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Maximizing Digester Gas Production to Create More Sustainable Maximizing...آ  2011-09-15آ ...

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  • Maximizing Digester Gas Production to Create More Sustainable

    Maximizing Digester Gas Production to Create More Sustainableto Create More Sustainable

    Wastewater Treatment Facilities to Create More Sustainable

    Wastewater Treatment Facilities

    Dave Reardon PE BCEEDave Reardon PE BCEEDave Reardon, PE, BCEE National Director

    Water Sustainability

    Dave Reardon, PE, BCEE National Director

    Water Sustainability

  • To Be Truly Sustainable, You Want to To Be Truly Sustainable, You Want to Optimize the Impacts of the PlantOptimize the Impacts of the PlantOptimize the Impacts of the Plant Optimize the Impacts of the Plant

    Inputs/OutputsInputs/Outputs

    Energy (Electricity, Gas, Fuels)

    Air Emissions

    Chemicals Biosolids

    Various Supplies

    Solid Waste

    TreatedS pp

    Raw Sewage, FOG Septage

    Treated Effluent

    RenewableFOG, Septage, Food Waste

    Renewable Resources

  • Today, We Are Going to Look at Today, We Are Going to Look at One InputOne Input

    Energy (Electricity, Gas, Fuels)

    How do we get to zeroget to zero

    energy?

  • Can Your Plant Be Energy Can Your Plant Be Energy llNeutral?Neutral?

  • Few Wastewater Treatment Plants in the Few Wastewater Treatment Plants in the World Claim to Be Energy Self SufficientWorld Claim to Be Energy Self SufficientWorld Claim to Be Energy Self SufficientWorld Claim to Be Energy Self Sufficient

    Strass Wastewater Treatment Plant, Austria

  • Treatment Process Selection Has a Treatment Process Selection Has a P f d I t E /S t i bilitP f d I t E /S t i bilitProfound Impact on Energy/SustainabilityProfound Impact on Energy/Sustainability

    Energy 5,000

    6,000

    Energy Intensity (kWh/MG) 3,000

    4,000

    1,000

    2,000

    Conventional Activated

    Conventional Activated Sludge

    Membrane Bioreactor

    0

    Activated Sludge

    Activated Sludge with Nitrification-

    Denitrification

    Bioreactor (MBR)

  • Here’s How We Get to ZeroHere’s How We Get to Zero Gap: 11% Solar, Wind, More FOG, or Food Waste Carbon Credits90

    100

    Resolve Overdesign 5%

    6% 5%

    Waste, Carbon Credits

    70

    80

    90 EMS (Energy Management System)

    Optimize Primary Clarifier FOG (Fats, Oil, and Grease) and Food Waste Digestion

    25% 50

    60

    70 Contribution

    % of Plant Power

    4% 8%30

    40

    50Power

    Fuel Cell Cogeneration

    6% Precondition WASPrecondition WAS

    Conventional Cogeneration (Engines)30% 10

    20

    Energy Reduction or Energy Production Ideas

  • First and Foremost, You Will Need First and Foremost, You Will Need A bi Di ti fA bi Di ti f Bi lidBi lidAnaerobic Digestion of Anaerobic Digestion of BiosolidsBiosolids

    C ti l Di tConventional Digesters

    Egg-Shaped Digesters

    Cambi

  • So… How Can You Produce More So… How Can You Produce More Biogas So That You Can AchieveBiogas So That You Can AchieveBiogas So That You Can Achieve Biogas So That You Can Achieve

    Net Zero Energy?Net Zero Energy? 1. Capture more biosolids in raw wastewater

    and divert to digesters 2. Don't burn up biosolids

    in the aeration system 3. Condition biosolids (WAS)

    prior to digestion 4. Anaerobic digestion optimization 5. Digester detention time5. Digester detention time 6. Co-Digestion (FOG and food waste)

  • But First.. How Much Biogas Will But First.. How Much Biogas Will Di t P d ?Di t P d ?Digesters Produce?Digesters Produce?

    About 10,000 to 12,000 cfd digester gas per mgd

    f l t fl (d ti I use 10,000 cfdof plant flow (domestic strength)

    I use 10,000 cfd

    This will produce 20 to 25 kW in a cogeneration faciityg y

  • 1. Capturing More 1. Capturing More BiosolidsBiosolids -- Improving Improving Primary Clarifier Performance Can MakePrimary Clarifier Performance Can MakePrimary Clarifier Performance Can Make Primary Clarifier Performance Can Make

    A DifferenceA Difference

    I d h d li d b ffli• Improved hydraulics and baffling can increase suspended solids (SS) removal b 10%by 10%

    • SS = BOD = Energy inSS = BOD = Energy in activated sludge processprocess

    Wh t W ld H if W R d 95%What Would Happen if We Removed 95% of SS Prior to Aeration?

