Evaluation of a combined anaerobic baffled reactor–downflow hanging sponge biosystem for treatment of synthetic dyeing wastewater

Abstract Highly colored wastewater from the textile industry, can threaten the natural environment if discharged into water bodies without any treatment. In this study, a laboratory–scale system combining an anaerobic baffled reactor (ABR), with the total volume of 10 L and a down–flow hanging sponge reactor (DHS), with the total volume of 4.14 L was designed to treat synthetic dyeing wastewater containing the commercial azo dye Hellozol HSR Reactive Black at 30 °C with a hydraulic retention time (HRT) of 23.2 h. Synthetic wastewater with 260 ± 40 mg.L − 1 of chemical oxygen demand concentration (COD) and 1020 ± 70 Pt/Co of true color level was prepared based on the characteristics of an actual effluent from an Indonesian textile factory. The combined system showed maximum COD and color removal efficiencies of 90% and 58%, respectively, with the removal majority taking place in the ABR. Moreover, microbial community analysis conducted on sludge retained from the ABR indicated that Proteobacteria, Firmicutes, WWE1, Spirochaetes, Bacteroidetes, Chloroflexi, OP8, andEuryarchaeota were predominant phyla. Among them, Clostridium sp was discovered and reported to have potential to degrade a wide range of azo dyes.