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

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.

Efficient degradation of the organic UV filter benzophenone-3 by Sphingomonas wittichii strain BP14P isolated from WWTP sludge.

Benzophenone-3 (BP3) is a widely used organic UV filter present in many environmental compartments. One way BP3 is released into the environment is through effluents from wastewater treatment plants (WWTPs). These plants are possible sources for degradation activity and WWTP sludge may potentially degrade BP3. Our goal was to identify any BP3 degrading microorganism(s) in WWTP sludge and to investigate whether the degradation was co-metabolic. Initial WWTP sludge microcosms spiked with BP3 showed 100% degradation after 20 days. Multiple transfers of these microcosms, while maintaining a strong selective pressure for BP3 degradation capabilities, resulted in the dominance of one bacterial strain. This strain was identified as Sphingomonas wittichii BP14P and was subsequently isolated. It was shown to degrade BP3 in a growth dependent manner. Strain BP14P utilized BP3 as the sole energy and carbon source and completely degraded BP3 after 7 days in minimal media. We tested the capability of BP14P to degrade nine other UV filters, but the degradation ability seemed to be restricted to BP3. However, whether this specificity is due to the lack of degradation genes, cellular transport or low bioavailability of the other UV filters remained unclear. The efficient degradation of BP3 by a group of bacteria well known for their potential for xenobiotic degradation is an important step forward for a complete risk assessment of the long-term environmental impact of BP3.