Q4. For a chlorine contact basin with design discharge of 2000m3/d, the experimental data to find the optimal chlorine dosage are presented in the tables below. After analyzing the data, the amount NT of chlorine to be used was fixed at 35.5kg/d. The data suggest that Chick-Watson form loge %3D No -k'C12T is applicable for inactivation of Giardia, which has lately been a cause of concern for the locality where the basin is installed. 1. Calculate free chlorine residual.[3] 2. To achieve 99% Giardia inactivation, what should be hydraulic detention time T of the contact basin. [5] Data: Dosage (mg/L) Residual (mg/L) 1.4 1 2.9 2 4.3 2.97 5.9 3.94 Page 1 of 2 7.4 4.3 8.8 3.7 10.4 2.7 11.8 1.6 13.4 1 14.5 1.7 16.2 2.8 Free Cl Time, Percent Giardia (mg/L) min Surviving 0.5 10 96 0.5 20 84 0.5 30 74 0.5 50 62 0.5 100 40 1.75 20 50 1.75 25 30 1.75 35 22 1.75 45 15 1.75 55 10