Answer Happy

The flow of water through the long rectangular sedi- mentation tank was analyzed by injecting a pulse of a dye tracer in the influent. The concentrations of dye in the effluent at time intervals of 20 min starting from injection of the dye were as follows: Time (min) Concentration (pg/l) Time (min) Concentration (ug/l) 0 20 40 0 (start) 0.00 0.40 0.75 1.42 (peak) 1.20 120 140 160 180 200 220 0.78 0.52 0.25 0.08 0.02 0.00 60 80 100 1 Draw a residence time distribution curve as shown in a Figure 7b, locate the theoretical detention time of 120 min, and calculate and plot the mean residence time (centroid). (Answer t5o = 96 min)