Environmental change and rising DOC trends: Implications for public health

Lead Research Organisation: NERC Centre for Ecology and Hydrology
Department Name: Parr

Abstract

This highly integrated multidisciplinary project engages the skills of environmental scientists, mathematical modellers, analytical chemists, toxicologists and public health scientists to address health vulnerability issues resulting from future environmental change impacts on soil-water ecosystems at a regional scale. It will address the health implications of a recently observed alarming trend for rising Dissolved Organic Carbon (DOC) concentrations in aquatic ecosystems used for potable water abstraction. Over the past two decades the concentration of dissolved organic carbon (DOC) in many source waters of these source waters has more than doubled and continues to rise (Freeman et al., 2001). There is increasing evidence to suggest that the process is being driven by environmental changes such as a decline in acid deposition (Evans et al., 2006; Monteith et al. 2007), combined with rising temperatures, increased frequency of drought and changes in the seasonal distribution of rainfall. We aim to analyse data from monitoring programmes and various other studies to allow us to predict the likely impact of future changes in climate and air pollution on DOC concentrations in water entering reservoirs and water treatment works. The increase in the level of DOC reaching water treatment works has major implications for human health. Organic matter in raw water is only partially removed by conventional treatment using inorganic coagulants; what remains may react with disinfectants. During chlorination of water supplies the chlorine reacts not only with the microorganisms but also with most of the other organic material present in the water, either dissolved or in suspension. This produces a range of organic compounds known as disinfection by-products (DPBs) including a group of chemicals called trihalomethanes (THMs), plus haloacetic acids, halonitriles, haloaldehydes and chlorophenols. We will carry out laboratory experiments to test the likely implications of the future changes in DOC we have predicted for the generation of these compounds within the water treatment system. Furthermore, a wide variety of other chemical contaminants, derived from air pollutants from industry, fertilizer application and urban waste water may bind (by sorption) to natural organic matter and be transported into reservoirs and water treatment works in association with DOC. Their fate within the treatment system, i.e. whether they are removed or remain within solution, depends heavily on the type of contaminant, the nature (or quality) of the DOC, the chemistry (e.g. pH and ionic strength) of the aqueous solution and the type of treatment process. We will carry out laboratory experiments to determine the extent to which these contaminants are bound to DOC at the point they enter the water treatment process and what is likely to happen as a result of the process, e.g. the extent to which contaminants are likely to be removed or remain in solution. Living organisms respond in various ways and on a spectrum of timescales when exposed to chemical contaminants. Some effects in organisms are immediate while others effects may be delayed and not show up for 10 or 20 years or more; for example, cancer in humans. We will draw on existing risk assessment approaches from national and international (EU) governmental agencies to evaluate the potential human health impacts of changes in levels of a range of contaminants under environmental change scenarios. Finally, we will bring together the findings of our research in the form of a Decision Support System (DSS) that will provide information to the water industry, the environmental agencies and other stake holders. The DSS will provide predictions of likely DOC trends under future climate change scenarios and the likely importance of predicted changes for wider water quality and human health.

