Module 3 (I & II) Flashcards
T/F: The performance of bioprocesses for the treatment or conversion of organic waste depends on the dyanamic of microbial growth and substrate utilization, which are proportional.
False: they are inversely proportional (or INTERCORRELATED)
List the phases of bacterial growth in a batch system in order
- Lag
- Exponential growth
- Stationary
- Death
_______ _______ _______ is the ratio of biomass produced to the amount of substrate consumed.
Biomass synthesis yield
T/F: Biomass synthesis yield is defined relative to the electron acceptor used
False: electron DONOR (substrate)
T/F: The biomass synthesis yield can be expressed in measurable quantities - g biomass/g COD consumed, but NOT g biomass/g BOD consumed.
False: both g biomass/g COD and g biomass/g BOD can be equated to the biomass synthesis yield.
____ is the parameter used most commonly to follow _______ _______ in full-scale bio wastewater treatment systems because its measurement is _______, and minimal _______ is required for analysis.
VSS
biomass growth
simple
time
What is the formula for biomass synthesis yield?
VSS (g)/ BOD (g) OR COD (g)
What is the formula for the substrate utilization rate (r_su)?
dS/dt = r_su = (kXS) / (K_s + S)
What is “k” and what are its units?
maximum specific sub utilization rate (g sub/g microorgg*d)
What is “K_s” and what are its units?
half-velocity constant (sub concentration @ 1/2 max specific substrate utilization rate), g/m^3
What does the “b” in bCOD stand for
biodegradable COD
T/F: If S is infinitely larger than K_s, then r_su = kX
True
T/F: If S «< K_s, r_su = kX/K_s + S
False: remove the S from the denominator
What is the formula for bacterial growth rate from substrate utilization (in cases of limiting substrate)?
dX/dt = r_g = (mu_max*XS) / (K_s + S)
T/F: The bacterial growth rate and the substrate utilization rate are related by the biomass synthesis yield.
True: r_g = Y*r_su
Which case do we deal with the most in biological treatment processes, and why?
- K_s»_space;> S
- K_s «< S
Case 1: the purpose of treatment is to reduce S in the outlet stream
What is the formula for net biomass growth rate (r_X)?
r_X = (Y*r_su) - bX
*Rate of biomass growth minus the endogenous respiration rate (or dead rate)
b = specific endogenous decay coefficient, g VSS/g VSSd
T/F: The biomass synthesis yield for VSS on BOD will be smaller than that for VSS on COD
True: COD is a theoretical case, so will always be higher than BOD
What is the formula for the rate of O2 uptake in aerobic biological processes?
r_o = r_su - (1.42*r_x)
What is the significant number 1.42 seen in this course?
The COD of biomass: g COD/g VSS
Temperature influences not only the _______ _______ of the microorganism, but also a significant impact on performance-related factors such as gas-transfer rates, _______ of biomass, etc.
Metabolic activities
settleablity
What is the formula for the reaction rate constant?
k_T = k_20*(theta^(T-20))
theta = temperature-activity coefficient (can vary from 1.02 to 1.25)
T/F: In batch reactors, S is constant, while in CSTRs, S is not constant.
False: opposite is true
When does “t” start in a batch reactor?
t begins at the start of the REACTION
What is “t” in the context of a CSTR?
t = reaction time; average amount of time that feed particles/molecules spend inside the bioreactor from the time they enter to the time they exit.
What is Biomass Retention Time (SRT), why is it important?
Average time that biomass stays in the bioreactor; both removal efficiency and biomass/MLVSS concentration are affected by SRT.
What is the formula for the hydraulic retention time (HRT)?
volume of bioreactor (m3) / volumetric flowrate (m3/d)
What is the formula for the solid retention time (SRT)?
mass biomass (solids) in bioreactor (g) / biomass removal rate (g/d)
Can we control SRT without sludge returning? If so, how?
Yes - we can prevent biomass washout by providing a surface for organisms to build a biofilm (ie. biofilm carrier or media)
List the main biofilm development phases
- Attachment [to a surface]
- Growth
- Detachment
What are the two types of biological treatment processes?
- Suspended-growth processes (maintained in liquid suspension by app. mixing)
- Attached-growth processes (attached to an inert packing material)
What are the three types of attached growth processes?
- Non submerged (ie. trickling filter)
- Partially submerged (ie. Rotating Biological Contactor)
- Fully submerged (ie. Moving-bed biofilm reactor, MBBR)
T/F: when using a fully submerged attached growth process, we tend to use packing material with higher density than water so they can collect microorganisms that settle to the bottom of the tank.
False: densities similar to water so they move inside the tank/bioreactor. Hence, moving beds
What are some benefits to MBBR?
- Higher surface area for org material collection
- Diff shapes, materials, sizes (economically feasible)
- Can allow reactor to take on higher org load
