culated? (c) What is the overall plant efficiency?

It is estimated that the BOD of raw sewage received at a treatment plant serving a population of 20,000 will be 300mg/l. It is estimated that the per capita BOD loading is 0.17ilm/day. 30% of the influent BOD is removed by settling. One single stage high rate trickling filter is to be used to reduce the plant effluent to 50mg/l. Recirculation is from the filter effluent to the primary settling influent. (a) Assuming a design flow of 1.35MGD, what is the total organic load on the filter? (b) Assuming an incoming volume of 1.35MGD and an organic loading of 60lbm/day-1000ft3, what flow should be recirculated? (c) What is the overall plant efficiency?