A data-independent acquisition approach based on HRMS to explore the biodegradation process of organic micropollutants involved in a biological ion-exchange drinking water filter.

Drinking water producers continuously develop innovative treatment processes to effectively remove organic micropollutants from raw water. Biological ion-exchange (BIEX) water treatment is one of these new techniques under development and showing great potential. In order to investigate if biodegradation is highly involved in such a removal technique, cultures were prepared with microorganisms sampled on the resins of a BIEX filter. Then, organic micropollutants were spiked into these cultures and their (bio)degradation was followed over 30 days by ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS). The purpose of this study was firstly to develop an analytical method using UHPLC-HRMS able to monitor the degradation of three spiked organic micropollutants in culture. Beyond quantification, this method allowed the simultaneous recording of fragmentation information via the use of a data-independent acquisition approach to perform a non-exhaustive search of transformation products related to the spiked micropollutants in culture aliquots. Secondly, a data treatment approach was developed to process raw spectral data generated by aliquots analysis by optimizing the precursor isolation mass windows, the accurate mass tolerance, peak intensity thresholds and choice of database. The use of this new method with a post-data acquisition treatment approach completed by the exhaustive study of fragmentation spectra allowed the tentative identification of 11 transformation products related to the spiked compounds. Finally, 16S rRNA gene amplicon sequencing revealed that bacterial genera known for their ability to degrade the spiked micropollutants were present in the microbial community of the BIEX drinking water filter.