TCEQ WASTEWATER EXAM A

Describe proper design of force main wastewater lines - Answer-Minimum 2 fps velocity with the smallest pump operating alone. Minimum 4 inch diameter pipe 150 psi rating. What is Standard Dimension Ratio? - Answer-Ratio of outside pipe diameter (OD) to wall thickness (PVC) Describe proper design of gravity wastewater lines. - Answer-Designed to flow half full under normal conditions at a minimum of 2 fps maximum of 10 fps. A primary clarifier should remove how much BOD and TSS? - Answer-30% to 40% BOD 50% to 70 % TSS What is a wastewater outfall line? - Answer-Main line that carries the wastewater to the treatment plant. What are the minimum slopes for pipe sizes six, eight, ten, and 12 inches? What are these slopes designed to achieve? - Answer-6 inch - 0.50 ft slope per 100 ft 8 inch - 0.33 ft slope per 100 ft 10 inch - 0.25 ft slope per 100 ft 12 inch - 0.20 ft slope per 100 ft You have 3900 feet of 10-inch pipe on a grade of 0.25. What is the elevation difference from one end to the other? - Answer-3900/100 = 39 sections of pipe 39 ( 39 x 0.25 = 9.75 ft = 9 ft 9 inc A 12-inch line is on a 0.20 foot/100 foot grade. Point A is at an elevation of 127.6 feet. Point B is 600 feet downstream of point A and point C is 500 feet downstream of point B. What is the elevation of points B and C? - Answer-A = 127.6 600 600 x (.2 ft / 100 ft) = 1.2 ft B = 127.6 - 1.2 = 126.4 ft 500 x (.2ft/100ft) = 1 ft C = 126.4-1= 125.4