Comparison between fixed bed and conventional activated sludge processes in the treatment efficiency of industrial wastewaters containing propylene glycol
Subject Areas : environmental management
Keywords: Biological treatment, Organic loading, propylene glycol, attached growth, activated sludge,
Abstract :
Propylene glycol is an organic chemical compound which has wide applications in different industries and its release in the environment poses adverse health and environmental effects. Fixed bed activated sludge process is one of the biological treatment processes that has advantages such as higher biomass concentrations, possibility for a higher rate of treatment, or more efficiency in the same flow rate compared with the conventional activated sludge processes. The main objective of this study was to compare the effects of organic loading variations on the biological removal efficiency of propylene glycol in fixed bed and conventional activated sludge processes. In the first stage, bench scale bioreactors were operated in four HRT of 8, 6, 4 and 2 hrs and constant propylene glycol concentration of 500 mg/l. In the second stage, constant HRT of 6 hr and propylene glycol concentrations of 1000, 1500, 2000 and 2500 mg/l were applied to bioreactors. Propylene glycol removal efficiency of fixed bed activated sludge bioreactor in HRT of 8, 6, 4 and 2 hr was 14.6, 24.5, 41.16 and 57.6 % more than that of conventional activated sludge bioreactor, respectively. Besides, propylene glycol removal efficiency of fixed bed activated sludge bioreactor for propylene glycol feed concentrations of 1000, 1500, 2000 and 2500 mg/l was 19.8, 33.8, 39.45 and 25.96 % more compared to that of the conventional activated sludge.