biosolids management feasibility study for city of wyoming clean

Biosolids Management Feasibility Study for

City of Wyoming Clean Water Plant

Team 7: Blackwards

Eyosias Ashenafi, Rachel Gaide, Andrew Mitchell, and Katherine Vogel

Engineering 339: Senior Design Project

Calvin College

December 2013.

© 2013 Team 7 and Calvin College

(Eyosias Ashenafi, Rachel Gaide, Andrew Mitchell, and Katherine Vogel)

Executive Summary This project is focused on designing an anaerobic digester (AD) for biosolids produced

by City of Wyoming Clean Water Plant (CWP). The City of Wyoming and the City of Grand

Rapids partnered to form the Grand Valley Regional Biosolids Authority (GVRBA) to address

strict regulations and implement a better and more efficient biosolids management. However,

this design regards only the City of Wyoming’s biosolids flows.

The team decided to use an anaerobic digester as a method for stabilization. This choice

was made over chemical and aerobic options based on many factors. Some of the key requests of

the client were to achieve a Class A product, to use a newer technology, and to explore nutrient

recovery options. The anaerobic digester is a newer technology that enables the plant to produce

Class A product.

Thickening was then explored in order to decrease flow volume and therefore decrease

digester costs. Thickening options include centrifuges, rotary drums, belt presses, and CAMBI.

Centrifuges were determined to be the best alternative because there are currently two units in

practice that can be utilized in the proposed new process.

After the anaerobic digester was selected as the stabilization option, the need for

dewatering was evaluated. It was decided that for ease of transportation, a dewatering step was

needed. The methods for dewatering were the same as those for thickening, without the benefit

of having two on site. Despite this, centrifuges still proved to be the best option for the plant.

The team plans to build a bench scale model in the spring semester, analyze those results,

and optimize a few key variables. The optimization will be for the production of methane and for

a Class A product coming out of the digester. With these variables, the anaerobic tank’s efficacy

can be determined. The team also plans to look into potential ways to capture the nutrients lost in

this process.

The team will produce the site plan for the proposed project. This site plan will address

all of the space constraints for the digesters and additional thickening and dewatering units. This

site plan will also provide details on the constraints of operation throughout the year. Post

treatment storage must be able to store all of the biosolids that cannot be land applied due to

seasonal constraint. Initial cost estimate for incorporating an anaerobic digester at Wyoming is

$1.75 million for equipment.

Table of Contents

Executive Summary ....................................................................................................................................... i

Table of Figures ........................................................................................................................................... iv

Report Tables ............................................................................................................................................... iv

Abbreviations ................................................................................................................................................ v

1. Introduction ............................................................................................................................................... 1

1.1 Purpose Statement ............................................................................................................................... 1

1.2 The Project .......................................................................................................................................... 1

1.3 Overview of Wastewater Treatment ................................................................................................... 1

1.4 Overview of Biosolids Classification ................................................................................................. 2

2. The Client.................................................................................................................................................. 3

2.1 City of Wyoming ................................................................................................................................ 3

2.2 Wyoming Clean Water Plant .............................................................................................................. 3

2.2.1 Overview .......................................................................................................................................... 3

2.2.2 Current Waste Water Treatment Practices ....................................................................................... 3

2.2.3 Current Biosolids Management ....................................................................................................... 4

3. Design Considerations .............................................................................................................................. 5

3.1 Class A Status ..................................................................................................................................... 5

3.2 Energy Capture and Environmental Concerns .................................................................................... 6

3.3 Adherence to Government Regulations .............................................................................................. 6

3.4 Effect on Water Treatment .................................................................................................................. 6

3.5 Nutrient Capture .................................................................................................................................. 6

4. Flows and Loads ....................................................................................................................................... 6

5. Thickening / Dewatering Design .............................................................................................................. 8

5.1 Overview of Thickening / Dewatering Alternatives ........................................................................... 8

5.2 Thickening / Dewatering Alternatives Design Matrix ........................................................................ 9

6. Stabilization Design ................................................................................................................................ 10

6.1 Type of Stabilization ......................................................................................................................... 10

6.2 Class A Requirements ....................................................................................................................... 11

6.3 Anaerobic Digestion Operating Temperature ................................................................................... 13

6.4 Tank Design ...................................................................................................................................... 14

6.5 Methane Production .......................................................................................................................... 14

6.6 Proposed Biosolids Management ...................................................................................................... 14

6.6 Cost Analysis .................................................................................................................................... 15

7. Storage Needs ......................................................................................................................................... 16

8. Bench Scale Model ................................................................................................................................. 16

8.1 Construction of Model ...................................................................................................................... 16

8.2 Testing of Model ............................................................................................................................... 17

8.2.1 Methods ...................................................................................................................................... 18

8.3 Optimization of Model ...................................................................................................................... 19

9. Project Management ............................................................................................................................... 20

9.1 Team Description .............................................................................................................................. 20

9.2 Schedule ............................................................................................................................................ 20

10. Future Work to Be Completed .............................................................................................................. 20

Acknowledgements ..................................................................................................................................... 20

References ................................................................................................................................................... 21

Bibliography ............................................................................................................................................... 22

Appendix A: List of Design Projects Considered ....................................................................................... 24

Appendix B: Work Breakdown Schedule ................................................................................................... 25

Appendix C: Formatted Selections from Clean Water Act Part 503 .......................................................... 26

Appendix D: Anaerobic Digestion Design Calculations ............................................................................ 34

Table of Figures

Figure 1: Layout of a Conventional Wastewater Treatment System .............................................. 1

Figure 2: Aerial View of Wyoming CWP ...................................................................................... 3

Figure 3: Current Wastewater Treatment at Wyoming CWP ......................................................... 4

Figure 4: Current Biosolids Management at Wyoming CWP ........................................................ 5

Figure 5: Proposed Schematic of Biosolids Management ............................................................ 15

Figure 6: Cost Curve for Installing CHP Anaerobic Biodigestor ................................................. 15

Figure 7: Bench Scale Model Diagram ......................................................................................... 16

Report Tables

Table 1: Sludge Characteristics..................................................................................................................... 5

Table 2: Design Specifications ..................................................................................................................... 7

Table 3: Biosolids Flow Predictions ............................................................................................................. 8

Table 4: Thickening Design Matrix .............................................................................................................. 9

Table 6: Stabilization Design Matrix .......................................................................................................... 10

Table 6: EPA CWA Pollutant Limits .......................................................................................................... 13

Table 7: Digester Operating Temperature Characteristics .......................................................................... 14

Table 8: Current Storage Capabilities ......................................................................................................... 16

Table 9: Parameters Analyzed from Manure Samples ................................................................................ 17

Table 10: Bench Scale Optimization Variables .......................................................................................... 19

Abbreviations

AD Anaerobic Digestion

BOD Biological Oxygen Demand

°C degrees Celsius

CHP Combined Heat and Power

COD Chemical Oxygen Demand

CWA Clean Water Act

CWP Clean Water Plant

DAF Dissolved Air Floatation

EPA Environmental Protection Agency

EQ Exceptional Quality

gpm gallons per minute

GVRBA Grand Valley Regional Biosolids Authority

kg kilogram

lb/day pounds mass per day

m3/day cubic meters per day

mg milligram

mgd million gallons per day

MPN Most Probable Number

NPDES National Pollutant Discharge Elimination System

PS Primary Sludge

THP Thermal Hydrolysis Process

TPAD Temperature Phase Anaerobic Digestion

TSS Total Suspended Solids

tWAS Thickened Waste Activated Sludge

UV Ultraviolet

VAR Vector Attraction Reduction

VS Volatile Solids

WAS Waste Activated Sludge

WWTP Wastewater Treatment Plant

WWTPs Wastewater Treatment Plants

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1. Introduction

1.1 Purpose Statement The purpose of this project is to design a modern, efficient and environmentally friendly

biosolids management system for the City of Wyoming Clean Water Plant (CWP). This

document will elaborate on the preliminary design process and future work to be completed.

1.2 The Project The City of Wyoming Clean Water Plant was built to handle waste water from the

surrounding area. In 2003, the Grand Valley Regional Biosolids Authority (GVRBA) was

created to manage the combined biosolids flow from both the CWP and the Grand Rapids Waste

Water Treatment Plant (WWTP). Calvin College’s Engineering Program has all seniors

complete a year-long senior design project. As part of the class associated with this project, the

design team was formed and pursued appropriate project alternatives considering the previous

studies of the team members. Dr. David Wunder, the team’s faculty advisor, suggested that the

team approach the City of Wyoming CWP for potential design projects. The team then met with

Myron Erickson, Superintendent of the CWP, and with Aaron Vis, GVRBA Project Manager.

During the meeting, the team was informed that GVRBA was currently collecting bids from

consulting firms regarding potential stabilization alternatives to current. Upon further consulting

with Myron Erickson, the team decided to design an anaerobic digester for biosolids

management for the City of Wyoming.

1.3 Overview of Wastewater Treatment In general, municipal wastewater is collected from residential areas, businesses and

industries, and pumped to wastewater treatment plants (WWTPs). Conventional treatment

systems have four major stages (Figure 1).

Figure 1: Layout of a Conventional Wastewater Treatment System

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I) Preliminary Treatment is the first step in wastewater treatment. Rags and floatables

present in influent stream are physically removed using bar screens by size exclusion.

