1. 1 The town of Camp Verde has been directed to upgrade its primary WWTP to a secondary plant that can meet an effluent standard of 25.0 mg/L BOD, and 30 mg/L suspended solids. They have selected a completely mixed activated sludge system for the upgrade. The existing primary treatment plant has a flow rate of 2,506 m³/d. The effluent from the primary tank has a BODs of 240 mg/L. Using the following assumptions, estimate the required volume of the aeration tank: a. BOD5 of the effluent suspended solids is 70% of the allowable suspended solids concentration. b. Growth constant values are estimated to be: K, = 100 mg/L BODs; kd =0.025 d 1; μm-10 d1; Y= 0.8 mg VSS/mg BOD, removed. c. The design MLVSS is 3,000 mg/L.

A small town has been directed to upgrade its primary wastewater treatment plant to a secondary plant that can meet an effluent standard of 25.0 mg/L BOD5 and 30.0 mg/L suspended solids. They have selected a completely mixed activated sludge system. The following data are available from the existing primary plant. Existing plant effluent characteristics: Flow = 0.2000 m3 /s soluble BOD5 = 80 mg/L Assume that the BOD5 of the suspended solids may be estimated as equal to 50% of the suspended solids concentration, the microorganism concentration in the aeration tank (MLVSS) is 2000 mg/L, and the net activated sludge produced is 400.0 kg/d; also assume the following values for the growth constants: bacterial decay rate = 0.10 day-1 , yield coefficient = 0.60 mgVSS ∙ mg-1 BOD5 removed, maximum specific growth rate constant = 2.50 day-1 , and half saturation constant = 100 mg/L. (1) Estimate the volume of the aeration tank; (2) Compute the F/M ratio; (3) If the BOD5 is 60% of the ultimate…

2. The average wastewater flow from a community of 20,000 is 125 gpcd. The 5 day, 20 deg C BOD is 250 mg/L. The suspended solids content is 300 mg/L. A final plant effluent of 50 mg/L of BOD is to be achieved through the use of two sets of identical settling tanks and trickling filters operating in parallel. The settling tanks are to be designed to a standard of 1000 gpd/^2. The lbm/1000*3 Ibm/1000.^3.d. trickling filters are to be 6^ deep and operated at an organic loading of 55 There is no recirculalon. (1) What settling tank surface area is required? In ft^2 (A) 2500 ft^2 (B) 3000 ft^2 (C) 3500 ft^2 (D) 4500 ft^2 (2) What settling tank diameter is required? In ft (A) 40 ft (B) 50 ft (C) 65 ft (D) 80 ft (3) Estimate the BOD removal in the settling tanks? In percent % (A) 15% (B) 30% (C) 45% (D) 60% (4) What is the trickling filter diameter? In ft (A) 65 ft (B) 75 ft (C) 85 ft (D) 95 ft

2. The average wastewater flow from a community of 20,000 is 125 gpcd. The 5 day, 20 deg C BOD is 250 mg/L. The suspended solids content is 300 mg/L. A final plant effluent of 50 mg/L of BOD is to be achieved through the use of two sets of identical settling tanks and trickling filters operating in parallel. The settling tanks are to be designed to a standard of 1000 gpd/^2. The trickling filters are to be 6^ deep and operated at an organic loading of 55 lbm/1000^3 d. There is no recirculalon. (1) What settling tank surface area is required? In ft^2 (2) What settling tank diameter is required? In ft (3) Estimate the BOD removal in the settling tanks? In percent % (4) What is the trickling filter diameter? In ft domeved Ward

A secondary effluent that has "pinpoint" floc escaping over the weir indicates Select one: O A Over aeration. O B. Too low of a return sludge flow. O C. Nitrification OD. Rising sludge. O E Bulking sludge

a) A wastewater treatment plant consists of primary treatment followed by an activated-sludge secondary system. The plant processes 7000 m3/d of wastewater with 180 mg/L of BOD5 and 150 mg/L of suspended solids. The primary sludge contains 500 kg of dry solids per day with 4.5% solids content. The plant produces 760 kg of total sludge (primary and secondary) per day. Assume 30% removal efficiency of the primary clarifier and F/M ratio of 0.2 for the aeration tank. b) The thickened sludge from problem a) is to be digested in a standard-rate mesophilic anaerobic digester (MAD). The sludge has 68% organic content, and approximately 60% of the organic fraction is digested after a 30-d period. The digested sludge has a solids content of 6% and is stored for a period of 90 d. Calculate the volume of the standard-rate digester

a) A wastewater treatment plant consists of primary treatment followed by an activated-sludge secondary system. The plant processes 7000 m3/d of wastewater with 180 mg/L of BOD5 and 150 mg/L of suspended solids. The primary sludge contains 500 kg of dry solids per day with 4.5% solids content. The plant produces 760 kg of total sludge (primary and secondary) per day. Assume 30% removal efficiency of the primary clarifier and F/M ratio of 0.2 for the aeration tank. Determine the following: a. Primary sludge volume and removal efficiency of primary clarifier b. Influent and effluent BOD5 of the secondary activated-sludge system c. Volume of secondary sludge with 1% solids content. b) In problem a), the primary and secondary sludges are mixed in a gravity thickener and sent for further treatment. The thickened sludge contains 4% solids. Calculate the percent volume reduction in the gravity thickener. c) The thickened sludge from problem b) is to be digested in a standard-rate mesophilic…

A wastewater with a BOD of 25mg/L is discharged through an outfall to a freshwater stream of mean velocity 0.1m/s. The DO downstream of the outfall is 8.5mg/L. Assume the deoxygenation rate is 0.25/d, the reaeration rate is 0.4 /d and the temperature of 20 degree C (DOs = 9.09mg/L). Compute for the ff: a) Critical distance b) minimum DO c) Oxygen deficit d) Critical time

12.50 Determine the activated-sludge aeration volume required to treat 2.64 mgd with a BOD of 120 mg/l based on the criteria of a maximum BOD loading of 40 lb/1000 ft³/day and a minimum aeration period of 5.0 hr. Assuming an operating F/M of 0.20 lb BOD/day per lb of MLSS, calculate the MLSS to be maintained in the aeration tank. Estimate the operat- ing sludge age (mean cell residence time), assuming an effluent suspended solids of 30 mg/l and the daily amount of waste-sludge solids from Figure 13.1. Determine the diame- ter and side-water depth of two identical final clarifiers of the type shown in Figure 10.12 for this activated-sludge system.

An activated sludge wastewater treatment system was designed and operated in a steadystate under the following conditions:• Reactor volume of 10,000 m3in total;• Sludge concentration (MLSS) of 3200 mg/L in the reactor;• Return sludge concentration at 8000 mg/L (the underflow of the secondary clarifier)• Each day, 400 m3 of underflow sludge (return sludge) was wasted as excesssludge;What is the average Sludge Residence Time (SRT)?