acceptance of food waste at the mwra -...
TRANSCRIPT
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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
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Massachusetts Water Resources Authority
Environmental Business Council
Acceptance of Food Waste at the MWRA:
Transport & Processing
David Duest Manager, Deer Island Process Control
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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
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MWRA Residuals Recycling
Deer Island Treatment Plant: Removes 94+% solids & organics from WW
End Result: Class A Fertilizer & Renewable Fuel for Energy Recovery
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Deer Island Treatment Plant Processes
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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
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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
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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