to digest or incinerate sludge…that is the question
TRANSCRIPT
© 2014 O’Brien & Gere
ToDigestorIncinerateSludge…ThatistheQuestion
Ohio WEA‐AWWA 2014 Technical Conference & Expo, Columbus, Ohio, August 29, 2014
MarkGreene,O’Brien&Gere
© 2014 O’Brien & Gere
Today’s Presentation
To Digest or Incinerate Sludge…That is the Question
Statistics
Incineration Basics
Anaerobic Digestion Basics
SWOT
Moving Forward
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Energy Usage Distribution By Treatment Process Train
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Energy Usage Distribution Within Solids Handling Stream
3.7% of WWTP total
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US Biosolids Disposal Practices
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Ohio Sludge Disposal Practices
2002– OhioEPAestablishessewagesludgeregulations OhioAdministrativeCoderule3745‐40
2005– OhioEPAreceivesEPAdelegationforthesewagesludgeprogram. 1ofonly7States
2011revisedrules2003‐2009biosolidsreports 30%offacilitiesprocess90%ofthebiosolids
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Ohio Biosolids Generation (2004‐2009)
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Ohio Biosolids Disposal Practices (2004‐2009)
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Ohio Biosolids Disposal Practices (2004‐2009)
Beneficial reuse requires
sludge stabilization
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How to Stabilize?
• Dewater cake to 20%+ solidsAnaerobic Digestion
• Produce inorganic ash, use as landfill cover
Incinerate Sludge
• Dewater cake plus add lime, 25%+ solids
Chemical Stabilization
• Sludge drying• Other methodsCombination
• Digestion and IncinerationFocus of this presentation
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Solids Handling Operating Costs
Fuel/Electricity0%
Chemical17%
Landfill Fees64%
Labor/Benefits19%
Anaerobic Digestion
Fuel/Electricity25%
Chemical16%
Landfill Fees3%
Labor/Benefits56%
Incineration
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INCINERATION
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Sewage Sludge Incinerators
~170SSIplantsinoperationinUS
Threemaintypesofincineratorsareused
>80%areofthemultiplehearthdesign
~15percentarefluidizedbedcombustors
3percentareelectric
MostlocatedintheEasternUnitedStates
AlsoasignificantnumberontheWestCoast
NewYorkhasthelargestnumberoffacilities(33)
Pennsylvania(21)andMichigan(19)havethenext‐largestnumbersoffacilities
Ohiohas~10plantswithSSI’sSource: AP-42, Compilation of Air Pollutant Emission Factors, EPA, 2012
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Incineration Practices in Ohio
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Other Biosolids Practices in Ohio
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Maximum Achievable Control Technology (MACT)
Incinerationnolongerfallsunder“domesticsewageexclusion”provisionoftheCleanWaterAct,butunderSection129oftheCleanAirAct
CompliancedateisMarch21,2016 SSIclassificationdeterminationisnecessary Emissionstestingisrequired
Additional/NewControlsmayberequired Mercuryscrubbingsystem Causticadditiontowetscrubberventuris
› SulfurdioxidecomplianceandimprovedHClemissions Additionofwetelectrostaticprecipitator
› Cadmium,lead,andparticulatescompliance SelectiveNonCatalyticReductionsystem
› InjectammoniainexhaustgasexitforNOxreduction
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Incineration
StrengthsTurn on/off as needed
Ash residual (solids reduction)
Proven Technology
Operator familiarity
Lower initial capital cost
WeaknessesMore fossil fuel (higher utility cost)
Larger carbon foot print
Limited grant potential
Not "Green"
Odor from sludge handling
Higher operation cost
Limited tipping fee potential
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Incineration
Opportunities
Merchant Facility: Accept outside sludge
for revenue
Threats
Utilize original/rebuilt incinerators
Future cost to replace
Potential changes in air emission regulations
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ANAEROBIC DIGESTION
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Anaerobic Digestion
Primarilyforsolidsstabilizationaspartofanoverallsolidshandlingsystem
Mesophilicdigestionismostprevalent 95ºto98ºF(35ºto37ºC)
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Mesophilic Digestion
Featuresofawell‐designedandwell‐operatedmesophilicdigestionprocess Uniformfeedofscreenedandde‐grittedrawsolids
› semi‐continuous/continuous
Automaticremoval(positivecontrol)offloatables,scum,andfoam
Completemixing
Adequateheating
Improvedpre‐thickeningoffeed
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Anaerobic Digestion
Strengths"Green"/ sustainable technology
Reduced carbon footprint
Tipping fee generation
Energy recovery
Proven Technology
Closed vessel/no odors
No incinerator stacks
Grant potential
Weaknesses
Biological process
Capital cost
Operational skill (new skill set/training required)
Residual sludge/digestate disposal
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Anaerobic Digestion
Opportunities
Grant potential
Tipping Fees
Rate stabilization
Third party performance contracting
Public Relations ‐ Community Good Neighbor
Future SSO waste & regulations/compost fee
Threats
Sour digester if not property operated
Odors if not operated properly
Toxicity
Overfeed/underfeed/loading
Market competition for outside sources – new mind set
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Digeste YES, Incinerate NO
Dairywhey Saladdressing Fats,oils,andgrease Manure Outdatedbeerandsoda Pulverizedfoodwaste
Smallparticles,nocontamination,nogrit
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Municipal Solids Waste to Landfill
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Future Sludge Management Options
Incineration
•Business as usual
•Uncertain Long Term Solution
Anaerobic Digestion
•New sources of revenue•Operating
cost reduction
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Benefits of Anaerobic Digestion
• Good neighbor technology
Anaerobic Digestion
• Can be treated by this technology
High Strength Waste
• Tipping feesRevenue Potential
• Electricity purchaseCost Avoidance
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Harvest Carbon or Waste Carbon?
Sludge 75%VSbeforedigestion 60%VSafterdigestion
AnaerobicDigestion Removessomecarbonduringthe20dayprocess
Convertsittocarbondioxideandmethane
RemainingCarbon Stillinthesludgecake Hauledtocompostingorthelandfill
Incineration Destroysvirtuallyallofthecarbonandvolatilesolids
RemainingAsh Mostlyinert,inorganicmaterial
Suitabletobeusedasdailycoveratthelandfill
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Hub and SpokeSmall Plant Sludge
Small Plant Sludge
Small Plant Sludge
Small Plant Sludge
Medium Plant
Anaerobic Digester
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One Size Fits All?Thedecisiontodigestorincineratesludgemustbedoneonacase‐by‐casebasis
Notcosteffectivetodigestorincineratesludgeatsmallwastewaterplants
Maybecosteffectivetodigestsludgeatmediumsizefacilities,butnotcosteffectivetoincinerate
Possiblycosteffectivetodigestandincineratesludgeatlargefacilities
© 2014 O’Brien & Gere
To Digest or Incinerate Sludge…That is the Question
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Ohio WEA‐AWWA 2014 Technical Conference & Expo, Columbus, Ohio, August 29, 2014
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