A$4$MGD $(20,000$m$/$day$)$ of industrial wastewater having BOD$5$ concentration of $1000$my L$,$ and reaction rate of $4\mathrm{.}0/$day is generated by industries at a city's industrial park.Because of the high BOD$5,$ there is a plan to build an industrial pre$-$treatment system at an industrial park. Effluent from the pre$-$treatment will be discharged into the city sewer for final polishing at the city wastewater treatment plant. Determine percent BD$5$ removal if the wastewater is treated in two continuous flow stirred tank reactors in parallel with equal flow to each reactor having a volume of $2500$m$*?$