DEVELOPMENT OF AN INTEGRATED HAULED WASTE · PDF fileDEVELOPMENT OF AN INTEGRATED HAULED WASTE PROGRAM ... stock than to store gas ... generator sets, each ~600 kW

DEVELOPMENT OF AN

INTEGRATED HAULED

WASTE PROGRAM

Royce Hammitt, Des Moines Wastewater Reclamation Authority (WRA)

Des Moines Wastewater

Reclamation AuthorityAltoona - Ankeny - Bondurant - Clive - Cumming - Des Moines -

Greenfield Plaza/Hills of Coventry - Johnston - Norwalk - Pleasant Hill –

Polk City - Waukee - West Des Moines - Polk and Warren Counties -

Urbandale/Windsor Heights and Urbandale Sanitary District

Working together to protect

public health and enhance the

environment by recycling

wastewater and being the

preferred treatment facilities

for hauled liquid wastes

Operating Contractor - City of Des Moines

8/19/14 Midwest Governor's Association Tour 2

• The Des Moines WRF serves a population of 500,000

• Treated nearly 26 billion gallons of wastewater or about

72 million gallons per day in 2009

• Actively seeks to improve efficiency in use of resources


Water19%

Aviation10%

Building Services

7%

Civic Center3%

Library1%

Misc1%

Parks3%

Street Lights30%

Traffic3%

Wastewater23%


Water and Wastewater Demands Energy

Source: Texas Comptroller of Public Accounts

Typical Large City Electrical Usage

Wastewater Plants Can Produce Enough Electricity to

Meet Demands


Aeration and

other liquid

processes

Solids processes

Pumping

Lighting

Anaerobic

digestion of

wastewater solids

Additional energy from

biosolids and other

renewable sources

Electric Demand Potential Electric Supply

Other organic waste

including FOG (fats, oils,

and grease)

Source: David L. Parry, CSWEA, Oct. 2010

A Wastewater and Organic Waste Treatment

Center


Hauled organic wastes account for 42% of the feed to the

anaerobic digesters

Des Moines Wastewater Treatment Plant, Des Moines, IA

2010 WERF Interim Report – Waste

Characterization




Hauled Wastes• Sources

• Sludges from regional

WWTP’s

• Industrial and food

processing wastes

• Issues• Spikes in biogas

• Foaming

• Received 24/7!


Original Trucked Liquid

Waste (TLW)

• Little storage

• Loads transferred to

digester as they arrive

and unload

New TLW Facility

• Storage

• 160,000 gallons

• Carry over of wastes

through weekend

• Costs less to store feed

stock than to store gas


COMBINED HAULED WASTE

PROJECT


NEW UNLOADING

FACILITY

Trucked Liquid Waste Storage


COMBINED HAULED WASTE

PROJECT RESULTS

• Tanker unloading time

reduced by 50%

• Areas of congestion

eliminated

• Customers (haulers)

give positive comments


WRF Hauled Waste -- Regional8/19/14 Midwest Governor's Association Tour 16


“If you build it – they’ll come”


0

100

200

300

400

500

600

700

800

900

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun

x 1

00

0 g

all

on

s

Restaurant Grease Hauled to WRF

FY13

FY12

FY11

FY10

FY09

FY08

FY07

FY06

Existing Facilities8/19/14 Midwest Governor's Association Tour 19

Tasks & Objective of the BioEnergy

Master Plan


Enhance biogas

production

Maximize use of

biogas

Develop Economic Model

Improve digester

facilities

Reliable,

Flexible System

for the Future

EvaluationProcess

WRA’s Existing Program


AnaerobicDigestion

BiogasStorage

50 MGD

0.14 MGD

Sludges

Hauled Wastes

Biosolids to Land Application

Process Heating

Building Heating

Power Generation

Industrial User

Primary and Secondary Treatment

> 30 loads/day

0

250,000

500,000

750,000

1,000,000

1,250,000

1,500,000

1,750,000

2,000,000

2,250,000

1/8/07 2/27/07 4/18/07 6/7/07 7/27/07 9/15/07 11/4/07 12/24/07 2/12/08 4/2/08 5/22/08 7/11/08 8/30/08 10/19/08

