Example $12\mathrm{.}73$

An aerated lagoon with a $10-$ft depth and liquid volume of $175,000cu.ft.$ treated an average of $0\mathrm{.}20mgd$ wastewater with a BOD of BOD$/$day$).$ The anticipated temperature extremes the aerating wastewater range from $10C$ in winter to $30C$ in summer. The $($two $15-$hp$)$surface aerators recommended for adequate mixing and oxygenation have themanafacturer's guarantee to provide an oxygen transfer of $2\mathrm{.}5l\frac{b}{h}p*hr$ under standard conditions. Based on laboratory treatability studies, the wastewater has the following characteristics: $k_{20}=0\mathrm{.}68$ per day, $=1\mathrm{.}047,=0\mathrm{.}9,=0\mathrm{.}8,$ and an oxygen utilization rate of $1\mathrm{.}0lb$ of oxygen to satisfy $0\mathrm{.}8lb$ of BOD removal. Ts the lagoon adequately sized? For a minimum BOD reduction of $75\%,$ is the aeration capacity adequate?