This stages increases downstream load capacity while preventing damage to pumping

equipment

II) Primary Treatment is the second stage which removes sediments by a gravity

settling and skimmers. Sludge is allowed to settle inside a primary clarifier. Skimmers

remove suspended solids and grease material on the top surface.

III) Secondary Treatment is a biological treatment with an aeration and settling stage. It

is commonly referred to as activated sludge. During aeration, microbes feed on

organic matter inside a circular tank fitted with air diffusers. After a certain period of

time, the waste stream is sent to a secondary clarifier. Sludge settles inside the

clarifier. Some portion of the sludge produced is recycled back to the aeration tank to

maintain microbial growth while the remaining is sent for further treatment.

IV) Tertiary Treatment (Disinfection) is the final step in wastewater treatment before

supernatant or treated effluent is sent to water bodies. Common disinfection schemes

include chlorination, ozonation, and Ultraviolet (UV) radiation.

Several variables are considered in the design and construction of WWTPs including

operating capacity and regulations. Population growth and industrial expansion is accounted for

in determination of design flow. Treatment facilities and government agencies assess the quality

of supernatant water and by-product sludge to ensure it meets Environmental Protection Agency

(EPA) and National Pollutant Discharge Elimination System (NPDES) standards.

1.4 Overview of Biosolids Classification Biosolids are residual solids left over after waste water treatment. Treated biosolids can

be classified as either Class A or Class B. Class A Biosolids can also be categorized as

“exceptional quality” (EQ) if they satisfy pollutant concentration limits. Biosolids can be

applied to land, placed on a surface disposal site, or fired in a sewage sludge incinerator.1 In

land application, treated biosolids are used to moisturize the soil and as a fertilizer. “Surface

disposal site” is another name for a landfill. From an environmental perspective, land

application is the best option for final disposal place of treated biosolids.

The end location of the biosolids determines what regulations are applicable from Part

503 of the Clean Water Act (CWA). There are three parts to achieving Class A designation for

biosolids. First, the pathogenic content of the sludge must be reduced sufficiently. Second, there

must be sufficient Vector Attraction Reduction (VAR). Third, inorganic pollutants must be

below certain maximum values. These issues are explained in context more in Section 6.2 Class

A Requirements.

Class A Biosolids, with appropriate pollutant loads, can be land applied to agricultural

and non-agricultural land, public contact sites, a reclamation site, lawns, home gardens. Class A

Biosolids can be given away and it can be sold. Class B Biosolids are restricted regarding where

and when they can be land applied.

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2. The Client

2.1 City of Wyoming The city of Wyoming lies within the Grand Rapids Metro area in western Michigan. It

occupies an area of 24.9 square miles and caters to a population of 73,000 people. The area also

includes several major industries including Gordon Food Services, Michigan Turkey Producers,

Country Fresh, and Keebler Company.

2.2 Wyoming Clean Water Plant

2.2.1 Overview Wyoming’s CWP is located on Ivanrest Avenue on the southwestern edge of Wyoming (

Figure 2). The plant treats wastewater from the city of Wyoming, the city of Kentwood, Gaines

Township, and Byron Township, and has a design capacity of 24 million gallons per day (mgd).

Current average daily flow through the plant is 16 mgd, 12% of which originates from industry

waste. Treated water from the plant discharges into Grand River.

Figure 2: Aerial View of Wyoming CWP

2.2.2 Current Waste Water Treatment Practices Raw wastewater from the City of Wyoming, the City of Kentwood, Byron Township, and

Gaines Township is collected at Wyoming CWP. Bar screens remove large sediments and

materials present in incoming wastewater. The flow proceeds to primary clarifiers where large

granular molecules are removed by gravity sedimentation. Currently, there are four primary

clarifiers with removal rate of 10-40% biological oxygen demand (BOD) and 50-60% total

suspended solids (TSS). Clarified effluent from primary treatment proceeds to one of three

aeration basins. The basins are equipped with fine bubble diffusers to aerate and provide

conducive environment for microbial growth. Mixed liquor is sent periodically to secondary

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clarifiers. Flocculated and dense, suspended solids in mixed liquor settle inside the clarifiers.

Recently, a biological phosphorus removal process (anoxic/anaerobic zone) has been

incorporated into secondary treatment. Six pumps recycle thickened activated sludge to the

aeration basins. Clear low-BOD, low-TSS clarified effluent is chlorinated and de-chlorinated for

disinfection. Finally, treated supernatant is sent to Grand River. An overview of the treatment

process is shown in Figure 3.

Figure 3: Current Wastewater Treatment at Wyoming CWP

2.2.3 Current Biosolids Management Biosolids produced by Wyoming and Grand Rapids WWTPs are currently managed by

the GVRBA. The authority was formed in 2003 to address strict regulatory requirements, and

manage regionally-produced biosolids efficiently.

Sources of biosolids at Wyoming CWP are the primary and secondary clarifiers (Figure

4). On a daily basis, nearly equal amount of primary sludge (PS) and waste activated sludge

(WAS) is pumped to sludge holding tanks. Certain volume of WAS from secondary clarifiers is

thickened using centrifuges. Thickened WAS (tWAS) is stored in one of three wet wells before it

sent to GVRBA pumping station or storage tanks. Solids concentration of PS, un-thickened and

thickened WAS is given in Table 1. To prevent phosphorus release, WAS is thickened to

maximum of 2% total solids (TS), and the wet wells are aerated and treated with ferric chloride.

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Table 1: Sludge Characteristics

Sludge %TS by weight

Primary Sludge 3.5

Un-thickened WAS 0.7

Thickened WAS, max. 2

Currently, 75% of biosolids from Wyoming CWP are stored in three tanks with a

combined capacity of 6 million gallons. The biosolids are then lime stabilized and then used for

farm application. This process is shown in Figure 4. The remaining 25% is pumped to GVRBA

storage tanks in Grand Rapids WWTP through two 3-miles long pipelines. Incoming flow is

combined with biosolids from the City of Grand Rapids WWTP. The resulting flow is

dewatered by centrifuges and stored in a landfill.

Figure 4: Current Biosolids Management at Wyoming CWP

The team has sought out to design a new process with regards to specific goals including

energy and nutrient capture, environmental concerns and government regulations.

3. Design Considerations

3.1 Class A Status Because Class B Biosolids are limited in how often, when and where they can be land

applied, the market results are considerable. If multiple municipalities are competing for land,

this means that demand is high. Since the supply of land available for land application of

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biosolids is limited, it is becoming increasingly difficult for the municipalities to land apply their

biosolids. Because Class A designation increases supply by allowing increased frequency and a

larger application area, attaining Class A will be extremely advantageous to our client. For this

reason, Class A designation is a high priority for this project.

3.2 Energy Capture and Environmental Concerns Biosolids have the potential to generate significant amount of energy. Microbes digest

the biosolids and produce methane as a byproduct. This methane can then be captured and

combusted in a generator to convert the chemical energy into electrical energy. This electrical

energy can be used for on-site processes which lowers the power demand of the CWP.

Flow transported to GVRBA unit in Grand Rapids is landfilled with no stabilization.

This is not an ideal solution in terms of environmental friendliness because it does not capture

the potential energy within the biosolids. Instead the energy is lost into the atmosphere slowly

over time while the physical materials take up space and must be managed to make sure that they

doesn’t affect ground water quality. Energy capture is a major goal of this project.

The biosolids flow handled by the Wyoming CWP are stabilized using lime. This lime

must be mined, processed, and shipped. Anaerobic digestion utilizes microbes for stabilization,

which is a renewable resource. Utilizing renewable resources is a major goal of this project.

3.3 Adherence to Government Regulations Current practice manages the biosolids so that pathogenic content is not released into the

Grand River. Untreated biosolids can contain pathogens such as enteric viruses, fecal coliform,

helminth ova, and salmonella, which cannot be released untreated into a water source per EPA

regulation2. To attain feasibility of this project, government regulations must continue to be met.

3.4 Effect on Water Treatment

Because any water within the biosolids flow is untreated, it must be recycled back into

the water treatment side of the Wyoming CWP. The CWP was not designed to handle this

recycle flow. The team will take into consideration that the chosen design should have minimal

effects on the existing water treatment.

3.5 Nutrient Capture

As per the client’s interests, the team will include in the design a process that will capture

phosphates and nitrates. These nutrients are both a constituent in terms of government

regulations regarding water quality and a valuable resource that can be sold to fertilizer

manufacturers.

4. Flows and Loads The City of Wyoming Clean Water Plant was designed to handle 24 mgd. Because of the

recent recession, the City of Wyoming has not grown as quickly as predicted in 1998. It

currently handles less that the predicted flows at about 16 mgd3. Myron Erickson has expressed

that he would like the team to design for 24 mgd. He also suggested that we should use the

predicted flow quality for 2015 (See Table 2) as the design values.

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Table 2: Design Specifications

Plant Design Criteria 1998

Projected 2015

based on 1998 Parameter

Population 182,886 249,869

Wastewater Flow

Annual 24 hour average, mgd 16 22

Maximum 30 day average, mgd 18 24

Peak flow, mgd - 42

Wastewater Characteristics,

Maximum Month / Annual Average

BOD5, mg/L 340/312 340/312

TSS, mg/L 258/237 258/237

NH3-N, mg/L 17/17 17/17

Organic Nitrogen, mg/L 11/11 11/11

PO4-P, mg/L 9/8 9/8

VSS/TSS Ratio 0.8 0.8

Temperature Range, °C 10 to 23 10 to 23

Plant Design Basis, lb/day

BOD5

Annual Average 41630 57250

Maximum Month 49910 68050

Peak Day/Max Month Ratio 1.5 1.5

TSS



NH3-N




Organic Nitrogen




PO4-P



Primary Clarifer Removal Rates

BOD% 35 30

TSS% 70 60

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It has been suggested that the best way to increase methane input is to separate all

industrial “greasy” flows to avoid dilution and to place those flows directly into the digester.

