A 150-mm ID potable water distribution pipe has water flowing at a velocity of 1.52 m/s. The water entering the pipe contains 1.1 mg/L of chlorine. The walls of the pipe are covered with an aggressive biofilm that completely consumes the chlorine (i.e., the chlorine concentration at the pipe wall is zero). Calculate the chlorine consumption rate by a 1.0 km length of pipe, using the Gilliland correlation for the mass transfer coefficient. The water temperature is 25? C. For the purposes of this calculation, assume that the 1.1 mg/L chlorine concentration is maintained constant in the bulk water through the entire length of pipe. Based on your calculated results, is this assumption reasonable? (When is an assumption reasonable? What makes a good assumption, anyway?) If the assumption is not reasonable, how would you have to modify your approach to solve the problem correctly?