DNP level to 2mg/l. Assuming the Freundlich parameters, k=0.258 and 1=0.146, are to be used, 1- Determine carbon dose in mg/l needed in 1stage, 2 stages with equal doses and 3 stages with equal doses. What is the effect of number of stages on the required amount of PAC? 2- Determine the dose in each stage of the two stage system that will minimize the total carbon required. Compare this to that involving two stages with equal doses. Solve this problem by solving equations and then compare to solution obtained by using figure 6.6. 3- What amount of PAC will be required if the wastewater is to be treated in a countercurrent operation in 2 stages. Solve by using figure 6.9 and compare it with the results of