Elena Gomez

Recharging aquifers with treated wastewater provides multiple benefits for sustainable water management, but micropollutants in effluents can threaten groundwater quality, aquatic ecosystems, and human health. Infiltration-based recharge can improve water quality and remove micropollutants, a performance that can be enhanced by reactive barriers. Advanced treatments such as nanofiltration or ozonation can also achieve high micropollutant abatement. This study evaluated micropollutant removal through reactive barrier infiltration alone and coupled with nanofiltration or ozonation, using three identical lab-scale columns containing a reactive barrier of 70% sand, 25% sawdust, and 5% compost over 37 days. Influent waters were wastewater effluent, ozonated effluent, or nanofiltration permeate. Redox zonation developed in all columns, with substantial removal of nitrogen species and sulphates, while dissolved organic carbon slightly increased in outlets. Positively charged micropollutants metoprolol and venlafaxine were highly removed (>90%), whereas neutral and negatively charged compounds showed variable behaviours. Biodegradation contributed to the removal of sulfamethoxazole (~60%), irbesartan (~30%), and oxazepam (<20%), while fluconazole, carbamazepine, and diclofenac were largely refractory. Microbiological indicators confirmed effective pathogen removal in all scenarios. Coupling reactive barrier infiltration with nanofiltration or ozonation improved overall micropollutants removal: at least 5 of 8 micropollutants were removed over 80%, and 7 were removed over 50%. Only fluconazole and carbamazepine remained refractory to ozonation-reactive barrier and nanofiltration-reactive barrier coupling, respectively. These results demonstrate that combining low-cost infiltration with advanced treatments can substantially enhance micropollutant removal, supporting safe water reuse for managed aquifer recharge.

Introduction: Population growth and increasing water demand have exacerbated water resource scarcity. Treated wastewater (TWW) is a valuable alternative resource, but its complex composition, including micropollutants, raises concerns about reuse risks. Reactive barriers (RB) made with natural materials offer a solution to remove TWW contaminants. Evaluating RB process effectiveness and comprehending contaminant fate remain challenging. Recent advances in High-Resolution Mass Spectrometry (HRMS) and non-target analysis (NTA) provide an opportunity to identify contaminants and evaluate RB processes. The study aims to develop an NTA approach to assess RB effectiveness and understand the NTA contribution for broadening perspectives on the impact of reactive barrier treatment.Methods: In a serie of batch experiments, TWW was mixed with a RB under two conditions: TWW in contact with RB (TWW+RB) and TWW alone (TWW). After 1 h of contact, samples were extracted and analyzed using HPLC-HRMS. NTA workflow and statistical comparison between the two sample conditions were applied for data treatment. Additionally, a quantitative method was applied to 28 pharmaceutical residues. Sorption (%) was calculated by comparing concentrations in TWW+RB and TWW experiments. NTA’s applicability for sorption estimation was investigated using intensities from differential analysis.Results: Differential analysis shows significant differences in compounds that decrease or increase after contact with BR. A prioritization workflow identified and annotated 115 compounds. Natural products predominantly increased after RB contact, while compounds exhibited a significant 75% decrease in peak area are mainly pharmaceuticals. Notably, 61% of these molecules were sorbed at more than 50%. The sorption of emerging contaminants (ECs) estimated by NTA correlated satisfactorily with sorption quantified through target analysis, although caution regarding the matrix effect is necessary.Discussion: NTA provides a comprehensive view of RB treatment performance, giving information on the compounds released by the barrier and its sorption capacity. NTA emphasizes the benefits of RB treatment while highlighting the need to study compounds reloaded by RB. It is a powerful tool for understanding the advantages of nature-based reactive barrier treatment in improving the quality of TWW.

The fate of emerging contaminants from runoff/storm waters in urban areas has aroused widespread concern as it poses a threat to the water managing. Contaminated water can reach, for instance, the river that passes through the area, contributing to the degradation of the aquatic ecosystem, or the aquifer that supplies drinking water to the community. In this framework, one of the objectives of the URBANWAT project is to evaluate the capacity of the Barcelona urban soil to retain the contaminants of emerging concern from runoff waters in order to propose an improvement of tools and criteria for groundwater management in urban areas.To this aim, a set of batch and packed soil column experiments were performed. The soil selected for the study is located in the Barcelona urban area at 20 m depth and composed of 48 % quartz, 28 % albite and 24 % microcline. It is constituted by 91 % sand, 7 % silt and clay and 2 % gravel, being the sand particle size dimension the one selected to perform the column experiments. The resident water in contact with the soil was analysed by ICP-MS and has a conductivity of 723 µS/cm and pH of 7.9. A list of representative emerging contaminants has been selected from diverse pharmaceutical families and UV filters based on the concentration values found in the runoff waters of the Barcelona urban area.The batch experiments were carried out first to verify if the soil already contained the target contaminants and second to know the soil sorption capacity. The target contaminants have different properties (pka, charge) that cause them to be sorbed with variable efficiency by the soil tested (80-100 % sorption for Paroxetine and Venlafaxine, 60-80 % for Cocaine and Caffeine, 40-60 % for Tradadol and Climbazole and low sorption (< 40 %) for a list of more than 15 emerging contaminants). Sorption capacities obtained in the batch experiments were also identified in the percolation tests, obtaining significantly different breakthrough curves for the studied target contaminants. By means of the percolation column experiments, the effect of the flow rate on the soil retention capacity was evaluated and the two main processes involved in the pollutants retention mechanism (sorption and biodegradation) were quantified to verify the specific contribution of each process to the global procedure.

