Question

T/F (true/false) Wastewater Treatment A principle objective of the conventional activated sludge process is to lower BOD. During the conventional activated sludge process, ammonium is converted to nitrate. A key requirement of the conventional activated sludge process is that it be carried out under strictly anaerobic conditions. In typical systems, denitrification occurs in an aerobic step after the activated sludge step. In the Modified Ludzak-Ettinger (MLE) process (and its variants), "mixed liquor" from the end of the aerobic step is recycled primarily to improve nitrogen removal. If the effluent from a treatment plant will be directed into a water body, ozone is better as a disinfectant than Cl2. as a disinfectant than Cl2.

Answer 1

1. True : In activated sludge process,the Biochemical Oxygen Demand (BOD) of the waste water is lowered using methods like surface aerated basin systems. Since BOD is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period, it can be seen as a parameter to monitor the quality of water. Lower the BOD higher the quality of the water.

2.True: During the nitrification process (two step autotrophic process) in BNR (Biological Nitrogen Removal), the ammonium is converted to nitrite by ammonia-oxidizing bacteria (AOB) and then nitrite is oxidized to nitrate by nitrite-oxidizing bacteria (NOB).

3. False: Activated sludge process mainly uses aerobic conditions, although some process involve anaerobic methods.

4. False: After nitrification, denitrification is carried out to remove the formed nitrate from water. Denitrification is an anaerobic process in which nitrate is converted nitrogen gas.

5. True: Modified Ludzack Ettinger Process (MLE) uses an internal recycle which carries nitrates formed in the nitrification process during the aerobic step along with the mix liquor to be mixed in the influent to the anaerobic step.

6. True: Ozone is a very powerful disinfectant, even though chlorine (Cl₂) can deactivate bacteria and viruses it cannot be used against organisms like protozoa. But ozone is active bacteria, viruses and even protozoa. Moreover it has some added benefits against other disinfectants like chlorine like it leaves no taste or odor after treatment and disinfection byproduct formation is minimal.