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.

62 throughts 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,


  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.

      1. What is the basis of the assumption of 0.8 for both alpha1 and alpha2.?

        How can I determine it for other cases?

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

  6. Dear sir,
    if it is using jet aerators (30 hp) and blower(5 hp) then find the air producing rate per hour

    1. You can see the manufacturer catalog, model to model it will vary and depends on Depth of installation,the output air CFM vary, plz ask the supplier, normally @ 0.5 kg/cm2 pressure you can install that jet aerator upto 4 meter depth?

  7. Dear Sir,
    Can u tell me how to calculate quantity of mbbr media required in stp/etp.

  8. Mr.Shivanandan, what should be the optimum depth of aeration tank to get maximum SOTE ?

    1. suggested depth 4 to 5 meter, but SOTE ! influence many factor depth, bubble size, temperature of the medium, bubble travel either it travels direct upward from the bottom of diffuser or certain inclination / angels.

      1. Dear Sivanandan,
        Can u tell me how to calculate quantity of mbbr media required in stp/etp.

  9. sir my air requirement is 650cum/h my aeration tank depth is 4mt how to calculate blower capacity

  10. how can we select blower pressure?
    here directly it is given to select 0.5kg/cm2.
    on which factor we can select?

  11. Please provided details calculation xygen 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

  12. Sir please provide detail calculation for pipeline distribution and diffuser requirements for the above capacity

  13. Our aeration tank capacity is 95 cu.m x 3nos=285cu.m.Sir how can I find matching aeration pump capacity for this plant? Recently we have 3.7kw x 3nos submersible pumps.

  14. Sir, for alpha factor, it is for clean water right? may i know how to calculate alpha factor?
    Then for the O2 required in the calculation is the total oxygen supply by the blower to all diffuser in the aeration tank right?

  15. Hello Sir,

    I would like to Know that IF iwant to select the Air blower for MBBR tank as well as Eqt tank and Sludge tank then how to calculate the Air Requirement.

    Please Explain

  16. How did you went from 1750 kg/day to 11790 kg/day pls give detailed step. Thanks for the information, looking forward for your reply

    1. Hi, 1750 is real O2 require, calculate 2 alpha factor 0.8 and 0.8 (1750/0.8 =2187.5/0.8=2734) further available oxygen in the air 23.2 %
      so, divide 2734/0.232= 11784 so 11790 Air Require /Day(Don’t confuse this Air Quantity not Oxygen Qty)

      Hope you understood well

Leave a Reply

Your email address will not be published.