Direction: An activated sludge system (sketched below) is operating at equilibrium with the following information. Waste water related data: flow rate=500 m³/hour, influent BOD = 150 mg/l, effluent BOD = 10 mg/l. Aeration tank related data: hydraulic retention time = 8 hours, mean-cell-residence time = 240 hours, volume = 4000 m³, mixed liquor suspended solids = 2000 mg/l. Influent Aeration tank Secondary Effluent clarifier Sludge recycle Solids wasted 2. The mass (in kg/day) of solids wasted from the system is

Answer question 13

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3. Circular clarifiers are used to remove solid materials from water. They allow continuous treatment of water and can handle fairly large flows. Solids settle to the bottom of the clarifier and are carried away by a small stream of water (the waste stream). Most of the water exits the tank as treated effluent. Assume a clarifier receives a flow of 0.10 m3/s with a solid concentration of 800 mg/L. If the waste stream consists of 3% of the incoming flow and carries 90% of the incoming solids,   a) what is the solids concentration in the waste stream, and b) what is the solids concentration in the treated effluent?

D Q1: Design an activated sludge process to treat a wastewater of 15000 m³/day with a BOD5 of 180 mg/l following primary treatment. The effluent BODs and SS are to be 20 mg/l. Assume Xr-15000 mg/l, X=2500 mg/l, ec=10 days, y=0.60, Kd=0.05. Determine the reactor volume, the sludge production rate, the circulation rate, the hydraulic retention time and oxygen required?

2. (a) Design a gravity thickener to concentrate the mixture of sludge obtained from primary and secondary settling units in an activated sludge wastewater treatment plant. Make appropriate assumptions in your calculations. Sludge waste flow rate in the primary settling unit= 140 m³/d; and concentration = 2.5% Sludge waste flow rate in the secondary settling unit= 350 m/d; and concentration = 0.6% Qi ci Solids Loading Rate (SLR) = 40 kg ds / m².d, and SLR : A ci Qi Tc Expression for thickening zone depth= 0.75Cu A Ci: Incoming mixed sludge concentration Qi: Incoming mixed sludge flow rate A: Cross section area of the thickening tank Cu: Target underflow concentration (=5%) Tc: Time in compression zone (=2 days)

A completely mixed activated sludge process operating at equilibrium is designed to treat 300 MLD of waste water. The influent and effluent BOD are 200 mg/1 and 18 mg/1 respectively If the F M then the hydraulic retention time is A 0.125 day B 4.21 hours C 8.42 hours D 0.225 day = 0.3 and MLSS is 3800 mg/1,

Given:Flow rate of water = 500 L/minSuspended solids concentration in influent water = 100 mg/LRequired effluent suspended solids concentration = 10 mg/LFiltration rate = 10 m^3/m^2/hrFiltration tank dimensions: Length = 5 m, Width = 3 m, Depth = 4 mCalculate:o Calculate the total suspended solids (TSS) load in the influent water:o Calculate the filtration tank surface area:o Calculate the required filtration tank capacity:o Calculate the required detention time in the filtration tank:   Q2) DisinfectionGiven:Flow rate of water = 2000 m^3/hChlorine residual required in effluent = 0.5 mg/LInitial chlorine concentration in influent water = 2 mg/LChlorine decay rate in disinfection tank = 0.05 per hourDisinfection tank volume = 300 m^3Calculate:o Calculate the chlorine demand in the influent water:o Calculate the chlorine dosage required:o Calculate the chlorine dosage rate:o Calculate the actual chlorine dosage rate considering chlorine decay:

The quantity of sludge produced from an aeration tank is 2,453 kg/day. The volume of the aeration tank is 8,500 m3 and the yield is 0.55 mg VSS/mg BOD5. The water retention time is 1 day and the inlet BOD5 is 540 mg/L. Calculate the outlet BOD5 in the tank?

Waste activated sludge can be described as a Newtonian fluid with a kinematic viscosity of 20 x 10 ft/sec. At the same temperature, the kinematic viscosity v of water is 10 ft/sec. The relative roughness of the piping system is 0.001. The pressure drop for flow of water at a Reynolds number of 10' in this piping system was determined to be 1.0 psi. If waste activated sludge flows at the same velocity through the piping" system, the pressure drop (psi) is most nearly: