Rob Sage, water resources manager at the Veolia Water Partnership, assesses the impacts on public supply of declining groundwater quality
Raw water quality in the majority of major UK aquifers used for public water supply is deteriorating. Groundwater currently provides around 30% of the national public water supply and supports many river flows. The continuing pollution of groundwater, linked to increasing water quality standards, is decreasing the amount of groundwater available for public supply. Traditionally, contaminated groundwaters have been blended, treated or abandoned. Such end-of-pipe solutions for public water supplies have already cost £745M (UKWIR, 2004), and water customers have been subsidising the historical poor practice of other industries. Estimates of the cost of meeting future requirements vary from £30M to £60M/pa.
Faced with increasing demand, particularly in the south-east of England, there are increasing pressures on – and competition for – water resources. Preventing pollutants from entering the system and cleaning up existing pollution are targets we should all aspire to, subject to economic considerations. Despite some local successes, there is little evidence that current anti-pollution initiatives are significantly reducing the loading on groundwater systems. Limited funding is available for pollution prevention, and there is little sign of the ‘polluter pays’ principle working.
The Water Framework Directive objectives are to remove the sources of pollution and return water quality to a more ‘natural’ state, but in the case of many groundwaters, this process will be measured in decades, even if the ‘pollution’ were to cease now. The water industry must work with government, regulators, agriculture and other industries to develop holistic land management practices that will minimise polluting activities whilst retaining agricultural production and employment in the rural sector. In addition, innovative ways of using (or even re-using) available water resources need to be developed, whilst undertaking cost-effective remediation of existing pollution to benefit both the environment and future generations.
The state of the status quo
Groundwater is used widely throughout the UK for public supply, industry and agriculture. Of the total water used for public supply, about 27% is derived from groundwater (BGS 2004). However, in parts of the south and east of England this percentage can rise to 100%, where a significant amount is derived from the chalk. Groundwater also supports many river flows and can cause stress to the ecosystems of these rivers if it contains pollutants.
Traditionally groundwater has been thought of as ‘pure’ and requiring little treatment. In reality, however, the quality of groundwater has deteriorated significantly and many sources now require complex treatment processes, increasing both capital and operational costs. It is estimated that around 50% of the groundwater currently used for public supply in the UK requires some form of treatment.
Historically, contaminated groundwaters, particularly those associated with diffuse pollutants, have been blended (18%) or treated (58%) prior to use. In other cases, boreholes have been abandoned and taken out of supply (24%), frequently to be replaced by an alternative resource from elsewhere.
Such end-of-pipe solutions for public water supplies mean that water customers have been – and are – subsidising the historical poor practice of other industries and historical neglect and lack of respect for environmental issues. These reactive solutions have cost £745M over the past 28 years. Not all of the pollutants are man-made, and contaminants include such as iron manganese, arsenic and microbiological organisms such as Cryptosporidia. Increasing water quality standards for drinking water also have a role to play, so that once compliant waters now require treatment.
Groundwater pollution is frequently slow to show, due to long travel times, and thus can also take a long time to recover even if the source of pollution is removed. This is reducing the availability of groundwater for public supply and requires increasing levels and complexity (hence cost, both capital and operational) of treatment required. Prevention of pollution to aquifer systems has largely been ignored. Water companies constantly deal with the threat of pollution as a major risk element in their work, in addition to managing and treating currently polluted sources. The proposed drinking water safety plans are an important vehicle for raising awareness of the issues.
In a 2004 study, UKWIR undertook an evaluation of the threat posed by pollution, carrying out a study of returns from most of the UK’s water companies. The increasing volume influenced by quality issues is shown in the graph, along with the action and the cause of the problem. There has been a marked increase from 1985 onwards, and in 2004 some 2,450Ml/d was affected by either blending, treatment or replacement of the source. This is just under half of the total groundwater supplied. These figures have been checked to ensure that double accounting of sources, where treatment from more than one element is present, have not influenced the total volume.
