IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 128 NOM and Aquatic Systems Thursday, 27 August 2026 / Hall C shifts in samples from WTP A. Growth potential calculations likewise indicated the highest microbial growth in WTP A samples, particularly following phosphorus addition, suggesting phosphorus limitation in this system. Across all plants, AOC concentrations decreased during incubation but were not fully consumed, indicating that not all AOC constituents are equally bioavailable. These findings highlight that the formation of BOM and its ability to contribute to microbial growth depend strongly on the treatment strategy and nutrient context. By integrating flow cytometry, AOC measurements, and ultrahigh-resolution mass spectrometry, this study provides a comprehensive assessment of BOM from both functional and compositional perspectives. The results demonstrate that combining microbiological growth analyses with molecular-level characterisation improves our ability to detect subtle but treatment-relevant changes in DOM bioavailability. Furthermore, nutrient amendment experiments underline the importance of considering phosphorus limitation when evaluating biostability. Overall, this work advances our understanding of how treatment processes shape BOM and microbial regrowth potential, contributing to improved strategies for maintaining biological stability in drinking water distribution systems. References 1. van der Kooij, D., Journal AWWA 84(2) (1992), 57–65 2. Prest, E. I., Hammes, F., van Loosdrecht, M. C. M., & Vrouwenvelder, J. S., Frontiers in Microbiology 7 (2016) 3. Krzeminski, P., Vogelsang, C., Meyn, T., Köhler, S.J., Poutanen, H., de Wit, H. A., Uhl, W., Journal of Environmental Management 241 (2019), 427–438
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