Evaluation of the degradation capacity of WWTP sludge enrichment cultures towards several organic UV filters and the isolation of octocrylene-degrading microorganisms

Abstract

Organic UV filters are present in wastewater treatment plants (WWTPs) due to the use of these compounds in many personal care products (PCPs) and their subsequent release into the wastewater system from showering/bathing. Once in the wastewater system, organic UV filters generally partition into the solid phase but might also undergo other processes, such as degradation by microorganisms. To further understand the fate of organic UV filters in WWTPs, the degradation of 7 UV filters by WWTP sludge was investigated The UV filters 2-ethylhexyl salicylate (ES), homosalate (HS), butyl methoxydibenzoylmethane (BM) and octocrylene (OC) were degraded after 20–60 days. The rest of the filters tested, namely, bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT), methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT) and diethylhexyl butamido triazone (DBT), did not degrade even after 120 days of incubation. The microbial community from the microcosms degrading ES, HS, OC and BM was transferred every 30 days into new microcosms to enrich for microorganisms capable of utilizing the individual UV filters for growth. The enrichment cultures continued to degrade throughout 20 transfers. The microbial community was clearly different between the enrichments degrading ES, HS, OC and BM, meaning that the microbial community was strongly influenced by the UV filter present. Furthermore, several strains were isolated from OC-degrading cultures and two of these strains, Gordonia sp. strain OC_S5 and Sphingopyxis sp. strain OC_4D, degraded OC with and without other carbon sources present. These experiments show that several organic UV filters can be degraded by a specific set of microorganisms. The lack of degradation observed for BEMT, MBBT and DBT is probably due to limited bioavailability. Indeed, this is the first biodegradation study of these filters, in addition to being the first description of ES and HS degradation in microcosm experiments.