Design a continuous flow stirred tank activated sludge process to treat 10 m3 /min of settled wastewater having 170 mg/l of BOD5. The effluent is to have 24 mg/l BOD after activated sludge tank. Assume that the temperature 20°C and that the following conditions are applicable:-          Design mean cell residence time = 12 day-          Mixed liquor volatile suspended solids Inside tank = 2450 mg/l-          Effluent suspended solids = 24 mg/l-          Decay rate = 0.12-          Cell Yield = 0.67-          Influent mixed liquor volatile suspended solids to the reactor are 200 mg/l-          Return sludge concentration = 12500 mg/l 1-    Effluent BOD ………mg/l

A used water treatment facility in a town treats an average daily influent waste sludge at a mass flowrate of 8000 kg/day. Assume that the sludge in all streams at all stages have a temperature of 30°C,pressure of 1 atm and density of 1000 kg/m3. The treatment process is as follows:1) Thickening centrifuges thicken waste sludge.2) Anaerobic digesters remove organic matter in the thickened sludge.3) Dewatering centrifuges thicken digested sludge.On one particular day, the influent waste sludge into the used water treatment facility was measured tohave a COD of 470 mg/L. Assume a COD consumption of 85%, an universal gas constant of0.08206 atm.L/mol.K and the heating value of methane to be 55 MJ/kg. The biogas produced is thenused to generate electricity.(a) Calculate the maximum volume of biogas produced in one day, assuming a methane content of 70%in the biogas. (2 points)(b) Determine the amount of electricity produced per day in kWh when the conversion efficiency frombiogas to electricity of 45%. (2 points)The allowable COD limit discharged into the waterways is 60 mg/L.(c) Can this effluent be discharged without further treatment? Explain. If no, suggest one way to lowerthe COD in the effluent. (2 points)(d) Name one implication of discharging an effluent that is above the allowable COD limit. (1 point)

A wastewater sample with an initial dissolved oxygen (DO) concentration of 8 mg/L is incubated in a BOD bottle at 20°C for 5 days. After incubation, the DO concentration decreases to 3 mg/L. Calculate the BOD₅ of the wastewater sample.a.50 mg/Lb.250 mg/Lc.5 mg/Ld.25 mg/L◄ Previous page

Marks: 4% -- A food processing plant has an average wastewater flow of 5,000 m3/day over a24-hour processing period and a peak flow rate of 800 m3/hour. The plant discharges to amunicipal sewer after passage through a perforated plate screen with 5mm diameter holes.However, the ‘trade waste charges’ for the suspended solids discharged are relatively high,and the plant owners wish to install a new primary clarifier (sedimentation tank) to removesolids. The wastewater TSS median value is 1,100 mg/L.a. Calculate the plan and depth dimensions of circular and rectangular tank options.Prepare plan and elevation outline sketches of the two tank options and label keydimensions (in metres).b. Discuss the advantages and disadvantages of each tank shape and recommend apreferred shape.c. Calculate the median TSS concentration in the effluent after the primary clarifier andthe settled sludge mass (in kg Dry Solids) removed from the clarifier each day.d. If the sludge removed from the clarifier base has a concentration of 4% Dry Solids,what is the sludge volume removed each day

There are five tanks of 500 ml each. In five tanks 1, 2, 3, 4 and 5, there are five different chemicals (liquid) which are to be mixed.There are four outlets from each tank to the other four tanks.The flow of liquid through each outlet is as followstank 1 is 20 litre/mintank 2 is 30 litre/mintank 3 is 25 litre/mintank 4 is 12 litre/mintank 5 is 48 litre/min.Which tank empties first? (Assume all tanks are opened simulteneously)

Determine the BOD5 for a 10 mL sample, collected from wastewater stream in Jamdoli that is diluted to a total volume of 300 mL when the initial dissolved oxygen is 8.5 mg/L and after 5 days, has been reduced to 2.5 mg/L.