Acceptance of Food Waste at the MWRA -...

Acceptance of Food Waste at the

MWRA - Capacity

Dave Duest

Manager of Process Control

Deer Island, MWRA

Environmental Business Council of New England

Energy Environment Economy

Massachusetts Water Resources Authority

Environmental Business Council

Acceptance of Food Waste at the MWRA:

Transport & Processing

David Duest Manager, Deer Island Process Control

Dave.Duest@mwra.com

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Agenda

• An Introduction to MWRA / Deer Island Treatment Plant

• How does MWRA receive/treat residuals

• Source Separate Organics / Co-Digestion Pilot

• MWRA Guidance on Food Waste Grinders

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An Introduction to MWRA

• MWRA provides wholesale water and wastewater services to over 2.5 million customers in 61 communities (34% of Mass. Population)

• On average, MWRA delivers 200 million gallons per day to its water customers

• MWRA collects and treats an average of 365 million gallons of wastewater per day

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The Deer Island Treatment Plant

• Constructed from 1990-2001, $3.8 billion Boston Harbor Project

• Second largest wastewater treatment plant in the country

• Average flow of 365 million gallons/day

• Peak capacity 1.3 billion gallons/day

• Treated wastewater is discharged 9.5 miles

into >100 ft waters of Mass. Bay – Effective dilution 75-350x

MWRA Residuals Recycling

Deer Island Treatment Plant: Removes 94+% solids & organics from WW

End Result: Class A Fertilizer & Renewable Fuel for Energy Recovery

Deer Island Treatment Plant Processes

Deer Island Treatment Plant – Residuals Processing

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Residuals Processing Statistics for Deer Island

• Sludge to Digestion – 246 dry TPD

– 70% as Primary sludge – from gravity thickening

– 30% as Waste Secondary sludge – from centrifuge thickening

– Residence Time in Anaerobic Digestion: 21 days avg.

– 62% Volatile Solids destruction (industry avg. is 45-55%)

• Sludge to Pelletizing Plant – 106 dry TPD

– Pellet Plant dewaters, dries, & pelletizes all digested sludge

– All pellets go to beneficial re-use:

• turf farms

• golf courses

• fertilizer blenders

• cement kiln

– Pellet rating as a slow release

fertilizer: 4-3-0

Treatment Processes – Energy Profile

Generation by Source

• Energy Demand – 152 M kWh annually

• On-Site Generation – 40 M kWh annually (26%, 24% by green sources)

• Digester Gas – An important Energy Source on DITP

• 189 kscfh (>97% beneficially utilized)

• 28-30 M kWh in electricity

• 98.4% of heat of boiler heat met by Digas

• 62% of DITP total energy profile, $18.7 M value in FY13

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Source Separate Organics / MWRA Co-Digestion Program to Date

• Digester Gas System Capacity Analysis (complete)

• Determine bottlenecks in existing Digas Utilization Processes

• Co-Digestion Feasibility Study (complete)

• Evaluate overall Co-Digestion Feasibility & Costs

• Further Evaluate CHP options to enhanced Green Energy Potential

• Co-Digestion Bench Scale Study (complete)

• Refine performance parameters to improve cost analysis

• Co-Digestion 1-2 Digester Pilot (expected start – June 2, 2014)

• Further refine performance parameters and operational impacts

• Measure impacts to Operation & Determine Future Program if any

Co-Digestion – Pilot (1-3 years, starting June 2, 2014)

• Receive Pre-processed Source Separated Organics

(“PSSO”) via Tanker Trucks

• Pilot operational plan Year 1:

Time Quantity Digas Sludge to FRSA

Baseline 246 dtpd to digestion 186 kscfh 106 dtpd

Month 0-1 Phase in up to 7 dtpd 0 to +4.2% 0 to +1.4%

Month 1-4 7 dtpd (+2.8%, 20% to 1 dig) +4.2% +1.4%

Months 5-7 14 dtpd (+5.7%, 40% to 1 dig) +8.5% +2.9%

Months 8-9 14 dtpd (20% to 2 dig) same same

Months 10-12 21 dtpd (+8.5%, 30% to 2 dig) +12.7% +4.3%

7 dtpd @ 14% = 12,000 gpd digester feed rate. 2 - 3 trucks/day 5 day schedule.

21 dtpd @ 14% = 36,000 gpd digester feed rate. 6 - 7 trucks/day 5 day schedule.

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Food Waste Management – an MWRA Perspective

• MWRA Guidance – Food Waste Transport to Sewer System via Garbage Disposal

– Recently published Draft Guidance in response to customer inquiries

• Draft presented to MWRA Board of Directors - Sept 2013 Meeting

• Residential & Commercial Use Discussed

• Guidance based on MWRA Sewer Use Regulations (360 CMR 10.000).

These regulations allow for garbage disposals

• Guidance provided no formal recommendations or regulations

• Lists Key cautions from Sewer Use Regulations:

– Avoid sewer disposal methods that could contribute to sewer clogs/blockages

– Prohibits Fats, Oils & Grease > 300 mg/L to sewer (360 CMR 10.024)

– Avoid material that will cause or contribute to the creation of a public nuisance…which result in the presence of toxic gases (H2S formation)

– Prohibits Water or Wastewater discharges with a pH <5.0 or >12.0

– Prohibits “Any Slugs”

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Food Waste Management – an MWRA Perspective (continued)

• Residential Use Guidance

– Discusses environmental benefits of food waste grinders

• Food waste to DITP produces methane gas which helps produce renewable energy

• DITP produces fertilizer. FW improves fertilizer quality.

• Results in a reduction in costs & emissions that would occur transporting household waste

– Concerns:

• FOG can cause clogs in household & municipal plumbing. Cautions its disposal by sewer.

• Commercial Use Guidance

– Guidance is still emerging as regulations develop

– MWRA recommends not using disposals or grinders (not a regulation):

• Food waste is highly organic. Can cause or contribute to significant H2S formation in local sewer pipes creating hazards & pipe destruction

• FW can cause or contribute to pipe blockages.

• Other avenues exist to better dispose of the material: Commercial haulers are readily available to pick up source separated material for a variety of beneficial uses, including for use in DITP’s pilot co-digestion project.

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Conclusions

• MWRA utilizes Organic Residuals in a Green Way

• Digester Gas is a valuable resource to MWRA

• MWRA Source Separated Organics Program is developing quickly

• 1-2 Digester Pilot / Co-Digestion ready to kick off June 2, 2014

• MWRA Guidance on Food Waste Grinders

– Guidance as drafted recommends, does not regulate

– Residential Use – a good thing, avoid FOG

– Commercial/Industrial Use – MWRA would like Source Separation to prevail, not sewer discharge to prevent blockages, H2S formation, pH failures & slugs