The oxygen utilization rate in biological reactors depends on which of the following factor(s)? (i) microorganism concentration (ii) substrate availability (iii) dissolved oxygen (DO) concentration
- AOnly (i)
- B(i) and (ii)
- C(ii) and (iii)
- D(i), (ii) and (iii)Correct
Solution
Concept
Oxygen utilization rate in biological reactors
Formula
OUR = a' × (dS/dt) + b' × X
Step-by-step solution
1. Oxygen uptake rate (OUR) represents dissolved oxygen consumed per unit time in biological aeration. 2. Microorganism concentration (MLSS) drives endogenous respiration, confirming (i). 3. Substrate concentration (BOD) dictates food availability for bacterial synthesis, confirming (ii). 4. Dissolved oxygen level dictates oxygen transfer rates into cells per Monod kinetics, confirming (iii). 5. Hence, oxygen utilization rate depends on (i), (ii), and (iii). Answer: D
Explanation
Oxygen utilization rate in aerobic biological reactors depends on active microorganism concentration (MLSS driving endogenous respiration), substrate availability (BOD providing organic food for synthesis), and dissolved oxygen concentration (driving oxygen transfer across microbial cell membranes per Monod kinetics).
Why the other options are wrong
A) Biomass concentration alone does not account for substrate synthesis demand. B) Ignores oxygen mass transfer dependence on dissolved oxygen concentration. C) Omits active microorganism biomass concentration.
Shortcut
OUR = f(Biomass concentration, Substrate food, DO level) -> depends on (i), (ii), and (iii).
Common mistake
Excluding dissolved oxygen concentration, assuming oxygen uptake is independent of DO.
Correct answer: D) (i), (ii) and (iii)