Nitrate and pesticides have been by far the largest problem faced by the water companies, followed by Cryptosporidium, a microbiological contaminant. Most of these contaminants have been introduced by man. These are often linked to indifferent historic practices and a lack of joined-up thinking. There has been little in the way of holistic catchment management, and enforcement of groundwater regulations has been patchy. One of the primary aims should be to stop these pollutants from entering the system.
Preventing pollution has, of course been attempted in the past, and there have been a plethora of initiatives, which have met with varying degrees of success. In the 1970s and 1980s, licensing of waste disposal sites and their management improved significantly. However, many historic locations have not been treated in the same way and in reality are pollution time-bombs waiting to go off. Recent small-scale spills, particularly of hydrocarbons, have been dealt with rapidly and the culprits successfully prosecuted and forced to clean up the problem, although in many cases the level of fines imposed do not act as a deterrent. However, this is not the case with historic ‘orphan’ locations, and diffuse pollutants such as nitrates and pesticides.
The designation of nitrate-vulnerable zones and guides such as good agricultural practice have played their part, but there appears to be little positive impact, and these schemes are voluntary, with little evidence that they are being effective. Conversely, one very successful campaign has been the Railtrack Initiative, where selected stretches of railway, adjacent to public water supply sources, are managed in a different way and the spraying of selected herbicides has been banned. This has led to locally significant reductions in compounds such as atrazine, demonstrating the benefits of
co-operation and partnership in addressing such issues.
Faced with increasing demand, particularly in the south-east of England, there are increasing pressures on and competition for water resources. The worst case scenario would be where there is no blending possible, no treatment option, no alternative sources, no funding, and thirsty customers. This would already have been the case for some communities, but for the security-of-supply benefits brought about by the development of integrated supply networks. Thus, the question of where additional water can be derived from to meet these increasing demands (and what additional treatment could be used to increase available resources) is one that needs to be addressed now. It is my belief that we have already run out of good-quality groundwater for public water supplies.
Cleaning up existing pollution and preventing new pollutants from entering the system – these are targets that should be aimed for, subject to economic considerations. Despite some local successes, however, there is little evidence overall that current anti-pollution initiatives are significantly reducing the loading on groundwater systems. Limited funding is available for pollution prevention and there is little sign of the ‘polluter pays’ principle working. In many cases, ‘not knowingly permitting the pollution to occur’ has been acted as a defence, resulting in continuing contamination or further delays in remediation and, again, water customers having to pick up the bill for dealing with the contamination.
The UKWIR study also looked at future scenarios, based on the historic record, and took a view as to where the water industry may be in the future. Estimates for meeting future requirements vary from £150M to £300M for each five-year AMP period, including associated increases in operating costs. In one example, it was postulated that blending, treatment and closures would continue at the same linear rate as in the past. However this example did not take into consideration factors for new and emerging pollutants or renewal of existing plant that will have reached its operational lifetime. In this case, all groundwater would require treatment by 2029. However, this does not take into account the availability of water for blending or for any factors related to implementation of the Water Framework Directive’s goal of returning waters to a more ‘natural’ state.
Another scenario assumed that curtailment of treatment of groundwater would be implemented after 2010 to comply with DWPA
objectives stated within the WFD. This would produce a shortfall in supply of some 1,800Ml/d by 2027, which would have to be replaced from new sources – and that is assuming no overall increase in the demand for water over current rates. This has significant planning and cost implications. The Environment Agency (EA) stated in 2001 that extensive areas of the major aquifers are already over-exploited and that there is no extra water available. Summer surface water is even less available. Thus, only winter surface water is potentially available, which would require additional storage capacity to be built. Studies for these have been allowed for in the current AMP period.
To illustrate some of the difficulties caused by pollution, let us take the example of a case which occurred in 2000 in Hertfordshire, when Three Valleys Water discovered a large-scale pollution of the chalk aquifer by bromate, impacting on two sources totalling 18Ml/d (2% of our current supply). Early investigations quickly identified the source as a former chemical works, which is now a housing estate. This area was designated under part IIa of the Contaminated Land regulations in 2002. However, to date, no remediation notice has been served.
