Chapter 4: Activated Sludge Modelling - IqTMA-UVa

SolutionBy definition D = Q/V = 0.55 h -1 and HRT = 1/D = 1.82 hUsing S = DK s /(µ m – D), S = 0.33 g L -1 and X = Y(S 0 -S) = 0.201 g L -1At D = 0.3 h -1 and S 0 = 1 g L -1 : S = 0.03 g L -1 and X = 0.291 g L -1At D = 0.6 h -1 : S = 1 and X = 0: washout!Conclusions: A CSTR cannot be operated at too high dilution rate,otherwise the cell do not grow fast enough to compensate the cell lost.The cell concentration rapidly drops and the process fails! Lower dilutionrates allow better efficiency but require higher reactor volume (atconstant flow).11