Module 3 (I & II)

Question 1

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.

Answer 1

False: they are inversely proportional (or INTERCORRELATED)

Question 2

List the phases of bacterial growth in a batch system in order

Answer 2

1. Lag
2. Exponential growth
3. Stationary
4. Death

Question 3

_______ _______ _______ is the ratio of biomass produced to the amount of substrate consumed.

Answer 3

Biomass synthesis yield

Question 4

T/F: Biomass synthesis yield is defined relative to the electron acceptor used

Answer 4

False: electron DONOR (substrate)

Question 5

T/F: The biomass synthesis yield can be expressed in measurable quantities - g biomass/g COD consumed, but NOT g biomass/g BOD consumed.

Answer 5

False: both g biomass/g COD and g biomass/g BOD can be equated to the biomass synthesis yield.

Question 6

____ 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.

Answer 6

VSS
biomass growth
simple
time

Question 7

What is the formula for biomass synthesis yield?

Answer 7

VSS (g)/ BOD (g) OR COD (g)

Question 8

What is the formula for the substrate utilization rate (r_su)?

Answer 8

dS/dt = r_su = (kXS) / (K_s + S)

Question 9

What is “k” and what are its units?

Answer 9

maximum specific sub utilization rate (g sub/g microorgg*d)

Question 10

What is “K_s” and what are its units?

Answer 10

half-velocity constant (sub concentration @ 1/2 max specific substrate utilization rate), g/m^3

Question 11

What does the “b” in bCOD stand for

Answer 11

biodegradable COD

Question 12

T/F: If S is infinitely larger than K_s, then r_su = kX

Answer 12

True

Question 13

T/F: If S «< K_s, r_su = kX/K_s + S

Answer 13

False: remove the S from the denominator

Question 14

What is the formula for bacterial growth rate from substrate utilization (in cases of limiting substrate)?

Answer 14

dX/dt = r_g = (mu_max*XS) / (K_s + S)

Question 15

T/F: The bacterial growth rate and the substrate utilization rate are related by the biomass synthesis yield.

Answer 15

True: r_g = Y*r_su

Question 16

Which case do we deal with the most in biological treatment processes, and why?

1. K_s&raquo_space;> S
2. K_s «< S

Answer 16

Case 1: the purpose of treatment is to reduce S in the outlet stream

Question 17

What is the formula for net biomass growth rate (r_X)?

Answer 17

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

Question 18

T/F: The biomass synthesis yield for VSS on BOD will be smaller than that for VSS on COD

Answer 18

True: COD is a theoretical case, so will always be higher than BOD

Question 19

What is the formula for the rate of O2 uptake in aerobic biological processes?

Answer 19

r_o = r_su - (1.42*r_x)

Question 20

What is the significant number 1.42 seen in this course?

Answer 20

The COD of biomass: g COD/g VSS

Question 21

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.

Answer 21

Metabolic activities
settleablity

Question 22

What is the formula for the reaction rate constant?

Answer 22

k_T = k_20*(theta^(T-20))

theta = temperature-activity coefficient (can vary from 1.02 to 1.25)

Question 23

T/F: In batch reactors, S is constant, while in CSTRs, S is not constant.

Answer 23

False: opposite is true

Question 24

When does “t” start in a batch reactor?

Answer 24

t begins at the start of the REACTION

Question 25

What is “t” in the context of a CSTR?

Answer 25

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.

Question 26

What is Biomass Retention Time (SRT), why is it important?

Answer 26

Average time that biomass stays in the bioreactor; both removal efficiency and biomass/MLVSS concentration are affected by SRT.

Question 27

What is the formula for the hydraulic retention time (HRT)?

Answer 27

volume of bioreactor (m3) / volumetric flowrate (m3/d)

Question 28

What is the formula for the solid retention time (SRT)?

Answer 28

mass biomass (solids) in bioreactor (g) / biomass removal rate (g/d)

Question 29

Can we control SRT without sludge returning? If so, how?

Answer 29

Yes - we can prevent biomass washout by providing a surface for organisms to build a biofilm (ie. biofilm carrier or media)

Question 30

List the main biofilm development phases

Answer 30

1. Attachment [to a surface]
2. Growth
3. Detachment

Question 31

What are the two types of biological treatment processes?

Answer 31

1. Suspended-growth processes (maintained in liquid suspension by app. mixing)
2. Attached-growth processes (attached to an inert packing material)

Question 32

What are the three types of attached growth processes?

Answer 32

1. Non submerged (ie. trickling filter)
2. Partially submerged (ie. Rotating Biological Contactor)
3. Fully submerged (ie. Moving-bed biofilm reactor, MBBR)

Question 33

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.

Answer 33

False: densities similar to water so they move inside the tank/bioreactor. Hence, moving beds

Question 34

What are some benefits to MBBR?

Answer 34

• Higher surface area for org material collection
• Diff shapes, materials, sizes (economically feasible)
• Can allow reactor to take on higher org load