A wastewater treatment plant must disinfect its effluent before discharging the waste water to a near-by stream. The wastewater contains 4.5x10^5 fecal coliform colony-forming units (CFU) per liter. The maximum permissible fecal coliform concentration that may be discharged is 2,000 fecal coliform CFU/L. It is proposed that a pipe carrying the waste water be used for disinfection process. Determine the length of pipe required if the linear velocity of the wastewater in the pipe is 0.75 m/sec. Assume that the pipe behaves as a steady- state plug-flow system and that the reaction rate constant for destruction of the fecal coliforms is 0.23 min^-1