We evaluated the feasibility of five sustainable materials (clay, zeolite, biochar, compost, and woodchips) to be included in a reactive barrier intended to improve the removal of pharmaceutical active compounds (PhACs) during soil aquifer treatment (SAT). The potential of the five materials to sorb PhACs was assessed and compared to sand capacity through batch experiments. Materials with high organic carbon content (biochar, compost, and woodchips) exhibited a greater capacity to sorb PhACs than materials with a low organic carbon content (clay and zeolite). The ion speciation of the molecules is a major parameter controlling the fate and transport of PhACs during SAT operations. Anionic species are the ones with the highest risk of reaching the aquifer since they are generally less sorbed compared to cationic and neutral species. Experimental parameters such as contact time, solid:water ratio, and grain size had no a significant effect on the sorption of PhACs in the studied materials. The incorporation of biochar, compost, and/or woodchips into reactive barriers will promote the sorption of PhACs and will boost the ability of the SAT system to improve the quality of the recharged water.

There is growing evidence of the presence of pharmaceuticals in natural waters and their accumulation in aquatic organisms. While their mode of action on non-target organisms is still not clearly understood, their effects warrant assessment. The present study assessed the metabolome of the Mediterranean mussel (Mytilus galloprovincialis) exposed to a 10 µg/L nominal concentration of the antidepressant venlafaxine (VLF) at 3 time-points (1, 3, and 7 days). Over the exposure period, we observed up- or down-modulations of 113 metabolites, belonging to several metabolisms, e.g., amino acids (phenylalanine, tyrosine, tryptophan, etc.), purine and pyrimidine metabolisms (adenosine, cyclic AMP, thymidine, etc.), and several other metabolites involved in diverse functions. Serotonin showed the same time-course modulation pattern in both male and female mussels, which was consistent with its mode of action in humans, i.e., after a slight decrease on the first day of exposure, its levels increased at day 7 in exposed mussels. We found that the modulation pattern of impacted metabolites was not constant over time and it was gender-specific, as male and female mussels responded differently to VLF exposure.

Scientists often set ambitious targets using environmental metabolomics to address challenging ecotoxicological issues. This promising approach has a high potential to elucidate the mechanisms of action (MeOAs) of contaminants (in hazard assessments) and to develop biomarkers (in environmental biomonitoring). However, metabolomics fingerprints often involve a complex mixture of molecular effects that are hard to link to a specific MeOA (if detected in the analytical conditions used). Given these promises and limitations, here we propose an updated review on the achievements of this approach. Metabolomics-based studies conducted on the effects of pharmaceutical active compounds in aquatic organisms provide a relevant means to review the achievements of this approach, as prior knowledge about the MeOA of these molecules could help overcome some shortcomings. This review highlighted that current metabolomics advances have enabled more accurate MeOA assessment, especially when combined with other omics approaches. The combination of metabolomics with other measured biological endpoints has also turned out to be an efficient way to link molecular effects to (sub)-individual adverse outcomes, thereby paving the way to the construction of adverse outcome pathways (AOPs). Here, we also discuss the importance of determining MeOA as a key strategy in the identification of MeOA-specific biomarkers for biomonitoring. We have put forward some recommendations to take full advantage of environmental metabolomics and thus help fulfil these promises.

Pharmaceuticals are present in natural waters, thus contributing to the general exposure of aquatic organisms, but few data are available on the accumulation of these substances in marine organisms. The present study evaluated the in vivo bioconcentration of an antidepressant—venlafaxine (VLF)—in marine mussels (Mytilus galloprovincialis) during 7 days of exposure at nominal 10 μg/L concentration, followed by a 7-day depuration period. The bioconcentration factor (BCF) was 265 mL/g dry weight (dw). VLF accumulation reached an average tissue concentration of 2146 ± 156 ng/g dw within 7 days, showing a first-order kinetics process. N-desmethylvenlafaxine (N-VLF) and O-desmethylvenlafaxine (O-VLF) metabolites were quantified in mussel tissues, whereas N,N-didesmethylvenlafaxine (NN-VLF) was only recorded as being detected. These three metabolites were also quantified in water, indicating an active metabolism and VLF excretion in Mediterranean mussels. Complementary experiments conducted at nominal concentrations of 1, 10, and 100 μg/L for 7 days confirmed the VLF bioconcentration and metabolism and allowed us to quantify a supplementary metabolite, i.e., N,O-didesmethylvenlafaxine (NO-VLF), in mussel tissues. These results encourage further research on a more complete characterization of metabolism and on any disturbances linked to bioconcentration of VLF on bivalves.