2. For an industrial wastewater activated sludge process, the amount of bsCOD in the influent wastewater is 300 g/m³ and the influent VSS concentration is 50 g/m³. The influent flowrate is 1,000 m³/d, the biomass concentration is 2,000 mg/m³, the reactor bsCOD concentration is 15 g/m³ and the reactor volume is 105 m³. Determine the net biomass yield (gVSS/g bsCOD), assume that maximum specific substrate utilization rate is 5 g/(g*day), half velocity constant is 40 mg/L bsCOD, endogenic decay coefficient is 0.1 gVSS/(g VSS d)

The BOD3 of a wastewater is determined to be 270 mg/L at 20 o The rate constant (k) value is known to be 0.34 per day as first order. (C: 12 g/mol, H: 1 g/mol, O: 16 g/mol) Note: Reaction should be stoichiometricly balanced CH2O + O2    ------>    CO2 + H2O (a) What would be BOD5 value if tests were run at 20 oC? (b) What is the concentration of formaldehyde (CH2O) in wastewater?

After primary treatment, a municipal wastewater contains 150 mg/L BOD5. The wastewater flow of 0.44 m³/s (10 MGD) is then treated in an activated sludge system with an SRT of 12 d and an HRT of 6 h. Given the biokinetic parameters tabulated below, determine the effluent BOD5 (mg/L). Parameter Himax Ks ka Y Value 3 d ¹ 60 mg/L BOD, 0.10 d ¹ 0.6 mg VSS/mg BOD, K

A completely mixed activated sludge plant treats wastewater at a rate of 2,565 m³/d. The influent BOD is 280 mg/L, and the MLVSS in the aeration tank is 2,500 mg/L. The F/M ratio for the aeration tank is 0.35 kg BOD/kg MLVSS.d. Assuming 30% of BOD is removed in the primary tank, determine the organic loading rate in kg BOD/m³.d and the volume of the aeration tank in m³.

A municipal wastewater treatment plant processes an average of 14,000 m3 / day. The peak flow is 1.75 times the average. The wastewater contains 190mg/L BOD and 210 mg/L suspended solids at an average flow and 225 mg/L BOD and 365 mg/L suspended solids at peak flow. Determine the following for a primary clarifier with a 20-m diameter.  Assume eff. BOD of 20 mg/L and effluent TSS of 30mg/L for average and peak flows.    1. Surface overflow rate and the approximate removal efficiency for BOD 5 and suspended solids @ average flow.  2. Surface overflow rate and the approximate removal efficiency for BOD 5 and suspended solids @ peak flow.  3. Mass of solids (kg/day) that is removed as sludge from average and peak flow conditions.

A coagulation treatment plant with a flow of 0.5 m3/s is dosing alum at 20 mg/l. Concentration of suspended solid is 25 mg/l. The effluent suspended solid concentration is 12 mg/l. The sludge content is 1 % and specific gravity of sludge is 3 %. What volume of sludge must be disposed of each day?

After primary treatment, a municipal wastewater contains 150 mg/L BOD5. The wastewater flow of 0.44 m³/s (10 MGD) is then treated in an activated sludge system with an SRT of 12 d and an HRT of 6 h. Given the biokinetic parameters tabulated below, determine the limiting value of the minimum SRT (d). Parameter Hmax Ks ka Y Value 3 d¹ 60 mg/L BOD, 0.10 d ¹¹ 0.6 mg VSS/mg BODS

A wastewater treatment plant treats a wastewater at a flowrate of 10 million liters per day. The wastewater has zero dissolved oxygen when it leaves the plant. The NPDES requirements include a minimum dissolved oxygen concentration of 2 mg/L in the discharge to protect the river. As an engineer, you must design a reaeration system to provide a minimum dissolved oxygen concentration of 3 mg/L (using a 1.5 safety factor). Use the reaeration data for the reactor with the largest volume to design a system. Assume each reactor that you used in lab represents the capacity of one aerator. How many aerators will be required to reaerate the water?

Raw primary sludge at a solids concentration of 4% is mixed with waste activated sludge at a solids concentration of 0.5%. The flows are 20 and 24 gal/min, respectively. What is the resulting solids concentration? This mixture is next thickened to a solids concentration of 8% solids. What are the quantities (in gallons per minute) of the thickened sludge and thickener overflow (water) produced? Assume perfect solids capture in the thickener.

The PEF, Inc. firm desires to utilize a complete-mix activated-sludge system with recycle to treat their municipal wastewater after primary sedimentation. The design parameters are: Flow rate=0.92m³/s Influent Soluble BOD5 = 292mg/L MLVSS=2,500mg/L Mean cell residence time = 7.24 d For any missing parameters, use typical values of growth constants for domestic wastewater (provided in your text, page 494). Assume that the solids lost in the secondary clarifier effluent are minor and can be neglected. Assuming a BODs (S) concentration of 24 mg/L, the detention time (residence time or theta) in the activated sludge system is most nearly: O 28 hours O 6.5 hours O 168 hours O 53 hours