List of top Water & Wastewater Treatment and Management Questions on Kinetics and reactor design

A continuous flow stirred tank reactor (CSTR) operates under a steady-state condition with a flow rate of 300 L per hour. The influent concentration of a substrate entering the reactor is 150 mg/L.
To give a treatment efficiency of 76% for the substrate that decays according to half-order kinetics with a rate constant of 0.05 (mg/L)^1/2 per hour, the required volume of the reactor is ______ m³ (answer in integer).

A facultative pond system for sewage treatment consists of two ponds in series. The hydraulic retention time (HRT) of each pond is 6 days. The total BOD\(_5\) reduction through the entire pond system is 90 %. If the ponds are considered to be completely mixed, then the rate constant describing the BOD\(_5\) removal is _______ day\(^{-1}\) (rounded off to two decimal points). Assume that the entire rate constant is the same for both the ponds.