City of Bellingham City of Bellingham Biosolids Biosolids and Energy Evaluation and Energy Evaluation Post Point Wastewater Treatment Plant Post Point Wastewater Treatment Plant David L. Parry, PhD, PE, BCEE June 7, 2010 Overview Overview Community interest in environmentally sustainable C it i t t i i t ll t i bl biosolids and energy solutions Various options available for evaluating or modifying existing solids handling system Existing system has served the City well but is aging Solids handling options are being evaluated to develop a forward looking plan focused on energy d l f d l ki l f d opportunities 1
Evaluation is Considering Multiple Evaluation is Considering Multiple Evaluation is Considering Multiple Evaluation is Considering Multiple Objectives Objectives Objectives Objectives Economically Viable – life-cycle costs (capital and operating), y ( p p g), Economic Economic benefit from existing assets Environmentally Responsible – meet air permit requirements, manage Environmental carbon footprint, recover green energy Socially Acceptable – provide acceptable aesthetic, acoustic, Social and odor control solutions Operator Friendly – provide proven reliable, flexible systems Operational that are operator and maintenance friendly, support wastewater treatment operations Solids Handling at the Post Point Plant Solids Handling at the Post Point Plant Thickening equipment is currently operating well Reliable solids handling has complimented wastewater treatment in the past Currently wastewater treatment is adversely impacted from 5 day multiple hearth furnace operation Aging multiple hearth furnaces are consuming rather than producing energy, require continued maintenance, have limited redundancy and will require upgrades to meet pending air permit regulations 2
Solids Process Overview Solids Process Overview Furnaces MHF1: 37 years old today 63 years old in 2036 Gravity Belt Thickeners MHF2: 17 years old today 17 years old today 43 years old in 2036 43 years old in 2036 Centrifuge Mechanical equipment life Mechanical equipment life 17 years old today 43 years old in 2036 expectancy is typically 20 yrs expectancy is typically 20 yrs Thickening Storage Dewatering Incineration Limitations of Existing Limitations of Existing Multiple Hearth Multiple Hearth Furnaces (MHFs) Furnaces (MHFs) Both MHFs are required to meet Sand Seal solids loading requirement Repair on Require regular repair and MHF 1 maintenance Consume significant energy (465 therms natural gas/day) (465 therms natural gas/day) No energy recovery on either MHF Obtaining MHF replacement parts is difficult and costly Pending air regulations will require costly upgrades Post Point Plant MHFs, Bellingham 3
Solids Handling Improvements Solids Handling Improvements Compatible with Any Future Alternative Compatible with Any Future Alternative Need: Reduce impact of dewatering stored sludge from 5 day operation Solutions: Switch to 7 day operation Add dewatered cake storage To eliminate impacts from dewatering and provide flexibility for 5 day or 7 day incineration operations Dewatered Cake Storage, Cobb County, GA Solids Handling Improvements Solids Handling Improvements Compatible with Any Future Alternative Compatible with Any Future Alternative Need: Reduce Fats Oils and Grease (FOG) in sewers Solution: FOG collection program and FOG receiving facility tied in with i i f ilit ti d i ith solids handling Fats Oils and Grease (FOG) Receiving, FOG buildup in the conveyance Des Moines, IA system is 25% of the sewer main cleaning costs 4
Solids Handling Improvements Solids Handling Improvements Compatible with Any Future Alternative Compatible with Any Future Alternative Dewatered Cake Storage Dewatered Cake Storage Admin/Lab Building Admin/Lab Building olids Handling Building olids Handling Building Fats Oils and Grease Fats Oils and Grease Receiving Receiving Receiving Receiving So So Potential Biosolids Potential Biosolids Handling Alternatives Handling Alternatives Land Land Application Amendment Thickening Anaerobic Land Application Digestion Soil Amendment Fertilizer Drying Drying Dewatering Dewatering Ash Gasification Ash Dewatering Incineration 5
