Announcements
1. HW2 going out today, due next Friday
2. Wiley next Wed3. March 20th Field trip w/ Jason
Assoiline4. Email me about DimDim Recordings5. Tentative Carpool Plan –
Time/Location1. Merced to Clovis is 1hr drive
6. Experiment with mic’s and video
Roadmap
1. Background Review - Today2. Stoichiometry - Today3. Energetics - Wed4. Microbial Growth Kinetics - Wed
Purpose of Biological Treatment 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 Transform or remove nutrients (N
and P) Oxidize consituents into an
acceptable end product
Suspended Growth
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
Bacteria
C5H7O2N Growth rates
double every 10ºC until optimum temp reached
pH optimum 6.5-7.5
Nutrients may be limited in industrial wastewaters
Quantifying Biomas
Bacteria Cells = Biomass Often measured as volatile suspended solids
(VSS) Is VSS entirely biomass? Other approaches: particulate COD, protein, ,DNA
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)?
Biomass Yield (Y = g cell/g substrate)
Cellular Mass Balance (Stoichiometry) Assume substrate as glucose Neglect nutrient other than N
How much substrate leaves system as sludge vs. gas?
What is the yield (Y) based on this stoichiometry?
Biomass Yield (Y = g cell/g substrate)
COD Mass Balance (Stoichiometry) Assume substrate as glucose Neglect nutrient other than N
What is the yield (Y) based on this stoichiometry?
COD of Glucose (g O2 / g glucose)
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)?
COD of Glucose (g O2 / g glucose)
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)?
Theoretical Yield [(g cell / g glucose) / (g COD O2 / g glucose)]
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
COD of Cell Tissue (g O2/g cell)
Recall that biomass must be removed by settling (as sludge) or effluent will have large BOD
Calculate COD of Cells given,
COD of Cell Tissue (g O2/g cell)
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,
Example 7-1
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)
Example 7-1
“COD removed”: Decrease in substrate COD. Ignores COD of biomass.▪ Calculate as difference of CODin and CODout