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    Sludge and Biosolidsanagemen ec no og es

    ADB Workshop, Manila16-17 November 2011

    Ms. Echo LeongAssociate Director, AECOM Asia Co. Ltd.

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    Outline of Presentation

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    Management Practices

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    Raw Slud e:By-product of sewage treatment

    High organic, nitrogen and phosphorus contents

    May contain heavy metals in trade effluent

    Primary Secondary/

    Sludge

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    Trends in Sewage TreatmentGHG / Energy

    Micro-constituents

    1. Increased levels of ollutant removal What & Where?

    Resource Management

    2. Protection of public health

    Organics Tertiary Treatment

    Solids Enhanced Water Qualit

    Secondary Activated Sludge

    Result in increase of sludge production

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    Developing Countries

    - PRC for exam le

    on ry ons

    Total sewage sludge production of 2010 was about 9.7 M dry tons

    disposed of at landfills

    Only about 20% of the sludge is further stabilized, of which about 6% is utilized

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    Developed Cities

    - Hon Kon for exam le

    At present, landfilling isthe only means for

    disposal of sewagesludge in Hong Kong.

    Sludge generated fromsewage treatment

    works is transported byvesse s n o aand by trucks (25% intotal) to landfills fordis osal.

    About 250 dry tons ofsludge is currently

    daily.

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    -

    Emission of greenhouse gases e.g. CH4

    Emission of odour (strong for raw sludge)

    High moisture content (70-80%), affecting landfill stability

    Occupying landfill space

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    Developed Countries

    50%

    2001

    40%

    2002

    2003

    2004

    30%2006

    20%

    10%

    0%

    Land recycled Landfill Compost Incineration

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    Developed Countries

    - . .

    Year Land Application Landfilling Incineration

    Class A Class B Raw Raw

    1998 13% 48% 19% 20%

    2002 18% 40% 25% 17%

    2004* 23% 34% 23% 20%

    Class A processing has been increasing

    Class B land a lication has been decreasin

    Incineration and landfill disposal of raw sludge remaineconomical solutions for some regions

    *

    10

    ,

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    Drivers for New Sludge

    Management Practices

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    Trends in Sludge Management

    - Slud e reco nized as resource and utilization isa trend:

    - Nutrient: land application & fertilizer- Energy: heat and/or power

    - erna ve ue o n us r es

    - Also, technology advancements

    Sludge to Products

    Sludge to FertilizerMethodBenefits

    12

    Sustainability

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    Carbon Footprint Distribution

    -

    Process Transport, Other,1%,

    17%

    Electricity,77%

    Pumping+

    Aeration

    Biosolids influences all of these parameters

    UK Water industry > 5 million tonnes CO2e

    Only the power industry emits more carbon footprint

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    Energy

    - Energy Inflation Oil in excess of $100/barrel 20

    40

    60

    80

    100

    120

    OilPrice[$/barrel]

    Electricity up by a third between 2003 2010

    Gas rice doubled in same eriod

    0

    1998 200 0 200 2 2004 2006 2008 2 010 2012

    High volatility

    -Technolo which consumes lar equantities of energy will be exposed Drying, incineration, treatment without

    di estion

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    Energy

    - Energy Security UK has become net importer of

    1968

    Russia switching off supplies toUkraine

    - Fertilizer costs closely linkedwith energy prices

    Fertiliser Prices

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    Phosphorous

    -

    emand

    Becoming urbanized Changing food habits

    D

    .tonnes in 3 years (equivalent to USAconsumption)

    - Peak P predicted at 2035?