This is something that the team will potentially test with a bench scale model in the spring if time

allows.

The flow that would be handled by the anaerobic digester is a fraction of the flow that

comes into the plant. The anaerobic digester will handle primary sludge and waste activated

sludge. Table 3 below shows the flow rates for each of these flows. The waste activated sludge

is thickened using on site centrifuges before sending to Grand Rapids for treatment by the

GVRBA. Thickened Waste Activated sludge cannot be combined with Waste Activated Sludge

for a total flow.

Table 3: Biosolids Flow Predictions

Annual Average 2005 2015 2025

Primary Sludge, gpd at 3.5% solids 75,677 89,600 104,516

Thickened Waste Activated Sludge, gpd at 2.0 % solids 105,390 133,742 148,016

Waste Activated Sludge, gpd at 0.7 % solids 301,114 382,118 422,902

Maximum Month

Primary Sludge, gpd at 3.5% solids 89,219 106,866 124,218

Thickened Waste Activated Sludge, gpd at 2.0 % solids 128,490 158,256 174,425

Waste Activated Sludge, gpd at 0.7 % solids 367,113 452,159 498,356

5. Thickening / Dewatering Design

5.1 Overview of Thickening / Dewatering Alternatives

Currently, dewatering at Wyoming CWP is performed with two centrifuges with a

capacity of 265 gallons per minute (gpm) for each unit. Feed stream typically has 0.5-1% solids

concentration, and influent is thickened to 4-5% solids before stabilization. Mannich and

emulsion polymers are used accelerate the process. Existing centrifuge units were considered as

a thickening alternative. Primarily, a thickening step increases tank detention time, reduces

operation costs and lowers capacity demand downstream in biosolids processing and storage.

Wastewater treatment facilities at different municipalities use a variety of approaches to

thicken sludge effluent from primary and secondary clarifiers. Several thickening alternatives

were considered in the design process (Table 4). Cambi’s Thermal Hydrolysis Process (THP) is a

new pre-digestion technology that is becoming popular worldwide. The largest Cambi system is

installed at the Washington D.C. WWTP. San Francisco is another US city that utilizes this

technology.

Two centrifuges are currently used to thicken the biosolids on the Wyoming CWP. Both

centrifuges are 24 years old, however one was rebuilt in 2012 and the other will be rebuilt in

2013. The plant expects another 10 years of use out of the centrifuges.

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5.2 Thickening / Dewatering Alternatives Design Matrix All values were chosen with the understanding that the more attractive the feature, the

higher the score. This leads to values that seem in conflict with categories that describe

weaknesses rather than strengths.

Table 4: Thickening Design Matrix

Category Weights Centrifuge Cambi THP Rotary Drum Belt Press

Sustainability 6 10 4 6 7

Effluent Quality 8 7 10 7 7

Progressive Technology 5 7 10 7 5

Capital Costs 9 10 5 7 7

Operating Cost 10 8 4 8 6

Safety 6 9 6 9 8

Expandability 3 7 5 7 7

Total 47 396 290 345 315

Category Considerations:

1. Sustainability: How much energy is required to operate this technology? What form of

energy is used and how is it produced? How much equipment is already owned by the

client and can be reused for this project? Does this technology require nonrenewable

resources in order to function? How efficient is the technology at completing the required

process?

2. Effluent Quality: Does this technology affect the amount of methane produced? Does this

technology make achieving Class A easier/possible?

3. Progressive Technology: Would the novelty of this technology improve public image of

the facility?

4. Capital Costs: How much does the equipment cost to obtain? How much will it cost to

install? How much time will it take employees to train on using the new equipment?

5. Operating Costs: How much does the technology cost to operate each month?

6. Safety: Is the technology difficult to operate or does the technology utilize conditions that

could cause employee injury during machine malfunction?

7. Expandability: Assuming that the future will require increased production can this

technology be expanded easily?

Explanation of Scores:

- Cambi Process: The Cambi process heats the influent for 40 minutes. This process is

costly for both the heat and the equipment to achieve this incurring the low scores in

capital and operating costs. The Cambi process increases the potential methane

production and makes Class A designation easier to achieve which is why it has greater

score in the categories of sustainability and capital costs. This technology is just

beginning to emerge into the market as a proven operation which is why it has a high

score for the progressive technology category4.

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- Rotary Drum: The rotary drum operates very similar to the centrifuge with one major

difference. There are no rotary drums currently on the site and thus this would make the

capital cost for the drum much higher than that of the centrifuge.

- Belt Press: The operation prices for the belt press are slightly more than that of the

centrifuge or the rotary drum. Belt presses have been used in industry for over a century,

thus the low score in progressive technology. Other than these slight difference, a belt

press also requires more space than the rotary drum or the centrifuges.

- Centrifuge: The centrifuge yields a higher score in capital costs and sustainability

because there are already two centrifuges on site that could be used for this project. The

centrifuge does not make Class A designation more likely nor does it make it

automatically achievable. It does allow for some expansion as the addition of another

centrifuge would be possible with the provided space.

6. Stabilization Design

6.1 Type of Stabilization

All values are chosen with the understanding that the more attractive the feature, the

higher the score. This leads to values that seem in conflict with categories that describe

weaknesses rather than strengths. Table 5 shows the design matrix for stabilization.

Table 5: Stabilization Design Matrix

Category Weight Chemical Anaerobic Aerobic

Capital Cost 8 9 5 7

Operating Cost 7 7 3 7

Progressive Technology 6 2 8 6

Sustainability 6 2 10 7

Reliability 6 7 8 8

Design Life 7 6 8 8

Effluent Quality 10 0 10 2

Effect on Plant 3 10 4 10

Potential Energy Production 9 0 10 0

Total 62 259 475 337

Category Considerations:

1. Capital Costs: How much does the equipment cost to obtain? How much will it cost to

install? How much time will it take employees to train on using the new equipment?

2. Operating Costs: How much does the technology cost to operate each month?

3. Progressive Technology: Would the novelty of this technology improve public image of

the facility?

4. Sustainability: How much energy is required to operate this technology? What form of

energy is used and how is it produced? How much equipment is already owned by the

client and can be reused for this project? Does this technology require nonrenewable

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resources in order to function? How efficient is the technology at completing the required

process?

5. Reliability: Does this technology depend on operator input for changes in feed flow?

Does this technology produce a product that is consistent over time?

6. Design life: How often will this technology need to be replaced?

7. Effluent Quality: Does this technology affect the amount of methane produced? Does this

technology make achieving Class A easier/possible?

8. Effect on Plant: If the effluent water is recycled into the plant, will the composition of the

stream cause the water treatment process to be less effective?

9. Potential Energy Production: Will this technology result in methane production?

Explanation of Scores:

- Lime Stabilization: Lime is corrosive which makes its plant life a little less than that of the

other stabilization options. Lime has to be mined and therefore is a limited resource which

contributes to the low score in the sustainability. The other huge drawback of lime

stabilization is the safety hazards that it presents. It is a caustic chemical with severe health

risks when in direct contact of the skin. Lime would not allow a Class A product to be

achieved with reasonable operating procedures. Lime is not a new technology as it has been

around for over a century. For comparison on a cost scale, lime is difficult to accurately

represent as the cost varies a great deal.

- Aerobic Digestion: For aerobic digestion, there are a few factors that must be considered.

This process does not allow for the product to be Class A. Aerobic digestion is sustainable in

the sense that it does not use limited resources to purify the product, but it is also wasting a

perfectly good energy source with the methane that gets buried in a landfill. Operation costs

for the aerobic digestion are fairly inexpensive as heating is limited.

- Anaerobic Digestion: The capital cost for the anaerobic digester is much greater than that of

the aerobic digester because of the additional thickening and dewatering stages that must be

included in the process. The operating costs are greater because of the heating required for

the digester as well as the operating costs for the thickening and dewatering units. Anaerobic

digesters are the newest proven technology in the municipal waste treatment industry. This is

also the best option in terms of sustainability because not only are limited resources such as

lime not implemented, the methane is utilized providing green energy from what was once

greenhouse gas emissions. This gas can also be used on site to become a self-sustaining

plant. Anaerobic digestion also has the capability to make the effluent quality that of a Class

A product. This is a very factor because this is something that the customer has specified that

would need to result, if a change in current practice were to be implemented.

6.2 Class A Requirements In order to obtain Class A designation for the end product of the anaerobic digester, three

requirements must be met. First, the biosolids must have satisfactory pathogen content

reduction. There are six alternatives for meeting pathogen content reduction. The anaerobic

digestion shown below meets Alternative 1. This involves two parts. First, either the biosolids

must have a fecal coliform level less than 1000 Most Probable Number (MPN) per gram of total

solids or the biosolids must have a salmonella level less than three MPN per four grams of total

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solids. Research has shown that this level can be achieved using a thermophilic anaerobic

digester 5. Second, the time and temperature of the stabilization must meet one of four options.

