Application of biofilters developed under different influent characteristics in attenuating emerging contaminants from wastewater

Emerging contaminants (ECs) in treated effluent possess substantial risks to the aquatic life of the receiving surface waters. This study tried to explore the scope of activated carbon based biofiltration in efficient removal of ECs from municipal wastewater effluent. Four biofilters, developed under different feed characteristics, were compared to understand the attenuation pattern of eighteen target ECs in the wastewater effluent. The performance of the biofilters was assessed by studying the attenuation of eighteen ECs with changing microbial abundance and empty bed contact time (EBCT). The removal percentages of the target ECs showcased positive correlation with increasing microbial abundance and longer EBCTs. Compounds including naproxen, ketoprofen, sulfamethoxazole, ibuprofen and triclosan were completely removed. A similar trend was also seen in the removal of specific UV absorbance. Trimethoprim was attenuated in all biofilters, confirming its high bioavailability. Longer EBCTs facilitate better contact between biofilm and ECs in the aqueous matrix thus leading to greater removal percentages. The majority of the ECs showed better removal with 30 min EBCT, particularly well-known recalcitrant compounds including carbamazepine and bisphenol-A. Decreasing carbon concentration in feedwater also negatively affects the removal efficiencies of the biofilters. The present results confirmed the co-metabolic pathway of degradation of the target ECs. The enzyme-substrate interaction was explained by the first order Michaelis-Menten reaction model. The enzymes used in metabolizing the primary substrate helped in biodegradation of the ECs. 20 transformation products formed from 11 target ECs were identified with the majority of them being detected in the biofilter with high microbial abundance.