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The widespread use of chemicals has led to significant water quality concerns, and their use is still increasing. Hence, there is an urgent need to understand the possible future trends in chemical emissions to water systems. This paper proposes a general framework for developing emission scenarios for chemicals to water using the Shared Socio-economic Pathways (SSPs) based on an emission-factor approach. The proposed approach involves three steps: (i) identification of the main drivers of emissions, (ii) quantification of emission factors based on analysis of publicly available data, and (iii) projection of emissions based on projected changes in the drivers and emission factors. The approach was tested in Europe for five chemical groups and on a national scale for five specific chemicals representing pharmaceuticals, pesticides, and industrial chemicals. The resulting emission scenarios show widely diverging trends of increased emissions by 240% for ibuprofen in SSP3 (regional rivalry) to a 68% decrease for diclofenac in SSP1 (sustainable development) by 2050. While emissions typically decrease in SSP1, they follow the historical trend in SSP2 (middle-of-the-road scenario) and show an increase in the regional rivalry scenario SSP3 for most selected chemicals. Overall, the framework allows understanding of future chemical emissions trends as a function of the socio-economic trends as captured in the SSPs. Our scenarios for chemical emissions can thus be used to model future aqueous emissions to support risk assessment. While the framework can be easily extended to other pharmaceuticals and pesticides, it heavily leans on the availability and quality of historical emission data and a detailed understanding of emission sources for industrial chemicals.

Additional file 2: Overview of the NORMAN-SLE website (DOCX format) as of 30 May 2022 [82].

The potential water demand for fracturing fluids along with the possible flowback and produced water production is assessed for the Dutch Posidonia shale. Total water demand estimated for 25 years of the field development using historic data from the U.S. plays varies between 12.2 and 36.9 Mm3. The maximal annual water consumption of 0.95–2.88 Mm3 is expected in the peak years of shale gas production. These figures are much lower than the availability of any potential water sources, which include drinking water, fresh and brackish groundwater, river water, effluents of wastewater treatment plants (WWTP) and sea water. River water is considered the most promising water source for fracturing fluids in the Dutch Posidonia shale based on its availability (>6·104 Mm3/year) and quality (only bacterial composition needs to be controlled). Total wastewater production for the whole period of the field development is estimated between 6.6 and 48.0 Mm3. Wastewater recycling can cover significant part of the source water demand for fracturing fluid. However, high mineral content of the wastewater as well as temporal and spatial discrepancies between wastewater production and water demand will form obstacles for wastewater recycling. The assessment framework developed in this study may be applied for other shale gas fields with high uncertainties regarding subsurface properties, connate formation water characteristics and future legislative framework.

With the Green Deal the EU aims to achieve a circular economy, restore biodiversity and reduce environmental pollution. As a part of the Green Deal a ‘one-substance one-assessment’ (OS-OA) approach for chemicals has been proposed. The registration and risk assessment of chemicals on the European market is currently fragmented across different legal frameworks, dependent on the chemical's use. In this review, we analysed the five main European chemical registration frameworks and their risk assessment procedures for the freshwater environment, covering 1) medicines for human use, 2) veterinary medicines, 3) pesticides, 4) biocides and 5) industrial chemicals. Overall, the function of the current frameworks is similar, but important differences exist between the frameworks' environmental protection goals and risk assessment strategies. These differences result in inconsistent assessment outcomes for similar chemicals. Chemicals are also registered under multiple frameworks due to their multiple uses, and chemicals which are not approved under one framework are in some instances allowed on the market under other frameworks. In contrast, an OS-OA will require a uniform hazard assessment between all different frameworks. In addition, we show that across frameworks the industrial chemicals are the least hazardous for the freshwater environment (median PNEC of 2.60E-2 mg/L), whilst biocides are the most toxic following current regulatory assessment schemes (median PNEC of 1.82E-4 mg/L). Finally, in order to facilitate a successful move towards a OS-OA approach we recommend a) harmonisation of environmental protection goals and risk assessment strategies, b) that emission, use and production data should be made publicly available and that data sharing becomes a priority, and c) an alignment of the criteria used to classify problematic substances.

Direct industrial discharges of Chemicals of Emerging Concern (CEC) to surface water via industrial wastewater treatment plants (IWTP) gained relatively little attention compared to discharges via municipal sewage water treatment plants. IWTP effluents may however seriously affect surface water quality. Here we modelled direct industrial emissions of all 182 Dutch IWTP from 19 different industrial classes, and derived their impact on Dutch surface water quality and drinking water production. We selected industrial chemicals relevant for drinking water production, however a lack of systematic information on concentrations in IWTP effluents for many chemicals of interest was found. Therefore, we used data from the European Pollutant Release and Transfer Register and data on Dutch IWTP as surrogate. We coupled these to a detailed hydrological model under two extreme river discharge conditions, and compared the predicted and measured concentrations. We derived relative impact factors for the IWTP based on their contribution to concentrations at surface water locations with a drinking water function. In total, a third of the abstracted water for drinking water production is influenced by the IWTP. From all Dutch 182 IWTP, only a limited number has - based on the model approach using surrogate parameters - a high impact on surface waters with a drinking water function. Mitigation measures can be taken cost-efficiently, by placing extra treatment technologies at the IWTP with high impact. Finally, we propose recommendations for licensing and controlling industrial aqueous emissions and give suggestions to fill the currently existing knowledge gaps and diminish uncertainties in the approach.

