After exiting the coagulation$/$flocculation stage, $127000$ USG$/$d of a floc suspension in water is sent to a clarifier for sedimentation at $11\backslash$deg C$.$ The clarifier is rectangular, $24\text{'}$ long by $16\text{'}$ wide, and $11\mathrm{.}5\text{'}$ deep. The composition of the stream is as follows:

$15\mathrm{.}5$ w$/$v$\%$ flocs

$1\mathrm{.}2$ w$/$v$\%$ residual alum coagulant, pH $=8\mathrm{.}8$

Chlorine disinfection is performed in the clarifier during the sedimentation process. The detention time for the solids in the clarifier is the same as the chlorine contact time. What residual $($free chlorine$)$ concentration, in ppm$,$ would be expected in the water?