How to Calculate Aeration Tank Air Quantity?

This example in connection with our previous post,

How to calculate Aeration Tank Volume?

 

Total BOD to be removed (Influent) = 250 mg/l (assume) x 1400  = 350 kg/Day (we consider 1400 M3/Day Effluent Plant)

Hence O2 to be transferred =350 kg/Day

Method of Aeration = Fine Bubble Diffuser

SOTE (Standard O2 Transfer Efficiency For 300 mm disc type diffuser submergence) =20%

Hence O2 required 350/0.20 =1750 kg/day.

Assuming alpha Factor (Ratio of SOTE in clean water to effluent water)=0.8 and

Another alpha Factor (Factor for fouling of diffusers) =0.8

Oxygen requirement =2734 kg/day {Oxygen % in the atmospheric air = 23.2%}

Hence, Air Requirement =11790 kg/day {With Sp.gravity of Air at 50°C =0.8 kg/M³}

Air requirement = 14737 M³/Day = 614 M³/Hr

Allowing 5% extra, So 650 M³/Hr @ 0.5 kg/cm2 blower can be select 

further note below points too.,

one more point to be consider the Depth of aeration Tank,  suppose it is 4 metre depth select 0.5 or 0.6 kg/cm² in blower side.

 

Author: T.P.Sivanandan

31 thoughts on “How to Calculate Aeration Tank Air Quantity?”

  1. The info is very useful . For my clarification, in Air requirement of aeration tank topic

    Total BOD to be removed = 250 (assume) x 1400 = 350 kg/Day; What does 1400 denotes?
    And for more details to know can you provide me the contact mail id. since I work in STP concern I like to know more about Calculation and process details from your website.

    Thank you,

      1. Nice Post!! Really helpful.

        Can you tell me roughly SOTE % for a tubular fine bubble (say 600 mm to 1000mm) & Disc Type Coarse Bubble(80mm, 150mm)?
        Is there any thumb rule for calculating it?
        waiting for your reply

        1. How to find out this value? – explain

          Oxygen requirement =2734 kg/day
          Hence, Air Requirement =11790 kg/day

          1. 2734 kg/day /23.2% (Oxygen % in the atmospheric air = 23.2%) = 11784 kg/day air

  2. Hi Sir,

    Thank you for your valuable knowlege.

    You have mention that Sp.gravity of Air at 50°C =0.8 kg/M³ , but this value is about 1.05 kg/M³

    This will change the Air requirements,

    Regards,
    Dnyaneshwar

  3. How come oxygen required-2734 kg/d,
    How much O2 required for Per kg of BOD.
    Plz elaborate.

    1. O2 required 350/0.20 =1750 kg/day.and use Two alpha factor efficiency i.e %sote and fouling of diffuser [(1750/80%)/80%].
      KG of O2 required for carbonaceous BOD removal can range from 0.7 Kg/Kg BOD for high rate activated sludge with short detention of Biomass (low sludge age) up to 1.5 kg/kg BOD for extended aeration with long detention of Biomass (MLSS, i.e., (long sludge age) in the bio system,
      we account 1kg/kg of BOD.
      Hope, you will clear.

  4. Sir useful information but what is mean by sote for submergence of diffuser and what is mean by fouling of diffuser

    1. Submergence mean depends on depth of aeration tank the the sote will vary more depth more percentage of oxygen transfer but increase air blower power,similarly fouling mean it affects air discharge due to excess of MLSS and other colloids in aeration tank.

  5. What will be the % oxygen transfer efficienty for 1000 mm long x 67 mm OD fine bubble tubular air diffuser silicone basaed membrane

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