anaerobic wasterwater treatment
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The Wastewater Treatment
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INTRO: WWT Process Categories
Suspended Growth Process microorganisms
are maintained afloat in the reactor by an
appropriate mixing method, i.e. activatedsludge, ponds and lagoons, and digesters.
Attached Growth Process microorganisms
are fixed to some object, i.e. trickling filters,
rotating biological contactors.
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INTRO: Types of Treatment
Aerobic Treatment with oxygen
Anaerobic Treatment without
oxygen
Anoxic Treatment BNR
NOTE: selection depends on degreeof treatment and pollution load
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Anaerobic WWT Process
Breakdown of organic matter bymicrobiological population in an
oxygen-free environment
Literally means without air
Used for high organic load
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Anaerobic WWT Process
a multi-stage process occurringsimultaneously
Every stage is accomplished bydifferent group of bacteria eachproducing by-products
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Anaerobic Metabolic Steps
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Acidogenesis & Acetogenesis
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Acidogenesis
acid production process
fermenting bacteria
volatile acids (butyric, propionic),alcohol, carbon dioxide, and
hydrogen
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Acidogenesis & Acetogenesis
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Methanogenesis
production of methane
aceticlastic and H2-oxidizing
methanogens (domain Archaea)methane and carbon dioxide
N.B. within a certain range of pH (6.5-
7.6) and temperature (35-37)
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A Closer Look at the H2Productionvia Anaerobic Oxidation
Rxn2 FermentationH2 produced is small
Most H2 comes from
oxidation of volatileand long chain fattyacids, Rxns 3 & 4called anaerobicoxidation
Rxns inhibited byhigh H2 partialpressures
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Interspecies Hydrogen Transport
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Interspecies Hydrogen Transport
where vikis the stoichiometric coefficient for component i in
reaction k withmkcomponents, a
iis the activity of component
i, R is the universal gas constant, and T is absolute temperature
A close syntrophic relationship exist among microbial species
The same relationship and phenomenon occurs with butyrate
and propionate conversion to acetic acid and H2
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Interspecies Hydrogen Transport
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Interspecies Hydrogen Transport
where J is the flux of H2bet. the organisms
(mol.sec-1); Rtis the H2 turnover rate (sec-1),Mdis the H2 mass in solution (mol); Az is thedistancebetween species (cm); C, and C, arethe H2concentrations at the surface of theH2-producing and H2-consuming species,respectively (mol.cm-3); and A is the cross-sectional area across which diffusion occurs(cm2); D is the molecular diffusivity of H2inwater (cm2 sec-1).
Diffusion drives the H2 transportbetween producing and
consuming species
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Typical SRT in Anaerobic at 35oC
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Dis/Advantagesof Anaerobic Systems
Low production of sludge/biosolids
High treatment efficiency, up to
90% COD removalLow capital cost, reactor tank
No O2, low power reqt
Methane prodn, biofuel
Sensitive to temperature and pH
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THANK YOU
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The Case of Biofilm
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The Case of Biofilm
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The Case of Biofilm
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The Case of Biofilm