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Municipal solid waste miscellaneous

Municipal Solid Waste

Direction: A completely mixed activated sludge process is used to treat a wastewater flow of 1 million litres per day (1 MLD) having a BOD5 of 200 mg/l. The biomass concentration in the aeration tank is 2000 mg/l and the concentration of the net biomass leaving the system is 50 mg/l. The aeration tank has a volume of 200 m³.

  1. What is the hydraulic retention time of the waste water in aeration tank?
    1. 0.2 h
    2. 4.8 h
    3. 10 h
    4. 24 h
Correct Option: B

HRT =
Volume of tank
Inflow

=
200 × 10³
= 0.2 day
1 × 106 per day

= .2 × 24 = 4.8 hours.



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