 470 18.8

Ilaya, Mandaluyong City 2.5% None 195 7.80

Poblacion, Pasig City 2.5% None 129 5.17

Labasan and Taguig 2.5% 25% 10,825 43.3

Tapayan and Taytay 2.5% 25% 6,252 25.0

Hagonoy and Taguig 2.5% 25% 7,329 29.3

Total 32,085 157

Commissioning and operation schedules for the new WWTPs are programmed for first quarter of 2008. It is uncertain if the NJS scope for MTSP includes identifying potential reuse or disposal options for the dewatered sludge. However, initial information indicates that NJS has assumed that all dewatered sludge will be transported to Pampanga for lahar application.

4.6 Liquid Sludge Generation from MSSP WWTPs

MWCI is implementing and/or proposing wastewater projects in accordance with the upgrading of sewerage services the company provides under the MSSP. Table 11 presents the expected biosolids generation rates from these WWTPs. Liquid sludge generation rates are from information provided by the project consultants (JFE) through MWCI. JFE also advised that the sludge would have 0.8% solids and this is used to estimate the corresponding mass of dry solids produced from the WWTPs.

Table 11 Biosolids Generation Rates of MSSP WWTPs

Location Transport Volume (m3/day) as per JFE Information

Dry Solids (kg/day)

Philam Village 3.4 27

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Location Transport Volume (m3/day) as per JFE Information

Dry Solids (kg/day)

Kalayaan 11.2 90

Pag-asa Bliss 1.2 10

Sikatuna Bliss 1.0 8

Belarmino St. 2.7 22

Fisheries St. 1.4 11

Karangalan Village 15.5 124

Karangalan Village 3.5 28

Karangalan Village 1.1 8.8

Karangalan Village 21.3 170

Karangalan Village 1.0 8

Karangalan Village 0.8 6

Karangalan Village 1.2 10

Karangalan Village 16.2 130

Karangalan Village 13.1 105

Mandaluyong MRH 2.9 23

Guadalupe Bliss 4.9 39

A. Luna 17.4 139

Palosapis 25.8 206

Heroes Hill 13.5 108

Balara 0.4 3

Total 159 1,280

Excess sludge is temporarily stored on site in sludge holding tanks. It is assumed that the excess sludge will eventually be collected and transferred to the existing central septage holding facilities in Philam or Diego Silang. Eventually, it is programmed that liquid sludge will be transported to one of the three STPs proposed in the MWCI concession area.

4.7 Septage

All septage, including those generated from individual and communal septic tanks, will be transported to one of the proposed STPs to be operated by MWCI. Given that this study is focused on biosolids management, (i.e. end product of the STPs), a detailed discussion of septage generation and transport

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requirements has not been presented. However, optimisation measures for the transport of septage for inclusion in the short-term strategy are discussed in Section 8.

4.8 Filter Cakes from Proposed Septage Treatment Plants

According to information provided from MWCI consultants engaged on the STP design, the following filter cake volumes are expected.

??PRRC STP in Pinugay, Antipolo will produce 90 m3/day of stabilised sludge at ultimate design capacity. The filter cake generation is based on the proposed lime stabilisation of septage. The PRRC report indicates about 90,000 kg/day of dry solids to be produced from the plant. Plant commissioning is expected to be mid-2006.

??MTSP STP in Payatas, QC will produce 74 m3/day of dewatered sludge at 30% solids at the ultimate design capacity. Using the data provided by NJS and assuming a sludge density of 1,000 kg/m3, the expected biosolids generation is 22,200 kg/day. Commissioning is programmed for 2008.

??MTSP STP in FTI Complex, Taguig will produce 103 m3/day of dewatered sludge at 30% solids at the ultimate design capacity. Using the data provided by NJS and assuming sludge density of 1,000 kg/m3, expected biosolids generation is 31,000 kg/day. Commissioning is programmed for 2008.

A brief description of the STP projects is presented in Section 5.8. According to NJS, the ultimate STP capacities will be realised by year 2015 and the expected growth rate is as follows:

Table 12 STP Solids Generation Growth Rate in m3/day

Project 2008 2009 2010 2011 2012 2013 2014 2015

NJS Estimates 59% 62% 66% 73% 80% 86% 90% 100%

Liquid Septage Transport Volumes

Payatas STP 346 363 387 428 469 504 527 586

Taguig STP 481 505 538 595 652 701 733 815

PRRC STP 354 372 396 438 480 516 540 600

Septage Cake Transport Volumes

Payatas STP 44 46 49 54 59 64 67 74

Taguig STP 61 64 68 75 82 89 93 103

PRRC STP 53 56 59 66 72 77 81 90

Total 158 166 176 195 213 230 241 267

4.9 Summary of the Expected Biosolids Quantity

The generation rates estimated for the various biosolids generating facilities are shown in Table 13. Ultimately around 400 m3/day (180 dry tonnes/day) of biosolids will be required to be reused/disposed as shown in Table 14.

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Table 13 Summary of Biosolids Generation in Terms of Source

Source Dry Solids (kg/d)

Transport Volume (m3/d)

Type of Biosolids Remarks

Magallanes WWTP 1,500 to 2,000 4 to 7 Stabilised and Dried Sludge Anaerobic digester and sludge drying beds.

Pabahay Village WWTP 8 1 Liquid Sludge Sludge holding tanks on-site. To septage tanks.

Valle Verde WWTP 1.5 0.15 Liquid Sludge Sludge holding tanks on-site. To septage tanks.

Karangalan Village WWTP 7 0.4 Liquid Sludge Sludge holding tanks on-site. To septage tanks.

MSSP WWTPs (Chemitreat) 550 2.2 Wet Sludge Plate filter pressed on site. No stabilisation.

MTSP WWTPs 31,300 125 Wet Sludge Plate filter pressed on site. No stabilisation.

MTSP WWTPs 794 32 Liquid Sludge Thickening only.

MSSP WWTPs (JFE) 1,276 160 Liquid Sludge Holding tanks prior to transport to STP.

PRRC STP 90,000 90 Stabilised Screw press and lime stabilisation.

Payatas STP 22,200 74 Wet Septage Limited to dewatering of septage.

Taguig STP 31,000 103 Wet Septage Limited to dewatering of septage.

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Table 14 Summary of Biosolids Generation in Terms of Biosolids Type

Type of Biosolids Transport Volume (m3/day)

Liquid Sludge 194

Wet Sludge 127

Wet Septage 177

Stabilised Biosolids 90

Dried Sludge 4 to 7

Total 400

Note: Liquid sludge will be treated in one of the programmed STP facilities and therefore transport to disposal for this type of biosolids is assumed to be included in the wet septage and stabilised biosolids volumes.

4.10 Biosolids Quality

Information available on the biosolids quality being produced is currently limited to:

??A laboratory result for the Magallanes WWTP sludge conducted in November 1997.

??Organic fertilizer sample analysis conducted in September 2001.

?? Foliar fertilizer sample analysis conducted in May 2002.

4.10.1 Key Parameters

Biosolids quality has an impact on the suitability of a reuse or disposal option. Most of the industry-accepted guidelines characterises biosolids in terms of the following.

??Contaminant level (heavy metals, pesticides etc.)

??Stability (pathogens, odour potential etc.)

??Nutrient Content (Nitrogen, phosphorus)

Contamination grade refers to the characterisation of a biosolids batch according to the concentration of the potentially toxic elements contained in the batch. International regulatory bodies monitor and control the concentrations of these elements that are mostly heavy metals. A list of the controlled contaminants from the USEPA is provided in Table 15.

Table 15 List of Controlled Contaminants

Arsenic Mercury

Cadmium Molybdenum

Chromium Nickel

Copper Selenium

Lead Zinc

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Biosolids stability/ stabilisation grade refers to the quality of sludge according to the pathogen activity contained, its potential for vector attraction, and potential to generate foul odours. Pathogens are microorganisms such as bacteria and viruses, Helminths (worms), and protozoan parasites such as Giardia, Entamaeta and Cryptosporidium, which can cause disease in humans and animals. The type and level of treatment determines the stabilisation grade.

The contamination and pathogen levels in biosolids are characteristics regarded to have the most significant effect in human and animal health. These then become the most critical consideration in identifying the appropriate reuse or disposal mode for biosolids.

Nutrient content is important when considering the application of biosolids in agricultural lands. The suitability of biosolids and the sustainable loading rate are best determined by considering the type of crop and the quality of the soil. Loading of nitrogen in excess of the crop requirements can lead to the contamination of groundwater.

4.10.2 Expected Biosolids Quality

Given the minimal available information on actual biosolids quality, typical literature values for different types of biosolids are presented in Table 16 and values for septage are presented in Table 17. Septage characteristics for Metro Manila from previous GHD projects on septage management are presented in Table 18 (Note: The accuracy and reliability of this data may be questionable due to our current understanding on the poor quality of biosolids analysis performed by local laboratories).

4.10.3 Potential Impacts of Biosolids Quality on Downstream Processes

It is expected that the absence of industrial wastewater entering the MWCI wastewater plants will result in relatively low levels of heavy metals and organochlorine pesticides in the biosolids.

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Table 16 Typical Properties and Composition of Various Sludge Types*

Untreated Primary Sludge Digested Primary Sludge Item

Range Typical Range Typical

Activated Sludge

Total dry solids (TS), % 2 to 8 5.0 6 to 12 10 0.83 to 1.16

Volatile solids, % of TS 60 to 80 65 30 to 60 40 59 to 88

Grease and fats, % of TS

??Ether soluble

??Ether extract

6 to 30

7 to 35

-

-

5 to 20

-

18

-

-

5 to 12

Protein, % of TS 20 to 30 25 15 to 20 18 32 to 41

Nitrogen, % of TS 1.5 to 4.0 2.5 1.6 to 6.0 3 2.4 to 5.0

Phosphorus, % of TS 0.8 to 2.8 1.6 1.5 to 4.0 2.5 2.8 to 11.0

Potash, % of TS 0 to 1.0 0.4 0 to 3 1 0.5 to 0.7

Cellulose, % of TS 8 to 15 10 8 to 15 10 -

Iron (not as sulphide) 2 to 4 2.5 3 to 8 4 -

Silica, % of TS 15 to 20 - 10 to 20 - -

pH 5 to 8 6.0 6.5 to 7.5 7 6.5 to 8.0

Alkalinity, mg/L as CaCO3 500 to 1,500 600 2,500 to 3,500 3,000 580 to 1,100

Organic acids, mg/L as HAc 200 to 2,000 500 100 to 600 200 1,100 to 1,700

Energy content, Btu/lb 10,000 to 12,500 11,000 4,000 to 6,000 5,000 8,000 to 10,000

* from Metcalf and Eddy, 1991

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Table 17 Typical Septage Constituent Concentrations and Unit Loading Factors*

Concentrations, mg/L Unit Loading, kg/capita ? d Constituent

Range Typical Range Typical

BOD5 2,000 to 30,000 6,000 0.02 to 0.07 0.04

TS 4,000 to 100,000 40,000

SS 2,000 to 100,000 15,000 0.04 to 0.20 0.1

VSS 1,200 to 14,000 7,000

TKN 100 to 1,600 700

NH3 100 to 800 400

TP 50 to 800 250

Grease 5,000 to 10,000 8,000

* from Metcalf and Eddy, 1991

Table 18 Metro Manila Septage Characteristics

Parameter Unit1 Actual Lab Results

pH 7

BOD mg/L 4,338

COD mg/L 23,250

Suspended Solids mg/L 52,500

Total Solids mg/L 37,419

Oil and Grease mg/L 1,493

Ammonia Nitrogen mg/L 134

Zinc mg/L 218

Copper mg/L 29

Lead mg/L 1.99

Nickel mg/L 3.1

Cadmium mg/L 0.26

Silver mg/L 0.10

Mercury mg/L 4.24

TVS/TS % 60

1 Although the contaminants were expressed in mg/L, typically contaminants are expressed in mg/kg. There is considerable uncertainty regarding the accuracy of these results.

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5. Planning Considerations

5.1 General

In developing a biosolids management strategy, planning is required to consider the following:

??Compliance with existing local regulatory standards;

?? Identification of relevant international guidelines and standards;

?? The potential for new and emerging technologies;

?? International trends in biosolids management; and

?? The overall long-term operations of MWCI (ensuring upstream processes are aligned to the identified reuse and disposal options).

The following section looks at how regulations, trends in biosolids management and planned projects may affect the overall biosolids management strategy.

5.2 Review of Local Guidelines on Biosolids Management

Biosolids management in the Philippines is largely unregulated as there is no specific law governing biosolids reuse and disposal. Clarifications with the Department of Environment and Natural Resources (DENR) shows that biosolids does not fall under RA 6969 and therefore not required to have permits for managing the biosolids.

DENR may potentially review this issue given the recent signing of the Clean Water Act. Given this potential for change, international guidelines may be used as a basis for predicting the likely future legislation in the Philippines.

5.3 Review of International Guidelines on Biosolids Management

A review of the various international guidelines concerning the treatment and reuse of sludge has been conducted as planning criteria for the development of the management strategy. The review involved guidelines set by:

??US Environmental Protection Agency;

??Australian State Environmental Protection Agencies;

??European Economic Community Council; and

??Canadian Ministry of Environment.

An overview of these guidelines is presented in Appendix B.

The guidelines set out a number of classes of biosolids, based on the levels of metal and organic chemical contaminants and on the treatment processes that have been used to stabilise the biosolids to reduce pathogen levels (microorganisms), vector (rodent) attractants and odour.

In general, all guidelines have the following objectives:

??Encourage beneficial use of biosolids of acceptable quality, where safe and practicable, and to establish requirements for disposal;

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??Ensure that the statutory requirements of regulatory authorities are adequately specified;

??Set contaminant acceptance limits and stabilisation requirements which give adequate protection to the environment, human health and animal health, and agricultural products, whilst providing realistic and practical avenues for the utilisation or disposal of biosolids products; and

??Ensure that monitoring, reporting and auditing systems are adequate in terms of acceptable risks.

Each of these regulatory bodies has identified and set the maximum concentration of heavy metals in sludge that may be permitted for land application. These limits help define sludge classifications and the corresponding permissible reuse options. Table 19 summarises the limits set by the guidelines reviewed.

