Optimization of Propylene Removal in a Complete Mixed Activated Sludge Bioreactor by Taguchi Method

Background and Objective: Exposure to propylene glycol can lead to many health risks on blood, skin and kidney. Biodegradation of synthetic wastewater containing propylene glycol was studied in a continuous conventional activated sludge bench scale reactor. Optimum conditions of microorganismschr('۳۹') growth for biodegradation of propylene glycol were determined by Taguchi method. Materials and Methods: Primary microorganisms for start up of the bioreactor were obtained from sludge return line of a municipal wastewater treatment plant and adapted to different concentrations of propylene glycol in a conventional activated sludge reactor. Optimum growth conditions of microorganisms and also operational conditions of the system including pH, influent COD, source of nitrogen and salinity were determined in three levels by Taguchi method. Results: COD removal efficiency in conventional activated sludge reactor for influent concentrations of ۴۰۰, ۷۰۰, ۹۰۰, ۱۱۰۰ and ۱۳۰۰ mg/L were ۹۸%, ۹۵%, ۹۵%, ۹۰% and ۸۵% respectively. Optimization of the process by Taguchi method showed that source of nitrogen urea, pH = ۸, salinity of ۸% and influent COD of ۱۳۰۰ mg/L with importance priority of ۴۱%, ۲۵%, ۱۷.۱۱% and ۱۶.۱۴۲% were as optimum growth conditions of microorganisms and also operational conditions of the system for propylene glycol biodegradation respectively. Conclusion: According to the results obtained from this work, it can be concluded that optimum conditions of biological processes and improvement the efficiency of bioreactors can simply be done by the use of such experimental designs.

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Key words: Propylene glycol , Conventional activated sludge , Wastewater treatment , Taguchi method