Influent total solids levels of 5.8% means that this design must meet option D. The equation

shown below describes the relationship between temperature and minimum residence time for

this regulation.6

𝐷 =50,070,000

100.1400𝑡

In this equation, t stands for temperature in degrees Celsius (C) and D is residence time in days.

Since a thermophilic digester operates at a temperature of 55° C, this equation shows that our

residence time must be at least one day. The residence time chosen was 10 days; therefore this

constraint has been met.

The second requirement for Class A designation is Vector Attraction Reduction (VAR).

In layman’s terms, this means that the biosolids must not have enough energy to support large

populations of new microbes. There are 8 alternatives for meeting vector attraction reduction.

This design meets option 1, which reads as follows:

The mass of volatile solids in the sewage sludge shall be reduced by a minimum of 38

percent. (see calculation procedures in “Environmental Regulations and Technology—

Control of Pathogens and Vector Attraction in Sewage Sludge”, EPA–625/R–92/013,

1992, U.S. Environmental Protection Agency, Cincinnati, Ohio 45268).

Research has shown that VSS reduction for thermophilic anaerobic digesters is usually between

40 and 60% which meets this requirement7.

The third requirement for Class A designation is meeting pollutant restrictions. For this

requirement, the end location of the biosolids determines what regulation applies. All land

applied biosolids must be at or below the values shown in column 1 of Table 6. In addition, any

biosolids applied to agricultural land, forest, public contact sites, or reclamation sites must either

have a cumulative pollutant loading rate less than column 2 or must have a point concentration

less than column 3. Any biosolids sold or given away in a bag or another container for land

application must either have concentrations less than column 3 or must have a total annual

loading rate less than column 4.

13

Table 6: EPA CWA Pollutant Limits

Pollutant Ceiling

Concentration

(mg/kg)

Cumulative

pollutant

loading rate

(kg / hectare)

Monthly

average

concentration

(mg/kg)

Annual pollutant

loading rate

(kg / hectare / 365

day)

Arsenic 75 41 41 2

Cadmium 85 39 39 1.9

Copper 4300 1500 1500 75

Lead 840 300 300 15

Mercury 57 17 173 0.85

Molybdenum 75 n/a n/a n/a

Nickel 420 420 420 21

Selenium 100 100 100 5

Zinc 7500 2800 2800 140

Anaerobic digestion cannot purify the biosolids to the specified levels. For this reason,

extra treatment will need to be added to the system before it is de-watered. The method of

elimination will be looked into in the final report because this system is dependent on the

potential nutrient recovery system that the team selects.

6.3 Anaerobic Digestion Operating Temperature Anaerobic digestion can function at two different general operating

temperatures. Mesophilic and thermophilic which operate at 35°C and 55°C respectively. With

the differences in operating temperature come advantages and disadvantages. A big advantage

with mesophilic operation temperatures is the ease of operation. The mesophilic range does not

require nearly as much attention to operating details as the thermophilic range. However, this

comes at a price of needing nearly twice the tank space due to twice the hydraulic residence time

(20 days). The hydraulic time is longer because of the time it takes for the microbes to mature

and digest the material. The heating costs for mesophilic is not as high as thermophilic due to

lower heating temperatures but construction costs are much higher. With this process it is not

possible to reach Class A pathogen level.

Another option for anaerobic digestion is to get the reach the thermophilic temperature

range which is 55°C. This high temperature range makes for relatively high heating costs.

However, the tank volume is nearly half of that required for mesophilic digestion which lowers

construction costs considerably. Reaching the thermophilic temperature range also allows the

effluent to reach a Class A pathogen level. Another interesting fact about thermophilic design is

the tanks are commonly buried because of the geothermal temperature gradient allows for lower

heating costs.

Temperature phase anaerobic digestion (TPAD) is the combination of thermophilic and

mesophilic anaerobic digestion. This includes ranging and the solid residence times to find the

combination that fits the load into the digester. This process is the most effective and efficient

with space. TPAD systems have been proven to have better performance in volatile solids (VS)

destruction and gas production. This is a great alternative, however it is very costly due to

14

multiple tanks and because this system requires more operator attention. A summary of the

different operating temperature options is presented in Table 7.

Table 7: Digester Operating Temperature Characteristics

Category Mesophilic Thermophilic TPAD

Operating Temperature 35 ° C 55 ° C both

Energy Costs lowest highest middle

Residence Time highest lowest middle

Class B A both

6.4 Tank Design

An anaerobic digester in the thermophilic region was chosen through the design matrix

because of the Class A quality of the effluent stream as well as the construction costs will be

much less. The design of the digester started with considering redundancy and capacity. After

researching common practice, it was decided that the average month loads should be shared

between two digesters of the same size. For redundancy and capacity there will be a third

digester of the same size, which will then allow for max month loads to be handled by all three

digesters. For peak days, the storage tanks preceding the digesters will contain the exceeding

flows so the digesters will not have to continually turn on and off. Also, when the digesters are

running at relatively constant volumetric flow rates, the digester offline will be able to be

repaired if needed. In order to find the necessary tank volumes, the design flows and loads for

average month as well as hydraulic residence time was found. Each of the three tanks necessary

for this design has a volume of 66,000 ft3 with a radius and height of 27.6 ft. For heat transfer

and insulation reasons, it was decided to bury the ¾ of the digesters. The radius and height are

equal due to ideal heating conditions as well as ease of burial. All calculations can be found in

Appendix D.

6.5 Methane Production

The loads of the influent stream were found and documented in Table 2. These loads

were used in an anaerobic biomass equation to find the pounds of biomass produced per day. The

biomass produced was used to calculate the volume of methane produced which is 1,540 cubic

meters per day (m3/day). Then looking at past prices for raw methane, the approximate revenue

of the methane produced from average month loads is $153 per day.

6.6 Proposed Biosolids Management

Based on preliminary results, the team proposes implementing a biosolids management

scheme indicated in Figure 5. Detailed analysis, site layout and product recommendations will be

produced in the final report.

15

Figure 5: Proposed Schematic of Biosolids Management

6.6 Cost Analysis

According to the sizing and system requirements, the team performed cost analysis for

implementing an anaerobic digester at Wyoming CWP. Cost curve plot for implementing an

anaerobic digesters (with cogeneration) at WWTPs in the US was simulated (Figure 6). Based

on the curve, it will cost Wyoming CWP an estimated $1.75 million.

Figure 6: Cost Curve for Installing CHP Anaerobic Biodigestor

y = 62810x + 179799R² = 0.7778

$0

$500,000

$1,000,000

$1,500,000

$2,000,000

$2,500,000

0 5 10 15 20 25 30

Tota

l In

stal

led

Co

st

Plant Design Capacity (MGD)

Constructed Digesters

Proposed Digester

Linear (ConstructedDigesters)

16

7. Storage Needs Three biosolids storage tanks currently exist at the Wyoming CWP. All three biosolid

storage tanks are in good shape. The two southern biosolid storage tanks were built in the late

1980’s. Each has mixers and flat covers that were added in the late 1990’s. Each of these tanks

have a capacity of 1.9 million gallons. The northern biosolid storage tank was built in the early

2000’s. It has been suggested that we use this northern storage tank as a digester. The northern

biosolids tank has a capacity of 2.2 million gallons. These three tanks give us a combined

storage capacity of 6 million gallons. Specification for these tanks are shown in Table 8.

Table 8: Current Storage Capabilities

Tank

Number Year Built

Year Cover

and Mixer

Added

Capacity

[million

gallons]

1 late 1980's late 1990's 1.9

2 late 1980's late 1990's 1.9

3 early 2000's n/a 2.2

Total n/a n/a 6

8. Bench Scale Model

8.1 Construction of Model

Figure 7: Bench Scale Model Diagram

17

The team will build a bench scale prototype in January that will model the anaerobic

digester. The sludge will come from the CWP weekly to provide an accurate measurement of the

energy that can be extracted from their waste. The team will be unable to provide an accurate

representation of the digester that was determined to be the optimal for design for the plant.

However, the planned model will provide similar results on the bench scale level. The team will

use a semi-batch reactor opposed to the proposed continuous flow reactor because of the limited

space to store the influent and effluent. As depicted in the figure below, the feed tank will be a

40 gallon drum that will also function as a gravity thickener. The thickened waste will be

removed from the 40 gallon drum to a 5 gallon bucket. This bucket will serve as the heat

exchanger. The bucket will sit in a hot water bath. This bath will also include the digester. The

feed will be pumped into the digester when it has reached the operating temperature. The

digester will be another 5 gallon bucket that will have a motor with a propeller agitator secured

to the top of it. This bucket will have an air tight seal. A second hose will be attached to the top

of the digester that will collect the gas. This hose will be inserted in the side of a third bucket

near the bottom. This bucket will function as the gas collection unit. This bucket will have a

second bucket turned upside down to function as a seal to capture the gas. The lid will palpitate

with the production of the gas. The waste sludge will be emptied at the end of every day and new

sludge will be pumped in from the heat exchanger bucket. The feed will come from the bottom

of this bucket to eliminate chances of contamination with oxygen. Before the first influent is

pumped into the digester, the system will be flushed with nitrogen to ensure that the process is

anaerobic.

