ESM 214 05

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ESM 214 05
Lecture 9 Biological treatment, Advanced
Treatment, Solids Treatment and Disposal
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Anaerobic WastewaterTreatment

• Similar configurations to activated sludge,
  aerobic reactors, but no oxygen.
• Used more with industrial wastewaters
• Intermittent flows
• High COD
• Uses less energy, makes less sludge, makes CH4
  (energy), but..
• Biomass grows slowly, acidifies, partial
  treatment, no extra P or N removal

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Anaerobic Wastewater Treatment

• Breweries
• Dairy and cheese production
• Fish processing
• Leachate treatment
• Pulp/paper
• Meatpacking
• Distilleries
• Municipal waste

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Anaerobic WastewaterTreatmentConsiderations

• Mesophilic (25 to 35 C) conditions advantageous
• Long SRTs e.g. 20 days at 30 C
• May need to add CaCO3 to buffer
• May need to add nutrients
• Sensitive to
• Toxic metals and organics
• Ammonia
• Oxidized sulfur ---bacteria compete for COD

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Anaerobic Lagoon generic
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Anaerobic lagoon (ADI/BVF))
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Microbiology of Anaerobic Treatment

• CO2 or organics are e- acceptors
• C is from CO2 or organic compounds
• Energy is from organic compounds or H2
• Y 0.05
• Slow growing bacteria

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Conversions and operative groups of bacteria in
anaerobic digestion.
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Anaerobic digester microbiology

• 1 extracellular hydrolysis (e.g. cellulase)
• 2 fermentation leading to organic acids (VFAs),
  acetate, CO2 and H2
• 3 fermentation leading to acetic acid (CH3COOH),
  H2 and O2
• 4 methanogenesis leading to CH4,CO2 and H2O

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Anaerobic Digester
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2 stage digestion
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Methanogenesis

• By methanogens which are archaea
• By either
• Hydrogen utilizers (1/3)
• Acetate-splitters (2/3)
• pH sensitive (7 7.2)
• Slow relative to VFA production
• Lowers H2 which facilitates acetate formers

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What happens in digestion?

• Stabilization
• Reduce pathogen content
• Reduce odors
• Complete VFA production and conversion
• Volatile solids reduction (about 60)
• Gas production (70 CH4, 30 CO2) (anaerobic only)

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40 CFR Part 503 Biosolids Disposal

• Land application fertilizer (bulk or bagged)
• Surface disposal dedicated lagoons or other
  sites
• Pathogen and vector reduction
• Class A low pathogens and treatment choices
  specified (nurseries, gardens, golf courses)
• Class B lesser treatment (agriculture, landfill)
• incineration

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Composting

• 30 VSS destruction
• Aerobic, mostly
• Pasteurization (50 to 70 C)
• Static pile 28 days then 30 day cure
• Windrow 30 days, 55 C
• In vessel
• Feed sludge solids 40

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Composting
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Windrow Composting
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In vessel composting
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Feed solids and ammendment
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Advanced Treatment

• Better than secondary
• Filtration solids removal
• RO dissolved organics and inorganics
• Adsorption (e.g. GAC) organics
• Air Stripping volatile organics and ammonia
• Ion exchange dissolved nutrients