facultative pond.

$[4$ marks$]$

$($b$)$ A waste stabilization pond is designed for a residential estate of $25,000$ persons each one

generating $0\mathrm{.}12\frac{m^3}{?}$ person per day of domestic wastewater. The plant consists of a

facultative pond and maturation pond $($s$),$ arranged in series. The depths of both ponds are

$1\mathrm{.}5m$ and the hydraulic retention time $($HRT$)$ of the maturation pond is $5$ days. The first$-$

order BOD removal rate constant at $20C$ is $0\mathrm{.}3$ per day. The BOD of raw sewage is $200$

$m\frac{g}{L},$ the influent $FC$ is $1{10}^{t}F\frac{C}{100}ml$ and the operating temperature is $18C.$

Determine:

$($i$)$ The area and hydraulic retention time $($HRT$)$ of the ficultative pond. $[4$ marks$]$

$($ii$)$ The number of maturation pond $($s$)$ required to achieve the eflluent FC of $\frac{5000}{100}mL.$

$($iii$)$ The effluent BOD of the maturation pond.

$[3$ marks$]$

$|3$ marks$|$