Degradation of Methyl Paraben by the Aerated Pebble-bed Biofilm System

Abstract

Methyl parben is an often-used anti-septic chemical in personal care products, and its discharge along with domestic sewage or municipal wastewater resulted in the elevated concentration in natural water bodies. To mitigate its impact to the aquatic environment, this study aimed to investigate the methyl paraban degradation by an aerated pebble-bed biofilm system at various hydraulic retention times. The influent methyl paraben concentration was 10mg/L. The degradation of methyl paraben and synthetic municipal wastewater mixture was evaluated at their respective concentrations of 10mg/L and 50mg COD/L. The results indicated that the removal efficiency of BOD at 1 hour hydraulic retention time was 83.7%, and this efficiency increased to 92.54% as the hydraulic retention time increased to 3hours. The BOD removal efficiencies for methyl paraben and municipal wastewater mixture were higher than those for wastewaters containing only methyl paraben. The influent initial pH was around 4.7 because of hydrolysis of methyl paraben, during which hydrogen ions were released. The pH exhibited an increasing trend as the wastewater travelled through the system. For methyl paraben removal, the efficiencies for wastewater containing only methyl paraben were higher than those for methyl paraben and municipal wastewater mixture. An apparent competition between methyl paraben and municipal wastewater was observed. The methyl paraben degradation followed the 1st order kinetics.