Table 19 Maximum Average Concentration of Heavy Metals for Land Application (mg/kg)

Australia European Union Canada Element United States

Grade A Grade B

Arsenic 41 20 20 - 35

Cadmium 39 3 11 20 to 40 4

Copper 1,500 200 750 1,000 to 1,750 380

Lead 300 200 300 750 to 1,200 220

Mercury 17 1 9 16 to 25 1.4

Nickel 420 60 145 300 to 400 80

Zinc 2,800 250 1,400 2,500 to 4,000 840

In addition to sludge quality, these guidelines also present acceptable loading rates for heavy metals particularly for agricultural applications. Table 20 summarises the annual loading rates for some of the controlled heavy metals. Due to the high propensity of Australian soils to acidity, loading rates are generally lower than for other countries. This may also become an issue for lahar as there is a probability that lahar would have acidic characteristics as well. There is a need to confirm lahar acidity through the EDCOP study or additional testing. This may then confirm that Australian standards might be the most applicable for lahar field application.

Table 20 Allowed Annual Loading Rates (kg/ha/yr)

Element United States

Australia European Union

Canada

Arsenic 2.00 0.70 - 1.40

Cadmium 1.90 0.15 0.15 0.27

Copper 75.00 12.00 12.00 13.60

Lead 15.00 15.00 15.00 9.0

Mercury 0.85 0.10 0.10 0.09

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Element United States

Australia European Union

Canada

Nickel 21.00 3.00 3.00 3.56

Zinc 140.00 30.00 30.00 33.00

In addition to metal limits, sustainable biosolids application rates are also influenced by the nutrient content of the biosolids and the capacity of the applied land to utilise the nutrients. The soil characteristics will also influence this nutrient uptake capacity, and in the case of agricultural applications, the capacity will also be influenced by the type of crop (eg. Sugar cane). As the current application sites consist of lahar which is significantly different to the soil types considered in international guidelines, the issue of nutrient uptake capacity warrants special attention.

Most international guidelines also characterise biosolids according to pathogen content and stabilisation grade (vector attraction, odour potential). Combined with the metal levels, these characteristics enable biosolids to be categorised into various grades using a matrix approach. As a general rule, the highest grade biosolids require little or no restrictions in terms of handling and application. At the other end of the spectrum, the guidelines identify biosolids that are unable to be reused. The most common grades of biosolids can be applied to land providing annual and cumulative pollutant loading rates are not exceeded, and the soil can be sustainably managed.

The guidelines set out sampling and testing requirements for classifying biosolids products and, where appropriate, requirements for monitoring the environment where the biosolids are placed to determine and verify its compliance with environmental criteria.

The scope of these guidelines is limited to the land application and disposal of biosolids derived from wastewater treatment systems. It establishes the obligations of the producers, re-processors, appliers and users of biosolids products. It also provides a framework for the classification of biosolids products, based on their quality, and sets requirements for application procedures for biosolids products of different qualities.

Either the Australian or the US EPA guidelines could be used as a reference approach in terms of what the DENR may likely propose at some stage in the future.

Refer to Appendix BAppendix A for further details on the international guidelines.

5.4 Review of US EPA Guidelines on Land Application of Domestic Septage

A review of the US EPA guidelines governing the land application of domestic septage was also conducted as part of this study. This guideline is only relevant for the land application of domestic septage on non-contact areas, i.e. sites not frequently visited or used by the public including agricultural land, forests, and reclamation sites.

Domestic septage is defined in Title 40 of the Code of Federal Regulations (CFR), Part 503 as the liquid or solids materials removed from a septic tank cesspool, portable toilet, type III marine sanitation device, or a similar system that receives only domestic septage (household, non-commercial, non-industrial sewage). Domestic septage contains mostly water, sewage, inorganic materials like grit, and organic fecal matter. Small amounts of polluting substances caused by normal to household activities can also be present.

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Pathogen and vector attraction reduction is a key requirement under this guideline. Other requirements for land applications includes:

??Utilisation of land where domestic septage was applied shall be restricted crop harvesting and animal grazing

?? Land owner shall ensure that site access will be restricted;

??Application rate of domestic septage is largely dictated by the nitrogen requirements of the crop being cultivated; and

??Application practices shall strictly comply with relevant requirements.

The requirements of the guidelines for land application on non-public contact sites are summarised in Table 21. Also provided in the table is a comparison with MWCI’s existing lahar application of septage.

Table 21 Comparison of US EPA Guidelines with MWCI Practices

Description US EPA Requirements MWCI Existing Lahar Application

Typical application rate

360 m3 per hectare per year (38,500 gal per acre per year)

200 m3 / hectare / year over a 2-month period

Records keeping Records of the following information shall be maintained for a minimum period of 5 years: ??Application site location

?? Time and date of application ??Applied area ??Amount of septage applied

??Crop grown on the land ??Certification that the required pathogen and

vector reduction requirements were carried out prior to application

Records are believed to be inadequate.

When pathogen reduction Option 1 is used, septage must meet any of the following options:

Option 1: Injection (must meet both requirements) ??Septage shall be injected below land

surface

??No significant amount of septage shall remain on surface within 1 hour after injection

Option 2: Incorporation ??Septage shall be incorporated into the

surface plow layer within 6 hours after application

??Dried septage observed deposited on the ground just prior to new application.

??We did not observe turning of the lahar for incorporating the septage into the soil.

Vector attraction reduction

When pathogen reduction Option 2 is used, pH adjustment will also serve as the vector reduction measure.

Not applicable. Current practice is for untreated septage to be disposed to land.

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Description US EPA Requirements MWCI Existing Lahar Application

Option 1: No Treatment ??Crops grown above the ground but touch

the soil shall not be harvested within 14 mos after application

??Crops grown below ground surface shall not be harvested within 38 mos after application

??Animal feed and food crops that do not touch the ground shall not be harvested within 30 days after application

?? Turf to be placed on land with high potential for public exposure shall not be harvested within a year after application

??Animals shall not be allowed to graze on the land until after 30 day from application

??Public access shall be restricted for 30 days after application

?? The 10-month harvest cycle for sugarcane is greater than the 30 day harvest restriction for “animal feeds and food crops that do not touch the ground”. However, measures to ensure that that the residual crop parts will not consumed by animals or humans should be included the management plan for biosolids application.

??Although the application site is located in a remote area, risk of human contact is still present without proper measures to deliberately restrict public access on site. Restriction to site shall include posting with no trespassing signs, and simple fencing to prevent any inadvertent entry by people residing close to the application site

Pathogen reduction

Option 2: pH of septage raised to 12 or higher for at least 30 mins prior to application

??Crops grown above the ground but touch the soil shall not be harvested within 14 mos after application

??Crops grown below ground surface shall not be harvested within 20 mos after application when the septage remained on land surface for at least 4 mos prior to incorporation into the soil

??Crops grown below ground surface shall not be harvested within 38 mos after application when the septage remained on land surface for less than 4 mos prior to incorporation into the soil

??Animal feed and food crops that do not touch the ground shall not be harvested within 30 days after application

?? Turf to be placed on land with high potential for public exposure shall not be harvested within a year after application

??No animal grazing restriction ??No site access restriction

Not applicable. Current practice is for untreated septage to be disposed to land.

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5.5 Global Trends

The trend in most countries is to limit the landfill disposal of biosolids and to focus more on greater beneficial reuse. Global advancements tend to dictate local trends in acceptable biosolids management practices. For instance, the ban on ocean dumping as a disposal option in most countries has driven local authorities to implement the same in 2001. It is therefore necessary for MWCI to consider global trends as part of the biosolids management strategy. Whilst landfilling of biosolids is still considered an acceptable approach in some countries, the general outlook for this option is poor. Although this option requires less stringent biosolids quality requirements, this practice is not without regulatory risk. Landfilling does not consider the reuse value of biosolids and the economic benefits that can be attained by choosing other reuse options.

Globally, the reuse of biosolids for agricultural purposes is becoming the most viable market for the beneficial reuse of biosolids.

5.6 Carbon Credit Opportunities

5.6.1 General

The Kyoto Protocol is an international agreement between approximately 180 countries to reduce the emission of greenhouse gases. Greenhouse gases of concern in biosolids management include:

??Carbon dioxide (CO2).

??Methane (CH4).

??Nitrous oxide (N2O).

Greenhouse gases contribute to the retention of a certain portion of solar energy to warm the earth’s surface and lower atmosphere, analogous to a garden greenhouse. However, an over abundance of greenhouse gases in the atmosphere increases the amount of solar energy retained within the atmosphere and this results in an increase in global temperatures, i.e. global warming and greenhouse effect.

The primary factor in the increased greenhouse effect is the increasing combustion of fossil fuels and land clearing. Fossil fuels release CO2 to the atmosphere, i.e. source of carbon dioxide, while land clearing decrease the capacity of plants to use carbon dioxide for metabolism, i.e. sink for CO2.

5.6.2 Biosolids Greenhouse Gas Emissions

Biosolids have the potential to produce both CO2 and CH4 during the biodegradation process. CO2 emissions are largely unavoidable whilst CH4 reduction would entail significant costs. However, replacing power consumption from fossil fuel sources would be the most significant greenhouse gas credit that might be attained for biosolids management.

A brief assessment of the potential management strategies for biosolids would point to potential significant credits, i.e. reduction sources and increase sinks, from:

??Reduction in fossil fuel burning due to more efficient transport of biosolids.

??Replacement of fossil fuel based power consumption to bioenergy.

?? Increase in carbon sink due to reforestation/silviculture reuse option.

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Anaerobic decomposition of unstabilised biosolids with no methane capture is likely to result in large greenhouse gas emissions. These conditions may exist at the Magallanes WWTP.

Based on previous GHD studies on biosolids management, greenhouse gas emissions can vary significantly depending on the treatment and reuse option selected. In general, the higher the energy requirement for the process, the higher the resulting greenhouse gas emissions. Table 22 presents the results from a recent options study on a Queensland plant.

Table 22 Comparison of Annual Greenhouse Gas Emissions for Management Options*

Option Description tCO2-e Basis

1 Transport to bioreactor landfill 108 1.079 kg CO2 -e per kWh

2 Thermal Drying - Conventional 7,588 53.1kg CO2/GJ for large natural gas users

3 Thermal Drying - Cyclonic 7,736 1.079 kg CO2 -e per kWh

4 Alkaline Stabilisation - Proprietary 5,158 1.079 kg CO2 -e per kWh

5 Alkaline Stabilisation - Generic 1,118 1.079 kg CO2 -e per kWh

6 Lagoon/HR Drying Bed 155 1.079 kg CO2 -e per kWh

From a Queensland wastewater treatment plant with the emission factor for electricity purchased/used/delivered of 1.079 kg CO2-e/kWh. Emissions are as CO2.

5.6.3 MWCI Biosolids Management and Greenhouse Gases

The programmed wastewater projects under the MSSP and MSSP programs are not expected to generate significant amount of greenhouse gas emissions nor carbon credits based on the current design description provided.

The minimal treatment design requirements for the planned STP projects under the MTSP would also indicate minimal greenhouse gas emissions. However, the STP project under the PRRC program is expected to contribute more greenhouse gases than the MTSP STPs due to the lime stabilisation treatment process being proposed.

Overall the MWCI programmed projects for sewerage and sanitation is expected not to contribute significant greenhouse gas emissions nor create opportunities for carbon credits.

5.7 Transport Alternatives

5.7.1 Existing Practice

It is understood that MWCI does not have direct management control of the transport and disposal of biosolids, i.e. a portion of the dried sludge from Magallanes and liquid septage. Biosolids are either given to third party for reuse as soil conditioner or contracted for disposal to private contractors.

Septage transport to reuse and disposal areas is currently undertaken by fuel trucks converted to septage haulers with capacities ranging from 16 to 25 m3. Transport operations are currently contracted out to private individuals and this includes the disposal to lahar fields in Pampanga.

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There is an inherent risk in the current trucking of septage to Pampanga as mentioned in Section 3.2.3. Drain valves on the trucks are unsecured and this might lead to accidental opening of the valves. Another issue of concern is the lack of emergency procedures should spillages occur. Given that the transport operation is currently being contracted out to third parties, it is uncertain if emergency procedures are in place for accidental spillage of biosolids along roadways. The type of biosolids being transported, i.e. liquid septage, increases the consequences and impacts of any accidental spillage that may happen during transport.

It is understood that MWCI has direct management control for the vacuum trucks collecting septage from septic tanks up to the Philam and Diego Silang septage storage tanks. Ideally the transport risks should be borne by the appropriately licensed contractors. However, as it is undertaken as part of MWCI operations, it is impossible to transfer full liability to the contractors. There is a need to closely monitor the private contractor activities to safeguard MWCI from potentially bad publicity from accidental septage spills. This also applies to the dried sludge being removed from the Magallanes WWTP.

5.7.2 Pipeline Transport to Reuse Site

It has been suggested by the World Bank to evaluate the potential for pipeline transport of biosolids to reuse/disposal sites. The idea is the reduction of transport costs and minimisation of risks arising from trucking operations.

The programmed projects for biosolids management points to a significant portion of the sludge as being dewatered and this would preclude pipeline transport of biosolids in the long-term. There is an opportunity to build the infrastructure for septage transport via pipelines to potential reuse/disposal sites for the current system. However, the proposed programme for the PRRC STP commissioning of mid-2006 would point to a very short period for this option to be feasible. The associated costs for the pipeline transport infrastructure are expected to be significant. Therefore, pipeline transport is not recommended for implementation as part of the biosolids management strategy.

5.8 Planning Issues

5.8.1 PRRC Projects

Key Objectives

The PRRC is undertaking the Pasig River Environmental Management and Rehabilitation Sector Development Program that aims to improve the Pasig River water quality and promote urban renewal and redevelopment along the riverbanks. The program covers the institutional, regulatory, technical and financial aspects of environmental management. Part of the program involves sanitation projects aimed at introducing regular septic tank maintenance and providing the necessary septage management treatment and disposal infrastructures. SKM is the lead consultant for the projects.

Impacts on Biosolids Generation

The PRRC feasibility study for the treatment, handling, and disposal of septage indicates:

??Average sludge production in Metro Manila is 32 liters per capita per year.

??Regular desludging for septic tanks is programmed to happen once every six years.

?? The proposed septage treatment plant (STP) will be located in Pinugay, Antipolo.

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??Screenings and grit from the STP will be disposed to landfill.

??Septage will be dewatered and lime stabilised.

?? Filtrate will be treated on site based on biological treatment processes, i.e. activated sludge.

The proposed septage management system under the PRRC would provide regular septic tank maintenance and therefore increase biosolids volume from the increasing service population.

