State the functions of each of the following unit operations in a wastewater treatment plant: biological treatment reactor secondary sedimentation tank The wastewater treatment plant in the town of Freemont serves a population of 136, 500 people. The maximum amount of wastewater produced per capita is 220 L/day. Given the following parameters, determine the volume of the biological treatment tank required to meet the water quality requirement for dissolved organics (BOD). BOD in influent 307 mg/L NPDES requirement for BOD in effluent 20 mg/L Steady state concentration of biomass in biological reactor 4250 mg/L Concentration of biomass in the influent 95 mg/L Yield coefficient 65 g biomass/100 g dissolved organics Microorganism decay rate 0.06/dy Microorganism growth rate 0.1/dy Solids retention time 4.5 dys