Problem No$.4($last year's exam question$)$

The following relationship between contact time and chlorine dosage was derived for $99\mathrm{.}9\%$ kill of adenovirus $($@pH $7)$:

C$^(0\mathrm{.}5)$t$=4\mathrm{.}3$ where: C$=$ chlorine dosage, m$($g$)/($L$)$

t$=$ contact time, min

$($a$)$ For the effluent flow of $5000($m$^(3))/()$ day, determine the volume of the contact chamber needed for $99\mathrm{.}9\%$ inactivation of this pathogen at chlorine dosages of $0\mathrm{.}1$m$($g$)/($L$)($pH$7).$

$($b$)$ If the treatment plant already has a $25$m$^(3)$ reactor, which can be converted to the contact chamber, what is the free chlorine concentrations required in the $25-$m$^(3)$ contact chamber?