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    Phosphorous- Biosolids is a good source of phosphorousand nitrogen

    1 tonne dr solids contains a roximatel 30 k P and 120 k N

    Currently worth $50/t

    - Thermal destruction does not recover this resource

    - Recycling of sludge to land

    Or recovery techniques Struvite (Magnesium ammonium phosphate MgNH4PO4.6H2O),

    good slow release fertilizer,

    Main technology involves addition of magnesium oxide

    Full-scale since 2006 Extraction (e.g. super critical wet air oxidation, SCWAO)

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    u r en or an pp ca on

    - More restrictive environmental regulations,Class A

    - u c percep on oppos on

    - Marketable end-products- Long-term issues:

    a ogen regrow

    Contaminants of concern

    Energy from Sludge- Rising energy costs

    - A promising option to reduce GHGemission, renewable incentives

    -

    - Using advanced digestion to increasebiogas production

    - Co-digestion

    - Closure to energy intensive facilities

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    Technologies

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    Raw Sludge (Thickened)

    DewateringDewatering Dewatering

    AnaerobicDigestion

    AnaerobicDigestion

    Dewatering

    TreatmentComposting

    Dewatering

    Drying Composting

    Stabilized and Sterilized Sludge for Land Application

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    Raw Sludge (Thickened)

    Dewatering Dewatering DewateringDewatering

    HeatDrying

    ThermalHydrolysis

    AnaerobicDigestion

    IncinerationAnaerobicDigestion

    HeatDrying

    Pyrolysis/Gasification

    HeatDrying

    Dewatering

    Dewatering

    Heat Recovery, Biogas or Alternative Fuel for Power Generation

    Residual Disposed to Landfill or Land Application

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    Option 1 Raw Incineration

    Thermal Hydrolysis

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    v v . v

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    Gasification

    Operation: 700-1000oC

    condition Converting carbon to

    Syngas

    Flue gas

    syngas, nc u ng , 2and CH4high energy

    recovery efficiency Limited installations, mainly

    located in Germany, Japanand Switzerland

    AirBottom ash

    High cost

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    Considerations in

    Selection of Technology

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    What are

    What areFeasible SludgeApplications?

    the ProjectObjectives?

    reatmentPractices?

    What is the

    Current

    RecommendSludge

    Management

    Situation? Strategy

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    What should be considered inthe Development of a Sludge

    as er an

    us a na eSludge Master

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    disposal- Study for PRC (for example)

    TR Identification: 9 core treatment technologies with 15 TRs

    1) landfilling of partially dried sludge

    2) anaerobic digestion (AD) + utilization of biogas and digested sludge

    3) thermal hydrolysis pre-treatment (THP) + AD + biogas and digested

    sludge utilizationme sta zat on + an app ca on

    5) incineration + heat recovery

    6) thermal drying + pellets applied to land

    8) thermal drying + substitution of coal in cement kilns/ power plants

    9) composting of dewatered sludge

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    1 Landfilling of partially dried sludge

    a without LFG recoveryTR: Thickenin + Dewaterin 80% MC + Heat Dr in 60% MC + Landfill

    b with LFG recoveryTR: Thickening + Dewatering (80% MC) + Heat Drying (60% MC) + Landfill

    2 Anaerobic di estion (AD) with bio as recover and di ested slud e

    a applied to landTR: Thickening + AD (Biogas Recovery) + Dewatering (80% MC) + Land

    Application

    b composted and applied to landTR: Thickening + AD (Biogas Recovery) + Dewatering (80% MC) + Composting +Land Application

    TR: Thickening + AD (Biogas Recovery) + Dewatering (80% MC) + Landfill

    d to landfill without LFG recoveryTR: Thickening + AD (Biogas Recovery) + Dewatering (80% MC) + Landfill

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    3 Thermal hydrolysis pretreatment (THP) followed by AD with biogas recoveryand digested sludge

    a applied to land TR: Thickening + Dewatering (84% MC) + THP + AD (BiogasRecovery) + Dewatering (80% MC) + Land Application

    b heat dried as coal substitute for cement kiln or power stationTR: Thickening + Dewatering (84% MC) + THP + AD (Biogas Recovery) +

    4 Lime stabilization, application of stabilized sludge to land

    TR: Thickening + Dewatering (80% MC) + Lime Treatment (65% MC) + LandApplication

    5 Incineration with heat recovery

    Disposal

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    6 Heat drying of sludge with pellets applied to land

