2. The average wastewater flow from a community of 20,000 is 125 gpcd. The 5 day, 20 deg C BOD is 250 mg/L. The suspended solids content is 300 mg/L. A final plant effluent of 50 mg/L of BOD is to be achieved through the use of two sets of identical settling tanks and trickling filters operating in parallel. The settling tanks are to be designed to a standard of 1000 gpd/^2. The trickling filters are to be 6^ deep and operated at an organic loading of 55 lbm/1000^3.d. There is no recirculalon. (1) What settling tank surface area is required? In ft^2 (A) 2500 ft^2 (B) 3000 ft^2 (C) 3500 ft^2 (D) 4500 ft^2 (2) What settling tank diameter is required? In ft (A) 40 ft (B) 50 ft (C) 65 ft (D) 80 ft (3) Estimate the BOD removal in the settling tanks? In percent % (A) 15% (B) 30% (C) 45% (D) 60% (4) What is the trickling filter diameter? In ft (A) 65 ft (B) 75 ft (C) 85 ft (D) 95 ft