8.2 Testing of Model

The anaerobic digester will be analyzed on several parameters including pathogens, total

solids, volatile solids, chemical oxygen demand (COD), and soluble chemical oxygen demand. It

will also be tested for the amount of biogas generated per pound of volatile solids destruction.

The team will try and optimize this parameter which is proportional to the amount of energy the

digester can produce with the given feed stream and operating conditions. The study will include

daily samples from the bench scale model (described above) that will be in operation for the

months of February, March, and April. For the digester, the degree of waste stabilization can be

claimed on significant differences, between mean influent and effluent concentrations of the

shown in Table 9.

Table 9: Parameters Analyzed from Biosolid Samples

Parameters

Total solids

Total fixed solids

Total volatile solids

Chemical oxygen demand

Soluble chemical oxygen demand

Biological oxygen demand

pH

Composition of volatile solids

18

Each sample will be a composite sample of the daily batch collected within a one hour

period. These samples will be analyzed in accordance with standard methods for testing waste

water. The influent was collected from the CWP. Due to the consistent agitation at the time of

sampling, it was determined that samples from different depths as called for by standard method

1684 will not be necessary. A small sampling valve on the side of the gas collection tank of the

bench scale model will be installed when building the model. The temperature of the influent

will be measured with an alcohol thermometer and recorded. The samples will be placed on ice

in a cooler as soon as they are obtained until testing can be done.

8.2.1 Methods

8.2.1.1 Gas Flow Biogas production measurements must account for all biogas produced. Biogas

production should be measured using an appropriate meter. Top inlet mechanical meters

designed to measure and record corrosive gas flows are suitable for this measurement. Other

types of gas meters, such as thermal mass flow meters, also are acceptable. The exact device to

be used for this will depend on what will be available when the model becomes fully operational.

8.2.1.2 Gas Composition The concentration of carbon dioxide by volume will be determined bimonthly using fluid

chemical absorption spectrometry for the expected concentration. The concentration will be

based on the average of three replicate measurements for each sampling period. In addition, the

amount of methane, carbon dioxide, hydrogen sulfide, and ammonia content by volume will be

analyzed least weekly. Each sample will be collected in a suitable gas collection bag and

analyzed using gas chromatography ASTM Method D 1945-03 (ASTM International, 2009) for

methane and carbon dioxide, ASTM Method D 5504-01 (ASTM International, 2009) for

hydrogen sulfide, and EPA Method 350.1 for ammonia. Results of samples containing more

than 10 percent of unidentified gases, typically nitrogen and oxygen, should be discarded due to

an unacceptable degree of atmospheric contamination.

8.2.1.3 Gas Production The procedure for determine the amount of TS, VS, and FS will be done according to

standard method 1684. Sample aliquots of 25-50 g of the sludge influent and effluent are dried

at 103°C to 105°C to drive off water in the sample. The residual is then cooled, weighed, and

dried again at 550°C to drive off volatile solids in the sample. The total, fixed, and volatile

solids are determined by comparing the mass of the sample before and after each drying step.8

8.2.1.4 BOD Biochemical Oxygen Demand (BOD) is an empirical test that determines the relative

oxygen requirements of wastewater, effluent and polluted waters. BOD tests measure the

molecular oxygen utilized during a specified incubation duration for the biochemical degradation

of organic material (carbonaceous demand) and the oxygen used to oxidize inorganic material

such as ferrous iron and sulfides. The standard method for BOD test consists of a 5 day period in

19

which a sample is placed in an airtight bottle under controlled conditions temperature, keeping

any light from penetrating the sample to prevent photosynthesis. The Dissolved Oxygen (DO) in

the sample is measured before and after the 5 day incubation period, and BOD is then calculated

as the difference between initial and final DO measurements. As BOD testing needs 5 days, this

test will be conducted weekly9.

8.2.1.5 COD COD is an indicator of organic pollutant in water. It gives an indication of the efficiency

of the treatment process. COD is measured on both influent and effluent water. The efficiency of

the treatment process is normally expressed as COD Removal, measured as a percentage of the

organic matter purified during the cycle. COD will be tested by standard method 410.4. This

method calls for the determination of COD by semi-automated colorimetry. Samples are heated

in an oven or block digester in the presence of dichromate at 150°C. After two hours, the tubes

are removed from the oven or digester, cooled, and measured spectrophotometrically at 600

nm.10

8.3 Optimization of Model There are several factors that could be optimized with a bench scale model, and several

that are set quantities based on the feed stream provided. Table 10 specifies whether a variable

can be optimized.

Table 10: Bench Scale Optimization Variables

Variable to be optimized

Ability to Optimize

without

pretreatment

The composition of waste being

digested

No

The solids concentration for good

digestion

Yes

The temperature of digestion Yes

The presence of toxic materials No

The pH and alkalinity No

The hydraulic retention time Yes

The solids retention time Yes

The ratio of food to microorganisms Yes

The rate end products of digestion

are removed

Yes

The effects of change on the digester takes several weeks; thus the team will only

optimize a few of these variables due to time constraints. Which variable the team will be

optimizing will be determined during the building process of the digester.

20

9. Project Management

9.1 Team Description

The team consists of four senior engineering students at Calvin College: three students

pursuing degrees in a civil/environmental concentration and one student pursuing a degree in a

chemical engineering. A faculty advisor, Professor David B. Wunder, Ph.D., P.E., DEE, was

assigned to the team to oversee the design process.

9.2 Schedule

The team met every Monday evening to collaborate on weekly goals and to make

necessary major decisions. The team also met every Thursday morning with Dr. Wunder to

review weekly progress and to consult him regarding potential feasibility issues. The teams

design progress can be found in the Work Breakdown Schedule in Appendix B: Work Breakdown

Schedule.

10. Future Work to Be Completed The team will do work in the future on several topics. The first is to look into the

potential nutrient recovery of phosphorus from the digester. This would include a possible

method to both capture the phosphorus for selling or just the elimination of it from the recycling

water. This would also include the need of the stream to be recycled through the plant

completely or if it could be introduced at a different point in the process. To accompany the

analysis of the recycle stream, a more in depth analysis of the effects of the recycle stream on the

plant will be done. The next item that the team would like to provide with the final project is an

analysis of the control systems needed for the additional units that will be needed for the

anaerobic digestion process. This would include the temperature, pH, and valve control for the

systems. The team hopes to provide a detailed analysis of the bench scale model including the

values for potential methane production, an improved bench scale model, and optimal conditions

for the influent. The final thing that the team will provide in the final report is a site layout for

CWP with the anaerobic process included.

Acknowledgements The team would like to thank Dr. David B. Wunder (Ph.D., P.E.), Professor at Calvin

College for serving as a team advisor and providing valuable information throughout the

semester. Myron Erickson (P.E.), superintendent at City of Wyoming CWP and Aaron Vis,

Project Manager of GRVBA have been active participants in our work. The team appreciates

their timely response to team requests and showing guidance. Finally, the team would like to

thank our industrial consultants, Jim Flamming (P.E.) and David Filipiak (CHMM) from

Fishbeck, Thomson, Carr and Huber, Inc. (FTC&H) have assisted the team in the design process

and evaluating alternatives.

21

References 1 Clean Water Act, §503.1(a)(1) , page 2.

<http://yosemite.epa.gov/r10/water.nsf/NPDES%2BPermits/Sewage%2BS825/$FILE/50

3-032007.pdf> 2 Clean Water Act, §503.8 (b)(1)-(b)(4), page 4. 3 Business Operating Plan, GVRBA 2009 4 Kleiven, Harald. Cambi; Recycling Energy. Norway: n.p., 2010. Print. 5 United States. Water Environment Federation. Laboratory Evaluation of Thermophilic-

Anaerobic Digestion to Produce Class A Biosolids. By Michael Aitken, Glenn Walters,

Phillip Crunk, John Willis, Joseph Farrell, Perry Schafer, Cliff Arnett, and Billy Turner.

7th ed. Vol. 77. Stockholm: Water Environment Research, 2005. Print. 6 Clean Water Act, Part 503, section (a)(3)(ii)(D), page 20 7 United States. Water Environment Federation. Laboratory Evaluation of Thermophilic-



7th ed. Vol. 77. Stockholm: Water Environment Research, 2005. Print. 8 United States. Environmental Monitoring Systems Laboratory. Office of Research and

Development. Chemical Oxygen Demand: [test] Method 410.4. By James O'Dell.

Cincinnati, OH: U.S. Environmental Protection Agency, 2001. Web.

<http://water.epa.gov/scitech/methods/cwa/bioindicators/upload/2007_07_10_methods_ 9 United States. Environmental Protection Agency. Office of Water. U.S. Environmental

Protection Agency. By Engineering and Analysis Division. N.p., 2001. Web.

<http://water.epa.gov/scitech/methods/cwa/bioindicators/upload/2008_11_25_methods_

method_biological_1684-bio.pdf>. 10 Eastern Research Group, Inc. Protocol for Quantifying and Reporting the Performance of

Anaerobic Digestion Systems for Livestock Manures. Rep. Lexington: n.p., 2011. U.S.

Environmental Protection Agency, 2011. Web.

22

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Abbasi, Tasneem, and Tauseef Abbasi. "Anaerobic Digestion for Global Warming Control and

Energy Generation—An Overview." Centre for Pollution Control and Environmental

Engineering 16 (2012): 3228-242. Elsevier. Web.

