Water flowing at 14 MLD undergoes biological treatment in a 4,800 m3 process tan
ID: 1714673 • Letter: W
Question
Water flowing at 14 MLD undergoes biological treatment in a 4,800 m3 process tank. The feed-water BOD is 300 mg/L and the MLSS is kept at 3600 mg/L, the MLVSS contributing 74% of the mixed liquor. 3.5% of the feed flow forms the sludge waste, which has a solids concentration 15% higher than the feed. The outlet BOD and suspended solids concentration are 20 and 30 mg/L respectively. Calculate:
a) The HRT in hours
b) The SRT in days
c) The F: M ratio in d-1
d) The percentage BOD removal ]
e) The operators want to reduce the outlet BOD from the process. What’s the simplest way of doing this without post-treatment?
I need help in part (e) only thanks
Explanation / Answer
To reduce outlet BOD, the simplest way is the aeration. This can be done in several ways. First and easy way is installing aeration pump at outlet, and speed up aeration. In return, this will increase rate of reoxygenation in effluent. Another way is spreading effluent over large surface area. This expose effluent to atmosphere and reoxygenation rate increases. Also, rate of decomposition increases due to exposure to sunlight. Areated lagoons is an advanced option for this kind. Just by providing aeration system, lagoons can reduce BOD effectively in very less time.
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