17.6. 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 clarifier underflow line. Sketch a recycle system similar to Figure 17.1b except that Qw (the waste solids flow) is a separate flow directly withdrawn from the aeration basin. Underflow from the clarifier is recycled to the aeration basin. Write steady-state solids balance equations for ISS and VSS for the system, aeration basin, and clarifier. 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 influent and clarified effluent are negligible? Reactor (aeration basin) Q, So V, Xv, Se Q+rQ Xy, Se Clarifier Q-Qw Xve, Se Solids Xur, Se to waste Qw rQ Xvr Se (b)