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M&M I-Practice Activated Sludge Math

The flow through an activated sludge plant is 15 mgd.  The BOD of the primary effluent is 110 mg/L and the BOD of the final effluent is 8 mg/L.  The rate of air flow to the aeration tank is 2,000 cfm.  The MLSS is the aeration tank is 2,500 mg/L.  The 30-minute settleable solids test is 225 mL/L.  The TSS of the primary effluent is 115 mg/L and the TSS of the final effluent is 12 mg/L.  The return sludge ratio is 20%.  60,000 gallons of 2% sludge are wasted each day.  The flow is split evenly between two rectangular aeration tanks.  All tanks are the same size.  Each tank is 175 feet long, 75 feet wide, and 12 feet deep.

  1. The perimeter of one aeration tank is ________ feet.

 

 

  1. The surface area of one aeration tank is ________ square feet.

 

 

  1. The volume of one aeration tank is ________ cubic feet.

 

 

  1. The volume of one aeration tank is ________ 1000-cubic feet.

 

 

  1. The total volume of both aeration tanks together is ________ cubic feet.

 

 

  1. The total volume of both aeration tanks together is ________ 1000-cubic feet.

 

 

  1. One aeration tank holds  ________ gallons.

 

 

  1. One aeration tank holds  ________ million gallons.

 

 

  1. The two aeration tanks together hold  ________ gallons.

 

 

  1. The two aeration tanks together hold  ________ million gallons.

 

 

  1. The return sludge flow is ________ mgd.

 

 

  1. The applied flow to the aeration tanks is ________ mgd.

 

 

  1. The applied flow to one aeration tank is ________ mgd.

 

 

  1. The applied flow to one aeration tank is ________ gpd.

 

 

  1. The detention time is ________ hours.

 

 

  1. The total organic load to both aeration tanks is ________ lbs BOD/day.

 

 

  1. The organic load to one aeration tank is ________ lbs BOD/day.

 

 

  1. The organic loading rate on one aeration tank is ________ lbs BOD/day/1000-cf.

 

 

  1. The MLSS in one aeration tank is ________ lbs MLSS.

 

 

  1. The MLSS in both aeration tanks is ________ lbs MLSS.

 

 

  1. The F/M is ________.

 

 

  1. The total amount of sludge wasted daily is ________  lbs WAS/day.

 

 

  1. The amount of sludge wasted from each aeration tank is ________ lbs WAS/day.

 

 

  1. The SRT is ________ days.

 

 

  1. The effluent TSS is ________ lbs TSS/day.

 

 

  1. The MCRT is ________ days.

 

 

  1. The influent TSS is ________ lbs TSS/day.

 

 

  1. The sludge age is ________ days.

 

 

  1. The SVI is ________

 

Solutions to I-Practice Activated Sludge Math

 

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