Implementation Schedule for Proposed Projects

The STP project has been advertised on a “design and construct” scheme by the MWSS. The STP commissioning is programmed for mid-2006. However, there is some uncertainty with the project meeting the programmed commissioning date as per previous MWSS projects.

Effects of Proposed Projects on Downstream Biosolids Management Infrastructure and Disposal

The increase in septage volume collected will put pressure on MWCI to provide additional equipment and infrastructure to address the increase. Additional vacuum trucks for collecting septage, manpower, additional contractors for disposal of septage cake, increased biosolids volume for disposal, etc., will also entail additional risks and requirements from MWCI.

The selection of lime stabilisation for the septage cake increases the cake volume and costs significantly. The PRRC report shows the lime stabilised cake volume (90 m3/d) is expected to be more than twice the volume produced by drying (38 m3/d). The PRRC report limited the comparison between these two options because:

??Composting would require green waste that is not readily available in Metro Manila.

??Vermiculture is still in its development stages and commercial viability would need to be confirmed.

Although there is an increase in volume of septage cake produced, this would have a wider range of reuse options available because of the anticipated stabilisation levels achieved. Biosolids generation rates for the project is presented in Section 3.4. Therefore, the increased transport requirements for the lime stabilised septage cake maybe offset by the potentially broader usage of the higher quality biosolids located at shorter distances to the STP site. A study of the economics for implementing the lime stabilisation should be conducted to confirm cost implications of the larger transport volume required vis a vis the potential shorter transport distances due to the higher quality biosolids being produced. This study might also feed into adopting the option of providing lime stabilisation to other STP projects, i.e. MSSP STPs.

5.8.2 MSSP Projects

Key Objectives

The MSSP is intended to help the government improve the quality of sanitation services in Metro Manila and enable the MWSS to:

??Radically expand its septage management program and establish the conditions needed for medium-term low-cost improvement of sewerage services in Metro Manila.

?? To reduce pollution in Metro Manila waterways and in Manila Bay, thereby reducing the health hazards associated with human exposure to excreta.

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Impacts on Biosolids Generation

The MSSP aims to provide communities with decentralized sanitation facilities through on-site treatment. This includes communal septic tanks and WWTPs as detailed in Section 3.4. Biosolids produced by the facilities would be dewatered and liquid sludge with generation rates as estimated in Section 4.4 and 4.6. No sludge stabilisation is proposed for the facilities. CSTs are programmed for upgrading to full treatment systems in the near future and biosolids generation are incorporated into the WWTP estimates. Project consultants have assumed that liquid sludge will be managed and co-treated with septage, i.e. to STPs, while dewatered sludge will be applied to lahar fields.

Implementation Schedule for Proposed Projects

It is expected that all the proposed WWTP projects will be commissioned prior to the end of 2004.

Effects of Proposed Projects on Downstream Biosolids Management Infrastructure and Disposal

Liquid sludge transport volumes from the WWTPs and CSTs to the STPs would be significantly larger than the transport volume requirement for dewatered sludge from the STPs to the re-use/disposal site. Dewatering will increase the solids content from around 40 g/L to at least 20% w/w dry solids, leading to a five-fold reduction in volume.

The biosolids produced from these projects are unlikely to achieve Grade A stabilisation classification. If the approach adopted by international guidelines is followed, the use of these biosolids should be restricted to minimise environmental and health and safety risks. If additional stabilisation is implemented, a wider range of alternative re-use options could be safely pursued.

5.8.3 MTSP Projects

Key Objectives

The key project objectives are to assist the Metropolitan Waterworks and Sewerage System (MWSS) to:

??Reduce the pollution of Metro Manila waterways;

??Reduce the health hazards associated with human exposure to sewerage in Metro Manila; and

?? Implement a 'decentralized' approach to sewerage and sanitation management in Metro Manila, mainly in the east zone, by expanding the MWSS septage management program and low cost sanitation facilities, in addition to a limited expansion of sewerage services.

Impacts on Biosolids Generation

A number of wastewater treatment facilities are programmed for the project. The proposed WWTPs will produce both liquid sludge and dewatered sludge without any stabilisation. Liquid sludge is proposed to be managed and co-treated with septage, (i.e. dewatered at the STP). The designers have assumed that dewatered sludge will be disposed to lahar fields without any additional treatment.

Implementation Schedule for Proposed Projects

It is programmed that all the MTSP projects, including WWTPs and STPs, would be commissioned by first quarter of 2008.

Effects of Proposed Projects on Downstream Biosolids Management Infrastructure and Disposal

The effects discussed for the MSSP projects discussed in Section 5.8.2 would also be applicable to the MTSP projects.

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5.8.4 MWCI Concession Requirements

MWCI is required to increase the sewerage and sanitation services coverage within the concession area as detailed in Table 2 and Table 3. This increase leads to a corresponding increase in the quantity of biosolids that needs to be managed, and disposed. However, the management system needs to match the targeted sewerage and sanitation services growth, i.e. expected increase in biosolids generation in a timely manner, and at the same time comply with potential biosolids management regulations that may be proposed/enacted in the Philippines.

It is understood that MWCI will operate the proposed STPs. The Pinugay STP project has been advertised for pre-qualification on a “design and build” delivery scheme with commissioning programmed for mid-2006. MTSP STPs is expected to be commissioned by 1Q 2008. Operations personnel for the STPs would require proper process knowledge of the plants to ensure optimal performance is met. Routine monitoring of septage cake quality would be required to check process performance and satisfy regulatory requirements (if applicable at the time).

MWCI have indicated a preference to minimise direct management control of the biosolids transport and reuse/disposal operations. The transport and reuse/disposal of biosolids can potentially be contracted out to private parties (as it is in Australia and elsewhere), however MWCI needs to confirm the following:

??Contractors have applicable licences for the transport and reuse/disposal of biosolids.

??Emergency procedures are in place for accidental spillage of biosolids during transport.

??Reuse/disposal practices are complying with guidelines set by MWCI internally and Philippine laws.

Formal agreements should be in place to include liability and compliance issues for the entire biosolids management system. This will safeguard MWCI interests and image should any untoward incidents happen in biosolids management practices.

5.9 Social Issues

The current MWCI biosolids management practices indicate a level of acceptance by end users of the biosolids and regulatory agencies, i.e. lahar field owners, farmers, Sugar Regulatory Agency, Fertilizers and Pesticides Authority, etc. However, there is still a need to ensure that any management strategy adopted by MWCI will be socially and politically acceptable over the whole spectrum of stakeholders.

As part of the implementation of the biosolids management strategy, it is recommended that consultation with relevant stakeholders be undertaken. This will ensure stakeholders gain commitment to the strategy and issues raised by each party are addressed during the implementation phase. A more generic education campaign on biosolids reuse is also worth considering. Possible topics may include:

??Biosolids characteristics.

??Biosolids handling practices.

??Health and safety.

??Benefits of biosolids to the community.

??Environmental aspects.

Adopting this approach is considered worthwhile as it will more likely lead to social acceptance of the biosolids strategy and minimise the likelihood of negative publicity.

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6. Biosolids Reuse and Disposal Assessment

6.1 Potential Reuse

In developing a biosolids management strategy, it is key that the specific requirements of target markets are considered. The preferred reuse and disposal option will largely impact the type of biosolids processing technologies, their cost-effectiveness, the quantity of additives used, and the quality of the biosolids suitable for the market’s purpose.

A breakdown of potential market sectors and their composition is provided in Table 23.

Table 23 Potential Biosolids Reuse Market Sectors

Market Sector Composition

Extensive Agriculture Livestock & pasture production, broad acre farming (cropping), plantation forestry (silviculture)

Intensive Agriculture Nurseries (wholesale production), fruit & orchard growing, market gardening, turf grass growing, viticulture

Land Rehabilitation Land/mine-site reclamation, rehabilitation, landfill rehabilitation, erosion stabilisation

Landscaping Landscaping, domestic horticulture, local & state government uses, retail nurseries, sportsground renovation

Energy Recovery Gasification, pyrolysis, ethanol, incineration, anaerobic digestion, bioreactor landfills

Bioremediation Contaminated sites & soils

6.1.1 Extensive Agriculture

The application of biosolids for extensive agricultural purposes is considered the most proven market sector for the beneficial reuse of biosolids in Australia, Europe and the USA. This practice presents a large opportunity for biosolids reuse when carried out in accordance with acceptable environmental management guidelines. This market sector is seasonal and sensitive to severe climatic conditions (eg. floods, drought). If managed well, it is projected that given the scale of agricultural industry, demand for biosolids could exceed the supply.

As a general rule in the application of biosolids, greater risk of human contact will require higher biosolids classification. Hence, key considerations in applying biosolids in crop production will include:

??Provision of additional barriers between biosolids and food chain (non direct food crops);

??Provision of additional barriers between biosolids and human or animal contact (soil incorporation); and

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??Enhancement of the long-term sustainability by using low application rates and a low frequency of reapplication.

MWCI has already engaged a number of farming sectors for the agricultural application of biosolids including wet and dried sludge, and wet septage. Permits are in place for the application of biosolids in the production of sugarcane, corn and other similar crops. If it is decided that a more aggressive development and implementation of biosolids application in this market sector will be pursued, it is recommended that following measures be considered during planning.

??Application of biosolids to land used for non-direct food crops.

??Application of biosolids at rates lower than the recommended guidelines, as far as possible.

?? Incorporation of biosolids into soil, following application (if unstabilised). Direct injection may be required for liquid biosolids.

Education and consultation of farmers and other interest groups is also key to avoid misconceptions associated with proposed biosolids land application schemes.

6.1.2 Intensive Agriculture

Given the greater risk of uncontrolled human contact, this market requires a relatively high quality of biosolids. The cost of maintaining this market and educating end-users would also be typically higher compared to extensive agriculture. This market is also sensitive to the impact of climate and season.

6.1.3 Land Rehabilitation

MWCI is currently practicing application of biosolids in the lahar fields of Pampanga as a land rehabilitation exercise. The sustainability and viability of land rehabilitation at Pampanga as a biosolids management practice is largely dependent on the size and quality of land to be rehabilitated.

MWCI is currently investigating the environmental impacts of biosolids application in the lahar fields as part of a separate project. It is recommended that the following items/issues be considered in assessing the appropriateness of the practice.

??Records of application details, i.e. volume applied, date, location, application practice, etc., are currently not being maintained. This monitoring data is an important aspect of sustainable land rehabilitation practices to ensure that over application does not occur for the area in question.

?? Lahar is perceived to be a poorly structured soil and prone to erosion. This could lead to potential release of the applied biosolids. The stability and erodability of lahar needs to be reviewed, and necessary measures to improve soil structure and stability identified. Such measures may include addition of topsoil or application of other binding materials.

?? Lahar is sandy and drains quickly, i.e. it does not retain water very well. Given this, there is a risk that a portion of the applied liquid septage may drain past the root zone and carry the nutrients and pollutants to the groundwater. During wet season, the poorly structured, well-drained lahar may permit leaching of contaminants, which were originally retained in the root zone, down to the groundwater.

?? The absorption capacity of lahar is unknown. Since this parameter is typically associated with the clay content of the soil, lahar may well be very poor in this aspect. Low absorption will allow phosphorus and heavy metals to be mobile in the groundwater. Absorption capacity may be even

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further reduced if the soil is acidic, which is a possibility for lahar. Literature (Controlled-Release Fertilizer for Lahar Affected and Coarse Textured Agricultural Soils, Clarita P. Aganon et. al.) shows lahar deposits are strongly to slightly acidic in nature (pH 4.35-6.7).

??Biosolids application should only be done to fields that is being prepared for planting. This will allow turning of the soil to mix the sludge cake into the soil structure. Sugarcane planting usually occurs only during crushing season, which is typically about 6 months per year. Application to sugarcane fields can only be carried out for a maximum period of 6 months between planting seasons. Otherwise, farmers might be unable or unwilling to turn the soil to and mix the liquid septage within the prescribed 6-hour period. Application to furrows between crops without turning is not an acceptable practice.

Should the reservations listed above be confirmed, the cost of applying biosolids/septage to lahar fields in a sustainable manner maybe considerably higher than the current practices.

6.1.4 Landscaping

Similar to intensive agriculture, use of biosolids for landscaping and domestic use requires high quality of biosolids due to the potential uncontrolled human contact expected from this usage. The actual market size for this market has not been determined as part of this study. It is likely that distribution of biosolids into this market sector would require the involvement of established market players.

6.1.5 Energy Recovery

There are several approaches available to recover energy from biosolids. The two dominant methods of generating excess bioenergy are anaerobic digestion and bioreactor landfills. Like most small anaerobic digester operations, other methods are available (eg. gasification, incineration, etc.) that generate bioenergy. However the energy content of the biomass is typically consumed in-situ to reduce external energy requirements.

Anaerobic digestion is not a market but a treatment technology, as digested biosolids will still require placement in downstream market/s.

Bioreactor landfills are an extension of leachate recirculation landfills, using enhanced microbial processes to stabilise the readily and moderately decomposable organic waste constituents within a comparatively short timeframe. However, the main driver for biogas generation would be organic content of municipal waste disposed to the landfill.

6.1.6 Bioremediation

Bioremediation is the branch of biotechnology that uses biological processes to overcome environmental problems. Recent concern over the environmental impact of recalcitrant, toxic organic compounds (e.g. pesticides and oil-derived products) has led to increased interest in methods of removing them from contaminated sites. One possible treatment is bioremediation, which utilises soil microorganisms and theoretically leaves behind no toxic end products.

The actual market size for this market has not been determined as part of this study.

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6.2 Disposal Options

It is important for MWCI to establish a biosolids disposal option as a contingency plan. Biosolids disposal options available include landfill and surface land disposal. As discussed previously, ocean disposal and incineration are understood to be prohibited under current legislation.

MWCI has little direct control on the daily fluctuations in biosolids quality (particularly metal levels). If spikes in metal limits are identified which cannot be blended to an acceptable level, there is a need to have a viable disposal option.

6.3 Short-listing of Options

Based on the preliminary market assessment undertaken, the following short-listed reuse options are presented in Table 24.

