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An activated sludge process is used to treat a wastewater flow of 2 MLD having a BOD5 of 400 mg/l. Determine the average time in hours for which the sewage flowing into the aeration tank remains in it if the volume of the aeration tank is 300 m3.
  • a)
    3.1
  • b)
    4.6
  • c)
    3.6
  • d)
    5.2
Correct answer is option 'C'. Can you explain this answer?
Most Upvoted Answer
An activated sludge process is used to treat a wastewater flow of 2 ML...
The average time in hour for which the sewage flowing into the aeration tank remains in the aeration tank = Hydraulic Retention Time (HRT)
HRT= (Volume of aeration tank)/(Rate of sewage flow in the tank)
V = 300m3, Q = 2MLD = 83.3 m3/h
HRT= 300/83.3=3.6 hour
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Community Answer
An activated sludge process is used to treat a wastewater flow of 2 ML...
Given data:
- Wastewater flow rate = 2 MLD (million liters per day)
- BOD5 concentration = 400 mg/L
- Volume of aeration tank = 300 m3

Formula:
The average time (T) for which the sewage remains in the aeration tank can be calculated using the formula:
T = (V/Q) * 24

Where,
T = Average time in hours
V = Volume of aeration tank (m3)
Q = Flow rate of wastewater (m3/day)

Calculation:
1. Convert the flow rate to m3/day:
2 MLD = 2 * 10^6 L/day = 2000 m3/day

2. Calculate the hydraulic retention time (HRT) using the BOD5 concentration:
HRT = (BOD5 * V) / (Q * 1000)

Where,
BOD5 = Biochemical Oxygen Demand (5-day) concentration (mg/L)
V = Volume of aeration tank (m3)
Q = Flow rate of wastewater (m3/day)

HRT = (400 mg/L * 300 m3) / (2000 m3/day * 1000)

HRT = 0.06 days

3. Convert the HRT to hours:
HRT (hours) = HRT (days) * 24

HRT (hours) = 0.06 days * 24

HRT (hours) = 1.44 hours

Therefore, the average time for which the sewage flowing into the aeration tank remains in it is approximately 1.44 hours, which is closest to option 'C' (3.6 hours).
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An activated sludge process is used to treat a wastewater flow of 2 MLD having a BOD5 of 400 mg/l. Determine the average time in hours for which the sewage flowing into the aeration tank remains in it if the volume of the aeration tank is 300 m3.a)3.1b)4.6c)3.6d)5.2Correct answer is option 'C'. Can you explain this answer?
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