Optimization of propylene glycol removal in a fixed bed activated sludge bioreactor by Taguchi method

Taguchi method is an experimental design approach based on, we can predicate the effect of factors and optimum levels of operational factors with a minimum number of experiments. Propylene glycol is a synthetic organic which can release to the environment and cause health and environmental effects. The objective of this study was to determine the optimum conditions of propylene glycol removal in a fixed bed activated sludge bioreactor by Taguchi method. Following the adaptation of microorganisms, which were obtained from a municipal wastewater treatment plant to different concentrations of propylene glycol in a fixed bed activated sludge reactor, optimum conditions of operational parameters of bioreactor such as hydraulic retention time, influent COD, source of nitrogen and volume of fixed bed of aeration basin with packing were determined in three levels by Taguchi method. COD removal efficiency of synthetic wastewater containing N and P based on C:N:P ratio of 100:5:1 in the fixed bed activated sludge reactor with HRT of 14 h and influent COD of 500, 700, 900, 1100, 1300 and 1500 mg/L was 95%, 92%, 91%, 86%, 81 and 77% respectively. Optimization of the process by Taguchi method showed that HRT of 6 hours, influent COD of 1000 mg/L, fixed bed volume of 30% and NH4Cl as the source of nitrogen with importance priority of 47.96%, 29.927%, 13.25% and 8.857% were determined as optimum conditions of operational parameters of the fixed bed activated sludge rector for propylene glycol biodegradation respectively. Results of this study indicate that by the use of Taguchi method, optimum operational conditions of fixed bed activated sludge reactor for propylene glycol can be predicted