Table 24 Short-listed Biosolids Market Options

Priority Market Sector Composition

Extensive Agriculture Livestock & pasture production, broad acre farming (cropping), plantation forestry (silviculture)

High

Land Rehabilitation Land reclamation, rehabilitation (Lahar fields), landfill rehabilitation, erosion stabilisation

Landscaping Landscaping, domestic horticulture, LGU uses, retail nurseries, sportsground renovation

Low

Intensive Agriculture Nurseries (wholesale production), fruit & orchard growing, market gardening

Options given a high priority are understood to have a relatively large market size and have limited requirements in terms of biosolids quality. These options are considered appropriate in the short to medium term.

Whilst the total market size for the lower priority options has not been identified, it is believed these markets are more fragmented and require a higher quality product. It is more likely that the total transport distances required to reach these markets is less. In the medium term, it is recommended to test high quality biosolids in these markets. In the long term, these markets can then become a viable and sustainable reuse option for MWCI.

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7. Biosolids Treatment Unit Processes

7.1 Introduction

Prior to the reuse or disposal of sludge derived from wastewater treatment, further processing may still be necessary to meet reuse and disposal standards and to allow for a cost-effective management of biosolids. Key considerations in sludge treatment usually involve volume reduction, pathogen reduction and reduction of vector attraction.

Primary objectives for sludge treatment typically include:

??Reduce water content.

??Stabilise sludge.

??Reduce pathogens.

An introduction into the key biosolids treatment processes is presented in the following section.

7.1.1 Sludge Thickening

Following wastewater treatment, the generated sludge normally contains about 92 to 99% water. Thickening of wet sludge is carried out to concentrate the solid content thereby reducing sludge volume. For most mechanical thickening processes, addition of polyelectrolyte has become a usual practice in order to achieve coagulation and flocculation, which accelerates the thickening. Available sludge thickening processes include:

??Gravity thickening;

??Dissolved air flotation;

??Centrifugation;

??Gravity belt thickening;

??Rotary drum or rotary screen thickening; and

??Rotary screw thickening.

Among these processes, gravity thickening, dissolved air flotation and gravity belt thickening are most commonly used.

7.1.2 Dewatering

Dewatering is a purely physical process that reduces the water content of sludge. No stabilisation or pathogen reduction is achieved during dewatering. Handling and transportation of dewatered sludge is easier since the volume has been considerably reduced.

Dewatering may be achieved on any of the following facilities/equipment.

??Sand drying beds;

??Drying pans;

?? Lagoons;

??Belt filter press;

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??Centrifuge;

??Rotary screw press and

?? Filter press.

Solid loading rates on sand drying beds are largely dependent on weather conditions, sludge characteristics and selection of sand. Dewatering on drying beds is most compatible with anaerobically digested sludge. Typical solid loading rates of 2.5%-3.5% total solids anaerobically digested sludge will vary between 20 to 40 kg/m². Sand drying beds are known to produce well-dried materials with 40 to 60% dry solids.

Belt filter presses and centrifuges have similar dewatering capacities. Stabilised digested sludge are usually dewatered to reach 20 to 25% dry solids content. Biological nutrient removal and extended aeration plant waste activated sludge (WAS) are more difficult to dewater and typically attains only about 11 to 15% dry solids content.

Prior to mechanical dewatering, polyelectrolytes can be also added as a sludge conditioner to enhance the dewatering process through coagulation. Polymer consumption for centrifuges is typically slightly higher than for belt filter presses.

7.1.3 Stabilisation and Disinfection

Sludge stabilisation is performed to reduce its pathogen content, minimise vector attraction, and reduce or eliminate the potential for putrefaction. Various stabilisation process or technologies available include:

??Anaerobic digestion.

??Aerobic digestion.

??Autoheated thermophilic aerobic digestion.

?? Lagoon stabilisation.

?? Lime stabilisation.

??RDP Envessel Pasteurisation.

??N-VIROTM soil.

??Composting.

??On-site stock pile.

?? Thermal Hydrolysis Process.

??Active sludge pasteurisation.

?? Incineration.

??Vermiculture.

7.2 Technology Options Overview

Depending on the quality of raw sludge and the target quality of the treated sludge, a system may require one or several treatment processes. A number of commercially available and developing treatment technologies are presented in the following table. They have been compared in terms of ability to achieve each of the primary objectives (stabilisation, pathogens, dewatering).

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Table 25 Sludge Treatment Overview

Process Vector attraction/odour

reduction

Pathogen Reduction

Dewatering

Anaerobic digestion ?? ? X

Aerobic digestion ?? X X

Autothermal thermophilic aerobic digestion ATAD

?? ?? X

Lime stabilisation:

- custom processes

- N-VIROTM Soil

- RDP Envessel pasteurisation

?

?

??

?

??

X

X

X

Composting ?? ?? X

Vermiculture ? ? ?

Incineration ?? ?? ??

Oil from sludge technology OFS ?? ?? ??

Thermal drying ?? ?? ??

Cyclonic Thermal Drying ?? ?? ??

Active Sludge Pasteurisation ASP ? ?? ??

Sludge lagoon ? ? X

Storage of dewatered sludge X X X

Filter presses N/A N/A ??

Bioreactor Landfill ? ? N/A

Drying beds ? ? ??

?? = Good ? = Medium X = Poor N/A = Not achieved by the process

A brief outline of the above processes are summarised in Appendix CAppendix C.

7.3 MWCI Technology Requirements

To establish a short-list of suitable technologies, due consideration of MWCI’s requirements and objectives is required. As discussed in Section 3.5, the key drivers of economics and environmental protection need to be considered. Given the local cost of labour, preference should therefore be given to options having a lower capital and energy cost.

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7.4 Short-listed Technologies

During the biosolids strategy workshop (27 May 2004), a number of these technologies were eliminated based on capital cost, system complexity and regulatory requirements. Technologies suitable in the local context include the following:

??Anaerobic digestion.

??Aerobic digestion.

?? Lime stabilisation.

??Vermiculture.

??Composting.

??Dewatering (filter presses, drying beds etc.).

??Bioreactor landfill.

These technologies are discussed further in the section below.

7.4.1 Anaerobic digestion

MWCI has experience with this technology at the Magallanes WWTP, although as previously discussed there are concerns over the current performance of this system. On larger units, a key benefit of this technology is the ability to collect methane and provide a means of energy recovery.

A key issue with this technology is the potential for nutrient release from the biosolids (particularly phosphorus). In many international WWTPs where the trend is towards nutrient removal from the wastewater, anaerobic digestion is seen to conflict with this goal.

In terms of international guidelines, biosolids produced from a well-operated anaerobic digester are unlikely to be suitable for unrestricted use (i.e. a bagged product sold for domestic purposes) without further processing. Biosolids from this process are however suited to restricted reuse applications (such as lahar rehabilitation and managed agricultural applications).

7.4.2 Aerobic digestion

This is discussed in detail in Appendix C. Similarly for anaerobic digestion, biosolids from this process are unlikely to be suitable for unrestricted use (i.e. a bagged product sold for domestic purposes) without further processing. Biosolids from this process are however suited to restricted reuse applications (such as lahar rehabilitation and managed agricultural applications).

7.4.3 Lime stabilisation

The designs of some proposed STPs have the flexibility to include lime stabilisation technology in the future if required. The key issues regarding lime stabilisation are as follows.

??High chemical cost (although the lime to sludge ratio varies, the volume of sludge typically increases by 40% to 100%).

??Potential health and safety concerns with lime handling and storage.

??Proven technology.

??STPs can incorporate the technology simply.

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??Ability to produce a highly stabilised product that may be suitable for unrestricted reuse.

Further details can be found in Appendix C. It is considered that lime stabilisation can be used in the medium term (if stabilisation is required). As it has a high operating cost, in the longer term alternative forms of stabilisation should be pursued.

7.4.4 Vermiculture/Composting

Vermiculture is not defined as a treatment process in most international guidelines.

Key issues regarding vermiculture and composting are as follows.

??Relatively low capital cost.

??Higher land requirements that more intensive processes.

??Higher unskilled labour requirements than high technology processes.

??Environmentally friendly.

?? Low energy requirements.

?? Final product has suitable characteristics for unrestricted reuse.

Further details can be found in Appendix C. There would be considerable risks in adopting a full scale system given the limited local understanding of the technology. To manage these risks, it is proposed that a pilot scale assessment of a vermiculture/composting (or other alternative) system be undertaken in the medium term.

7.4.5 Dewatering (filter presses, drying beds etc.)

Currently, programmed MWCI projects include the following treatment processes.

??Drying beds at the Magallanes WWTP.

?? Filter presses for sludge in a number of WWTPs.

??Dewatering for septage for the Payatas and Taguig STP. Type of dewatering process is still to be confirmed.

??Dewatering and lime stabilisation for the Pinugay STP.

Further details can be found in Appendix C. The final choice of dewatering equipment type is usually specified as part of the detailed design of each facility and will be strongly influenced by site constraints.

7.4.6 Bioreactor Landfill

Bioreactor landfill is an extension of leachate recirculation landfill that achieves waste decomposition and stabilisation within a comparatively shorter timeframe. Biosolids are a minor component of the total waste feed, which mainly comprises municipal garbage. Methane capture from the landfill enables energy recovery via electricity production. A suitable site would be required and the viability of this option would depend on a parallel effort by local authorities responsible for municipal waste.

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8. Enhancement of Existing Operations

8.1 Magallanes WWTP

Observations during the site inspection on the facility indicate potential improvement opportunities on the following items.

8.1.1 Sewer System Optimisation

The Magallanes WWTP is advised to have a peak instantaneous capacity of 460 L/s (40 ML/day) based on operation of the influent pump station. There are indications that storage within the reticulation system is providing attenuation of the peak flows entering the plant, which operational profiles indicate may well be considerably higher than the pump capacity (continuous, extended pump operation).

It is suspected that the system storage within the reticulation may be generating a number of issues including:

??Accidental overflows/discharges at times of peak storage and/or flows.

?? Inadequate scouring velocities in flooded sections of the reticulation allowing solids deposition within the sewer pipes that may seed the sewage and enhance biological activity in the pipes.

?? The flooded flow regime may be limiting natural reaeration of sewage in the pipes and turbulence at the manholes.

?? The combination of prolonged system detention periods, increased biological activity and reduced aeration is believed to be contributing to the septicity of the wastewater observed at the inlet of Magallanes, and generation of H2S in the reticulation.

Optimisation of the system may potentially be provided by a controlled flow storage facility that would permit normal flow regime in the reticulation system, minimise potential overflow events, control septicity, and permit the WWTP to operate up to the rated peak capacity of 40 ML/d. Initially, confirmation of the extent of system storage being utilised and actual hydraulic and biological conditions in the pipes should be obtained to confirm the suspected issues.

8.1.2 Anaerobic Sludge Digesters

The condition of the existing anaerobic digesters in Magallanes is uncertain. Although a gas management system was originally installed on both digesters, these have been disconnected at some stage. Corrosion of the associated gas management equipment was observed with indications that the corrosion originated from the inside of the digesters.

The digesters are intended to be anaerobic and therefore sealed from the atmosphere to prevent the introduction of oxygen. Currently, this is not possible and oxygen is entering and is expected to be contributing to a very aggressive environment, along with the H2S released by the sludge. As the digesters have been in this condition for many years, the internal condition may well be very poor. This may relate to the wall strengthening activities undertaken during the recent rehabilitation of the digesters.

In addition, grit removal facilities have only recently been provided for the plant and it is therefore likely that the volume of the digesters is affected by grit build up introduced from the primary sedimentation tanks. MWCI also advised that there was a previous incident where an explosion occurred in one of the

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digesters. The proportions of the tanks (relatively wide compared to the height) is noted as unusual for digesters and could contribute to difficulty mixing the sludge.

It is therefore necessary to undertake an inspection of at least one of the digesters to assess the internal condition of the tank and determine whether the most appropriate course is to rehabilitate the existing digesters (and remove the likely grit build-up) or construct new digesters. This may help address concerns on the sludge stabilisation levels achieved by the plant.

It is noted that there are significant health and safety issues regarding anaerobic digesters, primarily due to the risk of explosion.

8.2 Valle Verde Homes WWTP

Visual inspection indicated that the wastewater entering the plant has low turbidity. The WWTP treats septic tank effluent from communal septic tanks within the vicinity of Valle Verde Homes, and includes a lift station upstream of the plant and an outfall pipe. According to the operator, the WWTP has 3 aeration sections, each with separate submerged aerators. The WWTP has a single chamber where both aeration and settling operations are performed. A baffle separates the chamber near the outlet to provide an area for chlorination. No baffles or any other partitions separate the aeration sections. Drawings of the tank confirm this general description of the WWTP.

Aeration is continuously carried out with the aerators operating one at a time in an alternate cycle, i.e. each aerator is programmed to run for an hour and be idle for 2 hours. The WWTP operator further stated that based on his understanding, the treatment process is modification of the activated sludge system in the bioreactor. It is based on axial growth interval microbial aeration technique. We were not informed of any decant mechanism installed in the system. At the time of the visit, the operator advised that the WWTP has not been desludged for approximately 5 years. Recent information from MWCI advised that desludging of the WWTP was conducted on January 2004 but no specific data was provided regarding this activity. Effluent has consistently passed the DENR/ LLDA standards.

There are concerns with the WWTP design. It is our opinion that the absence of distinct aeration zones, i.e. with partitions, may not allow proper settlement of the sludge even with the turning off of the other aerators. Turbulence associated with the operating aerator may lift the sludge and/or hamper the settling process in the adjacent sections. There is a potential that settling is occurring at the chlorine contact section due to the baffle but this is also uncertain.

Even with the perceived shortcomings of the WWTP design, we observed that the effluent sampled at the outfall catch basin was remarkable with only a minimal amount of suspended solids. This together with the influent characteristics observed and low sludge generation being advised for the WWTP may point to a very weak raw sewage coming into the plant.

The March 2004 laboratory results for the effluent also shows values that are not typical for wastewater. The lab results show a BOD value of 1 mg/L while total suspended solids (TSS) is at 62 mg/L. Typical ratios for the BOD and TSS would be normally at 1:1 to 1.2. BOD to COD ratio is also out of the typical range, i.e. 1:2. The BOD to COD ratio for the effluent sample is 1:62.

There is a need to review the Valle Verde Homes WWTP further to ascertain the process operations of the plant and determine the performance levels being achieved by the treatment.

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8.3 Existing Karangalan Village WWTP

The existing Karangalan WWTP is pilot facility constructed prior to the privatisation and was designed to treat sewage from 10 to 15 houses within the area. A larger version of the facility is now being constructed to accommodate wastes from more households. The WWTP process is based on the bio-contact module system.

