Maximizing Digester Gas Production to Create More Sustainable Maximizing Digester Gas Production to Create More Sustainable to Create More Sustainable Wastewater Treatment Facilities to Create More Sustainable Wastewater Treatment Facilities Dave Reardon PE BCEE Dave Reardon PE BCEE Dave Reardon, PE, BCEE National Director Water Sustainability Dave Reardon, PE, BCEE National Director Water Sustainability
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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 Facilitiesto Create More Sustainable
Wastewater Treatment Facilities
Dave Reardon PE BCEEDave Reardon PE BCEEDave Reardon, PE, BCEENational Director
Water Sustainability
Dave Reardon, PE, BCEENational 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)
AirEmissions
Chemicals Biosolids
VariousSupplies
Solid Waste
TreatedS pp
Raw Sewage,FOG Septage
TreatedEffluent
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
Energy5,000
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 ZeroGap: 11% Solar, Wind, More FOG, or Food Waste Carbon Credits90
100
Resolve Overdesign5%
6%5%
Waste, Carbon Credits
70
80
90EMS (Energy Management System)
Optimize Primary ClarifierFOG (Fats, Oil, and Grease) and Food Waste Digestion
25%50
60
70Contribution
% 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 digesters2. Don't burn up biosolids
in the aeration system3. Condition biosolids (WAS)
prior to digestion4. Anaerobic digestion optimization5. Digester detention time5. Digester detention time6. 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 00.2
0.4
0 2 4 6 8 10SRT (days)
12 14 16 18 200.0
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
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 3XPanel 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 BenefitsAnother Another
Technology is Technology is Biosolids Reduction
I d Bi OpenCELOpenCEL: High : High Voltage Voltage
Increased Biogas
Carbon Source Denitrification ggMicropulsesMicropulses of of
ElectricityElectricityReduced 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
253035
Digester
1 MG Digester17,000 lbs/day Biosolids
101520
Digester SRT
(days)
05
10
2 3 4 5 6Feed 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%
• 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 Plant250 500
200
250
400450500
Digester Gas
Digester Gas
(1,000
Grease Feed (1,000 ll /
150250300350
( ,CFD) gallons/m
onth)
50
100
100150200250
0
50
050100
Grease Feed
2001 2005Nov 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
East Bay Municipal Utility District East Bay Municipal Utility District (EBMUD) Has Perfected Organics(EBMUD) Has Perfected Organics(EBMUD) Has Perfected Organics (EBMUD) Has Perfected Organics
Conversion to BiogasConversion to Biogas• 90% energy neutral now,90% energy neutral now,
soon to be 100%• Aggressive FOG and food gg
waste programs• Dedicated food waste
digestion and dewatering• Thermophyllic digestion
Probably will be the first WWTP in US to "Get to Zero"
• Energy master plan is underway (energy use optimization and energy production)
• Three IC engines (2 MW each) and gas turbine (4.5 MW)
Here’s How We Get to ZeroHere’s How We Get to ZeroGap: 11% Solar, Wind, More FOG, or Food Waste Carbon Credits90
100
Resolve Overdesign5%
6%5%
Waste, Carbon Credits
70
80
90EMS (Energy Management System)
Optimize Primary ClarifierFOG (Fats, Oil, and Grease) and Food Waste Digestion
25%50
60
70Contribution
% 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
Maximizing Digester Gas Production to Create More Sustainable
Maximizing Digester Gas Production to Create More Sustainableto Create More Sustainable
Wastewater Treatment Facilitiesto Create More Sustainable
Wastewater Treatment Facilities
Dave Reardon PE BCEEDave Reardon PE BCEEDave Reardon, PE, [email protected]