The impact of wastewater treatment works (WwTW) effluent on downstream river water quality is of increasing concern, particularly owing to the presence in effluents of a range of trace substances. In the case of contamination by metals the question of bioavailability has recently been accounted for in setting water quality standards for several metals. In the UK over the past decade the Chemical Investigations Programme (CIP) has generated upstream and downstream river quality data as well as associated WwTW effluent monitoring for over 600 sites, for the main contaminants of regulatory interest under the Water Framework Directive. Data presented here show that at a local level WwTW discharges have little impact for many contaminants. Soluble reactive phosphorus, hexabromocyclododecane (HBCDD), cypermethrin, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) have been shown to be the principal substances where downstream concentrations were at least 10 % larger than the upstream value. Otherwise, poor compliance with riverine water quality standards tends to be associated with contamination at the river catchment scale, with corresponding implications for the nature of remedial actions that are likely to be successful. Compliance with water quality criteria for metals, taking account of bioavailability, is high overall.

This paper reports summary data from a ten-year programme of investigation into the composition of wastewater treatment works' effluents in the UK. The so-called Chemical Investigations Programme focused on determinands of regulatory importance and involved monitoring of effluents for over seventy trace substances and sanitary determinands at more than 600 UK treatment works sites. The results provide a definitive overview of effluent quality. Although raw data are available, this publication of summary data provides a convenient résumé of the current state of knowledge. An analysis of changes in concentrations over the monitoring period between 2010 and 2020 shows that for several substances (nickel, diethylhexylphthalate, nonylphenol, tributyltin, the brominated diphenyl ethers and triclosan) significant reductions in wastewater concentration have occurred over the period of interest, these are likely to have resulted from a combination of tighter regulatory controls and/or improved wastewater treatment.

Iron dosing for phosphorus reduction during wastewater treatment is wide practised across the globe. However, the impacts of this dosing in terms of the speciation of phosphorus discharged and secondary effects on removing or introducing other trace elements from or into the effluent have not been studied. Results are presented for concentrations of a range of contaminants in over 600 wastewater treatment works, reported as mean concentration values derived from 20 effluent samples taken over a period of two years. Approximately half of the treatment works employed iron dosing to reduce concentrations of phosphorus in effluents. In addition to the expected effects on level of phosphorus discharged to surface waters, it is shown that these measures are shown to have unintended and beneficial consequences for concentrations of several other constituents of wastewater. Reductions of more than 40% in the concentrations of dissolved metals (copper, lead) benzo(a)pyrene and hexabromocyclododecane are observed. Lower but still significant decreases in concentration (>30%) are evident for dissolved cadmium, fluoranthene cypermethrin and biochemical oxygen demand. Small but less environmentally important increases are seen for iron and nickel, in the case of the latter this is presumably because nickel is a contaminant of the iron reagent used for dosing. These reductions are shown to offer significant benefits in terms of levels entering surface waters relating to the in-river environmental quality standards.

This study comprises a detailed analysis of data for perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) for over 600 wastewater treatment works effluents (WwTW) as well as samples upstream and downstream of each discharge of effluent into its receiving water. This has allowed an investigation of not only the effectiveness of removal of the perfluoroalkyl substances (PFAS) compounds during wastewater treatment but also implications for compliance with the environmental quality standard (EQS) set for PFOS under the Water Framework Directive. It is shown that effluents contain concentrations of PFOS that exceed the annual average EQS by a factor between 1.1-fold and 40-fold. The corresponding factors for PFOA are between 2-fold and 22-fold. The presence of high concentrations upstream, means that between a quarter and a third of individual effluents are found to reduce the concentration of fluorocarbons in the river downstream of the discharge point. The elevated concentrations upstream of the studied wastewater treatment works suggest inputs of these perfluoro compounds into the aquatic environment are ubiquitous and therefore difficult to address from simply setting permit conditions for individual WwTW. The freshwater EQS set for PFOS is based on several worst-case accumulation coefficients and large safety factors, which, when combined, result in a sub ng/L EQS. Consequently, the use of the biota derived quality standard may be a more realistic measure of environmental risk. It may be prudent, to assess the effectiveness of controls implemented in the last few years before considering widespread end-of-pipe treatment.

Phosphorus is a finite resource essential for global food production. However, excessive loss to river systems from diffuse sources (typically agricultural) and point sources (e.g. waste water treatment works and industrial effluent) can lead to negative environmental impacts, including changes to diatom and invertebrate community structure. Current environmental quality standards for phosphorus in the UK have been based on reactive phosphorus, which is poorly defined and comprises an unknown proportion of soluble reactive phosphorus and chemically extractable particulate phosphorus. This research assesses the influencing factors that may control soluble reactive phosphorus concentrations in rivers, including dissolved iron, as well as partitioning processes associated with the presence of total suspended solids, and questions the reliability of the assumptions used when setting environmental quality standards. The extensive phosphorus speciation monitoring carried out across a wide geographic area of England and Wales shows that not all phosphorus as measured by the molybdenum blue method is either soluble or necessarily bioavailable, particularly at concentrations in the range in which the Environmental Quality Standard for 'Good' status (typically less than 100 μg P L-1) has been set. Phosphorus speciation can change due to physico-chemical processes which vary spatially and/or temporally, including precipitation with iron and partitioning with suspended solids.

