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Codigestion Case Studies Enhancing Energy Recovery From Sludge

Dale Gabel, PE, BCEE

MWRD PWO Seminar

May 23, 2012

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What is Codigestion?

Direct addition of high-strength organic wastes to municipal wastewater anaerobic digesters Typical high-strength organic wastes • Fats, oils, and grease (FOG) • Restaurant food scraps • Food processing wastes • Off-spec cola syrups • Dairy wastes • Cheese Wastes • Brewery Wastes • Winery Wastes • Others

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Advantages of Codigestion

Technical • Removes FOG from sewer collection systems • Removes FOG materials from headworks and

primary clarifiers • Removes organic loadings on liquid treatment train • Increases digester utilization

Economic • Produces more biogas for beneficial uses (CHP,

dryer, vehicles, etc.) • New revenue streams from tipping fees • Reduces O&M costs for headworks and liquid

treatment trains

Environmental • Reduces landfilling of high-strength wastes (HSW) • Reduces emission of greenhouse gases

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Challenges of Codigestion

Possible need for digester upgrades Additional capital and O&M costs for FOG/HSW receiving and processing Additional paperwork for permitting, waste receipts, billings Debris removal and disposal Potential negative anaerobic digester performance impacts Potential anaerobic digester toxicity from HSW Potential increase in nutrient concentrations in sidestreams

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Key Elements of an Effective FOG Waste/HSW Processing System

Material Delivery Control/Traceability Volume of Material and Storage Requirements FOG Waste/HSW Unloading Considerations Storage and Conditioning Odor Control Feed Strategies

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Material Delivery Control and Traceability

Develop Application Process Collaborate with Haulers and WWTP Operators Train Drivers on Delivery/Unloading Procedures Sample Collection and Testing Record Keeping Security

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Volume of Material and Storage Requirements

Research Market • Number of potential hauling companies • Estimate deliveries per day • Delivery truck capacities • Billing: Basis and Method

Develop Storage and Feed Strategy • Design for anticipated peak day loads • Develop acceptable delivery schedule • Continuous feed or single shift

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FOG Waste/HSW Unloading Considerations

Access Control and Automation Unloading Method Debris/Sediment Removal Pumping Clean up

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FOG Storage Tanks

Heat Exchangers

Digester Feed Pumps

Influent/Mixing Pumps

Odor Control

Key Components of a Receiving Station

Rock Trap/ Grinders

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Codigestion Case Studies

Des Moines Metropolitan Wastewater Reclamation Authority, Iowa. • 136 mgd, various HSW

Douglas L. Smith Middle Basin WWTP, Johnson County, Kansas • 14.5 mgd, FOG/HSW

Gloversville-Johnstown Joint WWTF, New York • 13 mgd, yogurt/cheese whey

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Des Moines Metropolitan Wastewater Reclamation Facility (DMMWRF) – 50 mgd (134 mgd Capacity)

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HSW Processing System

Truck weigh stations (3) Rock traps (3) HSWs received and blended in HSW receiving tank HSW then blended in another tank with primary and waste activated sludge and fed sequentially to the digesters

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Unloading into Underground HSW Receiving Tank

Up to Three Trucks Can Be Received Simultaneously

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Foaming Control

Foaming events from selected HSW controlled by reducing accepted quantities of these wastes • corn oil and isopropyl alcohol (IPA)

Ongoing digesters upgrades expected to reduce foaming • Submerged-fixed covers • Internal draft tube mechanical mixers

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Feed Volumes

Predominant load is due to HSW

PS (gal/day)

TWAS (gal/day)

HSW (gal/day) Est.

