Topic: Ch 7
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HW2 going out today, due next Friday
Wiley next Wed
March 20th Field trip w/ Jason Assoiline
Email me about DimDim Recordings
Tentative Carpool Plan –Time/Location
1. Merced to Clovis is 1hr drive
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Experiment with mic’s and video
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Background Review - Today
Stoichiometry - Today
Energetics - Wed
Microbial Growth Kinetics - Wed
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Capture nonsetteable solids into a biological
floc or biofilm
 Biomass has specific gravity greater than water
 Must remove settled bacteria or won’t reduce
BOD
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Transform or remove nutrients (N and P)
Oxidize consituents into an acceptable end
product
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Typically aerobic (need aeration… energy!)
Sometimes anaerobic for cases of highly
concentrated wastewater
 Anaerobic typically used for sludge treatment but
this is not usually suspended growth
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C5H7O2N
Growth rates double
every 10ºC until
optimum temp
reached
pH optimum 6.5-7.5
Nutrients may be
limited in industrial
wastewaters
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Why does
death phase
occur?
Draw DO
curve?
Draw BOD
curve?
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Bacteria Cells = Biomass
 Often measured as volatile suspended solids (VSS)
 Is VSS entirely biomass?
 Other approaches: particulate COD, protein, ,DNA
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Biomass yield (Y) = g biomass produced / g
substrate consumed
 Substrate is typically the constituent in the
wastewater that is electron donor (energy source)
 What would be the units for the yield for nitrification
bacteria (what is the substrate)?
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Cellular Mass Balance (Stoichiometry)
 Assume substrate as glucose
 Neglect nutrient other than N
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How much substrate leaves system as sludge
vs. gas?
What is the yield (Y) based on this
stoichiometry?
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COD Mass Balance (Stoichiometry)
 Assume substrate as glucose
 Neglect nutrient other than N
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What is the yield (Y) based on this
stoichiometry?
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Cellular Mass Balance (Stoichiometry)
 Assume substrate as glucose
 Neglect nutrient other than N

What is the yield (Y) based on this
stoichiometry (change in O2 over change in
glucose)?
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Cellular Mass Balance (Stoichiometry)
 Assume substrate as glucose
 Neglect nutrient other than N
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What is the yield (Y) based on this
stoichiometry (change in O2 over change in
glucose)?
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Maximum yield… actual yield will be more
because not all substrate is converted to cell
mass (synthesis) since some is needed for cell
maintenance
Solve for the theoretical yield given the
following
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Solve for the theoretical yield
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Recall that biomass must be removed by
settling (as sludge) or effluent will have large
BOD
Calculate COD of Cells given,
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Organics molecules are converted into
cellular molecules but still are BOD
Recall that biomass must be removed by
settling (as sludge) or effluent will have large
BOD
Calculate COD of Cells given,
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Draw Schematic?
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Calculate Observed Yield (g cell / g substrate
COD removed) ?
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Calculate Observed Yield?
vs. Theoretical Yield?
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Oxygen Used per COD removed?
 “Oxygen Used”: oxygen consumed by bacteria
during synthesis of substrate.
▪ Calculate as difference between CODin and total COD
out (substrate COD out + biomass COD out)
 “COD removed”: Decrease in substrate COD.
Ignores COD of biomass.
▪ Calculate as difference of CODin and CODout
 “Oxygen Used”: oxygen consumed by bacteria
during synthesis of substrate.
▪ Calculate as difference between CODin and total COD
out (substrate COD out + biomass COD out)
 “COD removed”: Decrease in substrate COD.
Ignores COD of biomass.
▪ Calculate as difference of CODin and CODout
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Oxygen Used per COD removed?
Why is theoretical yield less than actual yield?
How was the sound quality today?
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High speed ethernet (not wireless)
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