Comparison of monitoring data with toxicologically-derived environmental quality standards (EQSs) forms the basis of assessments of the quality status of the water environment. Having established the status quo, the logical next step is to address instances of non-compliance with EQSs by applying remedial measures, including reducing the use or at least the emission of the substances of concern or by taking steps to reduce concentrations already present using technological solutions such as enhanced wastewater treatment. The selection of suitable remedial measures must be a compromise between cost, likely effectiveness and the timescale over which improvements might be acceptable. The decision on overall environmental management has also to take into account the need for demonstrable progress; this might mean that it is preferable to address some more readily achievable goal rather than to attempt to solve a more serious, but ultimately intractable problem. This paper describes the development and application of a generic modelling tool that provides a way of assessing the potential requirements for remedial actions and their likely outcomes over a timescale of up to forty years taking account of sediment partitioning, environmental degradation and biological accumulation. The tool was validated using a detailed UK wastewater treatment works effluent discharge dataset. Examples involving several chemicals that are of current concern are provided. Some substances (e.g.tributyltin, PFOS) are identified as likely to meet EQS values in sediments or biota in a relatively short timescale; others (PAHs, DEHP) appear to represent more intractable problems.

Results are presented for 170 wastewater treatment works sites (20 per substance in influent, effluent and 36 per substance in river water upstream and downstream of the WwTW discharge) over a period of two years between 2015 and 2017; this comprises data for approximately 3000 samples for effluent and 6000 for river samples taken downstream of effluent discharges. Seasonal trends in contaminant concentrations for several substances are reported. Two clear patterns of seasonal variation are proposed over and above all of the variables associated with environmental data including process technology, dilution and geography. Firstly, variation of riverine concentrations caused by seasonal fluctuations in river flow (sewage flow being relatively consistent) resulting in summer maxima and winter minima. Alternatively, variation is observed that is attributable to the improved performance of wastewater treatment processes under warmer conditions. This leads to the lowest concentrations in autumn when surface water/sewage treatment temperatures tend to peak. Seasonality for trace contaminants is more difficult to characterise than that of sanitary parameters owing to the higher variability in the concentration of the substances of interest. The data also provide an insight into the amplitude of such variations. This makes it possible to assess the likely effects of seasonality and its impact on aquatic life. For example, the existence of seasonality (perhaps due only to dilution effects) might be demonstrated, but the amplitude might be too small in relation to the potential ecotoxicological effects to be of any consequence.

EU legislation, including the Water Framework Directive, has led to the application of increasingly stringent quality standards for a wide range of chemical contaminants in surface waters. This has raised the question of how to determine and to quantify the sources of such substances so that measures can be taken to address breaches of these quality standards using the polluter pays principle. Contaminants enter surface waters via a number of diffuse and point sources. Decision support tools are required to assess the relative magnitudes of these sources and to estimate the impacts of any programmes of measures. This work describes the development and testing of a modeling framework, the Source Apportionment Geographical Information System (SAGIS). The model uses readily available national data sets to estimate contributions of a number of nutrients (nitrogen and phosphorus), metals (copper, zinc, cadmium, lead, mercury, and nickel) and organic chemicals (a phthalate and a number of polynuclear aromatic hydrocarbons) from multiple sector sources. Such a tool has not previously been available on a national scale for such a wide range of chemicals. It is intended to provide a common platform to assist stakeholders in future catchment management.

One of the most important functions of environmental monitoring is the detection of change. This can be the delineation of deteriorating circumstances or the identification of the success of remedial measures. The design of effective monitoring of change (and hence the optimisation of resources devoted to monitoring) relies on appropriate replication - knowing how many samples are required. Lack of information on the variance of the measured parameter is often a barrier to determining the optimum sampling strategy. An important new information resource on within-site variance of the concentrations of over 60 trace substances in wastewater treatment works effluents has been provided by the UK water industry research programme. This paper makes use of this resource in order to explore the potential to design monitoring programmes that will be capable of demonstrating the success of planned remedial measures that will be implemented in the coming years. Two approaches to experimental design (simple before-and-after sampling and detection of trends via correlation) are examined. It is concluded that for programmes involving numbers of samples of less than 30 the detection of a change in concentration of less than 50% might be very challenging for many of the trace substance of greatest interest. Knowledge of the difficulty of the task in hand should make it possible to design programmes that optimise the use of resources and the approaches taken, such that effects of interest are detected as soon and as economically as possible.

