California Wastewater Operator Exam, Process Math and Unit Conversions: all 36 questions

All questions from the Process Math and Unit Conversions section for California Wastewater Operator Exam, each with the correct answer.

• 9001A plant receives 2.5 MGD with an influent BOD of 220 mg/L. How many pounds of BOD enter the plant per day?
• 9002A plant treats 1.8 MGD. Influent TSS is 250 mg/L and effluent TSS is 20 mg/L. How many pounds of TSS are removed per day?
• 9003Influent BOD is 210 mg/L and effluent BOD is 18 mg/L. What is the percent removal?
• 9004A rectangular tank is 60 ft long, 20 ft wide, and 10 ft deep. Flow is 1.5 MGD. What is the detention time in hours?
• 9005A circular clarifier has a diameter of 50 ft and receives 1.2 MGD. What is the surface overflow rate?
• 9006A circular clarifier, 60 ft in diameter, has a weir around its circumference. Flow is 1.5 MGD. What is the weir overflow rate?
• 9007The chlorine dose is 8 mg/L and the flow is 3 MGD. How many pounds of chlorine are needed per day?
• 9008A chlorine dosage of 9.0 mg/L produces a residual of 1.5 mg/L after contact. What is the chlorine demand?
• 9009A wet well is 10 ft by 12 ft. The pump lowers the water level by 2.5 ft in 5 minutes. What is the pumping rate?
• 9010A sludge sample contains 5,000 mg/L of solids. What is this in percent solids?
• 9011Sludge is 3.2 percent solids. What is the concentration in mg/L?
• 9012A flow of 2.4 MGD is equal to how many gallons per minute?
• 9013A flow of 900 gpm is equal to how many MGD?
• 9014Water flows in a channel 4 ft wide at a depth of 1.5 ft. The flow is 9 cfs. What is the velocity?
• 9015A cylindrical digester has a diameter of 40 ft and a sidewater depth of 25 ft. What is its volume in cubic feet?
• 9016A digester receives 2,200 lbs of volatile solids per day. Its volume is 15,000 ft3. What is the volatile solids loading rate?
• 9017A trickling filter receives 0.8 MGD with 150 mg/L BOD. Its media volume is 40,000 ft3. What is the organic loading in lbs BOD/day/1,000 ft3?
• 9018A trickling filter has a surface area of 7,850 ft2 and receives 1.0 MGD. What is the hydraulic loading rate?
• 9019A pond receives 0.3 MGD with a BOD of 180 mg/L. The pond surface area is 12 acres. What is the organic loading rate in lbs BOD/acre/day?
• 9020A pond is 5 acres in area with an average depth of 4 ft. Flow is 0.25 MGD. What is the detention time in days? (1 acre-ft = 325,851 gal)
• 9021A sludge pump runs 15 minutes each hour at 40 gpm. The sludge is 5 percent solids. How many pounds of solids are pumped per day? (Assume 8.34 lbs/gal)
• 9022An aeration tank holds 1.2 MG and the MLSS is 2,800 mg/L. How many pounds of MLSS are in the tank?
• 9023Flow is 2.0 MGD, primary effluent BOD is 200 mg/L, the aeration tank is 0.8 MG, and MLVSS is 2,100 mg/L. What is the F/M ratio?
• 9024The 30-minute settled volume is 280 mL/L and the MLSS is 2,800 mg/L. What is the sludge volume index?
• 9025A 1-liter sample of mixed liquor settles to 250 mL in 30 minutes. The MLSS is 2,000 mg/L. What is the sludge volume index (SVI)?
• 9026An activated sludge system has 37,530 lbs of solids in the aeration tank and 6,000 lbs in the clarifier. Solids leaving per day are 3,336 lbs in the waste sludge and 167 lbs in the effluent. What is the MCRT?
• 9027Waste activated sludge is pumped at 0.04 MGD with a concentration of 7,500 mg/L. How many pounds per day are wasted?
• 9028The return activated sludge flow is 1.2 MGD and the influent flow is 3.0 MGD. What is the return rate as a percent of influent flow?
• 9029Influent ammonia nitrogen is 28 mg/L and effluent ammonia nitrogen is 2 mg/L at a flow of 1.5 MGD. How many pounds of ammonia nitrogen are removed per day?
• 9030A lab measures a sample temperature of 77 degrees Fahrenheit. What is this in degrees Celsius?
• 9031The water depth in a tank is 18 ft. What is the pressure at the bottom? (1 ft of water = 0.43 psi)
• 9032A pump delivers 500 gpm against a total dynamic head of 60 ft. Pump efficiency is 70 percent. What is the brake horsepower? (1 hp = 3,960 gpm-ft)
• 9033A circular clarifier has a diameter of 60 ft and a water depth of 12 ft. The flow is 2.0 MGD. What is the detention time in hours?
• 9034A 50 gram wet sludge sample leaves 2.5 grams of dry solids after drying. What is the percent solids?
• 9035A flow of 3 cfs is equal to how many MGD? (1 MGD = 1.547 cfs)
• 9036A plant feeds 12.5 percent sodium hypochlorite (about 1.04 lbs of available chlorine per gallon) to dose 4 mg/L at 1.5 MGD. How many gallons of solution are needed per day?

More topics

• Safety and Hazards26 questions
• Sampling, Laboratory Analysis and Wastewater Characteristics30 questions
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• Secondary Treatment (Activated Sludge, Trickling Filters, RBC)31 questions
• Stabilization Ponds16 questions
• Sludge Digestion and Solids Handling23 questions
• Disinfection and Dechlorination20 questions
• Regulations, Classification and Operator Certification29 questions