Anaerobic biological treatment of EG/PG water-soluble copolymer coupled with down-flow hanging sponge reactor

Water-soluble copolymers such as polyvinylpyrrolidone and polyvinyl alcohol have been widely used as detergents, paints, and chemical intermediates in many industrial processes, leading to environmental concerns associated with high-volume organic compound wastewater. Therefore, in this study, a combined upflow anaerobic sludge blanket (UASB) reactor and downflow hanging sponge (DHS) biosystem has been applied for the treatment of synthetic water-soluble copolymer wastewater. Copolymer consisted of ethylene glycol and propylene glycol with a total molecular weight of 8,500, commonly preferred in the automobile parts processing factory, were included in influent. Overall, the whole UASB–DHS system achieved a favorable chemical oxygen demand (COD) removal efficiency of 86% ± 7%. In more detail, with an organic loading rate of 2.12 kg-COD ⋅ m−3 ⋅ day −1, the UASB reactor enhanced the biodegradability of wastewater, and reached COD removal efficiency of 61% ± 16%. Meanwhile, gel permeation chromatography analysis indicated that the molecular weight of the wastewater was primarily reduced in the DHS reactor. In addition, massive 16S rRNA gene sequencing showed that polyethylene-glycol-degrading bacteria Pelobacter sp. was predominant in the UASB granular sludge.