22 Increasing pressures on natural resources has led to the adoption of water quality 23 standards to protect ecological and human health. Lakes and reservoirs are particularly 24 vulnerable to pressure on water quality owing to long residence times compared with rivers. 25 This has raised the question of how to determine and to quantify the sources of priority 26 chemicals (e.g. nutrients, persistent organic pollutants and metals) so that suitable measures 27 can be taken to address failures to comply with regulatory standards. Contaminants enter 28 lakes waters from a range of diffuse and point sources. Decision support tools and models 29 are essential to assess the relative magnitudes of these sources and to estimate the impacts 30 of any programmes of measures. This paper describes the development and testing of the 31 Source Apportionment Geographical Information System (SAGIS) for future management of 32 763 lakes in England and Wales. The model uses readily available national data sets to 33 estimate contributions of a number of key chemicals including nutrients (nitrogen and 34 phosphorus), metals (copper, zinc, cadmium, lead, mercury and nickel) and organic 35 chemicals (Polynuclear Aromatic Hydrocarbons) from multiple sector sources. Lake-specific 36 sources are included (groundbait from angling and bird faeces) and hydrology associated 37 with pumped inputs and abstraction. Validation data confirms the efficacy of the model to 38

Tightening quality standards for European waters has seen a move towards enhanced wastewater treatment technologies such as granulated organic carbon treatment and ozonation. Although these technologies are likely to be successful in degrading certain micro-organic contaminants, these may also destroy compounds which would otherwise complex and render metals significantly less toxic. This study examined the impact of enhanced tertiary treatment on the capacity of organic compounds within sewage effluents to complex copper and zinc. The data show that granulated organic carbon treatment removes a dissolved organic carbon (DOC) fraction that is unimportant to complexation such that no detrimental impact on complexation or metal bioavailability is likely to occur from this treatment type. High concentrations of ozone (>1mg O-3/mg DOC) are, however, likely to impact the complexation capacity for copper although this is unlikely to be important at the concentrations of copper typically found in effluent discharges or in rivers. Ozone treatment did not affect zinc complexation capacity. The complexation profiles of the sewage effluents show these to contain a category of non-humic ligand that appears unaffected by tertiary treatment and which displays a high affinity for zinc, suggesting these may substantially reduce the bioavailability of zinc in effluent discharges. The implication is that traditional metal bioavailability assessment approaches such as the biotic ligand model may overestimate zinc bioavailability in sewage effluents and effluent-impacted waters.

It is important to understand the statistical distribution of monitoring data for them to be of value in determining the parameters of environmental models. No such distributional information has been available for many trace contaminants in sewage effluents. This paper applies the data of a major UK sewage works’ effluent monitoring programme to determine the validity of the common assumption that data are lognormally distributed. Effluent quality was monitored at 162 wastewater treatment works over 1 year, generating over 3,000 results for each of over 40 substances, including metals, trace organic substances and pharmaceuticals. It is demonstrated that the lognormal assumption is clearly justified for the great majority of substances in the spatial case—for annual average effluent concentrations across different treatment works. In the site-specific, temporal case—for individual determinations of concentration at a single site over an annual period—lognormality is generally supported but not demonstrated so unequivocally for all site/substance combinations. The principal source of uncertainty was lack of sufficient numbers of observations reported to adequately low reporting limits.

Phosphorus is an element essential for life. Concerns regarding long-term security of supply and issues related to eutrophication of surface waters once released into the aquatic environment have led governments to consider and apply measures for reducing the use and discharge of phosphorus. Examples of source control include legislation to reduce phosphorus use in domestic detergents. This research shows that other domestic sources of phosphorus also contribute significantly to the domestic load to sewer and that overall, domestic sources dominate loads to sewage treatment works. Estimates provided here show that although the natural diet contributes 40% of the domestic phosphorus load, other potentially preventable sources contribute significantly to the estimated 44,000 tonnes of phosphorus entering UK sewage treatment works each year. In the UK, food additives are estimated to contribute 29% of the domestic load; automatic dishwashing detergents contribute 9% and potentially increasing; domestic laundry 14%, including contributions from phosphonates, but decreasing; phosphorus dosing to reduce lead levels in tap water 6%; food waste disposed of down the drain 1%; and personal care products 1%. Although UK data is presented here, it is anticipated that similar impacts would be expected for other developed economies. Consideration of alternatives to all preventable sources of phosphorus from these sources would therefore offer potentially significant reductions in phosphorus loads to sewage treatment works and hence to the aquatic environment. Combining all source control measures and applying them to their maximum extent could potentially lead to the prevention of over 22,000 tonnes-P/year entering sewage treatment works.