  • 2. Don't Burn Up 2. Don't Burn Up BiosolidsBiosolids in the in the A ti S tA ti S tAeration SystemAeration System

    0 8

    1.0

    1.2

    Sludge

    0 4

    0.6

    0.8Sludge Produced

    (lb WAS/lb BOD)

    0 0 0.2

    0.4

    0 2 4 6 8 10 SRT (days)

    12 14 16 18 20 0.0

    Typical sludge production of the suspended growth process (sludge production quantities at 20º C)

  • 3. Condition 3. Condition

    BiosolidsBiosolids Prior toPrior toBiosolidsBiosolids Prior to Prior to

    Digestion Digestion -- The The gg

    Wastewater Wastewater

    Treatment Holy Treatment Holy

    Grail: DestructionGrail: DestructionGrail: Destruction Grail: Destruction

    of WAS Cell Wallsof WAS Cell Walls

  • Oh, These Poor BugsOh, These Poor Bugs, g, g

    Pressure

    Heat Freezing

    Electricity Vacuum

    Cell Mechanical

    Ultrasonic Mechanical Abrasion

    Just About Everything Has Been Tried, with Mixed Results

  • One Interesting Approach/Concept: One Interesting Approach/Concept: C Di i t ti S tC Di i t ti S tCrown Disintegration SystemCrown Disintegration System

  • Flow Schematic Flow Schematic -- Crown Disintegration Crown Disintegration S t f thS t f th Bi tBi t AGAGSystem of the System of the BiogestBiogest AGAG

    3% 8% S3% to 8% TWASThickener of the Sewage

    Treatment Plant Digester

    External Signal ~30%

    Control

    Recycle 3X Panel Relaxation

    Tank

    Return NozzlePC

    Macerator

    Return Pump

    NozzlePC Pump 10 Bar

  • Benefits Claimed by Benefits Claimed by BiogestBiogestyy gg

    • Digester foaming “eliminated”

    • Biogas yield increased 16% to 40%

    Hi h VS d i ll 20%• Higher VS destruction; usually >20%

    • Reduced sludgeReduced sludge hauling; usually ~20%

    D t i i d• Dewatering improved 3% to 6%

    • Guarantees are offered

  • Claimed Benefits Another Another

    Technology is Technology is Biosolids Reduction

    I d Bi OpenCELOpenCEL: High : High Voltage Voltage

    Increased Biogas

    Carbon Source Denitrification gg MicropulsesMicropulses of of

    ElectricityElectricity Reduced Pathogens

    Reduced Odor yyReduced Odor Reduced Greenhouse Gas

  • But Wait! There is No Free Lunch… But Wait! There is No Free Lunch… C idC idConsider:Consider:

    All WASAll WAS pretreatment systems use electricity, and sometimes gobs of it

    Some may use chemicals

    Mechanical complexity (O&M)

    Performance claims verification

    Piloting is Needed for Feasibility Analysis

  • 4. Anaerobic Digestion Types Can 4. Anaerobic Digestion Types Can I Bi P d tiI Bi P d tiIncrease Biogas ProductionIncrease Biogas Production

    Acid Phase Digestion1 Thermophilic2

    Temperature

    g

    3

    Temperature- Phased

    Anaerobic Digestion

    (TPAD) Cambi4

  • 5. Digester Detention Time 5. Digester Detention Time -- Detention Time Detention Time is Impacted by Feed Solids Concentrationis Impacted by Feed Solids Concentrationis Impacted by Feed Solids Concentrationis Impacted by Feed Solids Concentration

    35 1 MG Digester

    25 30 35

    Digester

    1 MG Digester 17,000 lbs/day Biosolids

    10 15 20

    Digester SRT

    (days)

    0 5

    10

    2 3 4 5 6 Feed Solids (%)

    Higher SRT More Biogas

  • 6. Co6. Co--Digestion is the 900 lb Digestion is the 900 lb G ill i th RG ill i th RGorilla in the RoomGorilla in the Room

    FOG and Food Waste

  • FOG Digestion and Food Waste Can Increase FOG Digestion and Food Waste Can Increase Bi P d ti b 50 t 200%Bi P d ti b 50 t 200%Biogas Production by 50 to 200% Biogas Production by 50 to 200%

    • Virtually 100% volatile• Virtually 100% volatile solids destruction

    Hi hl d d bl• Highly degradable

    • Relatively easy to accept, process, and find

    • Very small increase inVery small increase in biosolids production

    • May improve volatile• May improve volatile destruction of primary/WAS

  • Digester Gas Production Digester Gas Production vs Greasevs Grease FeedFeedvs. Grease vs. Grease Feed Feed

    (City of Watsonville Wastewater Treatment Plant(City of Watsonville Wastewater Treatment Plant 250 500

    200

    250

    400 450 500

    Digester Gas

    Digester Gas

    (1,000

    Grease Feed (1,000 ll /

    150 250 300 350

    ( , CFD) gallons/month)

    50

    100

    100 150 200 250

    0

    50

    0 50 100

    Grease Feed

    2001 2005 Nov May Dec Jun Jan Aug Feb Sep Mar Oct Apr

    2002 2003 2004 2006 2007

  • We've Learned a Few Things Along We've Learned a Few Things Along th Wth Wthe Waythe Way

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