There is public and scientific concern about air, soil and water contamination and possible adverse environmental and human health effects as a result of hydraulic fracturing activities. The use of greener chemicals in fracturing fluid aims to mitigate these effects.This study compares fracturing fluids marketed as either ‘conventional’ or ‘green’, as assessed by their chemical composition and their toxicity in bioassays. Chemical composition was analysed via non-target screening using liquid chromatography - high resolution mass spectrometry, while toxicity was evaluated by the Ames fluctuation test to assess mutagenicity and CALUX reporter gene assays to determine specific toxicity.Overall, the results do not indicate that the ‘green’ fluids are less harmful than the ‘conventional’ ones. First, there is no clear indication that the selected green fluids contain chemicals present at lower concentrations than the selected conventional fluids. Second, the predicted environmental fate of the identified compounds does not seem to be clearly distinct between the ‘green’ and ‘conventional’ fluids, based on the available data for the top five chemicals based on signal intensity that were tentatively identified. Furthermore, Ames fluctuation test results indicate that the green fluids have a similar genotoxic potential than the conventional fluids. Results of the CALUX reporter gene assays add to the evidence that there is no clear difference between the green and conventional fluids.These results do not support the claim that currently available and tested green-labeled fracturing fluids are environmentally more friendly alternatives to conventional fracturing fluids.

Researcher and media alarms have caused plastic debris to be perceived as a major threat to humans and animals. However, although the waste of plastic in the environment is clearly undesirable for aesthetic and economic reasons, the actual environmental risks of different plastics and their associated chemicals remain largely unknown. Here we show how a systematic assessment of adverse outcome pathways based on ecologically relevant metrics for exposure and effect can bring risk assessment within reach. Results of such an assessment will help to respond to the current public worry in a balanced way and allow policy makers to take measures for scientifically sound reasons.

Organic contaminants in shale gas flowback and produced water (FPW) are traditionally expressed as total organic carbon (TOC) or chemical oxygen demand (COD), though these parameters do not provide information on the toxicity and environmental fate of individual components. This review addresses identification of individual organic contaminants in FPW, and stresses the gaps in the knowledge on FPW composition that exist so far. Furthermore, the risk quotient approach was applied to predict the toxicity of the quantified organic compounds for fresh water organisms in recipient surface waters. This resulted in an identification of a number of FPW related organic compounds that are potentially harmful namely those compounds originating from shale formations (e.g., polycyclic aromatic hydrocarbons, phthalates), fracturing fluids (e.g., quaternary ammonium biocides, 2-butoxyethanol) and downhole transformations of organic compounds (e.g., carbon disulfide, halogenated organic compounds). Removal of these compounds by FPW treatment processes is reviewed and potential and efficient abatement strategies are defined.

Worldwide, agricultural irrigation currently accounts for 69% of freshwater withdrawal. Countries with a temperate climate, such as the Netherlands, experience periodic freshwater shortages in agriculture. The pressure on available freshwater will increase due to climate change and a growing demand for freshwater by e.g. industrial activities. Possible alternative water resources are considered in order to meet the current and future water demand. In this study we explore where, and how much, sewage treatment plant (STP) effluent can directly be reused in agricultural sub-surface irrigation (SSI) during an average and a dry season scenario, for all active (335) Dutch STPs. SSI systems may have a higher water demand as part of the STP effluent is transported with groundwater flow, although aboveground irrigation has a loss of water due to interception. Furthermore, such aboveground irrigation systems provide direct contact of crops with irrigation water. SSI systems provide a soil barrier which may function as a filter and buffer zone. In the Dutch situation, direct intentional reuse of STP effluent can fulfill up to 25% of croplands SSI water demand present within a five-kilometer transport buffer from the STPs during an average season and 17% during a dry season. Hereto, respectively, 78% and 84% of the total available Dutch STP effluent would be used. Thus, the intentional direct STP effluent reuse in agricultural SSI has the potential to satisfy a significant amount of the agricultural water demand at a national scale, presuming responsible reuse: safe applications for humans and environment and no limiting effects on water availability for other actors.

Contamination with plastic debris has been recognized as one of today’s major environmental quality problems. Because most of the sources are land based, concerns are increasingly focused on the freshwater and terrestrial environment. Fate and transport models for plastic debris can complement information from measurements and will play an important role in the prospective risk assessment of plastic debris. We review the present knowledge with respect to fate and transport modeling of plastic debris in freshwater catchment areas, focusing especially on nano- and microplastics. Starting with a brief overview of theory and models for nonplastic particles, we discuss plastic-specific properties, processes, and existing mass-balance-, multimedia-, and spatiotemporally explicit fate models. We find that generally many theoretical and conceptual approaches from models developed earlier for other types of (low density) particles apply also to plastic debris. A unique feature of plastic debris, however, is its combination of high persistence, low density, and extremely wide size distribution, ranging from the nanometer to the >cm scale. This causes the system behavior of plastic debris to show a far wider variety than most other materials or chemicals. We provide recommendations for further development of these models and implications and guidance for how fate and transport models can be used in a framework for the tiered risk assessment of plastic debris.