An influent sample taken during the site visit from the inlet structure of the Karangalan WWTP indicates low turbidity wastewater is entering the plant. Interviews with the plant operators indicate that the pump suction may be collecting wastewater on the upper portion of the sump only, i.e. supernatant only with solids being retained in the sump. This may explain the apparently low solids concentration of the raw wastewater and the resulting low sludge generation rates in the WWTPs.

A review of the lift station design may be required to fully address this issue.

8.4 Diego Sillang WWTP Infrastructure

The Diego Silang WWTP was implemented by the Bases Conversion and Development Authority prior to MWCI gaining operational control in 1997. The facility is currently not operating with upgrading and rehabilitation works programmed for implementation prior to commissioning of the plant.

There are a number of reservations on the infrastructure as currently constructed including:

?? Inflow channel design has the potential to allow wastewater flows to the walkway.

??Proper flow split to the aeration tanks for each module is uncertain.

??Proper flow split for sludge recycling is uncertain for each module.

??Side aeration installed for each aeration tank and sludge digester. Type of diffuser for the aeration system was not confirmed. Inefficient oxygen transfer is expected for this installation.

??Aeration drop pipes are severely corroded.

?? Filter press seems to be undersized for the expected sludge generation from the plant.

?? Installed bunds do not conform to international standards. Bund wall is generally too close to the tanks and this has the potential to push liquids over the wall. Typical wall distance from the tank should be a minimum 1:2 ratio with the tank height.

?? Installed drainpipe for the bunded areas will not allow installation of valves for operation as normally closed.

?? Location of diesel storage tank may be a risk issue in terms of its proximity to the outer fence of the plant.

??Noise attenuation measures for the standby generator set maybe inadequate. Installed louvered doors were observed to allow noise from the outside to permeate into the generator room.

??Oily wastewater management seems to be inadequate.

??Septage screening is composed of a perforated plate on top of a steel channel. Screenings removal seems to be onerous to the operator and is perceived to be an occupational health issue.

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??Septage holding tank seems to generate a lot of odour and this may become an issue.

??Availability of statutory permits or approvals was not advised during the study. According to MWCI, DENR/ LLDA approvals are not required for septage holding tanks.

8.5 Lahar Application Practices

The septage application practices to lahar fields may not currently be optimal. The US EPA recommends that liquid septage should be injected to the soil subsurface or if overland application is practiced, turning of the soil is required to incorporate the septage into the soil. At this stage, MWCI may want to initiate discussions with the private contractors for the lahar application to ensure that liquid septage application to land complies with the intent of these international guidelines.

However, the overall feasibility and sustainability of lahar application practice is yet to be confirmed by investigating the concerns raised in Sections 3.2.3 and 6.1.3. The physical properties of lahar, particularly its erodability and absorption capacity, are the most critical parameter that will determine the sustainability of this practice. Once the necessary improvement measures are identified and its associated costs evaluated, MWCI will be able to determine if this is acceptable an option.

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9. Proposed Strategy

As discussed in the biosolids workshop (27 May 2004), an effective strategy would have the following features.

??A market driven approach (identify the market first, then select the most appropriate technology).

??A range of markets available to ensure flexibility of supply/demand.

??Can be incorporated, as much as possible, into planned MWCI projects.

?? In the long term, a higher quality/value biosolids product should be pursued to minimise risks/liabilities.

?? The use of pilot scale trials to test emerging technologies will minimise risks and ensure that MWCI can make necessary shifts in strategy in a timely and informed manner.

??Avoid significant capital investment on technologies that may not be suitable in the long term.

?? Flexibility will enable future technology advances to be incorporated.

Based on the outcomes of the study, a logical sequence of strategic measures over the short, medium and long term can be developed. This sequence of measures forms the basis of a proposed strategy and is presented below.

9.1 Short-term (Current to 2005)

9.1.1 Biosolids markets

?? Lahar application fully investigated. Lahar application dependent on surface and ground water monitoring, adsorptive capacity and erosion stability of lahar, computed agronomic rates for application, and timing of application with the crop production cycle and consideration of storage.

??Extensive Agriculture. Improvements to the current practice of septage application on agricultural sites in accordance with the guidance of the USEPA Part 503 rule (Biosolids to be injected below the surface, or incorporated within 6 hours of application to the land)

??Other markets. Commence discussions with fertiliser retailers to identify potentially higher value markets and other market opportunities for biosolids products. Assess interest with relevant parties in preparing a feasibility study for a landfill bioreactor.

?? Transport/Management. Improvements to the septage haulage practices as identified in this report. Formalize waste exchange agreements with Manila Fertilizer, farmers,etc. Commence development of a tracking system to ensure that biosolids despatched are handled and transported correctly with all appropriate checks and balances confirmed and documented. Commence preparation of educational material and stakeholder consultation processes and identify key stakeholders.

??Disposal. As a contingency plan, suitable disposal site(s) need to be identified. These sites will need to accept biosolids that are unsuitable/unable to be re-used.

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9.1.2 Technology

?? Stabilisation. No stabilisation required provided biosolids are applied to extensive agriculture and land rehabilitation (lahar) in accordance with acceptable practices (i.e. sustainable land application rates and in accordance with the guidance of the USEPA Part 503 rule).

??Dewatering. Dewatering progressively implemented to minimise haulage costs.

9.2 Medium-term (2005 to 2010)

9.2.1 Biosolids markets

?? Lahar application optimised and sustainable. The recommendations of the Environmental Impact Assessment for the lahar application of biosolids are adopted and implemented. Possible collaboration with other agencies (Department of Agriculture) to achieve this goal.

??Extensive Agriculture. Reuse practices monitored for compliance with local and appropriate requirements.

??Other markets. Test the market acceptance and economics (cost/revenue) of alternative biosolids products in pilot trial quantities.

?? Transport/Management. Tracking, handling and identification system fully implemented. Promote and seek expressions of interest from third parties to undertake biosolids management contracts with MWCI. Review international guidelines for advancements in biosolids management approaches. Distribution of educational material and continue stakeholder consultation processes.

??Disposal. Agreement with relevant regulatory bodies on the use of disposal sites.

9.2.2 Technology

?? Stabilisation. Plan and implement a pilot scale trial (~5m3/d) on an alternative stabilisation process (eg. vermiculture) at one of the WWTPs. If stabilisation is required as a contingency plan on full-scale plants, lime processes can be adopted.

??Dewatering. Optimisation of dewatering processes to minimise haulage costs.

9.3 Long-term (2010 onwards)

9.3.1 Biosolids markets

?? Lahar application. Volume of product used in this market is reduced as markets closer to Manila are developed.

?? Intensive agriculture and landscaping. Higher quality biosolids product (vermicast/compost or equivalent) is used extensively in these markets.

?? Transport/Management. Paperless tracking systems investigated and adopted. Engagement with local regulatory bodies to ensure development of guidelines is viable and aligns with MWCI practice. Distribution of educational material and continue stakeholder consultation processes in intensive agricultural and landscaping markets. Third parties undertake biosolids management contracts for MWCI on a competitive basis.

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9.3.2 Technology

?? Stabilisation. Lime facilities decommissioned, or kept as a back-up (if installed). Vermiculture, composting or other alternative process is adopted to generate high quality biosolids product suitable for intensive agriculture and landscaping markets.

??Dewatering. Review technology advances in dewatering (electro dewatering, microwave etc.) to further minimise haulage costs. Drying beds likely to be phased out due to increased concerns over odour issues.

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10. Risk Assessment

10.1 General

This section provides an overview of the qualitative risk analysis for the Biosolids Management Strategy Options Study. Time constraints for the project workshop did not allow a thorough discussion of the risk management aspect for the preferred biosolids management options. However, it was agreed that GHD would undertake an assessment of potential risks for the project in accordance with previous experience in biosolids management.

GHD identified potential risks associated with biosolids management and presented this as part of the project workshop. MWCI requested for additional aspects to be considered and included for evaluating the potential risk factors for the proposed strategy.

The following provides an overview of the risk identification and assessment process applied to the project. It should be noted that these are just the initial steps in implementing a full risk management system for the biosolids operations of MWCI. Further effort is necessary to thoroughly identify risks and evaluate the impacts on the implementation and operational phase of the project, and establishing an action plan to minimise and/or mitigate the risks involved.

10.1.1 Definition of Risk

Risk is the chance of something happening that will have an impact upon the project objectives. It is measured in terms of consequences and likelihood. The identification, assessment and management of risk is an essential element in maximising the possible project outcomes including:

??Project performance (including time, quality and cost issues);

?? Financial performance including profit, revenue return, project budget etc; and

??Enjoyment for participants from all activities and business opportunities.

10.1.2 Identification of Risk

Risk identification involves examining all sources of potential risk from the perspective of both internal and external stakeholders. Risk assessments may concentrate on one or more possible areas of impact, and it is essential that the individuals conducting this phase are knowledgeable about the activity, policy, or process being undertaken. Methods of identifying risk include:

??Site activity audits/physical inspections;

??Surveying staff opinions, questionnaires and workshops;

??Reviewing historical records of similar project success/issues;

??Conducting work breakdown analysis; and

??Brainstorming.

10.1.3 Risk Analysis

The level of risk is usually defined as a combination of likelihood and consequence. When the levels of risk or likely outcomes do not justify a detailed numerical analysis, qualitative methods are used. This

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qualitative method is of greater merit if the determination of risk is shared across a range of people from varying backgrounds and interests. This is usually conducted in a workshop environment. A ranking system is often used, and this can be best obtained by use of a skilled facilitator. The outcome of this phase is a list of prioritised risks for further action.

Risk analyses are not always directed to a negative outcome. They can identify and assist in the priority assignment of opportunities.

The current ranking was undertaken by GHD in accordance with previous experience in biosolids management projects. As the biosolids management practices adopted are implemented and evolve, MWCI will need to update the risks identified and re-assess the ranking.

10.1.4 Qualitative Risk Assessment

There are a number of techniques that can be used to identify and rank or prioritise risks. For the purposes of this study, a qualitative risk assessment was undertaken based on the procedures outlined in Australian Standard AS/NZS 4360:1999. The process requires that risks are identified and then a qualitative assessment of their consequence or impact and their likelihood of occurring is undertaken using the ranking system shown in Table 26 and Table 27.

Table 26 Qualitative Measures of Consequence or Impact of Any Single Incident

Level Descriptor Detailed Description

1 Insignificant No injuries, no financial loss, no time effect or no loss of quality

2 Minor First aid only, low financial loss, time effect in hours or minor quality impact

3 Moderate Medical treatment required, moderate financial loss, time effect in days or defective work requires replacement

4 Major Serious injuries, major financial loss, time effect in weeks or defective work requires redesign

5 Extreme Death or multiple injuries, huge financial loss, time effect in months, significant rework or possible abandonment of project

Table 27 Qualitative Measures of Likelihood

Level Descriptor Detailed Description

A Almost Certain Is expected to happen during the project

B Likely Will probably occur some time during the project

C Possible Might occur at some time during the project

D Unlikely Could occur at some time during the project

E Rare May only occur under exceptional circumstances

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From this identified risks are classified into one of four risk categories (extreme, high, moderate or low) using the risk analysis matrix shown in Table 28.

Table 28 Qualitative Risk Analysis Matrix

Consequence

Likelihood

1 2 3 4 5

A HIGH HIGH EXTREME EXTREME EXTREME

B MODERATE HIGH HIGH EXTREME EXTREME

C LOW MODERATE HIGH EXTREME EXTREME

D LOW LOW MODERATE HIGH EXTREME

E LOW LOW MODERATE HIGH HIGH

Following the classification of identified risk into one of the four risk categories, the risk management approach should be selected for each risk category. For this project the following initial risk treatment was adopted:

?? Low and moderate risks are most cost effectively managed by routine procedures and can be dealt with by project staff as and when required. These risks should be reviewed prior to the start of each new phase of the project (preliminary design, detailed design, construction implementation, operations) to ensure that the standard procedures are adequate for managing the risk.

??High and extreme risks require more specific management. Each risk should be identified separately and a specific action plan adopted to manage that risk based on the risk treatment philosophy deemed most cost effective.

10.2 Project Risk Assessment

Table 29 presents the qualitative assessment for identified risks during the implementation for the biosolids strategy.

Table 29 Qualitative Risk Assessment – Identified Risks

Risk Consequence Likelihood Category

Land Contamination – potential for pollutants to be introduced to the soil at levels that may be deemed envi ronmentally unacceptable

3 C HIGH

Surface and Ground Water Contamination – potential for pollutants to be introduced to water bodies at levels that may be deemed environmentally unacceptable

3 C HIGH

Odour Generation – generation of malodorous compounds at levels that may cause nuisance

1 B MODERATE

Noise Generation – generation of noise levels that may cause nuisance

1 B MODERATE

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Risk Consequence Likelihood Category

Dust Generation – generation of air borne particulates that may cause nuisance

1 D LOW

Visual Amenity – amendment of the aesthetic quality

1 B MODERATE

Process Reliability and Sustainability 3 C HIGH

Operability – complexity of operations that may need increased operator skills

4 D HIGH

Traffic Impacts – potential cause of traffic movement slowdown during normal operation

2 D LOW

Occupational Safety and Health – potential for human and vector contact with unstabilised biosolids

3 C HIGH

Accidental Spillage of Biosolids – accidental opening of drain valves, tipping over of trucks, etc.

3 D MODERATE

Climate – storm and flood events preventing application to land and constraints on trucking operations

3 B HIGH

Regulatory Risks – changes in legislation, additional conditions in environmental approvals, etc.

3 B HIGH

The above table is based on the identified risks and does not include the impact of any risk minimisation methods.

From the above table, there are seven (7) items that need specific management systems and action plan to manage the risk.

10.3 Discussion of the High and Extreme Risks

10.3.1 Land Contamination

The uncertainty in biosolids quality being reused for soil conditioning and land application creates a possibility for land contamination to occur. Potential consequences include:

?? Imposition of fines by the DENR or at worst a “Cease and Desist Order” thereby stopping land application.

??Requirements for site remediation.

??Medical treatment for human and livestock that come into contact with the soil.

??Bad publicity for MWCI.

The study has raised this as an issue as part of the proposed strategy for biosolids management. Mitigating measures should be in place including proper application techniques and required barriers

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against contact. However, there is still some potential that the proposed management strategy would not be followed strictly and this may cause the risk potential being mentioned.

