An industry has decided to treat its process wastewater in a biotower with a plastic modular medium (n = 0.55). The flow rate of the wastewater is 1400 m3 /d with a BOD5 of 630 mg/l. Average summer and winter temperatures are 22°C and 15°C, respectively. The treatability constant is 0.04 min–1 for the system at 20°C. Depth of the medium is 4 m. Calculate the area of the biotower required to produce an effluent with a BOD5 of 20 mg/l, with a recycle ratio of 2:1.