Per- and polyfluoroalkyl substances (PFAS) and industrial persistent, mobile, and toxic (iPMT) compounds pose growing risks to water quality. However, quantitative tools to prioritize compounds for remediation and evaluate exposure under varying environmental scenarios remain limited. This paper presents the first application of a Bayesian probabilistic early warning exposure assessment (EWEX) model to evaluate PFAS and iPMTs in indirect potable water reuse (IPR) systems. By integrating literature-derived and site-specific data, the model explicitly accounts for uncertainty and provides a flexible framework for scenario analysis. The model’s performance was demonstrated for PFOS, trifluoromethanesulfonic acid (TFMSA), and carbamazepine (CBZ), revealing sensitivity to data quality and emphasizing the importance of robust monitoring and transferable data sets. In addition to removal via treatment processes, dilution in the environment substantially reduces contaminant concentrations, highlighting the influence of the hydrological setting and the associated climate-related environmental factors on exposure outcomes. The EWEX framework serves as a decision-support tool for utilities and regulators, facilitating risk-informed management of emerging contaminants in water reuse systems. Future work should expand the data set for poorly studied compounds, refine treatment process representations, especially for short-chain PFAS, and validate model outputs through real-world monitoring.

Persistent and mobile (PM) substances are suspected to pass drinking water treatment; however, the extent of the treatment gap remains uncertain. This study aimed to determine the elimination of 115 potentially persistent and mobile substances (PM candidates) for four established (biological filtration, adsorption onto activated carbon, ozonation, reverse osmosis (RO)) and one developing treatment method (reductive treatment represented by catalytic hydrogenation) for drinking water supply individually and in combinations. In systematic lab-scale experiments, less than half of all PM candidates were eliminated above 80% by adsorption or ozonation at typical doses (10 mg/L with 48 h contact time, 0.67 mg O3/mg DOC), whereby adsorption indicated slightly higher elimination. Overall, RO achieved the highest elimination, exceeding 80% removal for 96% of all PM candidates. In three common combined treatment sequences, 16 PM candidates remained below 50% elimination and were therefore identified as critical for drinking water treatment, among them six halomethanesulfonates and seven components of ionic liquids. For adsorption onto activated carbon, polarizability, logD and solubility showed strong correlations with PM candidate eliminations, whereas for RO, strong correlations were observed between PM candidate eliminations, and molar mass and polarizability. These correlations provide suitable and readily accessible molecular properties to feed predictive models for the assessment of PM candidate elimination.

Biotransformation in sand filters and natural subsurface barriers is a key process for eliminating organic micropollutants from drinking water. However, underlying mechanisms are complex and knowledge on influencing parameters is fragmentary. There is still a knowledge gap regarding contaminants of emerging concern, such as persistent and mobile substances, and their fate in those processes. This study investigated sorption and biotransformation of 18 polar and potentially persistent contaminants in oxic sand columns, evaluating the effect of biodegradable dissolved organic carbon (BDOC, drinking water vs. surface water), hydraulic retention time (9 h vs. 25 h) and sand type (microbial community, technical sand vs. sand from a groundwater recharge site). Substance and operation specific extent of biotransformation was observed. Overall, nine substances were biodegraded, while nine indicated persistence. Negligible sorption was observed, only the cationic 1,3-di-o-tolylguanidine was retarded by four bed volumes. The highest impact on biotransformation was observed for the parameter BDOC, followed by hydraulic retention time and finally sand type. The strongest effect was observed for 2-methyl-2-propene-1-sulfonic acid (MPSA), which was readily biodegradable in surface water and persistent under BDOC limiting conditions. Previous classifications as persistent, e.g. of 2-acrylamido-2-methylpropane sulfonate and adamantan-1-amine, were confirmed. Three substances previously categorized as persistent (acesulfame, MPSA and 4-hydroxy-1-(2-hydroxyethyl)-2,2,6,6-tetramethylpiperidine) showed biotransformation. These results emphasize the complexity of persistence assessments and the potential for some polar contaminants to be eliminated in treatment processes relying on biotransformation in the subsurface or sand filters under oxic conditions.

Nature-based solutions (NBSs) are often considered to be cure-all remedies for mitigating risks arising from climate change, among others. This study explores the failure modes of NBSs in stormwater management, and analyses challenges across the different stages of their life cycles, including planning, design, and operation. The PRISMA methodology was applied to carry out a systematic literature review to identify the main triggers, consequences and potential mitigation measures for different failure modes and challenges, with a view to enhancing the long-term performance of NBSs. Each identified failure mode was classified along the three typological dimensions of severity, origin and preventability, with sub-dimensions for qualitative and quantitative analysis. Based on 76 reviewed studies, it was concluded that preventable and intrinsic failures dominate the early stages (planning and design), whereas induced and extrinsic failures tend to manifest during operation and maintenance. The application of interdisciplinary and catchment-scale thinking in planning reduces the probability and severity of failure in the design and operation stages. Standardised and data-based approaches are needed to mitigate NBS failures throughout the life cycle.