Publications

10 25 50
 
Description Long term water chemistry data for surface waters draining upland regions in northern Europe and north eastern America have shown substantial increases in dissolved organic carbon (DOC) over the past three decades. This is of particular concern to the water industry, as dissolved organic matter needs to be removed (normally by expensive coagulation procedures) prior to the addition of disinfection agents such as chlorine. Failure to do so can result in the generation of potentially toxic disinfection bi-products (DPBs - such as trihalomethanes). There is an increasing consensus that the primary driver of recent change in DOC has been the large reduction in acid pollutants that have resulted in increased solubility of soil organic matter. However, there is also evidence that regional warming and changes in precipitation patterns can affect DOC levels, and it is therefore important to consider both depositional and climate change effects, when considering how DOC levels are likely to change into the future. The main hypothesis of the project, involving teams from CEH, Bangor University, Utrecht University and the French School of Public Health, was that environmental change could compromise human health by driving a rise of dissolved organic carbon (DOC) in aquatic ecosystems used for potable water supplies. Moreover, these rising DOC levels could promote quantifiable increases in harmful pollutants and disinfection by-products following water treatment.
Water quality data from several British and French water bodies were used to examine how dissolved organic carbon (DOC) concentration varies quantitatively and quantitatively across landscapes and over time. CEH led a work package in which a simple linear model was developed that was highly effective in predicting dissolved organic carbon (DOC) concentrations and fluxes draining upland landscapes in the UK. Unfortunately it was not possible to expand the approach to the sites in Brittany due to differences in the type and extent of suitable calibration data available from the two regions. A scientific paper (Monteith et al., submitted) describing the UK model is currently in review, and the work was also the focus of an oral presentation given by Monteith at the 2014 Biogeomon conference in Bayreuth, Germany in July 2014. The statistical model has now been developed further to include a temporal dimension, and this provides strong evidence that regional scale trends in acid deposition have been sufficient to describe trends in DOC concentration over the last 20 years (Monteith et al., in prep) while variation in climate has had little impact. The key findings generated by the work package are that 1) DOC concentrations draining upland sites are normally highly predictable from basic geophysical predictors - a fact that should help in the assessment of potential local land management impacts on water quality; and 2) that DOC concentrations draining certain catchment types will be highly sensitive to any further reductions in sulphur deposition (despite the fact that UK sulphur deposition levels are generally quite low now and are unlikely to be reduced much further.
Parallel monitoring of a range of streams in upland and lowland locations in North Wales and Britanny was conducted to examine the influence of heavy rainfall events. These are predicted to become more frequent and intense in some regions as a result of future climate change. Some previous studies have suggested that changes to the quality of DOC during storm events results may result in greater production of DPBs per mass of carbon, so that any future increase in the frequency of storms would result in a disproportionate increase in DPB generation, thus posing even greater challenges for water treatment. This study showed that both DOC concentrations and the concentration of DBPs precursors in waters increased in both regions during and immediately following heavy rainfall events, but there was no change in DBP formation per milligramme DOC (this work is currently in review (Depla et al., submitted). Further experiments conducted on soil pH showed that as soils continue to recover from acidification it is expected that DOC export will increase but the propensity of this extra DOC to form DBPs is not expected to be different to differ from current conditions.
In a separate work package, a study focussing on a set of streams in the Wyre catchment of northwest England, sought to determine the potential consequence of increasing DOC inputs for the transport of a range of polycyclic aromatic hydrocarbons (PAHs). These are considered "priority hazardous substances" under the Water Framework Directive and are mostly unintentional by-products of fossil fuel combustion and, waste incineration emitted to the atmosphere and consequently deposited to ground surfaces. A significant positive relationship was found between concentrations of DOC and polycyclic aromatic hydrocarbons (PAHs) containing five or more aromatic rings, suggesting that both are supplied to the water together, probably after being released from the organic matter-rich soil. Heavy PAHs appear to be released into the water mainly together with organic matter as this dissolves and forms DOC; therefore soils appear to act as an important reservoir supplying heavy PAHs to the water. This work, now published in Environmental Science and Technology (Moeckel et al., 2014) should help to enhance interpretation of PAH monitoring data that are currently sparse both spatially and temporally, and thus enable more robust assessments of the potential risks of these environmental pollutants to sensitive aquatic organisms and human water supplies.
The final work package sought to bring together the key findings generated throughout the wider project, to develop a Decision Support Tool (led by the French partner) targeted primarily at water system managers and operators of small and medium scale treatment plants, and particularly those responsible for plant construction or renovation. A prototype was drawn up aimed at providing water stakeholders (sanitary authorities, water treatment operators and other stakeholders) with a holistic tool for identifying and assessing the risks posed by the complex range of pressures (agricultural, industrial, climatic, etc.) on water resources through their impact on DOC and a range of organic contaminants (e.g. steroids, pharmaceuticals, pesticides, bisphenol-a, polychlorobiphenyls, polycyclic aromatic hydrocarbons, petrochemical hydrocarbons and disinfection by-products. It is ultimately intended that the tool is able to inform on appropriate mitigation measures for enabling improvement of drinking water safety in small and medium supplies and assess the viability of a water treatment system in the context of further anticipated changes in DOC loads and concentrations. A description of the tool was recently published in the International Journal of Environmental Research and Public Health (Depla et al., 2014).
All the primary objectives of the work were met, and the research findings are being taken forward in a number of ways by the individual project partners. The primary area of continuing research development led by CEH concerns further development of tools for the prediction of DOC concentrations and loads over space and time, with a wider geographical scope. Further publications are planned, and CEH are now applying the findings in a Scottish Government (Centre for Expertise for Waters) funded project "Method to Assess the Role of Catchment Management in Helping to Protect and Improve Drinking Water Quality in a Cost-effective Way". Communication of the spatial modelling work at the Biogeomon Conference has led to new unfunded international collaboration to apply the model at an international scale under the auspices of the UNECE ICP Waters programme on which Monteith is the UK Focal Centre representative. It is hoped that the work will enable a clearer understanding of the key global physical controls on DOC and thus continue to aid fundamental process understanding of this key component of the global carbon budget and should lead to further publications.

