Review of risk from potential emerging contaminants in UK groundwater

This paper provides a review of the types of emerging organic groundwater contaminants (EGCs) which are beginning to be found in the UK. EGCs are compounds being found in groundwater that were previously not detectable or known to be significant and can come from agricultural, urban and rural point sources. EGCs include nanomaterials, pesticides, pharmaceuticals, industrial compounds, personal care products, fragrances, water treatment by-products, flame retardants and surfactants, as well as caffeine and nicotine. Many are relatively small polar molecules which may not be effectively removed by drinking water treatment. Data from the UK Environment Agency’s groundwater screening programme for organic pollutants found within the 30 most frequently detected compounds a number of EGCs such as pesticide metabolites, caffeine and DEET. Specific determinands frequently detected include pesticides metabolites, pharmaceuticals including carbamazepine and triclosan, nicotine, food additives and alkyl phosphates. This paper discusses the routes by which these compounds enter groundwater, their toxicity and potential risks to drinking water and the environment. It identifies challenges that need to be met to minimise risk to drinking water and ecosystems

Is the Hyporheic Zone Relevant beyond the Scientific Community?

Rivers are important ecosystems under continuous anthropogenic stresses. The hyporheic zone is a ubiquitous, reactive interface between the main channel and its surrounding sediments along the river network. We elaborate on the main physical, biological, and biogeochemical drivers and processes within the hyporheic zone that have been studied by multiple scientific disciplines for almost half a century. These previous efforts have shown that the hyporheic zone is a modulator for most metabolic stream processes and serves as a refuge and habitat for a diverse range of aquatic organisms. It also exerts a major control on river water quality by increasing the contact time with reactive environments, which in turn results in retention and transformation of nutrients, trace organic compounds, fine suspended particles, and microplastics, among others. The paper showcases the critical importance of hyporheic zones, both from a scientific and an applied perspective, and their role in ecosystem services to answer the question of the manuscript title. It identifies major research gaps in our understanding of hyporheic processes. In conclusion, we highlight the potential of hyporheic restoration to efficiently manage and reactivate ecosystem functions and services in river corridors. View Full-Tex

An uncertainty and sensitivity analysis applied to the prioritisation of pharmaceuticals as surface water contaminants from wastewater treatment plant direct emissions

In this study, the concentration probability distributions of 82 pharmaceutical compounds detected in the effluents of 179 European wastewater treatment plants were computed and inserted into a multimedia fate model. The comparative ecotoxicological impact of the direct emission of these compounds from wastewater treatment plants on freshwater ecosystems, based on a potentially affected fraction (PAF) of species approach, was assessed to rank compounds based on priority. As many pharmaceuticals are acids or bases, the multimedia fate model accounts for regressions to estimate pH-dependent fate parameters. An uncertainty analysis was performed by means of Monte Carlo analysis, which included the uncertainty of fate and ecotoxicity model input variables, as well as the spatial variability of landscape characteristics on the European continental scale. Several pharmaceutical compounds were identified as being of greatest concern, including 7 analgesics/anti-inflammatories, 3 β-blockers, 3 psychiatric drugs, and 1 each of 6 other therapeutic classes. The fate and impact modelling relied extensively on estimated data, given that most of these compounds have little or no experimental fate or ecotoxicity data available, as well as a limited reported occurrence in effluents. The contribution of estimated model input variables to the variance of freshwater ecotoxicity impact, as well as the lack of experimental abiotic degradation data for most compounds, helped in establishing priorities for further testing. Generally, the effluent concentration and the ecotoxicity effect factor were the model input variables with the most significant effect on the uncertainty of output results

Removal of Antibiotics in Biological Wastewater Treatment Systems—A Critical Assessment Using the Activated Sludge Modeling Framework for Xenobiotics (ASM-X)

Many scientific studies present removal efficiencies for pharmaceuticals in laboratory-, pilot-, and full-scale wastewater treatment plants, based on observations that may be impacted by theoretical and methodological approaches used. In this Critical Review, we evaluated factors influencing observed removal efficiencies of three antibiotics (sulfamethoxazole, ciprofloxacin, tetracycline) in pilot- and full-scale biological treatment systems. Factors assessed include (i) retransformation to parent pharmaceuticals from e.g., conjugated metabolites and analogues, (ii) solid retention time (SRT), (iii) fractions sorbed onto solids, and (iv) dynamics in influent and effluent loading. A recently developed methodology was used, relying on the comparison of removal efficiency predictions (obtained with the Activated Sludge Model for Xenobiotics (ASM-X)) with representative measured data from literature. By applying this methodology, we demonstrated that (a) the elimination of sulfamethoxazole may be significantly underestimated when not considering retransformation from conjugated metabolites, depending on the type (urban or hospital) and size of upstream catchments; (b) operation at extended SRT may enhance antibiotic removal, as shown for sulfamethoxazole; (c) not accounting for fractions sorbed in influent and effluent solids may cause slight underestimation of ciprofloxacin removal efficiency. Using tetracycline as example substance, we ultimately evaluated implications of effluent dynamics and retransformation on environmental exposure and risk prediction

Targeted monitoring for human pharmaceuticals in vulnerable source and final waters

