A completely mixed reactor (CSTR, CMFR) is to be used to treat an industrial wastewater.
(a) A tracer study is conducted to determine the true hydraulic residence time of the reactor. A slug of tracer (NaBr) is added to the reactor and allowed to wash out over time. The flow to the reactor is 10,000 L/d and the reactor volume is 40,000 L. The tracer data are given below. Using our mass-balance approach, determine the true hydraulic residence time of the reactor.
time (day) tracer concentration (mg/L) time (day) tracer concentration (mg/L)
0 50 6 2.5
1 30 7 1.5
2 18 8 0.9
3 11 9 0.6
4 6.8 10 0.3
5 4.1
(b) If the pollutant to be removed has a concentration of 100 mg/L and decays by 1st-order kinetics with a rate coefficient of 2.25 d-1, what percent removal is achieved if one uses the theoretical hydraulic retention time of the reactor?
(c) What percent removal is achieved using the true hydraulic residence time determined in part (a) of this problem?