# Streamline - Summer 2012 - (Page 47)

Wastewater Math QUESTIONS A lift station is receiving a flow of 420 gpm. The pump is running and the water level is still rising at a flow rate of 40 gpm. Find the capacity of the pump. a. 380 gpm b. 400 gpm c. 160 gpm d. Cannot be determined 1. An operator is using copper sulfate to control algae in a raw reservoir. The total alkalinity of the water is 78 mg/L as CaCO3. The surface area of the reservoir is 25 acres with an average depth of 15 ft. Calculate how many pounds of copper sulfate will be required. a. 22.5 lbs b. 337.5 lbs c. 135 lbs d. 130 lbs 2. 5. To determine a flow velocity, a tennis ball is dropped into a channel and is estimated to travel 20 feet in 15 seconds. Find the velocity in ft/sec? a. 1.3 ft/sec b. 1.0 ft/sec c. 2.0 ft/sec d. 1.5 ft/sec 8. What would the motor horsepower be if the brake horsepower is 80 and the motor efficiency is 92%. a. 100 b. 87 c. 92 d. 73.6 3. 4. 410 pounds of chlorine (12% available strength) is used to treat 2.5 MGD. What is the chlorine demand if the residual is 1.2 mg/L? a. 2.4 mg/L b. 3.0 mg/L c. 1.5 mg/L d. 1.2 mg/L A BOD bottle will hold 300 mL. If 60 mL of sample is to be tested (dilution water is added to completely fill the bottle), what is the sample volume in percent? a. 30% b. 15% c. 20% d. 60% 6. Determine the Suspended Solids in mg/L from the following data: Sample volume: 75 mL Prepared filter and pan: 9.7865 grams Final weight of pan, filter and residue: 9.8015 grams a. 200 mg/L b. .15 mg/L c. 150 mg/L d. 15 mg/L If the suspended solids are weighed to be 25,000 mg/L, what percentage are the percent solids? a. 2.5% b. 25% c. 10% d. .25% 7. Determine the desired MLVSS in lbs if the F/M ratio is 0.6 in a wastewater treatment plant that has a daily flow of 235,000 gallons when the average BOD loading rate is 150 mg/L? a. 600 lbs b. 4899 lbs c. 490 lbs d. 500 lbs 9. 10. How many milliliters of a 10N solution will be needed to make 200 milliliters of a 2N solution? a. 20 ml b. 40 ml c. 5 ml d. 100 ml Answers on page 48. www.vrwa.org 47 http://www.vrwa.org

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