single horizontal flow wetland $($also known as reed bed in Europe$)$ is used to treat

a domestic sewage. The surface area of the bed is $200$ m$2,$ and its average depth is

$0\mathrm{.}6$ m$.$ The daily flow rate of the wastewater is $15$ m$3$ d$-1.$ The average performance

data of this system is given in the following table, where $$influent$$ represents raw

sewage, and $$effluent$$ represents treated sewage.

$($a$)$ What is the rate constant value $($K$)$ for the removal of BOD in this system?

$($b$)$ NH$4-$N is removed by only $5\mathrm{.}5\%.$ From a microbiology point of view, analyze

the reason for the unsatisfactory NH$4-$N removal.BOD$5,$

mg L$-1$

COD,

mg L$-1$

NH$4-$N$,$

mg L$-1$

NO$2-$N$,$

mg L$-1$

NO$3-$N$,$

mg L$-1$

pH

Influent $32567250\mathrm{.}60\mathrm{.}000\mathrm{.}07\mathrm{.}1$

Effluent $10535047\mathrm{.}80\mathrm{.}020\mathrm{.}07\mathrm{.}0$