Derive an expression that can be used to compute the effluent concentration from a free surface constructed wetland system, designated as an ideal plug flow reactor, assuming removal of the constituent in the question can be described as follows

$($i$)$ a retarded first order reaction

r$=$kC$/(1+$r$\_$t t$)$

$($ii$)$ a retarded second order reaction

r$=($kC$^2)/(1+$r$\_$t t$)$

If the value of retardation coefficient rt is equal to $0\mathrm{.}2,$ compare effluent concentration with and without retardation? Assume the following values: C$0=1,$ k$=0\mathrm{.}1,$ t$=1$