    TR: Thickening + Dewatering (80% MC) + Heat Drying (40% or 65% MC) + Landpp ca on

    7 Heat drying of sludge with pellets applied to land

    TR: Thickenin + Dewaterin 80% MC + Heat Dr in 10% MC + Gasification(Syngas) + Tar/Ash for Disposal

    8 Heat drying of sludge used as coal substitute in cement kiln or power station

    : c en ng + ewa er ng + ea ry ng + oa u s u e

    9 Composting of dewatered sludge with sludge compost applied to land

    TR: Thickening + Dewatering (80% MC) + Composting + Land Application

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    disposal- Study for PRC (for example)

    Assessment and comparison of TRs based on the followingframework

    Criteria Sub-criteria

    EngineeringFeasibility

    Flexibility; compatibility; reliability; side-stream effects; trackrecords; implementation feasibility; occupational safety.

    nv ronmen aEfficiency

    omp ance w oca env ronmen a sc arge s an ar s;potential for beneficial sludge utilization (resource recovery);risk of secondary pollution; carbon footprint (CFP)

    Acceptance

    -

    customers; nearby communities; general public

    Financial Life-cycle costs; capital investment; O&M costs; financing and

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    Estimation of the relative carbon footprint (CFP) of the 15 TRs:- UK Water Industry Research (UKWIR) and its Carbon Accounting

    or oo s w up a es

    - Primary greenhouse gas (GHG) - carbon dioxide, methane and nitrousoxide

    - 2 p.a.)

    - Relative CFP assessment of different TRs based on the followingassumptions:

    Population served: 250,000 to 300,000 persons Wastewater treated: approximately 100,000 m3per day

    Dewatered sludge cake produced: 80 wet tons per day (80% MC)

    Total annual production of sludge: 5,840 tons dry solids

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    Carbon Footprint Assessment

    1,2951,295

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    Carbon Footprint Assessment

    TRs 2a, 2b, 2c, 3a, 3b and 8

    -Low CFP with energy recovery

    - c eve, or are c ose o ac ev ng, car on neu ra y

    -Energy recovery in sludge processing as a means of reducing CFPTRs 1b, 2d, 4, 5, 7, and 9

    - e um , some s w t ow cap ta cost

    -Results are sensitive to the assumptions made and particular local circumstances

    TRs 1a, 6a and 6b- g ue to energy- ntens ve ry ng process w t no energy recovery , or t rougfugitive emissions from landfill gas

    Summary

    -The wide range of CFPs suggests that CFP is a key factor in selecting sludge TRs

    -CFP results for a given TR will vary due to local factors - a project by project basiswith assum tions and values ad usted to the local situation

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    2 Anaerobic digestion with biogas recovery and digested sludge

    2a applied to land

    TR: Thickening + Anaerobic Digestion (Biogas Recovery) + Dewatering (80% MC)+ Land Application

    - 2-Nutrient and energy recovery

    - Low capital and operation costs

    - AD is a well-developed and common technology used in other

    Weaknesses -Not pathogen and odour-free, restricting land application- Biogas production depends on the organic content of sludge

    - Medium land requirement for sludge treatment

    - s requ rement or operat ng an system

    Suggestion -Should be promoted take into account sludge characteristicsand sludge product marketability

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    2 Anaerobic digestion with biogas recovery and digested sludge

    2b composted and applied to land

    TR: Thickening + Anaerobic Digestion (Biogas Recovery) + Dewatering (80% MC)+ Composting + Land Application

    --Compost sludge is usually pathogen and odour-free forunrestricted land application

    -Nutrient and energy recovery

    - Low ca ital and o eration costs- AD and composting are well-developed and common technologiesused in other countries

    Weaknesses -Potential odour concern-

    - High land requirement for sludge treatment- Skills requirement for operating an AD system

    Suggestion -Should be promoted; take into account sludge characteristics

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    3 Thermal hydrolysis pretreatment (THP) followed by Anaerobic

    3a applied to landTR: Thickening + Dewatering (84% MC) + THP + Anaerobic Digestion (BiogasRecovery) + Dewatering (80% MC) + Land Application

    Strengths -Near carbon neutralityCO2e: 211tons/yr-Enhanced nutrient and energy recovery- Pathogen and odour-free product for unrestricted land application

    - Lower land requirement- e um cap ta an operat on costs

    Weaknesses -THP is a proprietary process with limited vendors and itsperformance under the conditions of the PRC will be subject forreview.

