1. It is estimated that the BOD of raw sewage received at a treatment plant serving a population of 20,000 will be 300 mg/L. It is es1mated that the per capita BOD loading is 0.17 lbm/day. 30% of influent BOD is removed by settling. One single-stage high-rate trickling filter is to be used to reduce the plant effluent to 50 mg/L. Recirculation is from the filter effluent to the primary settling influent. Ten States' Standards is in effect, which specifies 100 gpcd in the absence of other information. (1) What is the design flow rate? In MGD (A) 0.9 MGD (B) 1.1 MGD (C) 1.4 MGD (D) 2.0 MGD (2) Assuming a design flow rate of 1.35 MGD, what is the total organic load on the filter? In lbm/day (A) 1700 lbm/day (B) 2100 lbm/day (C) 2400 lbm/day (D) 3400 lbm/day (3) Assuming an incoming volume of 1.35 MGD and an organic loading of 60 lbm/1000^3.d, what flow should be recirculated? In MGD (A) 0.6 MGD (B) 1.1 MGD (C) 1.2 MGD (D) 2.2 MGD (4) What is the overall plant efficiency? In precent% (A) 45% (B) 76% (C) 83% (D) 91%