10.3.2 Surface and Ground Water Contamination

The uncertainty in lahar soil structure stability and adsorption capacity indicates a potential for contaminant transport to both surface and ground water resources as discussed in Section 3.2.3. Contaminant transport to water resources may lead to the following:

?? Imposition of fines by the DENR or at worst a “Cease and Desist Order” thereby stopping lahar and/or land application.

??Requirements for site remediation.

??Medical treatment for people who ingest contaminated water.

??Bad publicity for MWCI.

Best practice for lahar and land application has been considered in the study and recommendations on mitigating measures are expected to result from the EDCOP study. The biosolids management strategy should incorporate the recommended measures for these issues as an initial risk management opportunity.

10.3.3 Process Reliability and Sustainability

The varying quality and quantity of septage and biosolids will require facilities to be designed with due consideration for reliability (including sufficient allowance for storage) over the range of operating conditions expected during the design period. This is specially true for the septage and wastewater treatment plants programmed for the MWCI concession area. Another issue associated with reliability is the provision of sufficient redundancy for critical equipment to allow for standby capacity in times of emergency, i.e. power failure and peak flow events.

The sustainability, i.e. applicability and appropriateness for the foreseeable future, of the selected management strategy is also a risk aspect for the selected processes and practices.

Consequences for inadequate reliability may include:

??Non-compliance with DENR regulations on WWTP effluent quality.

??Overflow/bypass of untreated wastewater through the WWTP.

?? Lower quality biosolids, i.e. unstabilised sludge and septage, which might be distributed/reused in an inappropriate manner (Refer to Sections 10.3.1 and 10.3.2 for associated issues).

?? Lower quality biosolids that might need to be disposed to landfill rather than reused.

?? Imposition of fines by the DENR.

??Requirements for a re-assessment and amendment of the biosolids management strategy proposed due to more stringent local and international requirements.

It is assumed that this issue has been taken into account in the design of the facilities, i.e. statistical analysis of loading patterns (flow and contaminant concentration), provision of standby capacity for critical equipment, sufficient storage facilities, etc. The biosolids management strategy options study has taken the question of sustainability into account and initial risk management opportunities are already

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incorporated. However, there is a need to review this aspect of the management strategy to ensure that the implemented procedures would continue to abide by international guidelines.

10.3.4 Operability

The complexity of the treatment processes and practices recommended for biosolids managements should be assessed against the skill level of MWCI operators. This will allow MWCI to identify any training and/or skill improvement requirements for the operators to ensure that performance efficiencies are optimised and potential risks for downstream processes are minimised.

10.3.5 Occupational Safety and Health

The collection and handling of biosolids including associated products, i.e. screenings and grit, would have potential risks in terms of human contact with pathogenic organisms, i.e. health issues from diseases. These issues may be a result of inadequate protection from sprays and/or immersion in liquid septage due to existing on site conditions, i.e. absence of working platforms.

There are also some safety issues with MWCI personnel scavenging through the collected septage. Anecdotal evidence of MWSS septage management operations suggests instances of people searching for valuables in the septage without the necessary protection, and worse swimming in wastewater process tanks.

Standard operating procedures including appropriate safety practices should be established and implementation monitored strictly to minimise these risks.

10.3.6 Climate

Storm events have the potential to disrupt the transport operations and recommended land application reuse options for biosolids. The selected land application sites are accessed through roads that historically have experienced periodic flooding. This may potentially delay biosolids transport out of Metro Manila to the reuse/disposal site. Flooding within Metro Manila also has the potential to limit septage collection and transport to the septage holding tanks or programmed STPs. Again, this has the potential to delay biosolids transport.

Storm events also have the potential to limit the ability to continuously apply biosolids to land. Sufficient biosolids storage facilities are required to balance the production rates with practical application rates.

As part of the workshop discussions, it was suggested that a landfill disposal option would play a significant role in contingency planning. This is a risk management option to protect against a potential disruption of operations due to climactic conditions and other unforseen circumstances.

10.3.7 Regulatory Risks

It is expected that the DENR will eventually establish rules and regulations for biosolids management in the future. This has been considered in terms of establishing the proposed MWCI biosolids management strategy. The recommended options have the potential to comply with foreseen regulatory amendments in the country. Sustainability assessment for the management practices was based on existing international guidelines and global trends for biosolids management. Therefore, best available and appropriate practices were part of the options study for the MWCI biosolids management.

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However, advancements in technology plus other tighter regulations over the longer term may still impact on the proposed management strategy in terms of:

?? Increased biosolids quality requirements for reuse options proposed.

?? Imposition of a total ban on landfill disposal for biosolids.

??Re-assessment and/or amendment of proposed treatment processes and reuse options adopted for biosolids management.

There is a need to continually assess new legislation on biosolids management, both locally and internationally, to ensure the appropriateness and applicability of the practices adopted in the future.

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11. Preliminary Costing of Preferred Options

11.1 Basis of Cost Estimates

The cost estimates presented in this section have been developed for the purposes of comparing options. The scope and quality of the works has not been fully defined. A functional design is recommended for budget setting purposes.

These estimates are typically developed based on cost curves, budget quotes for some equipment items, extrapolation of recent similar project pricing and GHD experience.

The accuracy of the estimates is not expected to be better than approximately ± 40% for the items described in this report.

Other allowances made include:

??Engineering -15%

??Contingency -20%

??Contractors Overheads and Profit -25%

11.2 Short Term (Current to 2005)

No capital investment is proposed during this period.

11.3 Medium Term (2005 to 2010)

11.3.1 Facilities and operational changes to lahar application

The requirements will be heavily dependent on the outcomes of the Environmental Impact Assessment currently being undertaken. For example, a blending facility using imported material may be required to improve the lahar application site to ensure the operation is environmentally sustainable.

Capital and operating costs are not available for this task at this stage.

11.3.2 Vermiculture Trial

Capital Costs

A ballpark capital cost for a 5m3/day vermiculture facility will be in the order of Php 18.5M. This includes the processing beds and associated equipment.

The trial facility will be optimised, and local knowledge on the capacity per unit area of equipment will be developed. This will then enable the costing of full-scale units to be refined.

Operating Costs

Estimated operating costs are Php 15,000 per day, including electricity, diesel and, labor (10 staff). It has been assumed that any additional materials (i.e. greenwaste) are freely available.

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11.3.3 Lime stabilisation

As an example, if the Payatas STP were to incorporate a lime stabilisation facility, the following capital and operating costs would be required.

Assumptions: 22 tonne dry solids/day dewatered to 20% dry solids.

Capital Cost

A ballpark capital cost for a facility using generic technology to handle the specified quantity of biosolids is Php 95M, excluding the cost of associated buildings and facilities (roads, fencing, security, odour control, workshop and storage). These are expected to increase the total project cost by 30-70%.

Operating Cost

Operating costs will include lime, labour, maintenance, electricity and product testing. For this example, annual operating costs are estimated to be around Php 28M.

11.4 Long Term (2010 onwards)

The scope and costs associated with the long-term capital projects will depend on the outcomes of the medium term projects. Costs for these projects would be best evaluated at a later date when the outcomes of medium term projects are fully evaluated.

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12. Conclusions and Recommendations

12.1 Conclusions

??Ultimately around 400 m3/day (around 180 dry tonnes/day) of biosolids will be required to be reused/disposed. This is after dewatering processes have been fully implemented.

??Biosolids produced from MWCI plants are unstabilised. The use of biosolids should be restricted and applied to land using internationally recognised practices.

??Current viable markets are for the rehabilitation of the lahar fields and in extensive agriculture at Pampanga

?? In the short term, management of the application of biosolids in these markets needs to be improved to avoid potential environmental harm in the long term. Further, it is necessary to review the distribution of dried sludge to third parties as MWCI may be exposed to liabilities arising from inappropriate application methods practiced by third parties.

?? The production of higher quality biosolids will create alternative markets. These markets are likely to be closer to Manila and transportation costs will be lower. Having a range of viable markets will reduce risks for MWCI in case the current options are restricted.

??Pilot scale evaluation of alternative stabilisation technologies will provide MWCI with an understanding of the technology and minimise the risks of any subsequent full-scale operation.

12.2 Recommendations

Based on the outcomes of this study, the following recommendations are made:

?? The proposed biosolids management strategy (Refer Section 9) be adopted and the short, medium and long term activities identified be undertaken.

??A more detailed review of the Magallanes WWTP operation be undertaken to ascertain the discrepancy between expected and actual solids generation rates.

?? The lahar application environmental assessment being undertaken by EDCOP needs to consider the following items:

– Lahar adsorption rates for nutrients from the septage to provide information on potential nutrient transport to surface and ground water resources.

– Erosion potential for lahar to provide a check on septage transport with surface runoff.

– Agronomic rates, i.e. maximum allowable septage application rates on lahar considering soil characteristics, irrigation practices, and plant uptake, to provide an upper limit on the septage applied per square meter of lahar area.

– An assessment of topsoil or binder addition (sourced from nearby regions) to lahar laden areas to prevent potential runoff of septage due to erosion. Optimisation of the biosolids/binder/lahar mix.

– A comparison of the unstabilised septage, dewatered septage (20% w/w) and lime stabilised dewatered septage (comprising 0.5 kg lime added per kg dry solids) to determine any benefits and disadvantages in achieving the above goals.

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13. References

GHD, Biosolids 2040 - A Long Term Strategy for the Management of Perth’s Wastewater Sludge and Biosolids, Water Corporation Western Australia, 1997.

Sinclair Knight Merz Inc. Consulting Engineers, Feasibility Study of Treatment, Handling and Disposal of Septage for the PREMRSDP Project Implementation, 2002.

Nippon Jogesuido Sekkei Co., Ltd and Tohmatsu & Co., Study on Water Supply and Sewerage Master Plan of Metro Manila - Final Report Volume III, 1996.

Ministry of Environment Canada, Guidelines for the Utilization Of Biosolids and Other Wastes on Agricultural Land, 1996.

NSW EPA, Environmental Guidelines - Use and Disposal of Biosolids Products, NSW Environment Protection Authority, 1997.

South Australia EPA, South Australian Biosolids Guidelines for the Safe Handling, Reuse or Disposal of Biosolids, Updated 1997.

US EPA, A Guide for Land Appliers on the Requirements of the Federal Standards for the Use or Disposal of Sewage Sludge 40 CFR Part 503, EPA Office of Enforcement and Compliance Assurance 1994.

Metcalf and Eddy, Wastewater Engineering 3rd Edition, McGraw-Hill Book Co., 1991.

Walmsley NA and Dougherty AP), Desludging of large facultative ponds with controlled sludge disposal to land, Unpublished technical paper, 1995.

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Appendix A

Environmental Management Bureau Classification of Domestic Sludge and Septage

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Appendix B

Review of International Guidelines on Biosolids Management

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Review of International Guidelines on Biosolids Management

US EPA Guidelines

Title 40 of the Code of Federal Regulations (CFR), Part 503 regulates the reuse or disposal of “sewage sludge” (biosolids) in the United States. Restrictions are imposed on the use of biosolids depending on the level of pollutant concentration, and the quality of pathogen and vector attractiveness reduction undertaken prior to disposal or reuse.

US EPA classifies biosolids as either Exceptional Quality (EQ) or Non-Exceptional Quality (Non-EQ). Sludge classified as EQ is considered comparable to standard fertilizer products and its use in land applications are not restricted by this rule. On the other hand, the EPA imposes restrictions on the application of Non-EQ sludge to protect human health and the environment from the increased levels of pathogen and/or pollutants compared to EQ sludge.

EQ biosolids are those that:

??Meet the specified instantaneous and monthly pollutant concentration limits.

??Has undergone one of the pathogen reduction alternatives specified by the US EPA to meet Class A requirements (eg. composting, heat drying, irradiation, heat treatment, etc.).

??Has undergone one of the options specified by the US EPA to reduce vector attraction.

Sludge that exceeds any or all of the requirements that define EQ biosolids is classified as Non-EQ.

Column 2 of Table 19 provides the maximum concentration limits for heavy metals set by the US EPA to be classified as EQ. Other heavy metals regulated by Part 503 include Chromium, Molybdenum and Selenium.

Part 503 also categorises sludge between Class A and Class B based on the treatment conducted to reduce pathogens. To be classified as Class A, the treated biosolids should have:

?? Fecal coliform densities of less than 1,000 most probable number (MPN) per gram of dry solid sample.

??Salmonella bacteria of less than 3 MPN per 4 grams of dry solids.

Some of the restrictions and management practices for the application of Non-EQ biosolids are as follows.

??Non-EQ biosolids shall not be applied to the land if it is likely to adversely affect threatened or endangered species or their designated critical habitat unless the applier can demonstrate that applicable management practices are met to avoid negative impacts.

??Approval should be sought prior to the application of bulk non-EQ sewage sludge to flooded, frozen, or snow-covered lands. The land applier should ensure that proper runoff control measures are in place to prevent sewage sludge from entering any bodies of water.

??Application of Non-EQ sludge shall not be permitted within 10 m from any water body or courses.

??Non-EQ sewage sludge shall be applied at a rate that is equal to or less than the agronomic rate for the site. Agronomic rate is the optimum sewage sludge application rate that provides the amount of nitrogen needed by the crop or vegetation whilst minimising nitrogen infiltration below the root zone.

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Sludge application rate that exceeds the agronomic rate could result in nitrate contamination of the groundwater.

Australian EPA Guidelines

The Australian EPA grades biosolids according to the stabilisation it has undergone, and the level of heavy metal and chemical contamination.

Stabilisation grading is based on the extent of treatment conducted to reduce pathogens and vector attraction, and control odours. Biosolids classified as Stabilisation Grade A are considered to have sufficiently low biological activity to have negligible risk of transmitting pathogens and is deemed suitable for uncontrolled human contact. After dewatering, Grade A biosolids have undergone any of the following:

??Ageing for not less than 3 years by air drying in a lagoon or by stockpiling at the treatment plant.

??Windrow composting that attained temperature of 55ºC or more for at least 15 days.

?? Lime stabilisation that achieved pH level of 12 and temperature of 52ºC, and less than 50% solid content during the initial 12 hours of treatment.

??Pasteurisation at temperature of 70ºC for at least 60 minutes that attained dry solid content of 75 and 90% for digested and undigested sludge respectively.

After these treatments, a 50-gram sample of produced biosolids should contain:

?? Less than 1 salmonella.

?? Less than 1 helminth ovum.

?? Less than 1 PFU total virus.

