Two biotowers operating in parallel are to be designed to treat a flow of 16,000 m³/d. The BOD⁵ in the influent to the primary clarifier is 200 mg/L and the clarifier removes 35% of the BOD5. The minimum wastewater temperature is expected to be 14∘C. The value of k is assumed to be 0.210 (Lps)0.5/m² at 20∘C and an effluent BOD5 concentration of 20 mg/L is to be achieved. The biotower depth = 6.1 m. Determine:

a. The radius (m) of each biotower.

b. The volume (m3) of biotowers.

c. The recycle flow (Lps/ft²) around the biotowers if the minimum wetting rate is 0.5 Lps/ft².

d. The recycle ratio (R).