Arnett, Clifford, Joseph Farrell, Daniel Hull, Steven Krugel, Billy Turner, Warren Uhte, and

John Willis. Biosolids Flow-Through Thermiphilic Treatment Process. Columbus Water

Works, assignee. Patent US 2004/0011718 A1. 22 Jan. 2004. Print.

Asada, Lucia, Gilberto Sundefeld, Carlos Alvarez, and Sidney Seckler. "Water Treatment Plant

Sludge Discharge to Wastewater Treatment Works." Water Environment Research 82.5

(2010): 392-400. Print. Badger Laboratories and Engineering. 2008. Quality Assurance Manual.

Camp Dresser & McKee Inc. Charting the Future of Biosolids Management: Final Report. Rep.

N.p.: Water Environment Research, 2011. Print. Digestion Systems for Livestock Manures. USDA.

Eastern Research Group, Inc. Protocol for Quantifying and Reporting the Performance of

Anaerobic Digestion Systems for Livestock Manures. Rep. Lexington: n.p., 2011. U.S.

Environmental Protection Agency, 2011. Web.

Environmental Research Information Center. Technology Transfer. Sludge Treatment and

Disposal. Cincinnati, OH: Environmental Protection Agency, Environmental Research

Information Center, Technology Transfer, 1978. Print.

EPA "Opportunities for Combined Heat and Power at Wastewater Treatment Facilities: Market

Analysis and Lessons from the Field." U.S. Environmental Protection Agency: Combined

Heat and Power Partnership (2011). Web. 14 Dec. 2013.

<http://www.epa.gov/chp/documents/wwtf_opportunities.pdf>.

Goldstein, Jerome. "Around the World with Anaerobic Digestion." Biocycle Energy 44.4 (2003):

78-81. Print.

Greer, Diane. "Funding Anaerobic Digestion Facilities." BioCycle Energy 52.3 (2011): 70-73.

Print.

Greer, Diane. "Vermont Builds Anaerobic Digestion Capacity." BioCycle Energy 52.10 (2011):

38-41. Print.

Informa Economics. National Market Value of Anaerobic Digestor Products. Rep. Innovation

Center for US Dairy, Feb. 2013. Web.

Khalid, Azeem, Muhammad Arshad, Muzammil Anjum, Tariq Mahmood, and Lorna Dawson.

"The Anaerobic Digestion of Solid Organic Waste." Waste Management 31.8 (2011):

1737-744. Print.

Kleiven, Harald. Cambi; Recycling Energy. Norway: n.p., 2010. Print.

Kopp, Ewert. "New Processes for the Improvement of Sludge Digestion and Sludge

Dewatering." Influence of Surface Charge and Exopolysaccharides on the Conditioning

Characteristics of Sewage Sludges. Ed. Hamburg Lengede. Vol. 5. N.p.: Springer, 1998.

N. pag. Print.

Mancl, Karen. Wastewater Treatment Principles and Regulations. Ohio State University, n.d.

Web. 13 Nov. 2013. <http://ohioline.osu.edu/aex-fact/0768.html>

Martin, J. 2007. A Protocol for Quantifying and Reporting the Performance of Anaerobic

23

Meringa, Joshua. "Grandville's Clean Water Plant: First of its Kind in Michigan." the review Jan.

2013: 27-30. Web. 14 Dec. 2013. <http://www.mml.org/thereview/review-

janfeb2013/offline/download.pdf>.

Panter, Keith, and David Auty. "Thermal Hydrolysis, Anaerobic Digestion and Dewatering of

Sewage Sludge as a Best First Step in Sludge Strategy: Full Scale Examples in Large

Projects in the UK and Strategic Study including Cost and Carbon Footprint." (n.d.): n.

pag. Print.

Pauley, Keith. Mid-Atlantic Technology, Research and Innovation Center. Rep. MARTIC

Research, 23 Mar. 2010. Web.

<http://depts.washington.edu/cpac/Activities/Meetings/Satellite/2010/Thursday/Pauley%

20Biomass%20Gasification%20presentation.pdf>.

United States. Environmental Monitoring Systems Laboratory. Office of Research and

Development. Chemical Oxygen Demand: [test] Method 410.4. By James O'Dell.

Cincinnati, OH: U.S. Environmental Protection Agency, 2001. Web.


method_410_4.pdf>.

United States. Environmental Protection Agency. Office of Water. U.S. Environmental

Protection Agency. By Engineering and Analysis Division. N.p., 2001. Web.


method_biological_1684-bio.pdf>.

United States. Massachusetts Department of Environmental Protection. Tapping the Energy

Potential of Municipal Wastewater Treatment: Anaerobic Digestion and Combined Heat

and Power in Massachusetts. By Shutsu Wong. Massachusetts: n.p., 2011. Print.

United States. Water Environment Federation. Laboratory Evaluation of Thermophilic-



7th ed. Vol. 77. Stockholm: Water Environment Research, 2005. Print.

Wilkinson, Kevin. "Development of On-Farm Anaerobic Digestion." BioCycle Global Jan. 2011:

49-50. BioCycle Global. Web.

Wills, John, and Perry Schafer. Advances in Thermophilic Anaerobic Digestion. Rep. no. 1114.

Rancho Cordova: Brown and Caldwell, n.d. Print.

24

Appendix A: List of Design Projects Considered

Customer: City of Wyoming

Problem to be solved: Optimization of Design of Odorous Air Filter

Key Constraints: Currently communicating with City of Wyoming for this information

Engineering Disciplines: Chemical and Environmental

Primary Tasks: TBD

Customer: City of Wyoming or Grand Valley

Problem to be solved: Design of Pilot Plant Anaerobic Bio-digester

Key Constraints: Currently communicating with City of Wyoming for this information


Primary Tasks: TBD

Customer: WERC

Problem to be solved: Greenhouse Gas Emission from an Open Pit Copper Mine

Key Constraints: WERC has yet to publish competition specs


Primary Task: TBD

25

Appendix B: Work Breakdown Schedule

Task Name Start Finish Actual Finish Resource Names

Gantt Chart Thu 9/26/13 Thu 12/19/13 Thu 12/19/13

Define Scope and Objectives Thu 9/26/13 Thu 10/3/13 Thu 10/3/13 Team

Background of Project (Introduction) Thu 9/26/13 Thu 10/17/13 Thu 10/17/13 Andrew

Flows and Loads Tech Memo Thu 10/10/13 Fri 11/8/13 Fri 11/8/13 Katie

Determine Operating Capacity Mon 10/14/13 Thu 11/7/13 Thu 11/7/13 Katie

Analytical Methods Tech Memo Fri 10/11/13 Fri 11/29/13 Fri 11/29/13 Rachel

Solids Management Alternatives Tech Memo Thu 9/26/13 Mon 12/2/13 Thu 12/19/13 Eyosias

Stabilization Thu 10/3/13 Mon 12/2/13 Thu 12/19/13 Andrew

Chemical Thu 10/3/13 Fri 10/11/13 Thu 12/19/13

Wet Chemical Thu 10/3/13 Thu 12/19/13 Thu 12/19/13 Katie

Lime Stabilization Thu 10/3/13 Thu 12/19/13 Thu 12/19/13 Rachel

Time and Temp Thu 10/3/13 Thu 10/17/13 Thu 10/17/13 Andrew

Biological Thu 10/3/13 Thu 10/24/13 Thu 10/24/13 Team

Aerobic Digestion Thu 10/3/13 Fri 10/11/13 Fri 10/11/13 Team

Anaerobic Thu 10/3/13 Thu 10/24/13 Thu 10/24/13 Andrew

TPAD Thu 10/3/13 Wed 10/16/13 Wed 10/16/13 Eyosias, Andrew

Thermophilic Thu 10/3/13 Wed 10/16/13 Wed 10/16/13 Andrew, Eyosias

Mesophilic Thu 10/3/13 Wed 10/16/13 Wed 10/16/13 Andrew, Eyosias

Dewatering Thu 9/26/13 Thu 10/17/13 Thu 10/17/13 Rachel

Thickening Thu 10/3/13 Thu 10/31/13 Thu 10/31/13 Eyosias

Government Regulations Mon 11/4/13 Mon 12/9/13 Mon 12/9/13 Katie

Major Components of Digester Thu 10/17/13 Thu 11/14/13 Thu 11/14/13 Team

Mixing method Thu 10/17/13 Wed 10/23/13 Wed 10/23/13 Team

Reactor Type Thu 10/17/13 Thu 11/7/13 Thu 11/7/13 Team

Heating Method Thu 10/24/13 Thu 10/31/13 Thu 10/31/13 Team

Complete Process Flow Diagram Thu 10/10/13 Fri 11/29/13 Fri 11/29/13 Eyosias

Optimization of Biodigester Design Fri 11/1/13 Tue 12/3/13 Tue 12/3/13 Rachel

PPFS 1st Draft Thu 9/26/13 Thu 11/28/13 Thu 11/28/13 Team

PPFS Editing Fri 11/22/13 Sat 12/14/13 Sat 12/14/13 Team

26

Appendix C: Formatted Selections from Clean Water Act

Part 503 § 503.13 Pollutant limits.

a) Sewage sludge.

1) Bulk sewage sludge or sewage sludge sold or given away in a bag or other container shall not

be applied to the land if the concentration of any pollutant in the sewage sludge exceeds the

ceiling concentration for the pollutant in Table 1 of §503.13.