Digesters HRT

Based on Blended Sludge (days)

Average (Minimum-Maximum)

132,000 (42,000−180,000)

98,000 (0−204,000)

160,000 (93,000−297,000)

33 (22−49)

Volumetric Fraction 35% 26% 42%

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Selected Data for Codigested Waste Streams

Brown Grease

Packing Plant DAF

Float

Biodiesel Production

Waste

Trucked Municipal Sludge

Tipping Fee, $/gal $0.0148 $0.026 $0.027 $0.0148 Wastes Accepted 24/7 24/5 24/7 24/5 Digester Feeding 24/7 24/7 24/7 24/7 Flow, gpd 16,700 33,300 32,300 20,100

pH(1) 4.7 (4.0−7.0)

5.7 (5.3−6.5)

5.8 (5.2−8.1)

5.1 (5.0−5.1)

COD(1), mg/L − − 40,000 (700−30,8000) −

TS(1), % solids 5.45 (2.04−9.24)

6.68 (0.91−12.77)

0.3 (0.08−0.68)

2.95 (1.49−4.11)

VS/TS(1), % 88.8 (75.8−95.7)

83.7 (64.9−92.8) − 76.3

(72.1−80.4)

(1)Average (Minimum−Maximum)

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Cargill Financed Part of the Project and Purchases a Fraction of the Produced Biogas for Use in Its Boilers

Cargill

Digesters

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Biogas Production and Utilization

Biogas, cfd Annual Total,

cf

Annual Distribution,

% Used in CHP(1) 524,000 174,000,000 35 Used in Boilers 94,000 50,000,000 10 Sold to Cargill 706,000 239,000,000 48 Flared 8,660 24,000,000 5 Total biogas 1,423,000 500,000,000 100

(1) About 8,800 MWh produced and 25,000 MWh purchased.

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Financial Benefits

Capital Cost New HSW tank $1,750,000 WRA Investment in Cargill biogas utilization project $1,100,000 New submerged fixed concrete digester covers $6,000,000 New digester mixing systems $6,500,000

TOTAL = $15.4 million Annual Revenue

HSW tipping fees revenue $200,000-400,000

Biogas sold to Cargill $300,000-800,000

Annual power produced $370,000(1) TOTAL = $0.9-1.6 million

(1) Calculated as 8,800 MWh produced annually at $0.045/kWh; expected to increase significantly with planned CHP engines and expected power price increase

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Johnson County, Kansas Middle Basin WWTP – 12.5 mgd (14.5 mgd Capacity)

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Process Flow Diagram

FOG/HSW are blended sequentially with primary sludge and thickened WAS

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FOG/HSW Receiving Facility

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Daily Receipts Highly Variable

-

5,000

10,000

15,000

20,000

25,000

30,000

Volu

me

of W

aste

s Rec

eive

d, g

allo

ns

FOG/HSW Received

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Foaming Overflow Events During Codigestion Startup

Were largely eliminated by reducing mixing energy

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Digester Parameters

Parameter Value

Digester dimensions, ft 55 (diameter), 30 (SWD)

Number of digesters 3 VSLR (design), lb VS/cf-d 0.15 VSLR (actual), lb VS/cf-d 0.12 HRT (actual), d 21.8 Mixing type Jet mix Mixing energy input per digester, HP 40(1) Gas Production Rate, cfd Above 250,000(2)

(1) Cycled 1-hour on and 4-hours off in the primary digesters

(2) Before FOG/HSW codigestion (2009) it averaged 125,000 cfd

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-

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

1/1/

2009

3/1/

2009

5/1/

2009

7/1/

2009

9/1/

2009

11/1

/200

9

1/1/

2010

3/1/

2010

5/1/

2010

7/1/

2010

9/1/

2010

11/1

/201

0

1/1/

2011

3/1/

2011

5/1/

2011

7/1/

2011

9/1/

2011

11/1

/201

1

1/1/

2012

3/1/

2012

Dig

este

r Gas

Pro

duce

d, c

ubic

feet

/day

Total Digester Gas 7 per. Mov. Avg. (Total Digester Gas)

Foaming Loss of HSW

Digester 4 Start-up

Start FOG

Addition

Digester Gas Production Increased with Addition of FOG Waste and Other High Strength Wastes