The impacted sources show an increasing trend in pollution levels, and a solution put in place to blend one of the sources has subsequently been rendered ineffective due to these higher levels of pollutant. To date, over £2M has been spent on addressing this issue. Long-term solutions have been identified, namely relocating the abstraction points away from the pollution plume, under the AMP4 process, with a price tag of over £7M. These costs are to be borne by the water company’s customers, not the polluter. Even if an appropriate person were identified as being responsible, consequential damage is not provided for under the regulations – thus a civil action would be required unless the polluter voluntarily paid up.
What is to be done?
Action is required now to prevent future pollutants entering the system and to remediate existing pollutants. Collective, partnership working is required, and remediation must be undertaken, where cost-effective, for the long-term sustainable use of groundwaters. The use of derogation in WFD terms is not a solution to these issues, owing to the length of time pollutants can exist in the aquifer systems. Large-scale changes in land use will be required, and some work is already being undertaken on this via the Water4all project (see www.water4all.com).
Alternative supply solutions are increasingly difficult to find. The scope for conventional source development is very limited, particularly in the south-east of England. New regional schemes can take as long to develop as it would take an aquifer to clean up naturally, assuming the source of pollutant was removed. New treatment processes will be complicated and expensive and, if the WFD ban on further treatment is upheld, may not be permitted in any case. In the meantime there is a need to continue supplying potable water to meet all customer demands.
Water resources planning has a strong reliance on leakage savings and demand management. The former is already at its economic level for most companies, and the latter is unproven and has ill-defined costs. Desalination has a role to play, but is not universally possible, and re-use is increasingly attractive, but still has public acceptability issues, despite significant improvements in treatment technology. One interim possibility could be to re-locate sewerage treatment outfalls up-catchment to provide increased flows in the rivers, and thus increased environmental benefits, even if not being re-used for public supply. However, such schemes are expensive and, again, the cost will fall on the consumer, not the polluter who restricted availability in the first place.
Even more exotic solutions may need to be considered. Should there be sacrificial catchments, where abstraction takes precedence over the ecology of the river system, and the river may even be dry for significant periods? This impact could be offset by returning other catchments to their ‘natural’ state, with no anthropogenic influences. Water companies could reduce the quality of water to non-potable status and rely on use of bottled water for consumption. The social and public health aspects of this are alarming, but it would allow public water suppliers to meet demand by utilising poorer-quality waters.
Whatever the solution, action needs to be taken now, to prevent further deterioration in groundwater quality and ensure appropriate debates are held to agree a way forward and to put the appropriate funding in place.
The best use of existing mechanisms to enforce the ‘polluter pays’ principle should be enacted. In addition, the Water Framework Directive objectives are to remove the sources of pollution and return water quality to a more ‘natural’ state, but in the case of many groundwaters, this process will be measured in decades, even if the ‘pollution’ were to cease now. The water industry must work with government, regulators, agriculture and other industries to develop holistic land management practices that will minimise polluting activities whilst retaining agricultural production and employment in the rural sector. In addition, innovative ways of using, or even re-using available water resources, need to be developed, whilst undertaking cost-effective remediation of existing pollution to benefit both the environment and future generations.
This article is based on a paper presented at Cranfield University’s Developments in Water Treatment and Supply conference, York, July 2005. The author wishes to thank Veolia Water and Three Valleys Water for permission to publish the paper. The views expressed are those of the author and do not necessarily represent those of Veolia Water or Three Valleys Water.
UKWIR (2004) Implications of changing groundwater quality for water resources and the UK water industry. Phase3: Financial and water resources impact. UKWIR Ref No. 04/WR/09/8.
Environment Agency (2001) Water resources for the future: a strategy for England and Wales. Environment Agency, Bristol.