Hybrid biofiltration–advanced oxidation process system for removing emerging contaminants from actual wastewater treatment plant effluent

Water reuse is increasingly considered a solution to increase freshwater supplies in communities with severe water shortages. Conventional wastewater treatment plants (WWTPs) are challenged in removing emerging contaminants (ECs) from effluent, leading to their persistent presence in aquatic environments, which might cause major environmental, human, and animal health hazards.. In this study, a biofiltration system was operated with and without pre-treatment for removing ECs from actual WWTP effluent. Two types of biofilter media- exhausted biological activated carbon (BAC) and expanded glass (EG) were explored, and an advanced oxidation process (AOP) - UV/TiO 2 photocatalysis was provided as the pre-treatment to the biofiltration system. Four ECs were detected at μg/L level only, namely: dibutyl phthalate (DBP), phenothrin (PHN), malathion (MAL), and 9-aminoacridine (9-AA). BAC removed 19 % of total organic carbon (TOC); removals increased to 60 % when preceded by UV/TiO 2 photocatalysis. BAC was found to perform better than EG biofilters for TOC, DBP, PHN, and MAL removal in both individual and hybrid systems. EG biofilters showed better removal in both biofiltration-only and hybrid systems for the 9-AA. Other ECs like xylazine (XYL), di(2-ethylhexyl) sebacate (DEHS), caffeine (CAF), and methylphenidate (MPD) were also identified, and removals were calculated based on peak areas. Biofilters demonstrated similar nutrient removal and improved performance with the application of AOP pretreatment. Overall, the findings show that combining UV/TiO₂ photocatalysis and biofiltration significantly enhances the quality of actual WWTP effluent by the removal of both conventional and emerging contaminants. AC demonstrated better performance than EG for the majority of compounds, although EG exhibited superior removal of 9-AA. This study introduces a novel approach by assessing a hybrid UV/TiO₂ photocatalysis and biofiltration system utilizing EG, an underexplored filter media, in real WWTP effluent in the UAE, and systematically comparing its performance to that of activated carbon. The results support the sustainable reuse of wastewater in arid conditions and offer important insights for improved removal of ECs. • The hybrid system showed better removal of emerging contaminants. • The BAC biofilter outperformed EG in the removal of TOC, DBP, PHN, and MAL. • EG biofilter performed better than AC in the removal of 9-AA. • The elimination capacity of both AC and EG biofilters was enhanced by AOP pretreatment.