A wastewater is to be disinfected with $35 \mathrm{mg} / \mathrm{L}$ of chlorine to obtain $99 \%$ kill of microorganisms. The number of micro-organisms remaining alive $\left(N_{t}\right)$ at time $t,$ is modelled by $N_{t}=N_{o} e^{-k t},$ where $N_{o}$ is number of micro-organisms at $t=0,$ and $k$ is the rate of kill. The wastewater flow rate is $36 \mathrm{~m}^{3} / h,$ and $k=0.23 \mathrm{~min}^{-1} .$ If the depth and width of the chlorination tank are $1.5 \mathrm{~m}$ and $1.0 \mathrm{~m},$ respectively, the length of the tank (in $m,$ round off to 2 decimal places ) is
A wastewater is to be disinfected with $35 \mathrm{mg} / \mathrm{L}$ of chlorine to obtain $99 \%$ kill of microorganisms. The number of micro-organisms remaining alive $\left(N_{t}\right)$ at time $t,$ is modelled by $N_{t}=N_{o} e^{-k t},$ where $N_{o}$ is number of micro-organisms at $t=0,$ and $k$ is the rate of kill. The wastewater flow rate is $36 \mathrm{~m}^{3} / h,$ and $k=0.23 \mathrm{~min}^{-1} .$ If the depth and width of the chlorination tank are $1.5 \mathrm{~m}$ and $1.0 \mathrm{~m},$ respectively, the length of the tank (in $m,$ round off to 2 decimal places ) is