The advent of increasingly stringent and wider ranging European Union legislation relating to water and the environment has required regulators to assess compliance risk and to respond by formulating appropriate pollution control measures. To support this process the UK Water Industry has completed a national Chemicals Investigation Programme (CIP), to monitor over 160 wastewater treatment works (WwTWs) for 70 determinands. Final effluent concentrations of zinc, polynuclear aromatic hydrocarbons (fluoranthene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(g,h,i)perylene and indeno(1,2,3-cd)pyrene), “penta” congeners (BDEs) 47 and 99, tributyltin, triclosan, erythromycin, oxytetracycline, ibuprofen, propranolol, fluoxetine, diclofenac, 17β-estradiol and 17α-ethinyl estradiol exceeded existing or proposed Environmental Quality Standards (EQSs) in over 50% of WwTWs. Dilution by receiving water might ensure compliance with EQSs for these chemicals, apart from the BDEs. However, in some cases there will be insufficient dilution to ensure compliance and additional management options may be required.

Steps taken to establish an environmental quality standard (EQS) for aluminium are described. The range of water types in England and Wales and the concentrations of low molecular weight (active) forms of aluminium have been assessed in order to evaluate the risk posed by aluminium in surface waters. Levels of low molecular weight forms of aluminium are mainly in the range 0-25 microg l(-1). Data suggest that dissolved aluminium might form the basis of a reasonably useful prediction of active aluminium leading to a simplified approach to compliance monitoring of an EQS set in terms of active aluminium.

The SKEP ERA-NET (Scientific Knowledge for Environmental Protection) is a consortium of European public sector organizations funding environmental research. The network is funded by the European Commission's Sixth Framework Programme (FP6). The aim of the network is to facilitate the improvement of science-into-policy processes and to support evidence-based regulation. This paper contains a description of the categorization and review of current environmental research within the network. It also illustrates how a comparison of current activities combined with perceptions of future needs can provide an analysis of research gaps. The importance of an assessment of relative research costs in such a gap analysis is emphasized. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment.

Current approaches to quality control in chemical analysis are examined. Issues that frequently cause problems are proposed. Future developments relating to ways in which the incidence of mistakes might be reduced are discussed as possible supplements to more well-established quality control measures.

Aluminium-based coagulants can be used during wastewater treatment to reduce phosphate loads discharged to surface waters. Aluminium is recognised as potentially toxic to fish under pH conditions where precipitation at the gill surface may occur. This is reflected in the way in which the proposed aluminium Environmental Quality Standard (EQS) has been set as a limiting concentration of 10 mu g/L for waters of a pH value below 6.5 and a limit of 25 mu g/L for waters of pH greater than 6.5. Field and laboratory studies have been undertaken to examine aluminium speciation in wastewater treatment works effluent and receiving waters under a variety of pH conditions. The practicalities of implementing the proposed EQS values were assessed. Field observations indicated consistent compliance with the proposed EQS aluminium levels for waters of relatively high pH value. Laboratory studies showed that for waters of pH value significantly less than 6.0, reactive aluminium concentrations naturally present through dissolution of aluminosilicate minerals tended to exceed levels discharged in a sewage effluent. After mixing between effluent and receiving water, changes in aluminium speciation were largely complete within a one hour period.

The long-term performance of laboratories is examined using results from three proficiency testing programmes in the water and environmental monitoring sector. A medium term proficiency test pass rate of greater than approximately 75% is suggested as a minimum target for routine analysis to demonstrate fitness for purpose. This pass rate is proposed as a practical yardstick to be used by QA managers and accreditation bodies. This recommendation is contingent on a laboratory's continued and largely uninterrupted participation in a PT programme.

The respective speciation of aluminium in sewage effluent and in river water receiving effluent, has been examined. Results showed that concentrations of reactive aluminium changed over a timescale of hours and were controlled predominantly by pH. A minimum concentration of reactive aluminium occurred at a pH of approximately 6.8, coinciding with the prevalence of non-reactive, insoluble Al(OH)3 species. For receiving waters of low pH value, typically < pH 5, a large proportion of the 'naturally present' aluminium can be present in a reactive form at concentrations higher than the proposed Environmental Quality Standard (EQS). Mixing of waters of this type with effluent of a higher pH value leads to the precipitation of aluminium hydroxide. Mixing of effluent of pH value in the range 7.5-8.0 with river water in the same (or slightly higher) pH range appears to result in no appreciable change in the proportion of reactive aluminium; the change in concentration tends to be related simply to dilution. On the basis of a theoretical knowledge of aluminium speciation, results obtained in this work indicate that it is possible to make predictions about the proportion of reactive aluminium present in a receiving water, based on the pH values of the effluent water mixture and the concentration in the effluent. Reasonable comparisons between measured and predicted values were obtained at higher pH values, but the relationship was less certain at pH values less than 6.5 for which levels of reactive metal tended to be higher than the quality standard value.