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Assignment 3 Fall 2013_SOLN_revised

# Assignment 3 Fall 2013_SOLN_revised - University of...

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University of Waterloo DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING EnvE 472 Wastewater Treatment Fall 2013 Assignment #3 In this assignment you will have the opportunity to: - analyze and design aerated lagoons - apply activated sludge process performance equations for organic matter removal 1.) A food processing wastewater that only contains dissolved organic matter is being treated in an aerobic biological wastewater treatment process that can be treated as a CFSTR. The following are the properties that have been determined for the raw wastewater: Average Flow: 1,000 m 3 /day Total COD concentration = 900 mg/L Total BOD 5 concentration = 500 mg/L Assume bCOD/BOD 5 = 1.6 In the bioreactor bCOD is removed and biomass is produced by aerobic heterotrophic biomass. The bioreactor effluent is characterized and found to have the following properties: - Volatile Suspended Solids (Biomass) Concentration = 300 mg VSS/L - Soluble BOD 5 Concentration = 25 mg BOD 5 /L - Assume COD/VSS ratio for grown biomass is 1.42 mg COD/mg VSS Estimate the mass flow of oxygen that was consumed by the biomass in the bioreactor. Solution: O 2 Required = bCOD removed - bCOD biomass = Q (So - S) - 1.42mgCOD/mgVSS * Px Note: Please try out the above form (the method from previous will work, but try and be comfortable with both) Where Px = QXvss Therefore: O 2 Required = Q (So - S - 1.42VSS) = 1000 m3/d [ 800mg/l - 40mg/l - 1.42(300 mg/l)] (1000l/m3)(1 kg/10^6 mg) = 334 kg/d 2.) An aerated lagoon is currently treating a wastewater at a temperature of 17 o C. A sample of the effluent is found to have a bCOD concentration of 15 mg/L.

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