# Streamline - Fall 2012 - (Page 35)

Wastewater Math QUESTIONS 1. What is the pressure reading at the bottom of a 10-ft. diameter storage tank after receiving a constant flow of 40 gpm for 12 hours? The tank is empty at start of fill. a. .213 psi b. 21.3 psi c. 49 psi d. 10 psi 2. A wastewater treatment plant is treating 1,500,000 gpd with a 12.5% sodium hypochlorite solution. If the necessary feed rate dose is 3 mg/L and the specific gravity of the hypochlorite is 1.03, how many gpd of sodium hypochlorite are required? a. 4.3 gpd b. 8.59 gpd c. 35 gpd d. 26 gpd 5. 6. 7. What is the log of 250? What is the antilog of 1? Find the mathematical mean of the following E-coli results: Monday – 10 Wednesday – 23 Thursday – 2 Friday – 150 3. a. b. c. d. If 160 is 42%, what is 78%? 270 297 300 Cannot be determined from the information given 8. 9. a. b. c. d. Find the number of colonies to report using geometric mean from the above E-coli results. 4. Given the following information, find the organic loading rate on a wastewater treatment pond in lb BOD5/d/acre: Influent flow = 160,000 gpd Surface are of the pond = 2.63 acre-ft. Influent BOD5 concentration = 180 mg/L a. 9.13 lb BOD5/d/acre b. 91.33 lb BOD5/d/acre c. 913.3 lb BOD5/d/acre d. 9,133 lb BOD5/d/acre What is the odor detection limit of chlorine gas? 0.2 ppm 0.3 ppm 0.5 ppm 1.2 ppm 10. What is the difference between a week acid and a strong acid? a. Taste b. Color c. Amount of hydroxyl ions released d. Amount of hydrogen ions released Answers on page 36 www.vrwa.org 35 http://www.vrwa.org

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