WST-052 Activated Sludge Calculations Activated Sludge Calculations MCRT (SRT) F/M Ratio Targeting a F/M Ratio by setting the WAS Flow Rate Targeting a SRT or Sludge Age by setting the WAS Flow Rate Activated Sludge Flows Flow Abbreviations PE = Primary Effluent SE = Secondary Effluent RAS = Return Activated Sludge WAS = Waste Activated Sludge Concentration Abbreviations MLSS = Mixed Liquor Suspended Solids CCSS = Clarifier Core Suspended Solids PESS = Primary Effluent Suspended Solids SESS = Secondary Effluent Suspended Solids WAS SS =Waste Activated Sludge Suspended Solids MLSS CCSS PESS SESS WAS SS Flow Nomenclature PE PE RAS RAS SE WAS MLSS CCSS MCRT MCRT MCRT = Mean Cell Retention Time SRT = Solids Retention Time Means same thing (MCRT = SRT) MCRT lbs/day System, Leaving Solids Suspendedlbs System, in Solids Suspendeddays Time, Retension Solids =Flow Nomenclature PE PE RAS RAS SE WAS MLSS CCSS MCRT | |( )( )( )( ) ( )( )( ) l 8.34lbs /ga MGD Flow, Plant mg/L SESS, l 8.34lbs /ga MGD Flow, WAS mg/L SS, WASl 8.34lbs /ga MG Vol, Clar mg/L CCSS, MG , Aer ation mg/L MLSS,day s ns ionTime, Solids Rete+||.|

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\|=Clarifier Solids Concentration Issues CCSS = Clarifier Core Suspended Solids Could be inaccurate measurement of solids in clarifier Concentration is different along column Average of Solids concentration in Clarifier can be estimated: Average SS concentration of sludge blanket (MLSS, mg/L + RAS SS mg/L)/2 Or you could ignore minor difference in concentration and just use MLSS throughout. MCRT ( )( )( )( )( )( ) ( )( )( ) l 8.34lbs /ga MGD Flow, Plant mg/L SESS, l 8.34lbs /ga MGD Flow, WAS mg/L SS, WASl 8.34lbs /ga MG Vol, Clar Aer ation mg/L MLSS,day s ns ionTime, Solids Rete++=Food/Microorganisms Ratio Food/Microorganisms Ratio F/M Ratio = Food/Microorganisms Ratio Measurement of the balance of Food (Nutrients) and the microorganisms (mostly bacteria) that eat the food Too little food and the bacteria start to die off Too much food and nutrients will slip by uneaten Food/Microorganisms Ratio F/M Ratio=BOD/MLVSS BOD = Biochemical Oxygen Demand Indirect measurement of how much food (nutrients) there is available How much O2 used up in 5 days Some might have been used by chemical reactions MLVSS =Mixed Liquor Volatile Suspended Solids Indirect measurement of how many microorganisms are present How much of solids burned off Some might have been organic compounds but not living Food/Microorganisms Ratio lbs MLVSS,lbs/day BOD,Ratio F/M =Food/Microorganisms Ratio ( )( )( )( )( )( ) l 8.34lbs /ga MG Bas in, Aer ation Volume mg/L MLVSS,l 8.34lbs /ga MGD Flow, mg/L BOD,Ratio F/M =