Papers in review:
Delpla, I., Jones, T.G., Monteith, D.T., Hughes, D.D., Baurès E., Jung, A-V, Thomas, O, Freeman, C. "Heavy rainfall impacts on THM formation in contrasting north-west European potable waters".
Monteith, D.T., Henrys, P.A.H., Evans, C.D., Malcolm, I., Shilland, E.M., Pereira, G. "Spatial controls on dissolved organic carbon in upland waters inferred from a simple statistical model."
Exploitation Route The findings should benefit all water companies serving upland areas of the UK where DOC rising levels of DOC represent a potential treatment problem. According to Welsh Water, UK, one of the project stakeholders, knowledge that DOC levels are on an increasing trend allows them, at an operational level, to plan strategically for the future. Removal of DOC is the major treatment cost involved in producing potable water across the industry. The presence of DOC in their raw water is of great significance because it can react with chlorine during the disinfection process to create disinfection by products (DBPs), and these are believed to have health risks associated with them. It is therefore essential for them to maintain low levels of DBPs (both to avoid risks to our customers and to comply with current legislation) and one of the key ways of achieving this is by treatments to minimise DOC. Knowledge of the DOC trends and chemical characterisations will allow Welsh Water and other water companies to identify water treatment works that are at risk of exceeding DBP limits, and to consider investments ranging from improvements to water (DOC) treatment, alternatives to standard chlorination, blending waters (diluting with low DOC sources), or even abandonment of certain works (and transport / piping of waters from more distant sources), where the cost of treatment improvements would be prohibitive.
Sectors Agriculture, Food and Drink,Environment

