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Example: <br />Given MLSS of 1621 Ibs/day <br />Given wasted MLSS is 42 Ibs/day <br />•: (1621 lbs/day)/(42 lbs/day) = 39 days <br />Wasting Rates Based on Mixed Liquor Suspended Solids <br />Wasting rates may be determined by the Mixed Liquor Suspended Solids test (MLSS). MLSS <br />should be in the range of 2,500 to 4,000 mg/l. MLSS should be kept at the higher end of the range <br />in the winter when the bacteria are less active. Testing should be done every weekday, along <br />with the settleability testing, and the SVI calculations. <br />Wasting Rates Based on Target Cell Residence Time Rate <br />Determining a wasting rate based on CRT, involves first deciding on a target CRT rate, and <br />knowing the pounds of MLVSS present in the aerator. <br />Wasting Rates Based on Target Cell Residence Time Calculation <br />(MLVSS lbs/day)/(CRT days) = Pounds to be wasted each day <br />Example: <br />Given MLVSS 1,211 lbs/day <br />Given CRT of 25 days <br />(1,211 lbs/day)/(25 days) = 48 Ibs/day to waste WAS VSS <br />To convert the lbs/day to gallons per day to be wasted <br />(WAS VSS lbs/day)/(RAS VSS mg/1) x (8.34 lbs/gal) = WAS mgd <br />Example: <br />Given 48 lbs/day of WAS VSS <br />Given 8,300 mg/I RAS VSS <br />(48 lbs/day)/(8,300 mg/I) x (8.34 lbs/gal) = 0.00068 mgd or 680 gpd <br />