Wastewater flow from a small town is with a BOD of 180 mg/l and SS of 210 mg/l. Size and sketch a layout for a stabilization pond arrangement consisting of two identical primary cells, which can be operated in parallel, and one secondary cell. The primary cells can have a maximum water depth of 1.5 m, and the secondary cell can have a maximum depth of 2.5 m. The minimum operating water depth in all cells is 0.5 m. Determine the dimensions of the ponds based on the following criteria:
(1) The BOD loading on the primary cells cannot exceed
(2) The water storage capacity considering all three cells must be at least 120 d between the minimum and maximum water levels, with allowance for a water loss of 2.0 mm/d by evaporation and seepage.