$26$ A two$-$stage high$-$rate trickling filter with $100\%$ recycle will be used to treat $.$ The influent BOD to the primary clarifier is and the primary removesof the incoming BOD. The effluent BOD should be or less. Assume that the design BOD loading to the trickling filter system is $,$ and a depth ofwill be used. Use the NRC equations for designing the trickling filter system and assume that the operating temperature is$.$ The coefficient $0\mathrm{.}0561$ in Equation $(7\mathrm{.}181)$ can be replaced with $0\mathrm{.}443,$ and the organic loadings must be expressed in and the volume of media in cubic meters. Determine: a$.$ The diameterof the high$-$rate trickling filter system. b$.$ The effluent BOD concentratio $($Mg$/$l$)$