(a) Explain the difference between partial nitrification and full nitrification
ID: 528765 • Letter: #
Question
(a) Explain the difference between partial nitrification and full nitrification in terms of different substrates and end products.
(b) Study the figure above. reading from the values in the figure, what is the percentage of nitrite accumulation in partial and full nitrification processes, respectively?
(c) Using the data in the figure above, calculate the specific microbial growth rate in unit of d-1 for partial nitrifying bacteria and full nitrifying bacteria, respectively.
(d) Please indicate if the following statement is true (T) or false (F):
1. Heterotrophic bacteria that degrade BOD are autotrophic. _____
2. Nitrifying bacteria are anaerobic. _____
3. Heterotrophic bacteria that degrade BOD grow faster than nitrifying bacteria. _____
(e) For the same bioreactor specified in the previous page, if SRT is increased, please indicate how the following parameters will change: increase (I), decrease (D) or no
change (N):
1. Solids production rate. ________________
2. Effluent ammonia concentration. ___________________
3. Effluent nitrite concentration. ______________
4. Oxygen uptake rate. __________________
5. Yield of biomass production. _______________
Explanation / Answer
The goal of this study was to compare the microbial ecology, gene expression, biokinetics, and N2O emissions from a lab-scale bioreactor operated sequentially in full-nitrification and partial-nitrification modes. Based on sequencing of 16S rRNA and ammonia monooxygenase subunit A (amoA) genes, ammonia oxidizing bacteria (AOB) populations during full- and partial-nitrification modes were distinct from one another. The concentrations of AOB (XAOB) and their respiration rates during full- and partial-nitrification modes were statistically similar, whereas the concentrations of nitrite oxidizing bacteria (XNOB) and their respiration rates declined significantly after the switch from full- to partial-nitrification. The transition from full-nitrification to partial nitrification resulted in a protracted transient spike of nitrous oxide (N2O) and nitric oxide (NO) emissions, which later stabilized. The trends in N2O and NO emissions correlated well with trends in the expression of nirK and norB genes that code for the production of these gases in AOB. Both the transient and stabilized N2O and NO emissions during partial nitrification were statistically higher than those during steady-state full-nitrification. Based on these results, partial nitrification strategies for biological nitrogen removal, although attractive for their reduced operating costs and energy demand, may need to be optimized against the higher carbon foot-print attributed to their N2O emissions.
d)1) Heterotropic bacteria that degrade BOD are autotropic TRUE.
2)False
3) TRUE
e) 1) solids production rate...INCREASED.
2) INCREASES.
3) DECREASES.
4) no change
5) INCREASES..
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