    - Requires specially trained staff for operationSuggestion -Should be promoted consider sludge characteristics, financial

    capability, and sludge product marketability.

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    3 Thermal hydrolysis pretreatment (THP) followed by Anaerobic

    3b heat dried as coal substitute for cement kiln or power stationTR: Thickening + Dewatering (84% MC) + THP + Anaerobic Digestion (BiogasRecovery) + Dewatering (80% MC) + Heat Drying (10% MC) + Coal Substitute

    Strengths - At carbon neutrality (CO2e: -543tons/yr- Enhanced nutrient and energy recovery- Pathogen and odour-free product, wider application

    - Feasibility depends on the reliability of product users-

    Weaknesses - THP is a proprietary process with limited vendors and itsperformance under the conditions of the PRC will be subject toreview.

    - .

    Suggestion - Suitable for large cities with strong financial capability and with acement kiln or power station nearby for utilization

    - Not recommended for small and medium-sized cities

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    8 Heat drying of sludge used as coal substitute in cement kiln or power

    TR: Thickening + Dewatering (80% MC) + Heat Drying (10% MC) + Coal Substitute

    Strengths - Near carbon neutrality (CO2e: 1,295tons/yr-Small land requirement for sludge treatment-Relative low capital cost compared to other energy recovery options

    Weaknesses -High operation cost-Feasibility depends on the reliability of product users

    Suggestion -Suitable for cities with limited available land for beneficial uses andwith cement kiln or power station nearby

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    Case StudCase Stud -- Hon Kon Slud e Mana ement PracticeHon Kon Slud e Mana ement Practice

    Sludge quantity: will increase from about 900 wet tpd in 2010 to 1,500 wet

    tpd in 2014/2015

    Current practice: landfilling

    Practice after 2013:

    with heat recovery

    DBO contract

    Under construction nc u e n sewage c arge

    Community facilities e.g. SPA

    About 260,000 tonnes

    GHG reduction per year

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    Conclusions

    Conclusion

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    Conclusion

    n eve op ng oun r es

    1)Drivers for a modern approach to sludge management:

    - rapidly increasing sludge production due to stricter legislation, populationncrease, more ur an za on

    - growing scarcity of landfill resources- Energy is becoming increasingly expensive

    - ,

    - Advanced digestion processes especially thermal hydrolysis

    - Alternative uses for biogas

    -

    2)Sludge management developed in line with government policy:

    - Sustainable means for utilization or disposal

    - orrespon ng s

    - Recovery of resources and energy

    - Low carbon solutions

    Conclusion

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    Conclusion

    e ec on.

    1)Where land application is viable, sludge utilization is likely to give the best balance ofenvironmental benefit and cost. Most of the TRs for land application are with AD as

    .

    2)Thermal hydrolysis is becoming more popular to enhance the performance of thedownstream processes for energy recovery or dewaterability

    ,explored

    4)Where landfilling is necessary, pre-treatment should precede the landfilling process for

    energy recovery and volume reduction. But, landfill cost is rising sharply in developedcountries and these trends will quite likely happen in developing countries too.

    Conclusion

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    Conclusion

    e ec on.

    1)No one solution fits all

    2)CFP a key factor in selecting TRs

    -Low CFP: options with energy recovery

    -High CFP: options involving thermal drying without energy recovery, or landfilling withoutlandfill gas management/ utilization

    3)Other factors: land, sludge volume and quality, financial and technical capacities, qualityassurance and public acceptance

    Increase awareness of the benefits of sludge utilization and adoption of low carbonsolutions

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    Thank You

    Contact:c o. eong aecom.com