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Digester Gas Cleaning, Storage and Utilization

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Project Financials

Capital cost of codigestion and cogeneration Improvements $10,000,000

Annual FOG/HSW tipping fee revenue $300,000

Annual electrical power from biogas $400,000

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Gloversville-Johnstown Joint WWTF, New York (GJJWWTF) - 6.7 mgd (13 mgd Capacity)

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Codigestion Process Flow Diagram

Secondary Digester

Primary Digester

Whey Flow Equalization

Tanks

Dairy Washwater

Pumped from Industrial Park

Primary Sludge

WAS

BFP Dewatering

Cake to Landfill

Ferric

Thickened Dairy Waste (considering re-routing to

the whey equalization tanks)

Day Tank

Gravity Belt Thickening

Recuperative Thickening

Recycle

Trucked Cheese Whey

Yogurt Whey Pumped from Industrial Park

Blended Raw

Sludge

Sludge Blending

Microstrainingand DAFT

Pretreatment

Sludge blending/equalization Whey equalization Recuperative thickening

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Yogurt Whey has the Lowest COD Concentration but Offers the Major Contribution to Loading and Gas Production

Source Flow (mgd)

COD (lbs/d)

TSS (lbs/d)

TKN (lbs/d)

Cappiello Whey (cheese) 0.012 10,010 270 110

FAGE Whey (yogurt) 0.056 23,600 3,020 470

Euphrates (cheese) 0.007 5,840 280 90

Yogurt whey COD ~ 30,000 mg/L and cheese whey COD ~ 100,000 mg/L

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2002 vs. 2011 Performance Comparison

Parameter 2002 2011(1) VS Loading, lb/cf-d 0.06 0.21 Hydraulic Retention Time, days 34 − Solids Retention Time, days 34 − Volatile Solids Reduction, % 40 − Digester gas Generation, cfd 83,000 310,000

Digester Gas Production, cf/lb VSR 13 − Methane Content, % 68 − Annual Electrical Production, MWh 816 5,000

Cake TS, % solids 18−20 14 (1) Projected based on January 2011 data

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Revenue from HSW Receiving

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000 19

99

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Trucked & Pumped Waste Revenue

$1,000,000 annual revenue for 6.5 mgd facility

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Facility is Largely Energy Self-Sufficient

Remains connected to the power grid for reliability

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Capital Cost

Total Project Cost $11,500,000

NYSEDRA Grant Funding $1,400,000

ARRA/NYSEFC Grant Funding $6,000,000

Total grand funding $9,600,000 Net Cost $1,900,000

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Project is Highly Profitable

Incremental Cost Incremental chemical cost $100,000 Incremental dewatered solids landfill disposal cost

$300,000

Incremental CHP O&M due to increased CHP capacity

$100,000

Biogas drying $50,000 Revenue Power generated $640,000 Pumped-trucked waste receiving fees

$992,000

(1) Power @ $0.12/kWh Annual revenue significantly exceeds cost

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Conclusions

The three analyzed facilities had different • Capacities • Codigested HSWs • Cost structure (tipping fees, unit power cost, biosolids disposal cost)

All three facilities realized significant increase in biogas production and electrical power savings Benefits included • Financial gains • Serving the local communities and industries • Environmentally sound utilization of the HSWs

An increasing number of HSW codigestion facilities are expected to continue being implemented

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Acknowledgements

John Kabouris, PhD, PE, CH2M HILL Tim Shea, PhD, PE, BCEE, CH2M HILL Larry Hare, Des Moines Metropolitan Wastewater Reclamation Authority, Iowa; Doug Nolkemper, Douglas L. Smith Middle Basin WWTP, Johnson County, Kansas; Operations staff at Gloversville-Johnstown Joint WWTF, New York

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Codigestion Case Studies Enhancing Energy Recovery From Sludge

Dale Gabel, PE, BCEE

MWRD PWO Seminar

May 23, 2012

Questions?