 
Description Long term water chemistry data for surface waters draining upland regions in northern Europe and north eastern America have shown substantial increases in dissolved organic carbon (DOC) over the past three decades. This is of particular concern to the water industry, as dissolved organic matter needs to be removed (normally by expensive coagulation procedures) prior to the addition of disinfection agents such as chlorine. Failure to do so can result in the generation of potentially toxic disinfection bi-products (DPBs such as trihalomethanes). There is an increasing consensus that the primary driver of recent change in DOC has been the large reduction in acid pollutants that have resulted in increased solubility of soil organic matter. However, there is also evidence that regional warming and changes in precipitation patterns can affect DOC levels, and it is therefore important to consider both depositional and climate change effects, when considering how DOC levels are likely to change into the future. The main hypothesis of the project, involving teams from CEH Lancaster, Bangor University, Utrecht University and LERES/EHESP, was that environmental change could harm human health by driving a rise of dissolved organic carbon (DOC) in aquatic ecosystems used for potable water supplies. Moreover, these rising DOC levels could promote quantifiable increases in harmful pollutants and disinfection by-products following water treatment. The project consortium aimed to: 1) Carry out extensive analysis of existing water chemistry time series analysis to identify environmental variables driving changes in DOC quantity and quality. 2) Integrate effects of changes in climate (precipitation and temperature) with deposition chemistry driven changes in soil water chemistry in a single processed-informed statistical model for the delivery of DOC to water treatment works. 3) Determine the impacts of modelled changes in DOC quality and quantity on the formation of disinfection by-products; and carry over through the treatment process of DOC-associated organic pollutants and trace metals. 4) Determine the implications for human health (through drinking water) of changes in potentially toxic disinfection by products and other hazardous or emergent substances associated with increasing DOC. The primary roles of the CEH Lancaster team were to a) develop a statistical model for the prediction of DOC concentrations both spatially and temporally, to enable a clearer understanding of where and how DOC levels might be expected to change in future, and b) explore the relationship between concentrations and fluxes of DOC and a range of Polycyclic Aromatic Hydrocarbons (PAHs) (a group of environmentally ubiquitous semivolatile, persistent, organic contaminants that have been identified as "priority hazardous substances" because of their toxicity and suspected carcinogenicity and mutagenicity). Findings from both studies would then contribute to the development of a Decision Support System, led by the French team, to provide guidance to operators of Small Scale Water Services in northwest Europe. The statistical modelling exercise demonstrated that DOC concentrations in surface across the UK uplands can be predicted to a high degree of accuracy, and validated the observations from assessment of time series data that DOC concentrations are sensitive to variations in sulphur deposition. This is making the soil organic carbon more soluble and increasing the size of the DOC pool that is available to leach out of soils into freshwaters. The modelling also suggested that further significant rises in DOC in these waters can be expected from even very small further reductions in sulphur deposition, but that levels would then begin to stabilise. This information is of interest to the water industry with respect to planning for future treatment requirements. Although peatland dominated systems were shown to export considerably more DOC than catchments dominated by organo-mineral soils, there was no evidence for strong effects of vegetation type or levels of soil degradation, raising questions regarding the likely efficacy of current upland catchment management programmes that are designed to stabilise or reduce DOC concentrations and fluxes. The CEH Lancaster team carried out an assessment of seasonal variation in PAHs over the course of one year in the catchment of the River Wyre in Lancashire. A significant positive relationship was found between concentrations of DOC and polycyclic aromatic hydrocarbons (PAHs) containing five or more aromatic rings, suggesting that both are supplied to the water together, probably after being released from the organic matter-rich soil. No significant or a negative relationship was found for most PAHs with four or less rings. Heavy PAHs appear to be released into the water mainly together with organic matter as this dissolves and forms DOC; therefore soils appear to act as an important reservoir supplying heavy PAHs to the water. The implication of work was that the recent increase in DOC flux may have led to concomitant increases in the flux of dissolved heavy PAHs. However this effect will have been counteracted by large reductions in the deposition of these contaminants over the same period. Analysis of time series data, led by the French team but also involving UK partners, also demonstrated the potential for undesirable impacts of climate change on drinking water quality in response to changes in seasonal rainfall distribution. Any increase in the frequency of drought and storm events would be expected to increase the export of organic matter to freshwaters due to the build up of partially decomposed organic material during periods of drought and the physical transport of it into lakes and rivers during rainfall events. There is emerging concern regarding water quality compliance in Small Water Supplies (SWS) in the context of the implementation of the WHO Water and Health Protocol. Revision of the Drinking Water directive in 2011 led to several recommendations including the need to increase implementation and enforcement of compliance of SWS. This decision has led to the constitution of a drafting group on SWS set by the European Commission (DGEnv) in which the French project partner, LERES, is one of the French representatives. The objective of this group is to propose actions to implement Risk Assessment/Risk Management approaches on SWS in order to improve water quality compliance on these systems. The project Decision Support System is currently under peer review, but is intended eventually to inform management practices. The tool is also designed to predict concentrations of substances potentially present after water treatment and assess the health risks related to these substances. Beneficiaries: According to Welsh Water, UK, one of the project stakeholders, knowledge that DOC levels are on an increasing trend allows them, at an operational level, to plan strategically for the future. Removal of DOC is the major treatment cost involved in producing potable water across the industry. The presence of DOC in their raw water is of great significance because it can react with chlorine during the disinfection process to create disinfection by products (DBPs), and these are believed to have health risks associated with them. It is therefore essential for them to maintain low levels of DBPs (both to avoid risks to our customers and to comply with current legislation) and one of the key ways of achieving this is by treatments to minimise DOC. Knowledge of the DOC trends and chemical characterisations will allow Welsh waters to identify water treatment works that are at risk of exceeding DBP limits, and to consider investments ranging from improvements to water (DOC) treatment, alternatives to standard chlorination, blending waters (diluting with low DOC sources), or even abandonment of certain works (and transport / piping of waters from more distant sources), where the cost of treatment improvements would be prohibitive.
First Year Of Impact 2013
Sector Agriculture, Food and Drink,Environment,Other
Impact Types Economic,Policy & public services