Each Each Biosolids Biosolids Handling Alternative Has Handling Alternative Has Different Characteristics to Consider Different Characteristics to Consider Emerging Outdated Proven Technology Technology Technology Energy Energy efficient Anaerobic Heat Gasification consuming FBI Digestion Drying MHF Complexity and Hauling Requirements Complexity and Hauling Requirements of Biosolids of Biosolids Alternatives Alternatives 60% residual Thick- Thick- Digest- Digest- Dewater- Dewater- Gasific- Gasific- Inciner- Inciner- Heat & Heat & Digestion Digestion Drying ening ion ing ation ation Power 13% residual Thick- Digest- Dewater- Gasific- Inciner- Heat & Drying Drying ening ion ing ation ation Power Utility 6% residual Thick- Thi k Dewater- D t G Gasific- ifi I Inciner- i Di Digest- t H Heat & t & Gasification Drying ening ing ation ation ion Power Optional 15% residual Heat & Thick- Digest- Dewater- Gasific- Inciner- Incineration Drying Power ening ion ing ation ation Trucking Gas Heat Electricity 6
Anaerobic Digestion Anaerobic Digestion Combined Heat and Power Thickening Storage Dewatering Pros: Cons: • Electrical and heat production • Requires sludge distribution • Frequent truck traffic • Fertilizer value • Requires long haul trucking • Structure height, visual impact • Proven technology • Large footprint • Limited land application sites for sludge • New lab techniques required Anaerobic Digestion Space Footprint Anaerobic Digestion Space Footprint Requirements at Post Point Requirements at Post Point Digestion space footprint f t i t requirements Digestion with Digestion with Combined Heat and Power Combined Heat and Power And Truck Loadout And Truck Loadout 7
Anaerobic Digestion Anaerobic Digestion Anaerobic Digestion, Combined Heat and Power System, Metro Biosolids Center, San Diego, CA Columbia Boulevard WWTP, Portland, OR Drying Drying Combined Heat and Power Thickening Storage Dewatering Pros: Cons: • Proven technology • Electrical and heat production • Requires sludge distribution • Multiple opportunities for land appl. • Fertilizer value • New lab techniques required • Reduced haul volumes • Class A biosolids • Risk of thermal event (combustibility) 8
Drying Drying Heat Dryer, Encina Water Pollution Control Facility, Carlsbad, CA Gasification Gasification Thickening Storage Dewatering Digestion Cons: Pros: • Unproven electrical production • New/unproven technology • Minimal ash haul volume • Low energy value gas • Long haul distance of ash • Potential heat production • Corrosive gas 9
Gasification Gasification Gasification, Sanford Wastewater Treatment Plant Sanford, Florida Fluidized Bed Incineration Fluidized Bed Incineration Thickening Storage Dewatering Pros: • Limited space footprint Cons: • Potential heat and power production • Limited number of unit processes • Long haul distance of ash • Minimal ash haul volume • Staff trained already • Compatible with new air permit regulations • Proven technology 10
Fluidized Bed Incineration with Heat Fluidized Bed Incineration with Heat and Power and Power Boiler Electricity Thickening Storage Dewatering Fluidized Bed Incineration Fluidized Bed Incineration Fluidized Bed Incineration, Cobb County, GA 11
Repairing Multiple Hearth Furnaces Repairing Multiple Hearth Furnaces Thickening Storage Dewatering Cons: Pros: • Aged and outdated equipment • Limited redundancy • Minimal ash haul volume • Limited unit processes • Requires 3 operators • Long haul distance of ash • Proven technology • Staff trained already • Consume significant energy • Pending air regulations • Limited space footprint • Obtaining parts difficult Multiple Hearth Furnaces Multiple Hearth Furnaces Post Point Plant MHFs, Bellingham, WA 12
Life Cycle Costs, Carbon Footprint and Life Cycle Costs, Carbon Footprint and Space Footprint Analysis Space Footprint Analysis Carbon Dioxide Projected Capital Footprint (tons Space Footprint Alternative Cost Annual O&M Cost CO 2 e/yr) (ft 2 ) 2 Anaerobic Digestion $32 M $1.1 M -1500 22,000 Drying $38 M $1.3 M 650 24,000 Gasification $36 M $1.3 M 2,100 5,500 Fluidized Bed $32 M $1.1 M 700 3,500 Incineration Summary Summary Numerous options exist for sustainable energy solutions Capital costs are similar, non-economic factors are Capital costs are similar non economic factors are important: Digestion is proven and has a low carbon footprint but requires solids hauling and has a large space footprint Drying is proven and has a high fertilizer value but has large space footprint and risk of a thermal event Gasification requires minimal hauling and potential heat recovery Gasification requires minimal hauling and potential heat recovery but is a newer unproven technology Fluidized bed incineration fits within existing space and provides energy recovery but requires long haul of the ash Keeping multiple hearth furnaces is proven and maintains minimal footprint but is dependant on outdated technology and consumes significant energy 13
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