USING FOG TO INCREASE ENERGY PRODUCTION AT A MUNICIPAL WASTEWATER - - PowerPoint PPT Presentation

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USING FOG TO INCREASE ENERGY PRODUCTION AT A MUNICIPAL WASTEWATER - - PowerPoint PPT Presentation

Sep 17, 2023 840 likes •1.08k views

USING FOG TO INCREASE ENERGY PRODUCTION AT A MUNICIPAL WASTEWATER TREATMENT FACILITY 2015 Pollution Prevention Roundtable Workshop By Clayton Brown Source Control Manager, Clean Water Services CLEAN WATER SERVICES Established in 1970

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USING FOG TO INCREASE ENERGY PRODUCTION AT A MUNICIPAL WASTEWATER TREATMENT FACILITY

2015 Pollution Prevention Roundtable Workshop

By Clayton Brown Source Control Manager, Clean Water Services

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  • Established in 1970
  • Water resources management utility

serving more than 560,000 residents of urban Washington County

  • 12 Partner Cities
  • Budget: $64.6M Operating/$66M Capital
  • Close working relationship with

Washington County, but a separately managed and financed public utility

CLEAN WATER SERVICES

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TUALATIN RIVER WATERSHED

ROCK CREEK FACILITY FOREST GROVE FACILITY HILLSBORO FACILITY DURHAM FACILITY

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  • Among the first watersheds in the nation

with a TMDL—1988, revised in 2001

  • 712-square mile basin, 80-mile river
  • Only source is rainfall
  • Cleaned water and release of stored

water is nearly 70% of summer flow

  • Water quality is better than it’s been

in decades

TUALATIN RIVER FACTS

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CORE BUSINESS AREAS

  • Resource recovery—treating wastewater to produce:
  • Clean water
  • Fertilizer
  • Energy
  • Stormwater/surface water management to:
  • Prevent pollution
  • Control drainage
  • Enhance river and stream health
  • Protect fish and wildlife habitat
  • Water supply
  • Flow monitoring and management
  • Long term planning for regional growth
  • Regional partnerships
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DURHAM WWTP ENERGY FACILITY UPGRADE

  • Replaced a 500 kW energy generation

facility with a 1700 kW facility

  • New facility provides 60% of the energy

used at the WWTP (13 million kWh/yr.)

  • New facility consists of FOG receiving

station, FOG storage tanks, gas storage, gas treatment system, two reciprocating engines, generators, and heat recovery system

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WHAT IS FOG?

  • Fats, oils and grease (FOG) from

food service establishments

  • Also known as “brown” grease
  • Distinguished from “yellow” grease
  • Caught in grease traps and

interceptors before it enters the sanitary sewer system

  • Often disposed of in landfills
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FOG IS A GAME CHANGER

  • Add FOG to the digesters at Durham, where it

will be converted to biogas

  • Biogas will be burned in the new cogeneration

facility, where it will produce electricity and heat

  • FOG will help the Durham plant triple its

energy production

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FATS AND GREASE ARE THE BEST WASTE FOR MAKING BIOGAS

Cubic meters of biogas production per ton of substrate

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CWS tested FOG and food waste from a local food processor at scale Outcome: FOG produced more than twice as much biogas as the food waste

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HOW DO WE GET FOG?

  • FSEs contract with FOG haulers to

clean their grease removal devices

  • The FOG haulers have to dispose of

the waste somewhere—why not here?

  • Two options:
  • 1) Develop an R&O and hang up a

“we’re open” sign OR

  • 2) Award contracts to selected haulers
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FOG TO ENERGY PROCESS

FOG Trucks →→FOG Receiving Station →→FOG Storage Tanks →→Digester →→Biogas →→ Biogas Storage→→Engine Generators→→ Electricity and Heat →→Treatment Plant Operations

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HOW MUCH FOG DO WE NEED?

  • 100,000 gallons per week (at 7%

solids)

  • About three 5000 gallon truck

loads per day

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RFP HIGHLIGHTS

  • All proposers must be Preferred

Pumpers

  • Proposers submitted:
  • A) proposed price
  • B) weekly volume range
  • Contractors selected based on

goals of maximizing revenue and maintaining stable FOG supply

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FOG ECONOMICS

  • CHP project construction cost:

$14.6 million

  • Grants received:

$5.8 million

  • Expected tipping fee revenue:

$350,000/yr.

  • Avoided power/heating costs:

$800,000/yr.

  • Simple payback

(including O&M cost): 9 yrs.

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FOG CHALLENGES

  • Variables outside of hauler control

impact reliability of supply

  • FOG haulers cannot guarantee a

specific quantity on a specific date

  • CWS uses large FOG storage

tanks (70,000 gallons) to compensate for this

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FOG CHALLENGES

  • FOG loads are highly

variable in volatile solids content

  • Energy content is a function
  • f volatile solids content
  • CWS uses large storage

tanks to blend several loads at a time

Percent Volatile Solids

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FOG CHALLENGES

  • FOG can contain contaminants that

are capable of causing damage to pumps and other treatment equipment

  • These include chunks of concrete

from FOG interceptors, bones, eating utensils, and rags

  • CWS has equipment that is

designed to manage contaminants, including a “rock trap”

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FOG CHALLENGES

  • Digester upsets can occur
  • A digester is a biological system
  • Adding FOG to a digester is like

eating rich food

  • Digester conditions must be

monitored at all times and adjustments made to FOG feed rates when conditions require

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IDEAS FOR USING FOG-TO-ENERGY PROGRAMS to Improve FOG Management

  • Require contract FOG haulers to be in

the Preferred Pumper Program

  • Establish a fund from FOG tipping fees

to assist restaurants with GRD upgrades

  • Charge lower tipping fees to haulers

serving restaurants that meet certain standards

  • Use tipping fee revenue to increase

staffing for regulatory oversight

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City of Gresham’s wastewater plant accepts FOG, generates about 18,000 kilowatt/hours per day, and is now energy independent

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QUESTIONS?