2) If bulk sewage sludge is applied to agricultural land, forest, a public contact site, or a

reclamation site, either:

i. The cumulative loading rate for each pollutant shall not exceed the cumulative pollutant

loading rate for the pollutant in Table 2 of §503.13; or

ii. The concentration of each pollutant in the sewage sludge shall not exceed the

concentration for the pollutant in Table 3 of §503.13.

3) If bulk sewage sludge is applied to a lawn or a home garden, the concentration of each

pollutant in the sewage sludge shall not exceed the concentration for the pollutant in Table 3

of §503.13.

4) If sewage sludge is sold or given away in a bag or other container for application to the land,

either:

i. The concentration of each pollutant in the sewage sludge shall not exceed the

concentration for the pollutant in Table 3 of §503.13; or

ii. The product of the concentration of each pollutant in the sewage sludge and the annual

whole sludge application rate for the sewage sludge shall not cause the annual pollutant

loading rate for the pollutant in Table 4 of §503.13 to be exceeded. The procedure used to

determine the annual whole sludge application rate is presented in appendix A of this

part.

b) Pollutant concentrations and loading rates—sewage sludge.

1) Ceiling concentrations.

Table 1 of §503.13 - Ceiling Concentrations

Pollutant Ceiling Concentration

(mg/kg)1

Arsenic 75

Cadmium 85

Copper 4300

Lead 840

Mercury 57

Molybdenum 75

Nickel 420

Selenium 100

Zinc 7500 1 Dry weight basis

27

2) Cumulative pollutant loading rates

Table 2 of §503.13 - Cumulative Pollutant Loading Rates

Pollutant

Cumulative pollutant

loading rate

(kg / hectare)

Arsenic 41

Cadmium 39

Copper 1500

Lead 300

Mercury 17

Nickel 420

Selenium 100

Zinc 2800

3) Pollutant concentrations

Table 12 of §503.13 - Pollutant Concentrations

Pollutant

Monthly average

concentration

(mg/kg)1

Arsenic 41

Cadmium 39

Copper 1500

Lead 300

Mercury 173

Nickel 420

Selenium 100

Zinc 2800 1 Dry weight basis

4) Annual pollutant loading rates

Table 13 of §503.13 - Annual Pollutant Loading Rates

28

Pollutant

Annual pollutant

loading rate

(kg / hectare / 365 day

period)

Arsenic 2

Cadmium 1.9

Copper 75

Lead 15

Mercury 0.85

Nickel 21

Selenium 5

Zinc 140

c) Domestic septage. The annual application rate for domestic septage applied to agricultural land,

forest, or a reclamation site shall not exceed the annual application rate calculated using equation

(1).

𝐴𝐴𝑅 =𝑁

0.0026 Eq. (1)

Where:

AAR = Annual Application rate in gallons per acre per 365 day period.

N = amount of nitrogen in pounds per acre per 365 day period needed by the crop or vegetation

grown on the land.

[58 FR 9387, Feb. 19, 1993, as amended at 58 FR 9099, Feb. 25, 1994; 60 FR 54769, Oct. 25, 1995]

§ 503.32 Pathogens.

a) Sewage sludge—Class A.

1) The requirement in §503.32(a)(2) and the requirements in either §503.32(a)(3), (a)(4), (a)(5),

(a)(6), (a)(7), or (a)(8) shall be met for a sewage sludge to be classified Class A with respect

to pathogens.

2) The Class A pathogen requirements in §503.32 (a)(3) through (a)(8) shall be met either prior

to meeting or at the same time the vector attraction reduction requirements in §503.33, except

the vector attraction reduction requirements in §503.33 (b)(6) through (b)(8), are met.

3) Class A—Alternative 1.

i. Either the density of fecal coliform in the sewage sludge shall be less than 1000 Most

Probable Number per gram of total solids (dry weight basis), or the density of Salmonella

sp. bacteria in the sewage sludge shall be less than three Most Probable Number per four

grams of total solids (dry weight basis) at the time the sewage sludge is used or disposed;

at the time the sewage sludge is prepared for sale or give away in a bag or other container

for application to the land; or at the time the sewage sludge or material derived from

sewage sludge is prepared to meet the requirements in §503.10 (b), (c), (e), or (f).

ii. The temperature of the sewage sludge that is used or disposed shall be maintained at a

specific value for a period of time.

A. When the percent solids of the sewage sludge is seven percent or higher, the

temperature of the sewage sludge shall be 50 degrees Celsius or higher; the time

period shall be 20 minutes or longer; and the temperature and time period shall be

determined using equation (2), except when small particles of sewage sludge are

heated by either warmed gases or an immiscible liquid.

29

𝐷 =131,700,000

100.1400𝑡 Eq. (2)

Where,

D=time in days.

t=temperature in degrees Celsius.

B. When the percent solids of the sewage sludge is seven percent or higher and small

particles of sewage sludge are heated by either warmed gases or an immiscible liquid,

the temperature of the sewage sludge shall be 50 degrees Celsius or higher; the time

period shall be 15 seconds or longer; and the temperature and time period shall be

determined using equation (2).

C. When the percent solids of the sewage sludge is less than seven percent and the time

period is at least 15 seconds, but less than 30 minutes, the temperature and time

period shall be determined using equation (2).

D. When the percent solids of the sewage sludge is less than seven percent; the

temperature of the sewage sludge is 50 degrees Celsius or higher; and the time period

is 30 minutes or longer, the temperature and time period shall be determined using

equation (3).

𝐷 =50,070,000

100.1400𝑡 Eq. (3)

Where,

D=time in days.

t=temperature in degrees Celsius.









ii.

A. The pH of the sewage sludge that is used or disposed shall be raised to above 12 and

shall remain above 12 for 72 hours.

B. The temperature of the sewage sludge shall be above 52 degrees Celsius for 12 hours

or longer during the period that the pH of the sewage sludge is above 12.

C. At the end of the 72 hour period during which the pH of the sewage sludge is above

12, the sewage sludge shall be air dried to achieve a percent solids in the sewage

sludge greater than 50 percent.




sp. bacteria in sewage sludge shall be less than three Most Probable Number per four





ii.

A. The sewage sludge shall be analyzed prior to pathogen treatment to determine

whether the sewage sludge contains enteric viruses.

30

B. When the density of enteric viruses in the sewage sludge prior to pathogen treatment

is less than one Plaque-forming Unit per four grams of total solids (dry weight basis),

the sewage sludge is Class A with respect to enteric viruses until the next monitoring

episode for the sewage sludge.

C. When the density of enteric viruses in the sewage sludge prior to pathogen treatment

is equal to or greater than one Plaque-forming Unit per four grams of total solids (dry

weight basis), the sewage sludge is Class A with respect to enteric viruses when the

density of enteric viruses in the sewage sludge after pathogen treatment is less than

one Plaque-forming Unit per four grams of total solids (dry weight basis) and when

the values or ranges of values for the operating parameters for the pathogen treatment

process that produces the sewage sludge that meets the enteric virus density

requirement are documented.

D. After the enteric virus reduction in paragraph (a)(5)(ii)(C) of this section is

demonstrated for the pathogen treatment process, the sewage sludge continues to be

Class A with respect to enteric viruses when the values for the pathogen treatment

process operating parameters are consistent with the values or ranges of values

documented in paragraph (a)(5)(ii)(C) of this section.

iii.

A. The sewage sludge shall be analyzed prior to pathogen treatment to determine

whether the sewage sludge contains viable helminth ova.

B. When the density of viable helminth ova in the sewage sludge prior to pathogen

treatment is less than one per four grams of total solids (dry weight basis), the sewage

sludge is Class A with respect to viable helminth ova until the next monitoring

episode for the sewage sludge.

C. When the density of viable helminth ova in the sewage sludge prior to pathogen

treatment is equal to or greater than one per four grams of total solids (dry weight

basis), the sewage sludge is Class A with respect to viable helminth ova when the

density of viable helminth ova in the sewage sludge after pathogen treatment is less

than one per four grams of total solids (dry weight basis) and when the values or

ranges of values for the operating parameters for the pathogen treatment process that

produces the sewage sludge that meets the viable helminth ova density requirement

are documented

D. After the viable helminth ova reduction in paragraph (a)(5)(iii)(C) of this section is

demonstrated for the pathogen treatment process, the sewage sludge continues to be

Class A with respect to viable helminth ova when the values for the pathogen

treatment process operating parameters are consistent with the values or ranges of

values documented in paragraph (a)(5)(iii)(C) of this section.









ii. The density of enteric viruses in the sewage sludge shall be less than one Plaque-forming

Unit per four grams of total solids (dry weight basis) at the time the sewage sludge is

used or disposed; at the time the sewage sludge is prepared for sale or give away in a bag

or other container for application to the land; or at the time the sewage sludge or material

derived from sewage sludge is prepared to meet the requirements in §503.10 (b), (c), (e),

or (f), unless otherwise specified by the permitting authority.

31

iii. The density of viable helminth ova in the sewage sludge shall be less than one per four




sewage sludge is prepared to meet the requirements in §503.10 (b), (c), (e), or (f), unless

otherwise specified by the permitting authority.



Probable Number per gram of total solids (dry weight basis), or the density of

Salmonella, sp. bacteria in the sewage sludge shall be less than three Most Probable

Number per four grams of total solids (dry weight basis) at the time the sewage sludge is

used or disposed; at the time the sewage sludge is prepared for sale or given away in a

bag or other container for application to the land; or at the time the sewage sludge or

material derived from sewage sludge is prepared to meet the requirements in §503.10(b),

(c), (e), or (f).

ii. Sewage sludge that is used or disposed shall be treated in one of the Processes to Further

Reduce Pathogens described in appendix B of this part.