A range of pharmaceuticals has been detected in soils, surface waters and groundwaters across the world. While the reported concentrations are generally low (i.e. sub μg l-1 in surface waters), the substances have been observed throughout the year across a variety of hydrological, climatic and land-use settings. As a result, questions have been raised over the potential for pharmaceuticals in surface waters to enter drinking water supplies and to affect consumers. In a previous Drinking Water Inspectorate (DWI) funded study, results from a simple exposure model were used alongside information on therapeutic doses of pharmaceuticals to identify pharmaceuticals that are likely to be of most concern in UK drinking water sources. However, this previous study was entirely desk-based and did not involve any experimental measurements of pharmaceutical concentrations. The current study was therefore performed to generate actual measurements on the occurrence of pharmaceuticals in source and treated waters in England. The study considered a range of pharmaceutical compounds and their metabolites that have either a) high predicted exposure concentrations; b) toxicological concerns; or c) a low predicted exposure to therapeutic dose ratio. An illicit drug and its major metabolite were also investigated. The study compounds (in total 17) covered a range of chemical classes and varied in terms of their physico-chemical properties. The study was done at four sites where concentrations in source water at the drinking water treatment abstraction point were predicted to be some of the greatest in England. The study therefore is likely to provide a ‘worst case’ assessment of potential human exposure to pharmaceuticals in drinking water in England and Wales. Ten of the 17 study compounds were detected in untreated source waters at sub-μg/l concentrations. Six of these compounds (namely, benzoylecgonine (a metabolite of cocaine), caffeine, carbamazepine (an antiepileptic medicine), carbamazepine epoxide (a metabolite of carbamazepine), ibuprofen and naproxen (both non-steroidal anti-inflammatory drugs) were also detected in treated drinking water. With the exception of carbamazepine epoxide, concentrations in treated drinking water were generally significantly lower than in source water. Even though England is a densely populated country and in some regions there is limited dilution of wastewater effluents, these observations, made at sites that were predicted to have some of the highest concentrations of pharmaceuticals in England and Wales, are in line with results from similar studies performed in other countries. Comparison of measured concentrations of the study compounds in drinking waters with information on therapeutic doses demonstrated that levels of these compounds in drinking water in England are many orders of magnitude lower than levels that are given to patients therapeutically. It would therefore appear that the low or non-detectable levels of pharmaceuticals and illicit drugs present in drinking waters in England and Wales do not pose an appreciable risk to human health

Modelling the Fate of Sediments and Micropollutants in Rivers

In industrialized countries, the assessment of water quality in rivers remains a timely topic even though problems of eutrophication have been overcome by wastewater treatment. In particular, hydrophobic organic pollutants that typically sorb to suspended sediments (e.g., PAH), and pharmaceuticals that are not included in regular treatment of WWTPs have gained environmental concerns. These pollutants occur at concentrations of nano- to micro-grams per liter in rivers. Continuous monitoring of these compounds is time- and cost-consuming. A modelling approach is advantageous and necessary to understand the interacting environmental processes that determine the fate of micropollutants in river systems. Sediment transport facilitates the transport of PAH, one group of micropollutants of interest in this thesis. Combining hydrological, hydraulic, and in-stream transport models can give good insights on sediment sources and transport on the catchment-scale, which is essential for investigating the fate of PAH. Therefore, I developed such an integrated sediment transport model to simulate sediment contributions from catchment and in-stream processes under different flow conditions. The characteristics of surface runoff essentially control the sediment supply from urban and rural areas. In the mainly groundwater-fed Ammer catchment, the weak rural surface runoff leads to a small rural sediment supply. By contrast, urban particles dominate the annual sediment load. The flow rate and river geometry determine the deposition and remobilization of sediments in the river. The modelled sediment trapping occurs in very mild reaches of River Ammer. I extended the integrated sediment transport model to a particle-facilitated pollutant transport model, which considers PAH interaction between water and sediment. This model allows to study the source, turnover, and legacy potential of PAH in river systems. The supply and composition of sediments determine to a large extent the PAH supply to a river. In the Ammer River, the high proportion of urban particles with high PAH content results in the dominant supply of PAH from urban areas. In steep reaches, sediment turnover governs the turnover of PAH, whereas in very mild river segments diffusion of PAH from the river bed to the mobile water is relevant and reduces PAH turnover times. PAH legacy occurs in river segments with slow sediment turnover. For River Ammer, the simulated sediment trapping reaches have acted as secondary PAH source over 10-20 years after the introduction of environmental regulations in the 1970s. Pharmaceuticals are emitted to rivers by WWTPs due to incomplete removal. I developed a one-dimensional reactive solute transport model considering transient storage to investigate the transport and fate of these compounds in the WWTP effluent-impacted River Steinlach. The degradation processes are substantially affected by the local conditions. Carbamazepine is relatively conservative, sulfamethoxazole is only biodegradable, while metoprolol and venlafaxine undergo both photo- and bio-degradation. The flow rate influences the relative transient storage and thus pollutant removal decreases with increasing flow rates, particularly under low-flow conditions. The combination of tracer experiments and the Lagrangian sampling approach of pollutants can improve model calibration and diagnose different attenuation mechanisms. This thesis aims at understanding major controls of transport of sediments as well as dissolved and sediment-bound micropollutants in two exemplary rivers to investigate the long-term fate of sediment-bound micropollutants (PAH) and the transport and transformation dynamics of dissolved micropollutants (pharmaceuticals). While I developed the models to meet measured data in Rivers Ammer and Steinlach, the framework is transferable to other small streams that are affected by anthropogenic micropollutants