Optimal design of multi-stage bioreactors for degradation of phenolic industrial wastewater: Theoretical analysis

An analytical relationship for the optimum design of continuousstirred tank reactors (CSTR’s) in series performing phenoldegradation was derived. The optimal design is based on theminimum overall reactor volume required for a certain degree ofphenol removal. It is assumed that cell growth kinetics follow theHaldanes kinetics model with respect to phenol and with no oxygenlimitation. The effect of operating parameters such as phenol inletfeed concentration, phenol removal efficiency and number ofCSTR’s in series on the optimum design are investigated. Thedesign equations compared the volume required for a certainpercentage of phenol removal for the optimum design and the equalvolume design which is currently practiced design criteria. Thisstudy shows that the optimum design (variable volume reactors) ismore efficient than equal volume design at relatively high inlet feedsubstrate concentration, high substrate conversion and increasingthe number of reactors. The percentage of degree reduction in thetotal volume using the optimum design compared to equal sizereactors can be up to 80 % depending on the operating parameters.Up to five CSTRs in series and PFR are described in this study.Experimental and kinetic data used in this optimization problemwere collected from the literature.