?? Less than 1 cyst or oocyst of Cryptosporidium and Giardia.

Stabilisation Grade B sludge are those that have been stockpiled for at least 1 year if digested and 3 years if undigested. Due to the limited stabilisation treatment conducted, materials under this classification are suitable for use where there will be minimal risk of uncontrolled human contact. Approval from EPA shall be secured prior to any land application of Grade B sludge.

Contamination grading is based on the concentration of potentially harmful heavy metals or organic chemicals contained in the sludge. The intent of grading according to this aspect is to avoid the application of biosolid that risk excessive uptake of metals by crops or animals or human ingestion. The maximum permissible concentrations of metals for each grade category are provided in Columns 3 and 4 of Table 19. Samples that exceed the limits provided are classified as Grade C.

Land application of Contamination Grade A biosolids are deemed suitable for uncontrolled human contact. However, its application in irrigated and commercial food crop production is still subject to EPA approval. Grade B biosolids on the other hand are suitable soil replacement where food crops will not be grown. Use of Grade C biosolids will only be permitted when blended or composted with other materials to dilute its contamination concentration.

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Table 30 Classification Requirements for Biosolids Reuse

Classification Minimum Grade Requirement

Stabilisation Contamination

Permitted Use without prior EPA Approval

Use Requiring EPA Approval

Unrestricted Urban Use

A A ?? home garden ?? urban landscaping ?? non-irrigated

agriculture ?? forestry ?? site rehabilitation

?? irrigated and commercial agriculture

Landscaping A B ?? urban landscaping ?? forestry

?? site rehabilitation

?? agriculture

Landscaping B B ?? urban landscaping

?? agriculture ?? forestry ?? site rehabilitation

Approved Use B C ?? agriculture ?? forestry

?? site rehabilitation

EPA imposes a general restriction for all reuse classifications. Biosolids shall not be applied to the following site conditions.

??Surface water or shallow groundwater level.

??Poor drainage (waterlogged soil).

??Rocky ground.

??Sloping land.

??High nutrient levels.

For the approved use classification, EPA imposes further restrictions in the land application of biosolids, which include:

??Biosolids are unlikely to be approved for application to any irrigated land that is or is likely in the future to be used for food production for animals or humans.

??Biosolids shall not be applied to soil that has a pH of less than 5.5 (ratio 1:2.5 soil / 0.01M CaCl2).

??Biosolids shall not be applied to land with a slope in excess of 5% without approval of the EPA.

?? The following buffer widths are recommended minima. Approval from the EPA will be required for lesser distances.

– Watercourse - 100 metres

– Farm Drives - 5 metres

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– Property Boundaries and Public Roads - 50 metres

– Dwellings on adjoining properties - 100 metres

European Economic Community Council Directives

The European Union adopted directives that govern the use and application of sewage sludge on agricultural lands of its member states. Known as the Council Directive 86/278/EEC, this legislature provides the minimum requirements from which the member states can draw up more stringent provisions for individual implementation. Some of the key requirements provided by this directive are as follows.

??Any use of biosolids in agriculture practices shall only be permitted if regulated by the respective member state.

?? The maximum concentration of heavy metals in the sludge set by the EEC is provided in Column 5 of Table 19.

??Member states shall prohibit the use of sludge with one or more heavy metals exceeding the limits specified.

??Prior to application in agriculture, sludge shall be treated in manner acceptable to the member state.

??Member states shall prohibit the use of sludge on:

– grassland or food crops if it is to be grazed or harvested within a minimum of three (3) weeks;

– soils in which fruit and vegetable crops are growing, with the exception of fruit trees; and

– ground intended for the cultivation of fruits and crops that are normally in direct contact with the soil and normally eaten raw, for a period of 10 months preceding harvest.

??Where the soil pH is below 6, permissible concentration of heavy may be revised to account for the increased mobility and availability to the crop.

Canadian Ministry of Environment Guidelines

Canadian Ministry of Environment (MOE) requires that prior to application of biosolids, the sludge and the receiving lands be subject to its approval prior to application. The MOE has set the maximum permissible heavy metal contents of the sludge as provided in Column 6 of Table 19.

MOE has identified aerobic and anaerobic digestion as the appropriate processes to stabilise sewage biosolids. These treatments are intended to minimize the odour potential and reduce the number of pathogenic organisms and other potentially harmful constituents to an acceptable level.

The characteristics of the receiving soils are likewise monitored by MOE. Application of biosolids to agricultural lands are restricted as follows.

??Biosolids shall not be applied within 10 meters from any watercourse or body of water.

?? The groundwater table should be at least 0.9 meters away from the surface of application.

??Sewage and other biosolids may be applied to soils greater than 1.5 metres deep. Shallow soils (1.5 m or less over bedrock) will be evaluated on a case-by-case basis.

?? The minimum separation distance from a residential area shall be 450 meters and from an individual residence 90 meters.

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?? The application site should be at least 15 meters from a drilled well that is greater than 15 meters deep or 90 meters for all other wells.

??Biosolids shall not be applied to soil with slope greater than 9% or 6 to 9% for moderate to slow permeability soils.

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Appendix C

Processing Technology Review

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Applicable Biosolids Process Treatment and Technology Options

Anaerobic Digestion

Anaerobic digestion is the biological degradation of organic substances in the absence of free oxygen producing methane, carbon dioxide and water in the temperature range of typically 30 to 38ºC. Destruction of volatile solids typically ranges between 30 and 60% depending on the age of the raw sludge, volatile solids content, total solids content, toxic effects and operating conditions. The digestion period varies between 30 to 60 days in most configurations.

Biogas is generated during anaerobic digestion. It is usually comprised of about 60 to 70% methane, which can be used to fire the sludge heater or boiler.

Anaerobic digestion is a common and well-understood stabilisation technology, which requires low energy input to operate, and, at the same time, produces biogas as fuel. However on the downside, anaerobic digestion process has the potential to produce offensive odours and release phosphorus from the sludge.

Sludge treated using this process is typically suitable for application in restricted agricultural uses. Non-agricultural uses include landscaping areas with restricted public access, forestry and land rehabilitation. To enable a more extensive agricultural land spreading, anaerobically digested sludge would have to undergo further treatment for pathogen reduction. This can be achieved via composting, lime addition, heating and drying or long term storage.

Aerobic Thermophilic Pre-treatment (or dual digestion)

The aerobic thermophilic pre-treatment digestion process was developed as an add-on process to conventional anaerobic digestion to improve reduction of volatile solids and pathogens, and result in a more stable product. The process takes place in insulated well-mixed tanks, with air or oxygen injection to maintain aerobic conditions. The mean digestion time is 18 to 24 hours and the sludge is maintained at a temperature between 55? and 65?C.

By definition, this process is only a pre-treatment step to anaerobic digestion; hence no final product is derived. The process improves several functions and parameters of a typical anaerobic digestion including pathogen and weed seed reduction, dewatering, hydraulic retention times in digesters, and generation of methane during digestion. Provision of foam suppression and odour control systems are key in adopting this process.

Aerobic Digestion

Aerobic digestion is the biological degradation of organic substances by mechanical surface aerators or other aeration system resulting to the production of carbon dioxide, ammonia and water. The volatile solid destruction under this process varies from 30 to 50% depending on the age of the raw sludge, volatile solids content, total solids content, toxic effects and operating conditions.

Typical retention times for various sludges are as follows

??Waste activated sludge: - 10-15 days

??Activated sludge without primary settling: - 12-18 days

??Primary plus waste activated or trickling filter sludge: - 15-20 days

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Supernatant from aerobic digestion has relatively low BOD, SS and ammonia content but the sludge will still require additional treatment for pathogen reduction. Aerobic digestion is also considered to have a lower capital cost and is simpler to operate than anaerobic digestion. However, the energy required during operation is significantly greater. The digested sludge can be more difficult to dewater.

Sludge produced from aerobic digestion is generally suitable for restricted agricultural uses except for food crops directly consumed by humans. Its non-agricultural uses include landscaping areas with restricted public access, forestry and land rehabilitation.

Autothermal Thermophilic Aerobic Digestion (ATAD)

ATAD is an aerobic stabilisation process that operates at thermophilic temperatures, i.e. 55 to 70?C. At

these temperatures, biosolids stabilisation and disinfection are achieved within a residence time that ranges from five to six days.

Key consideration in the process design is the level of volatile solids contained in the feed sludge. Thickening of the feed solids is required to maintain the heat balance for the system.

Volatile solid reduction achieved by the process typically ranges from 38% and 50%. Important factors that influence the quality of treatment attained include:

?? temperature control;

?? hydraulic retention time;

?? prevention of short-circuiting;

?? odour production and control; and

?? foam control.

The sludge is transferred into cooling/storage tanks after digestion. If the tanks are designed appropriately and sufficient time is allowed for cooling, further thickening of 6 to 9% ds will still be achieved at this stage.

The destruction of volatile solids achieved in the process reduces the volume of sludge to be disposed. After dewatering, digested sludge is usually applied on agricultural and forestry lands through bulk spreading. The product’s potential for liquid biosolid spreading purges the need for dewatering albeit possible high costs for transportation and handling to the final site of use. The process reduces pathogenic viruses, bacteria, viable helminth ova, and other parasites to below detectable levels.

The risks related to the treatment technology are considered minimal or manageable. Principally the risks include breakdown of equipment, odour generation, excessive foaming, insufficient volatile solids breakdown and capacity. The process does not achieve nitrification and the digested sludge has generally low dewatering quality. Unlike anaerobic digestion, ATAD requires a high level of control and operational skill.

Lime Stabilisation

Lime stabilisation is the process of mixing lime into dewatered sludge. Lime solutions that maybe used in this purpose include quick lime, CaO or hydrated lime or Ca(OH)2. The addition of lime in the sludge increases the pH level thereby destroying the microorganisms in the sludge.

The conventional lime treatment uses a pug mill or other similar device to mix the hydrated lime or quicklime with the dewatered sludge prior to being discharged in storage bins. Release of odours due to

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the stripping of ammonia and the poor mixing of lime into the sludge are the common concerns in using this process. Selection of a suitable mixing device and the enclosure of the lime-dosing unit with odour scrubbing are therefore recommended.

RDP Envessel pasteurisation and N-VIROTM Soil process are proprietary processes developed based on lime stabilisation. These processes are capable of achieving higher levels of stabilisation and pathogen reduction of the sludge compared to the conventional approach. Non-proprietary processes may also achieve similar stabilisation and pathogen reduction capabilities given sufficient process (temperature and time) control.

The lime to sludge ratio is dependent on the type of process the sludge was wasted from, the organic composition, the solids concentration and the required sludge quality base on the intended reuse or disposal. It was however observed that to meet similar stabilisation qualities, activated sludge from an extended aeration or BNR process will require addition of more lime compared to primary sludge.

Use of this process increases the biosolids’ suitability for application in acidic soils due to the increased liming value. However, the process increases the quantity of solids to be disposed of between 40% and 100%, therefore resulting in additional transportation and land spreading cost. The process also has the potential for odour risk.

Vermiculture

Vermiculture is the process by which organic material is fed to a variety of worm species with the purpose of converting the organic material into increased worm biomass and vermicast. Vermicast is the excreta from worms and is used as a plant growth medium and soil conditioner that has a wide range of applications including broad acre farming, turf farming, horticulture, viticulture and seedling propagation.

Vermiculture is not yet defined as a treatment process in most international sludge reuse and disposal guidelines. However given the biological basis of the process, it has the capacity to achieve a reliable level of pathogen reduction. Except for some dilution from the addition of clean organics and some minor absorption in the worm biomass, the total quantity of heavy metals in the sludge will be unchanged. But given the relatively low application rates of vermicast, the impact of heavy metal on soil should be inconsiderable.

Composting

Composting is the biological decomposition of organic material to produce a stable material suitable as a soil conditioner. Both raw and anaerobically digested sludge can be composted. However, raw primary sludge has a high potential for odour risk.

Principal factors to achieve successful composting include:

??maintain moisture content between 40% and 60%;

??maintain composting temperature between 50ºC and 60ºC;

?? keep pH of sludge to be composted between 6 and 9;

??maintain the carbon - nitrogen ratio between 20 to 35:1 by weight;

?? provide adequate aeration; and

?? sufficient and correct amendments and bulking material.

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The amount of amendment material required is controlled be the water content of the sludge. The final composted product will have a biosolids content ranging between 5 to 30% by dry weight.

Composting can be achieved through various methods. A brief outline for each is provided below and a comparative summary in Table 31.

?? Windrow

This method is carried out by piling the sludge mixture into long rows (windrows) and mechanically turning and mixing it at specific intervals for about 18 weeks or until composting is complete.

?? Aerated Static Pile

This method involves piling of the sludge and bulking agent mixture over a network of pipes on a hardstand area. Air is then drawn through the pile and exhausted through a compost filter for odour control. The pile may be covered with a layer of matured compost to further prevent odour release. This process takes about 8 to 10 weeks to complete.

?? In-Vessel enclosed System

Composting by this method takes place inside an enclosed reactor, in which process parameters can be closely controlled and odour release minimised. This results in a shorter composting time and a more consistent product quality in relation to pathogen reduction.

Table 31 Comparison of Various Composting Methods

Method Advantages Disadvantages

Windrow ?? low capital cost

?? low operation and maintenance cost

?? large area required

?? possible odour problems

?? difficult to achieve required temperatures

?? potential for poor mixing

?? long composting period

Aerated Static Pile ?? enhanced odour control

?? good temperature maintenance

?? shorter composting period

?? capital cost of aeration system

??moderate operating and maintenance costs

In-vessel ?? small area required

?? high degree of process control

?? very good temperature and odour control

?? high capital, operating and maintenance cost

?? applicable to large scale operation only

The quality of compost derived is dependent on the quality of initial sludge and process conditions particularly temperature and composting period.

Given the concerns regarding possible regrowth of pathogens in compost, there are reservations in treating sewage sludge by composting. Strict handling requirements are necessary to avoid such

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occurrences. Likewise, the amount of sludge to be treated will require a proportional amount of amendment and bulking materials hence, may not be cost efficient for large volumes of sludge.

Thermal Drying

Thermal drying process involves raising the temperature of gas from sludge and air to about 450ºC in a combustion chamber and then allowing it pass through a heat exchanger to heat the drying drums. Dewatered sludge mixed with under and oversized pellet products are introduced into the heated drum for drying. Odorous gases generated during drying are returned to the combustion chamber and burned off.

