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One Year of Energy Net-Zero Via Energy Efficiency and FOG Codigestion

at the Gresham, OR WWTP

Jeff Maag, Project Manager, Wastewater Services Division, City of GreshamJeff McCormick, Project Manager, Carollo Engineers

City of Gresham WWTP

Gresham’s Wastewater Treatment Plant

114,000 service population 13 mgd annual average flow

Secondary, Activated Sludge, Anaerobic Digestion Discharge to Columbia River Contract Operator: 17 FTE in Operations & Maintenance

(Veolia Water) 3 FTE in WWTP and PS Engineering (City of Gresham) One of a handful of Energy Net-Zero WWTP’s in the U.S. Energy Net Zero: producing more energy than consumed

City of Gresham WWTP 2

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New era of energy production began in 2005 with modern 400 kw Cogen No. 1

City of Gresham WWTP

Two 1 million gallon Anaerobic Digesters at WWTP Digesters treat solids in absence of air – biogas is

produced (65% methane, 35% CO2) Cogen burns biogas to produce electricity and hot water

CAT Model G3508LE

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Cogen 1 Has Been Very Successful

93% Runtime since 2005 (off about 48 hours per month) Produces power and heats buildings with jacket water heat 55% of WWTP Power needs $250,000 annual avoided electrical costs 2.1 cents per kwh operation/maintenance expenses 3.5 year payback

City of Gresham WWTP

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Several major developments in 2008 and 2009 on our path to energy net-zero

ACWA / Energy Trust “Energy Independence Project” studied 2 plants in Oregon, including the Gresham WWTP

Gresham City Council passed a Sustainability Policy Kicked off feasibility study of FOG Receiving Station and Cogen

Expansion Solar Array became operational

City of Gresham WWTP

Energy Independence ProjectEnergy Independence ProjectA Project for

Oregon Association of Clean Water Agencies and

The Energy Trust of Oregon

Prepared by Kennedy/Jenks ConsultantsJune 2008

Energy Independence Project

General Recommendations

▼ Do Energy Efficiency First!l Most cost-effective optionl An energy audit can help identify cost-effective

Energy Efficiency Measuresl Install identified EEMs and seek funding $

▼ Resource Optionsl Cogen engines are the most cost-effective for

producing renewable energyl Investigate a FOG Receiving program to enhance

digester biogas production and energy possibilities

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Gresham’s Sustainability PolicyKey Goals (2009)

1) 80% Reduction in City Greenhouse Gas Emissions by 2050

2) 100% Renewable Energy by 2030

3) Zero Waste in City Operations by 2020

4) Ongoing Protection of Natural Resources (including water quality and availability, and habitat)

5) Toxin Reduction and Eventual Elimination

WWTP had large potential to contribute towards goal 1 and 2.

City of Gresham WWTP

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FOG Feasibility Study Highlights

$40,000 Grant from State Economic Development Dept. Adding FOG Receiving Facilities is Economically Viable There is a market for this service in our area An additional 400 kw Cogenerator is economically viable FOG Tipping Fee of at least 3 cents per gallon required Need 7,000 to 11,000 gpd of FOG Estimated cost of $3.7 million Leverage $1.5 million in potential grants Simple payback of 7 years

City of Gresham WWTP

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420 kw Solar Array installed 2009 Installation Dec. 2009 420 kW peak capacity Provides 7% of WWTP power 1+ acre ground-mounted system Power Purchase Agreement with

SunEdison in July 2009 PGE net metering agreement No capital cost to City kwh charge 2/3 PGE rate Fixed annual escalation of 3%

City of Gresham WWTP

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2010 Energy Management Team

City of Gresham WWTP

Set Goal for Energy Net-Zero WWTP by 2015 Selected Energy Team Members (Team Leader, Ops

Manager, engineering, Maintenance Manager) Meet Monthly for 1 hour and talk only energy Develop Energy Management Plan (keep it simple) Update and discuss Monthly energy production and

consumption numbers every month Select, prioritize and evaluate projects Stay on track! Keep running agenda in Energy Management Plan

2011 Master Plan included continued study of “Energy Independence”

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FOG Receiving / Cogen Expansion and “Energy Independence” was included in our master planning process

City of Gresham WWTP

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New high efficiency Neuros blowers and

aerationdiffusers replaced aging equipment

City of Gresham WWTP

Linear Motion Mixer

Aging digester gas mixing was replaced by Linear Motion Mixers

Energy Conservation Project, 2012 - 16%Energy study funded by Energy Trust

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Replace aging, out of date blowers with

modern efficient blowers

Replace 2 Hoffman mutistage blowers (100 hpeach)

Install 2 Neuros Turbo blowers (100 hp each) Operating curves are much more efficient 50% variable speed turndown Air bearings

City of Gresham WWTP

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Inefficient Sock Diffusers

High Efficiency Disk Diffusers

City of Gresham WWTP

Linear Motion Digester Mixers

City of Gresham WWTP16

Replace aging biogas mixing system (3 - 40 hpcompressors)

Install Linear Motion Mixers (LMM) for both digesters

Each LMM has 20 hp motor and VFD

Currently operating at 75% speed and 5 hp.

