Biological Kinetics Flashcards
How do we utilize microorganisms to consume organics?
- Convert dissolved organics into suspended matter (bacteria)
- Remove the bacteria (typically through settling; often type II)
Why are aerobic processes typically the most effective for biological treatment?
- fastest
- inoffensive end products (CO2, H2O)
What needs to be determined for biological treatment design?
- How much time to allow process to occur
- How much O2 and bacteria are required
- How much biomass (sludge) is produced
- Volume of the treatment plant
Microbial Metabolism: Organisms require the following substrates:
- Source of energy
- Carbon source
- Inorganic elements
- Trace elements
What are heterotrophs and autotrophs?
Heterotrophs: use organic carbon to form cells (consumes organic matter)
Autotrophs: derive cell carbon from CO2 (just from the air)
What are four oxygen utilization pathways (types of bacteria)?
Aerobic bacteria: require molecular oxygen to live and multiply
Anoxic bacteria: tolerate absence of O2, but require other electron acceptors
Anaerobic Bacteria: use carbon as electron acceptor. O2 may kill
Facultative Bacteria: exist with or without O2, but uses O2 whenever available
How is bacteria reproduced in growth kinetics?
By binary fission
Time required: 20 min -> several days
What are the four main stages of typical bacteria growth?
- Lag phase
- Log growth
- Stationary Phase
- Log death
What is the lag phase?
Time required for bacteria to acclimatize to their environment and food before reproducing
What happens during log growth?
There is an excess of food (substrate) present during log growth.
Cells reproduce exponentially limited by their rate of reproduction.
OR
Rate of growth limited by microorganisms’ ability to utilize substrate
What happens during the stationary phase (also known as the declining growth phase)?
Food is limited during the stationary phase.
Population growth rate = rate of death
Rate of reproduction decreases until the number of viable bacteria is stable.
What happens during log death (or endogenous phase)?
No more food is available, so bacteria consume each other for food (endogenous growth)
Rate of biomass decrease is proportional to biomass present.
What is growth yield (Y)?
The amount of biomass (X_m) produced per unit of substrate (S_o) utilization
Why do we use volatile suspended solids (VSS) as a surrogate for X?
VSS is mostly attributable to bacteria in bio-treatment.
What 5 parameters describe biomass growth kinetics?
Y, k_e, Ks, k, μ_m
