To more precisely control the SRT$,$ laboratory studies are often conducted with recycle

systems incorporating CM or PF reactors, but the sludge is wasted directly from the

aeration basin as opposed to wasting sludge from the clari$$er under$$ow line. Sketch a

recycle system similar to Figure $17\mathrm{.}1$b except that Qw $($the waste solids $$ow$)$ is a separate

$$ow directly withdrawn from the aeration basin. Under$$ow from the clari$$er is recycled

to the aeration basin. Write steady$-$state solids balance equations for ISS and VSS for the

system, aeration basin, and clari$$er$.$

What is the SRT in this system if $10\%$ of the volume of the aeration basin is wasted

each day and VSS concentrations in the in$$uent and clari$$ed ef$$uent are negligible?