Influent and Effluent Quality

    1. Influent to Aeration Tank

    QAve = 10 mgd

    BOD5 into primary settling tank = 200 mg/l

    SS into primary settling tank = 200 mg/l

    30% of BOD5 removed in primary settling tank

    55% of SS removed in primary settling tank

    BOD5in = 200 (1 - 0.3) = 140 mg/l

    SSin = 200 (1 - 0.55) = 90 mg/l

    2. Effluent out of Settling Tank: According to Secondary Treatment eff. Criteria

    According to EPA effluent criteria,

    i). BOD5 of eff. < 30 mg/l, removal efficiency > 85%

    ii). SS of eff. < 30 mg/l, removal efficiency > 85%

    BOD5eff = 25 mg/l < 30 mg/l

    Therefore,

    MLVSS/MLSS = 0.8

    MLVSS Mixed-liquor volatile suspended solid (mg/l)

    MLSS Mixed-liquor suspended solid (mg/l)

    SSeff = 25 mg/l < 30 mg/l

    Soluble BOD5 = 25 - SS VSS/SS 1.42 0.68 = 25 - 25 0.8 1.42 0.68 = 6 mg/l

    3. Removal Efficiency

    For activated sludge process based on soluble BOD5 effluent

     

    BOD5 into Aeration Tank, S0 (mg/l): Soluble BOD5 eff., S (mg/l):

    (%)

    Overall efficiency, E,  for system based on BOD5 of effluent (primary + bio)

    BOD5 inf. (mg/l): Soluble BOD5 eff. (mg/l):

    (%)

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