Essentially trading 80 hp 24 hrs/day for 10 hp 24 hrs/day

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Linear Motion Mixer (Inside Digester)

HydroDisk Diameter 8 feetTravel (up and down) 20 inches30 cycles/minute

City of Gresham WWTP

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FOG Receiving Station, Phase 1, 2012

10,000 gallon FOG Receiving Tank FOG Grinder, FOG Unload/Tank Mixing Pump and FOG

Feed Pump FOG Heat Exchanger using Cogen Hot Water Loop

City of Gresham WWTP

FOG Receiving Station, Phase 1, 2012

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Advertised RFP for FOG Haulers 3 FOG Haulers Contracted – must be Preferred Pumpers 8 cent per gallon tipping fee 7,500 gpd received during phase 1 – small tank difficult to

operate effectively

City of Gresham WWTP

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Energy Net-Zero Project, Phase 2AFOG Receiving Station Expansion, 2014

Added 20,000 gallon receiving tank 30,000 gallon total capacity as of April, 2014 Major Increase in Biogas Production, now receiving

12,000 gpd, $300,000 in tip fees in 2015City of Gresham WWTP

Energy Net-Zero Project, Phase 2B:400 kw Cogeneration Expansion

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The flared biogas to be utilized in additional 400 kw Cogenerator 2

$2.8 million design and construction $1.4 million in grants Completed January, 2015

City of Gresham WWTP

Energy Net-Zero Project, Phase 2B400 kW Cogeneration Expansion

City of Gresham WWTP 22

COGEN 1 COGEN 2

Energy Building ?

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Biogas Production Trends

2014 Gas production up 60%+ from baseline Produced more energy than we consumed in 2015 Flared 20% of biogas production in 2015 (Future project?)

City of Gresham WWTP

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2010 2011 2012 2013 2014 2015

Biogas (SCF/day) and FOG Injection (Gal/day)

Biogas FOG

FOG Phase 1

FOG Phase 2A

Cogen 2 Phase 2B

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Biogas Scrubbing Required for Successful Cogen

City of Gresham WWTP

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Biogas Scrubber Media Largest Cost of the treatment system H2S Iron Sponge Media replaced every 60-120 days H2S media changed when treated biogas > 100 ppm Siloxane media Changed every year (switch tanks 6

months) 1 per year siloxanes testing, unreliable and expensive Storage required for media so it is ready to go Change cogen oil (if needed) when media is replaced for

½ day outage. $10,000 per H2S Media Changeout (3 per year) $6,600 per Siloxane Media Changeout (1 per year) About $0.01 per kWh O&M cost

City of Gresham WWTP

March 2015 – first net zero month

City of Gresham WWTP 26

NET-IMPORT

NET-EXPORT

March 2015Net-Export 68,000 kwh

NET-ZERO

This is possible with a net metering agreement with PGE

Need special Net Metering Meter (installed by PGE)

27City of Gresham WWTP

No electricity purchased from PGE sinceFebruary, 2015 - Energy Net-Zero Goal Met!

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Annual Energy Trends Since 2005

City of Gresham WWTP

Net-Exporter

2005-2015 Consumption and Production

17% reduction in Power Consumption One Year of Energy Net-Export in March, 2016 0 kWh PGE Utility Bill each month for a Year 595,000 kWh of Net-Exported power donated to PGE

(worth $22,000 wholesale rate)

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2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Gresham WWTP Power Production and Consumption (kWh)

Solar

Cogen 2

Cogen 1

Consumption

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Annual Savings

City of Gresham WWTP

Net-Exporter

2005-2015 Consumption and Production

Approximately $750,000 per year ongoing savings $3,500,000 in savings since 2005

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2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Annu

al S

avin

gs/R

even

ue10-Year Avoided Utility Costs and

FOG Tipping Fee Income

Cogen 1 Cogen 2 FOG Solar

Energy Projects Cost Summary

City of Gresham WWTP

Energy Trust Technical Assistance and Incentives State of Oregon BETC Program State of Oregon CHP Business Energy Incentive

$1,364,147

$2,254,938

$5,971,934

$0

$2,000,000

$4,000,000

$6,000,000

$8,000,000

$10,000,000

$12,000,000

10 Years of Energy Related WWTP Projects

Gresham

ODOE

Energy Trust

38% 

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Cogeneration O&M Costs

City of Gresham WWTP

Net-Exporter

About $0.03 per kWh O&M Costs Includes Labor & Materials for O&M.

¢ 2.1

¢ 1.2

¢ 8.0

¢ 0.0

¢ 1.0

¢ 2.0

¢ 3.0

¢ 4.0

¢ 5.0

¢ 6.0

¢ 7.0

¢ 8.0

¢ 9.0

2005 thru 2014

O&

M C

ost p

er k

Wh

400 kw Cogeneration O&M Cost Summary

BiogasTreatment

Cogeneration

Avoided Utility Rate

Awards and Recognition 2015 OR APWA Environmental

Project of the Year 2015 American Biogas Council

Project of the Year Award 2014 Clean Energy States

Alliance, State Leadership in Clean Energy Award

2015 ACWA Outstanding Member Agency

2015 Recognized in EPA report on Sustainable Water Future

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Questions?

City of Gresham WWTP

Jeff Maag, Project Manager, Wastewater Services Division, City of GreshamJeff McCormick, Project Manager, Carollo Engineers