Biological treatment of benzophenone-type UV filter wastewater in a sequencing batch reactor (SBR)

Benzophenone-n (BPs) is an emerging endocrine-disrupting contaminant that can be applied to different commercial products including UV-filters. BPs are toxic to microorganisms, coral, and animals. This study aims to demonstrate the use of laboratory-scale SBR to remove 2,4-dihydroxybenzophenone (BP-1) and oxybenzophenone (BP-3) and to investigate extracellular polymeric substance (EPS) production and functions under different hydraulic retention time (HRT) and operating stages. HRT period focused on removal of BPs and different stages focused on EPS content. The results show that the removal of BPs is high when HRT is increased from 8 (68.9% for BP-1/78.5% for BP-3) to 48 h (96.8%/98.0%, respectively); and favoured in reaction stage (aerobic condition) (80.33%/90.23%, respectively). In the view of EPS, protein (EPS-PN) content increases from 57.8 μg/L to 119.8 μg/L when HRT is increased from 8 to 48 h; however, polysaccharides (EPS-PS) show no relationship with HRT. In different stages, both EPS content reach the maximum (132.2 μg/L and 194.2 mg/L, respectively) during idle stage, and fluctuate in first 3 h of reaction stage and later recover to 117.1 μg/L and 160.6 mg/L, respectively. The next-generation sequencing (NGS) results show that different HRTs promote different dominant strains, but both communities are similar at different stages.