Cu

.Ft

/ D

ay

Date

Total Production

Total UsageObjective < 5% loss

Daily Biogas Production and Usage


Evaluation Process

• 11 economic and noneconomic criteria

• WRA staff developed weighting


0 25 50 75 100

Weight

Ease of O&M

Proven and Reliable

Lifecycle Costs

Task 1


Improve digester

facilities

Reliable,

Flexible System

for the Future

EvaluationProcess

Required Digester Improvements• Covers Evaluated


Fixed Steel Floating Gas Membrane

Submerged Fixed

Concrete

Submerged Fixed Cover Gas Dome


Gas Withdrawal

Gas Dome

Spray Nozzles

EmergencyLiquid Level

Overflow toStandpipe

NormalOperatingLevel

Normal Overflow to Standpipe(Embedded in Cover) Emergency Overflow

Pipe to U-Tube Gas Seal

3" Gas Pipeto Standpipe

Recirculation fromTank Bottom

Transflow3-Way Valve

Pressure VacuumRelief

Digester Covers Selected• Primaries – Submerged Fixed Covers

• Ease of O&M

• Foam control

• Increased capacity (~8%)


• Secondary – Gas Membrane– Biogas storage

– Biosolids storage

– Dewatering operations flexibility

Examples of Covers


Task 2


Enhance biogas

production

Improve digester

facilities

Reliable,

Flexible System

for the Future

EvaluationProcess

Methods Evaluated for Increasing Biogas

Production

• WAS pretreatment

– MicroSludge®

– OpenCEL

• Advanced digestion– Extended thermophilic

– Temperature phased (TPAD)


Conclusions for Enhancement Evaluation

• WAS Pretreatment• Limited benefit due to small fraction of TWAS

• Potential increase in biogas production ~ 7%

• Payback > 20 years

• Advanced Digestion• Increased capacity & Class A product

• Potential increase in gas production ~ 10-15%

• Payback >15 years

• Best Option• Increase hauled waste volume


Task 3


Enhance biogas

production

Maximize use of

biogas

Improve digester

facilities

Reliable,

Flexible System

for the Future

EvaluationProcess

Model Biogas Storage and Use


Biogas Storage Evaluation


Capacity

(cf)% of Biogas Flared

Current Future

475,000 6.1 13.8

805,000 5.8 13.6

Increased

storage is

important, but

not the key!

Natural Gas Use

Alternatives for Increasing Use

• Replace natural gas use at plant

– Supply additional boilers

– Produce biomethane for plant-wide use

• Produce additional power• More operating time

• Additional engine generators

• Sell to gas utility

• Increase volume sold to industry


Boilers

Misc.

Other

Natural Gas Usage in Plant Boilers



Additional Generation

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

1,800,000

Jun'13

Jul '13 Aug'13

Sep'13

Oct'13

Nov'13

Dec'13

Jan'14

Feb'14

Mar'14

Apr'14

May'14

KW's Purchased vs Generated

Purchased 19,424,008 Generated 12,758,651

Generated:Average: 39.6%Last Month: 44.7%

Current Engines


• 3 engine

generator sets,

each ~600 kW

• In 2010, used

over 190 million

cubic feet of

digester gas to

generate

almost 10

million kWh of

electricity

New Engines – (4) 1.4 MW Jenbacher


Compressed Biogas (CBG) Production

Options

• Pressure Swing Absorption (PSA)– Low energy (~60KW)

– Experience with biogas

– Operational flexibility

• CO2 Wash– High energy (~300KW)


Use of Biogas by Local Industry

• Averaging 700,000 cfd

• Capacity of 1,200,000 cfd

• Conveyance system limits

• Potential for 1,700,000 cfd in future


Use of Biogas by Local Industry


Staged Approach to Expanding Biogas Use

• Increase industry use preferred• Proven, reliable

• Minimal affect on O&M

• Backup power generation associated with High

Rate Treatment Facility (separate project)• Add 4 new 1.4 MW engine generators (2 CHP biogas, 2

Emergency)

• Use in boilers possible in future• Proven, reliable system

• Reduces natural gas dependence

• Payback ~ 12 years


Task 4


Enhance biogas

production

Maximize use of

biogas

Develop Economic Model

Improve digester

facilities

Reliable,

Flexible System

for the Future

EvaluationProcess

Process & Economic Model


Model

Primary& WAS

4 Different

Wastes

Digestion process

parameters

PowerNatural Gas

Tip FeesTreatment CostsLand Application

DewateringBiogas Options

Monthly Biogas Balance

Present Worth

OutputInput Parameters

Natural Gas Storage Range


Natural Gas Price Volatility


Example of Economic Model Output


•Reliable systems to

provide valuable

public services

•Increased revenue

potential

•Flexibility for multiple

uses of biogas will be

critical


Digestion / Biogas System Improvements will

Enhance WRA’s Overall Sustainability


Questions?

[email protected] 515-323-8001

mailto:[email protected]

Documents

DEVELOPMENT OF AN INTEGRATED HAULED WASTE · PDF fileDEVELOPMENT OF AN INTEGRATED HAULED WASTE PROGRAM ... stock than to store gas ... generator sets, each ~600 kW