Probable Number per gram of total solids (dry weight basis), or the density of

Salmonella, sp. bacteria in the sewage sludge shall be less than three Most Probable

Number per four grams of total solids (dry weight basis) at the time the sewage sludge is

used or disposed; at the time the sewage sludge is prepared for sale or given away in a

bag or other container for application to the land; or at the time the sewage sludge or

material derived from sewage sludge is prepared to meet the requirements in §503.10(b),

(c), (e), or (f).

ii. Sewage sludge that is used or disposed shall be treated in a process that is equivalent to a

Process to Further Reduce Pathogens, as determined by the permitting authority.

b) Sewage sludge—Class B.

1)

i. The requirements in either §503.32(b)(2), (b)(3), or (b)(4) shall be met for a sewage

sludge to be classified Class B with respect to pathogens.

ii. The site restrictions in §503.32(b)(5) shall be met when sewage sludge that meets the

Class B pathogen requirements in §503.32(b)(2), (b)(3), or (b)(4) is applied to the

land.

2) Class B—Alternative 1.

i. Seven representative samples of the sewage sludge that is used or disposed shall be

collected.

ii. The geometric mean of the density of fecal coliform in the samples collected in paragraph

(b)(2)(i) of this section shall be less than either 2,000,000 Most Probable Number per

gram of total solids (dry weight basis) or 2,000,000 Colony Forming Units per gram of

total solids (dry weight basis).

3) Class B—Alternative 2. Sewage sludge that is used or disposed shall be treated in one of the

Processes to Significantly Reduce Pathogens described in appendix B of this part.

4) Class B—Alternative 3. Sewage sludge that is used or disposed shall be treated in a process

that is equivalent to a Process to Significantly Reduce Pathogens, as determined by the

permitting authority.

5) Site restrictions.

i. Food crops with harvested parts that touch the sewage sludge/soil mixture and are totally

above the land surface shall not be harvested for 14 months after application of sewage

sludge.

32

ii. Food crops with harvested parts below the surface of the land shall not be harvested for

20 months after application of sewage sludge when the sewage sludge remains on the

land surface for four months or longer prior to incorporation into the soil.

iii. Food crops with harvested parts below the surface of the land shall not be harvested for

38 months after application of sewage sludge when the sewage sludge remains on the

land surface for less than four months prior to incorporation into the soil.

iv. Food crops, feed crops, and fiber crops shall not be harvested for 30 days after

application of sewage sludge

v. Animals shall not be grazed on the land for 30 days after application of sewage sludge.

vi. Turf grown on land where sewage sludge is applied shall not be harvested for one year

after application of the sewage sludge when the harvested turf is placed on either land

with a high potential for public exposure or a lawn, unless otherwise specified by the

permitting authority.

vii. Public access to land with a high potential for public exposure shall be restricted for one

year after application of sewage sludge.

viii. Public access to land with a low potential for public exposure shall be restricted for 30

days after application of sewage sludge.

c) Domestic septage.

1) The site restrictions in §503.32(b)(5) shall be met when domestic septage is applied to

agricultural land, forest, or a reclamation site; or

2) The pH of domestic septage applied to agricultural land, forest, or a reclamation site shall be

raised to 12 or higher by alkali addition and, without the addition of more alkali, shall remain

at 12 or higher for 30 minutes and the site restrictions in §503.32 (b)(5)(i) through (b)(5)(iv)

shall be met. [58 FR 9387, Feb. 19, 1993, as amended at 64 FR 42571, Aug. 4, 1999] §

503.33 Vector attraction reduction.

§ 503.33 Vector attraction reduction

a)

1) One of the vector attraction reduction requirements in §503.33 (b)(1) through (b)(10) shall be

met when bulk sewage sludge is applied to agricultural land, forest, a public contact site, or a

reclamation site.


met when bulk sewage sludge is applied to a lawn or a home garden.


met when sewage sludge is sold or given away in a bag or other container for application to

the land.


met when sewage sludge (other than domestic septage) is placed on an active sewage sludge

unit.

5) One of the vector attraction reduction requirements in §503.33 (b)(9), (b)(10), or (b)(12) shall

be met when domestic septage is applied to agricultural land, forest, or a reclamation site and

one of the vector attraction reduction requirements in §503.33 (b)(9) through (b)(12) shall be

met when domestic septage is placed on an active sewage sludge unit.

b)

1) The mass of volatile solids in the sewage sludge shall be reduced by a minimum of 38 percent

(see calculation procedures in “Environmental Regulations and Technology—Control of

Pathogens and Vector Attraction in Sewage Sludge”, EPA–625/R–92/013, 1992, U.S.

Environmental Protection Agency, Cincinnati, Ohio 45268).

2) When the 38 percent volatile solids reduction requirement in §503.33(b)(1) cannot be met for

an anaerobically digested sewage sludge, vector attraction reduction can be demonstrated by

digesting a portion of the previously digested sewage sludge anaerobically in the laboratory

33

in a bench-scale unit for 40 additional days at a temperature between 30 and 37 degrees

Celsius. When at the end of the 40 days, the volatile solids in the sewage sludge at the

beginning of that period is reduced by less than 17 percent, vector attraction reduction is

achieved.

3) When the 38 percent volatile solids reduction requirement in §503.33(b)(1) cannot be met for

an aerobically digested sewage sludge, vector attraction reduction can be demonstrated by

digesting a portion of the previously digested sewage sludge that has a percent solids of two

percent or less aerobically in the laboratory in a bench-scale unit for 30 additional days at 20

degrees Celsius. When at the end of the 30 days, the volatile solids in the sewage sludge at

the beginning of that period is reduced by less than 15 percent, vector attraction reduction is

achieved.

4) The specific oxygen uptake rate (SOUR) for sewage sludge treated in an aerobic process shall

be equal to or less than 1.5 milligrams of oxygen per hour per gram of total solids (dry weight

basis) at a temperature of20 degrees Celsius.

5) Sewage sludge shall be treated in an aerobic process for 14 days or longer. During that time,

the temperature of the sewage sludge shall be higher than 40 degrees Celsius and the average

temperature of the sewage sludge shall be higher than 45 degrees Celsius.

6) The pH of sewage sludge shall be raised to 12 or higher by alkali addition and, without the

addition of more alkali, shall remain at 12 or higher for two hours and then at 11.5 or higher

for an additional 22 hours.

7) The percent solids of sewage sludge that does not contain unstabilized solids generated in a

primary wastewater treatment process shall be equal to or greater than 75 percent based on

the moisture content and total solids prior to mixing with other materials.

8) The percent solids of sewage sludge that contains unstabilized solids generated in a primary

wastewater treatment process shall be equal to or greater than 90 percent based on the

moisture content and total solids prior to mixing with other materials.

9)

i. Sewage sludge shall be injected below the surface of the land.

ii. No significant amount of the sewage sludge shall be present on the land surface within

one hour after thesewage sludge is injected.

iii. When the sewage sludge that is injected below the surface of the land is Class A with

respect to pathogens, the sewage sludge shall be injected below the land surface within

eight hours after being discharged from the pathogen treatment process.

10) i. Sewage sludge applied to the land surface or placed on an active sewage sludge unit shall

be incorporated into the soil within six hours after application to or placement on the

land, unless otherwise specified by the permitting authority.

ii. When sewage sludge that is incorporated into the soil is Class A with respect to

pathogens, the sewage sludge shall be applied to or placed on the land within eight hours

after being discharged from the pathogen treatment process.

11) Sewage sludge placed on an active sewage sludge unit shall be covered with soil or other

material at the end of each operating day.

12) The pH of domestic septage shall be raised to 12 or higher by alkali addition and, without the

addition of more alkali, shall remain at 12 or higher for 30 minutes.

[58 FR 9387, Feb. 19, 1993, as amended at 64 FR 42571, Aug. 4, 1999]

34

Appendix D: Anaerobic Digestion Design Calculations

Anaerobic Digestion Calculation

Thermophilic Design (55 degrees Celsius)

Production Of Methane

Volume flow rate

Residence time

Anaerobic Biomass produced per day

Qwas 100000 gpd

r 10 days

max 0.91

day

Ks 0.3g

L

kd 0.061

day

Y 0.1177lbVSS

lbBOD

TS 0.058

S0 .6805lb

gal

S .5725lb

gal

Px

Y S0 S Qwas

1 kd r794.475 lbpd

VCH4 5.62 S0 S Qwas 1.42Px VCH4 5.436 104

ft

3

day

VCH4m VCH4.02832 1.539 103

m

3

day

metriccost .1dollars

m3

Costp .1VCH4m 153.936dollars

day

Costpyr Costp 364.25 5.607 104

dollars

year

35

Tank Volume

.13368 gallons to ft3

Digester height and radius are equal

.037037 ft3 to yd3

75% will be underground

Vft Qwas r .13368 1.337 105

ft3

Vone

Vft

26.684 10

4 ft

3

rVone

.333

27.618 ft

Vcubicyrd Vone 3 .037037037 7.427 103

yrd3

Costexcavation .75Vcubicyrd 105 5.848 105

dollars

biosolids management feasibility study for city of wyoming clean

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