a) What is the difference between a combined sewer system and a separate sewer system? Which is preferable? Why?
b) A rural town with sewered population of 4,500 has a daily wastewater flow of 1,590 m3/day with an average BOD of 280 mg/L including industrial wastes. The industrial discharges to the municipal sewers are 57 m3/day at 1,800 mg/L BOD from a slaughterhouse and 70 m3/day containing 32 kg of BOD from a soup-canning plant. Calculate the per capita contribution of domestic flow { in L/(person.day)} and BOD {in g/(person.day)}excluding the industrial wastewaters.
c) A sanitary sewer with a 450 mm diameter is constructed on the minimum allowable slope of 0.9 m/km. What is the full capacity of the sewer? At what depths of flow in the pipe are the velocities of flow equal to 0.6 m/s. Assume Mannings constant n = 0.013.
d) List some of the advantages and disadvantages of rectangular primary sedimentation tanks over circular sedimentation tanks which must be considered prior to the selection.
e) Two rectangular primary sedimentation tanks each 27 m long, 5 m wide and 3.8m deep treat 6000 m3/day wastewater from a community. Total effluent weir length is 50m (both tanks). Calculate the detention time, surface overflow rate (in m3/m2.day), and weir loading rate (in m3/m.day).