The main products of thermal drying are sludge granules or pellets that have a moisture content of less than 10% (w/w). Depending on the target classification of the final product, the temperate and solid contents of produced granules may range from 70 to 80ºC and 75 to 90% (w/w) respectively. These granules are predominantly used as commercial soil conditioners. The nutrient values of these granules are dependent on the quality of input sludge.

Thermal drying is a proven and widely accepted technology for treatment of biosolids. Already available are a number of proprietary units that offer specialised systems for this process. Some of the key advantages of adopting thermal drying include:

??Containment of odour and dusts during treatment;

??Produces highly marketable product with high soil conditioning value;

??Capacity to considerably reduce sludge volume thus minimising costs associated with handling;

??Requires a small footprint compared to land intensive sludge handling techniques being a relatively compact process; and

??Suitable source of fuel (similar calorific value to brown coal).

On the other hand, the perceived disadvantages of this process includes:

??Requires high capital and operational costs (note that the burner has to be fired using an external energy source); and

?? Includes potential risk for the product to self-ignite.

Thermal Cyclonic Drying

Thermal cyclonic drying is a patented technology of The Global Resource Recovery Organisation marketed under the brand name Tempest. Similar to the conventional thermal drying process, this technology uses cyclone hoppers to improve drying of solids achieved through:

??Higher airflows resulting in higher evaporation rates and moisture loss;

??Reduction of particle size due to impingement to the cyclone resulting to an increase in the surface area; and

??Enhanced solids separation.

Preheated biosolids are fed into the primary cyclone at a controlled rate. The required solids content are usually achieved in a secondary cyclone in series. After heating, the resulting dry material is then discharged from the bottom of the secondary cyclone whilst high moisture air is released from the top and passes through a scrubber to remove particulates and water-soluble compounds. Further emission treatments may still be added depending on the requirements.

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Depending on the drying temperature and final solids content, a relatively high level stabilisation is likely to be achieved through this process. Reuse options for the resulting biosolid products include agricultural land application, land rehabilitation, bioremediation or landscaping, applied in bulk or supplied to market in bags.

The process requires lower energy costs compared to the conventional drying systems. It also has a smaller footprint, hence lower land requirements.

Incineration/Energy Recovery Plant

Incineration is defined as the complete thermal destruction of materials to its inert composition in the presence of oxygen (Brunner, 1980). Its application to sewage sludge produces over 90% weight reduction of the input material. Carbon dioxide is the primary gas derived from the incineration process.

The key purpose of sewage sludge incineration is to:

?? dry the sludge cake;

?? destroy the volatile contents by heating up to 760?C to 980?C;

?? produce a sterile residue or ash; and

?? produce flue gas with zero visible emissions.

Sewage sludge has a volatile component, a fixed carbon component and contains organics that are usually non-combustible. Dewatering of sludge (usually untreated) prior to incineration is a critical step for the combustion process and results in lower fuel requirement for the incineration. Sludge is usually dewatered to 15 to 35% dry solids content.

With solids at about 30% of the sludge feed, autogenous combustion will take place, i.e. the sludge will burn without the need for supplemental fuel. The addition of combustible material to the dewatered sludge is sometimes practiced to increase its heat value relative to its moisture content.

Processing of sludge to obtain high solids content usually requires thermal conditioning of the sludge. The benefit of thermal conditioning is reflected in the quality of sludge generated. As opposed when polymer, ash, ferric salt or lime is added, the resulting sludge cake contains no additional inert solids that negatively affect the incineration process or the flue gas it produces.

There are two types of incinerators available in the market: the multiple hearths and the fluidised bed. Fluidised bed is generally considered a better technology than the multiple hearths system.

Incineration produces an inert and sterile ash that has potential for land application, road surfacing, as concrete aggregate, among others. The technology is relatively compact and requires a small footprint compared to land intensive sludge handling techniques. A number of equipment is available with emission guarantees that will meet stringent air pollution restrictions.

The process can readily take place at the location of sludge generation thereby minimising the need for additional transportation and handing. Waste heat from the process, which ranges from 420?C to 760?C, can be made available to produce steam for other unit processes on the sewage treatment plant.

Incineration requires high capital and operating expenses. Social acceptability is also a consideration as the process is largely perceived as a contributor to air pollution.

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Oil from Sludge (OFS) Technology

OFS technology is a patented thermochemical or pyrolytic process that converts the organic content of sludge to end products with energy content and to oil with properties similar to diesel fuel. This is achieved by heating of pre-dried sludge with approximately 5% moisture content in a reactor vessel in the absence of oxygen (pyrolysis) to about 450?C, at which point, approximately 40 to 50% (w/w) of the sludge is vaporised. These vapours are then contacted with the residue from the sludge (char) causing the conversion of the organic molecules to aliphatic hydrocarbons, which are the principal components of crude oil.

The process operates at relatively low temperatures (650 to 700?C) and at atmospheric pressure. Gas

products of a pyrolytic reaction include methane (CH4) and carbon monoxide (CO).

The process produces oil, char, non-condensable gas and reaction water. These latter products are burned in a hot gas generator (similar to a fluidised bed incinerator), which produces most if not all the energy for sludge drying and reactor heating. Likewise, the oil derived from the process is suitable for combustion in engines and the char from the reactor has similar properties to high value commercial activated carbons used for the adsorption of heavy metals.

OFS achieves satisfactory levels of sludge stabilisation, pathogen reduction and dewatering. The ability of the system to be its own energy source to perform sludge drying is an apparent advantage. However, considerable capital and operating costs are still required to establish the system. The overall emissions are lower than conventional incinerators. However, the technology can still be perceived as a contributor to air pollution, which may result to poor public acceptance.

Gasification

Gasification is a process similar to the OFS technology. Waste Gas Technology (WGT) UK Ltd. is developing the process primarily based on EU legislation. The main difference between these processes is that the gases generated in gasification are not converted to liquid hydrocarbons. The process produces char by-product and gas with low calorific value that ranges from 5 to 7 MJ/m3. Such gas is not easily utilised in conventional burners designed for natural gases, which has calorific value of 37 MJ/m3. The low energy content is caused by the mixing of the product and by -product (i.e. flue gas) streams.

The calorific value and composition of resulting gas product is dependent on the characteristics of the waste feed material and the reactor operating conditions, particularly temperature, gas residence time and solid retention time. Gases produced in the bioreactor under these conditions include methane, hydrogen, higher hydrocarbons, carbon monoxide and carbon dioxide.

The process achieves a relatively high level of stabilisation suitable for land application. Its emission rate is comparatively lower than the conventional high temperature incineration. Given that this technology is still developing, its suitability is yet to be proven on a commercial scale. High capital and operational costs are also expected in adopting the process.

Active Sludge Pasteurisation (ASP) Process

Active Sludge Pasteurisation (ASP) Process is a proprietary process that negates the need to stabilise the biosolids. This process achieves pasteurisation while enriching the sludge with nutrients N and P.

Pasteurisation is achieved through the addition of anhydrous ammonia (NH3). This raises the sludge temperature to 60ºC and the pH to 12. NH3 also reacts with the organic matter, which inturn consumes part of the ammonia.

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Phosphoric acid (H3PO4) is then added to neutralise the mixture thereby reducing the pH to 7 and raising the temperature to 70ºC. The non-chemically bound ammonia is evaporated and reused in succeeding treatments. Dry warm air is blown over a thin layer of final product to dry the sludge. The sludge is then separated from the moist air in a cyclone separator to produce the final pelletised or granular product, which has moisture content of about 15% (w/w).

The heat generated during the process goes into a heat exchanger and is used as an energy source for the overall process. This eliminates the need to provide an external energy source.

ASP reduces the volume of the sludge considerably and produces highly marketable agricultural product. Its nutrients N and P are bound into the organic matter as chelates, which make it readily available for plants.

ASP infrastructure is intended to have a modular design, allowing it to be customised for various sludge production rates. The process is relatively compact with a small footprint compared to land intensive sludge handling techniques. Capital and operating costs for this process are considered to be relatively high.

Solar or Agitated Air Drying of Dewatered Biosolids

Agitated Air Drying is a batch process that involves rapid drying of sludge. Biosolids are placed on drying areas (typically windrows) and are subjected to intermittent mechanical agitation that enhances the drying rate.

The process can be broken up into the following stages:

??Pre-blending of un-processed biosolids with processed biosolids and/or other inert material to obtain a relatively consistent initial blend.

?? Intermittent mechanical agitation often using a specialised windrow turning machine. Continuous creation of a new wet surface area to the atmosphere allows evaporation of moisture to take place.

??Determination of final product quality, which may result in:

– Back-blending of the processed product into the initial pre-blending phase, and/or

– Beneficial use of the processed product into a range of markets.

The process primarily aims for the rapid production of a higher solids product (up to 75%TS) without necessarily achieving high quality stabilisation in the short term.

Stockpiling of dewatered sludge for extended periods is still a necessity to achieve stabilisation. Hence, the quality of the resulting biosolid product becomes largely dependent on climatic variations. Depending on the level of stabilisation achieved, reuse options can include agricultural land application, land rehabilitation, bioremediation or landscaping.

The process is relatively simple to operate with low energy and capital costs. It however requires sufficient land area with adequate buffer zones to allow drying and stockpiling of sludge. Depending on the sludge type and pre-treatment processes, potential odour issues can become a concern particularly after windrow turning. Costs for transporting and handling of the product to the final reuse location are also key considerations in this option.

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Sludge Lagoons

Sludge lagoons are combined sludge storage and treatment method. The lagoons are relatively shallow earth basins about 1.0 to 3.5 m deep into which sludge is deposited. Solids are allowed to settle to the bottom of the lagoon where it accumulates and compacts. Natural anaerobic digestion takes place while the sludge is contained in the lagoon.

As the solids settle, some of the water that surfaces is evaporated whilst excess supernatant is decanted and returned to the treatment plant. The lagoon can be drained or the supernatant pumped out for re-treatment. The sludge can be left to air dry after which it will require removal from the lagoon and stockpiled until it is reused. It is often necessary to turn a pile of semi-dried sludge over when it has dried down to a depth of about 600 to 700 mm using a bulldozer or bobcat.

Sludge lagoons seldom produce significant odour problems whilst it is still full and covered with a layer of water. Objectionable odours usually occur when the lagoons are emptied and the sludge dried out.

Storing of digested sludge in lagoons achieves both storage and disinfection functions. Lagoons for this purpose are usually deeper at 3.0 to 5.0 m. If the lagoons are not loaded too heavily, i.e. less than 0.1 kg VSS/m2d, the growth of algae will maintain an aerobic surface, which will oxidise rising odours. Surface aerators can also used to create the aerobic surface.

Sludge lagoon is mainly an alternative to the digestion process. Whilst the sludge may be stored in the lagoons indefinitely, it should not be regarded as a disposal strategy but rather just an interim step prior to disposal or reuse.

The level of stabilisation will be determined by the length of time the sludge is kept in the lagoon and its final dry solids content. Depending on its solids content, the treated biosolids maybe used in land application through bulk application or injection.

Sludge lagoons generally have low capital and operational costs. It requires simple and straightforward operations. Key considerations for developing sludge lagoons will include land requirement, odour management and determination of retention times.

Short-term Storage of Dewatered Sludge

Depending on the sludge pre-treatment process, considerations and characteristics for adopting sludge storage may vary as follow.

Table 32 Short-term Storage Characterisations for Various Sludge Types

Type Description

Anaerobically Stabilised Sludge

??Well-stabilised sludge is typically dewatered to a solid content of 18 to 25% dry solids.

??Mechanical stockpiling can be accomplished easily.

?? Lime can be used to cover the outside layer of the pile to further stabilisation and limit odours.

??Subsequent decomposition takes place to produce a non-offensive product. Long-term storage is usually practiced.

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Type Description

Waste Activated Sludge (WAS)

??Depending on sludge age, WAS is typically dewatered to a solid content of 11 to 15% dry solids.

??Poor slumping characteristics limit the stockpiling height.

?? Limited stabilisation tends to produce foul odour and promotes vector attraction.

?? Long-term stockpiling of dewatered WAS is not advised as the outside layer dries whilst the inside is still wet. Increased odour is also expected, as the inside of the pile turns anaerobic.

Aerobically Stabilised WAS

??Aerobically stabilised WAS is typically dewatered to a solid content of 15 to 20% dry solids.

??Stockpiling is relatively easier compared to raw dewatered WAS.

?? Long term storage of poorly or partially digested sludge can lead to anaerobic decomposition and greater odour production.

Stabilisation is largely dependent on the treatment process and storage period. Under this process, biosolids dewatered to greater than 10% w/w dry solids and stockpiled for at least three years can achieve a high level of stabilisation.

Although stockpiling is a relatively inexpensive and simple process, its potential as a long-term and final step in the sludge treatment process is limited. This is usually regarded as a penultimate step in a disposal or reuse strategy. Considerable land requirement for this process is also a key consideration.

Bioreactor Landfill

Bioreactor landfills are extension of leachate recirculation landfills that achieve waste decomposition and stabilisation within a comparatively shorter timeframe. This is achieved through the addition of liquid and air, and varying of some or all of the process variables, such as leachate recirculation rate and moisture content, pH, temperature, nutrient addition and pre-disposal conditioning (eg. shredding), to enhance microbial processes.

Unlike the traditional landfills that simply recirculate leachate for liquid management, a bioreactor involves injection of leachate to stimulate the natural biodegradation process. To supplement leachate, the process also needs other liquids such as stormwater, wastewater, and wastewater treatment plant sludges in a controlled manner. Bioreactor technology relies on maintaining the moisture content at an optimal rate of about 35 to 65%.

The accelerated decomposition and stabilisation of waste reduces possible long-term environmental risks and landfill operating and post-closure costs. The process also results in a significant increase in the production of landfill gas particularly methane and carbon dioxide that can be captured for energy conversion. Bioreactor landfill process recovers airspace volume of about 15 to 30%, allowing a longer operating life of the landfills.

Development of an engineered bioreactor landfill system will require higher initial capital costs, and a more thorough monitoring and control system during operations. Key considerations in planning include expected increase in gas emission and odours, physical instability of the waste mass due to higher moisture content and density, land and groundwater protection measures, and landfill fires.

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Document Status

Reviewer Approved for Issue Rev No.

Author Name Signature Name Signature Date

0 A Latorre R van Oorschot D McIntyre 13 Aug 2004

1 A Latorre R van Oorschot D McIntyre