BOOK OF ABSTRACTS 117 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Thursday, 27 August 2026 / Hall C NOM and Aquatic Systems SL55 Biotransformation of Trace Organic Chemicals from Reclaimed Water during Managed Aquifer Recharge: The Role of Natural Organic Matter Magdalena A. Knabl1, Felicia Linke1, Jörg E. Drewes1 1 Technical University of Munich, Chair of Urban Water Systems Engineering, Am Coulombwall 3, 85748 Garching E-mail presenting and corresponding author: magdalena.knabl@tum.de Groundwater resources in Germany and worldwide are under pressure from human activities such as excessive water abstraction and the input of pollutants. Additionally, due to climate change, the natural recharge of aquifers is affected by droughts, while demand for water increases as temperatures rise. As a result, groundwater resources are declining and aquifer water quality is deteriorating. Managed aquifer recharge (MAR) can counteract these alarming trends by enhancing groundwater availability and quality, making local and regional water supply more resilient [1]. It is of utmost importance that water of appropriate quality is used for MAR, especially in cases where infiltrated water is intended to augment groundwater supplies leading to indirect potable reuse applications. Regarding potential contaminants, trace organic chemicals (TOrCs) are of particular concern, especially when surface water impacted by wastewater treatment plant (WWTP) effluent or reclaimed water is used for MAR. The low occurrence level of TOrCs, coupled with long-term exposure, may be linked to potential adverse effects on both human health and the environment [2]. Nevertheless, various TOrCs can be biodegraded during MAR, but the removal depends strongly on the engineered and environmental conditions prevailing at a given site [3]. Based on previous studies, it is expected that different fractions of dissolved organic carbon (DOC) in the infiltrated water play a key role in shaping the aquifer microbiome during MAR, thereby influencing the biotransformation capacity of TOrCs [4, 5]. To shape and optimize the biotransformation of TOrCs during MAR, the authors propose a hybrid MAR approach, where the water is pretreated prior to recharging the aquifer. It is hypothesized that different pretreatment technologies for reclaimed water determine the composition of DOC and specifically the natural organic matter (NOM) fractions that are provided to the microbial communities during the subsequent MAR infiltration step, resulting in significantly different TOrCs removal percentages. To test this hypothesis, different pretreatment approaches (cloth media filtration, coagulation + ultrafiltration, cloth media filtration + ozonation + biologically
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