A wastewater treatment plant must disinfect its effluent before discharging the wastewater to a nearby stream. The wastewater contains 6.5 x 105 fecal coliform – forming units (CFU) per liter. The maximum permissible fecal coliform concentration that may be discharged is 3000 fecal coliform CFU/L. It is proposed that a pipe carrying the wastewater be used for the disinfection process. Determine the length of pipe required if the linear velocity of the wastewater pipe is 0.85 m/s. Assume that the pipe behaves as a steady-state plug flow system and that the reaction rate constant for the destruction of the fecal coliform is 0.23 per min.

A wastewater treatment plant must disinfect its effluent before discharging the wastewater to a nearby stream. The wastewater contains 6.5 x 10⁵ fecal coliform – forming units (CFU) per liter. The maximum permissible fecal coliform concentration that may be discharged is 3000 fecal coliform CFU/L. It is proposed that a pipe carrying the wastewater be used for the disinfection process. Determine the length of pipe required if the linear velocity of the wastewater pipe is 0.85 m/s. Assume that the pipe behaves as a steady-state plug flow system and that the reaction rate constant for the destruction of the fecal coliform is 0.23 per min.