 
Description Centre of Expertise for Waters (CREW) (Scotland)
Amount £22,000 (GBP)
Funding ID CRW2014/17 
Organisation Government of Scotland 
Sector Public
Country United Kingdom
Start 08/2014 
End 05/2015
 
Description ICP Waters International exercise to model and understand drivers of change in dissolved organic carbon (DOC) concentrations in remote waters across regions 
Organisation Norwegian Institute for Water Research (NIVA)
Country Norway 
Sector Public 
PI Contribution My main contribution has been assisting in the statistical modelling of DOC concentrations in remote waters across the UK developed under the ERA-Net Environmental Health project. Together with partners from NIVA (Oslo) and other ICP Waters task Force members, we are testing hypotheses surrounding the relative importance of changes in acid deposition and climate on DOC concentrations.
Collaborator Contribution A number of parters affiliated to the International Cooperative Programme for the Assessment of Acidification of Rivers and Lakes, including focal centres from Noerway, the USA, Canada, Sweden, Finland amd the Czech Republic have contributed data and scientific expertise to this exercise.
Impact The only output to date has been an introductory presentation explaining the rationale for this exercise, given by D. Monteith at the annual ICP Waters Task Force meeting in Oslo in October 2014. A paper is currently in review in Nature GeoScience.
Start Year 2014
 
Description Presentation to range of upland water stakeholders and practitioners on subject of water colour and carbon at meeting of the Upland Hydrology Group organised by the University of Leeds. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Presentation was one of two in an afternoon breakout session involving circa 25 or the 100 conference delegates, around the theme of understanding the causes and implications of increasing Dissolved Organic Carbon in Upland Waters. This was followed by a discussion over the current consensus of understanding in the area and the key areas required for further research.
Year(s) Of Engagement Activity 2016
URL http://www.uplandhydrology.org.uk/
 
Description Project workshop engagement with Stakeholders 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Two project workshops were held in the UK (in Bangor 2-3rd December 2009 and London 8-10th January 2013, involving all official project partners, but also involving water engineers from Welsh Water with a specific interest in understanding DOC dynamics and the influence of environmental conditions on the formation of disinfection bi-products in the water treatment system.

The workshops have resulted in heightened awareness of practitioners in the water industry to the sensitivity of DOC levels and disinfection bi-product formation and the potential to predict problematic conditions and guide appropriate treatment steps.
Year(s) Of Engagement Activity 2009,2013