1. [25 points] You are asked to design a reactor to increase the level of oxygen in groundwater (to be used as drinking water) from 2 mg/L to 7 mg/L O2. Two different types of reactors are to be considered (1) a CFSTR, or (2) a sequencing batch reactor (SBR), in which the reactor is filled, left to react, emptied, and the cycle is repeated. It takes 5 min each to fill and empty the reactor (10 min total of filling and emptying time per cycle). In either configuration, air is bubbled through by diffusers in the bottom. Determine which reactor can achieve the treatment goal in less time, given the following information: VL = 10000 L QG = 15 L/min = 1.2 min-1 H@ 25C = 32.3 LL/LG Poz = 0.21atm T = 25C R = 0.08206 L - atm/mol - K Cin = 2 mg/L Cout = : 7mg/L 2. [25 points] A number of radioactive isotopes undergo multiple decays before arriving at a stable isotope. Consider the radioactive decay chain of KA KB A B C Name: With first order decay rate constant kA and KB. A liquid waste stream contains dissolved A at concentration CA,o (mol m-3) and no B or C. This waste stream has a flow rate of Q and enter a complete mixed reactor of volume V. (a) What is the expression for the steady state exit concentration for A? (b) What is the expression for the steady state exit concentration of B? (c) What is the expression for the steady state exit concentration for C? 3. [25 points] The following E(t) curves were obtained from single reactors with a total HRT of t. Describe each reactor (either in words or with a picture). E E E