Quality on tap

Water is one of our most vital natural resources, and it is therefore vitally important that the quality of drinking water in particular is maintained to the highest standard possible. Barry Hill examines the background behind how this is achieved by looking at the work of the Drinking Water Inspectorate.

WATER is not only essential to sustain life itself, but it also plays a crucial role in our economic development and social well-being. It is important therefore that our water bodies are protected from any sources of pollution and managed as a sustainable resource for all of the activities that depend on them. Pollution in the surrounding catchments can come from point sources such as industrial or sewage effluent discharges, or can be diffuse such as road or agricultural run-off. Today throughout Britain, these water bodies are important natural resources for agriculture, industry and fisheries, for amenity and recreational use, for their value to tourism and crucially, as sources of drinking water. Since 1990, drinking water quality in England and Wales has been regulated by the government through the Drinking Water Inspectorate (DWI).

“Ensuring the safety and good quality of drinking water is a never ending task of constant vigilance by many”

The main task of the DWI, the tap water watchdog, is to check that the water companies in England and Wales supply water that is safe to drink and which meets the standards set in the Water Quality Regulations. Dr John Gray is Deputy Chief Inspector with the DWI. A former Chief Chemist and Bacteriologist with West Kent Water and subsequently Head of Scientific Services for South East Water, he is now very much a poacher turned gamekeeper in his role with the tap water watchdog as he explains: “Our Inspectors carry out regular technical audits of water companies, the particular audits for each company being directed by a risk-based approach”.

The inspections cover two broad areas. Gray continues; “we check the results of tests on drinking water carried out by the water companies and visit the water companies to inspect specific aspects of their operating practice. Water quality is assessed on the basis of information provided by the water companies. Millions of tests are made each year to assess whether water meets the standards set down in law. Tests are carried out on treated water leaving water treatment works, on water in service reservoirs, in the distribution systems and on water taken from consumers’ taps in designated geographical areas called water supply zones. The individual water companies (or their appointed contractor) themselves perform the analyses and we audit a selection of the analyses to ensure that the results are accurate and true. Audit covers everything from the scheduling of the sample(s), sample collection, sample transport, sample receipt in the laboratory, analysis, data capture and storage and preparation of public record. We then check the test results and carry out inspections to ensure that the results are reliable and accurate and give a true picture of the quality of the water supplied. We have strict requirements related to the methods used to analyse water samples and how to report the results. We carry out independent checks that the testing has been carried out to a high standard of quality control. Laboratories who undertake water testing must follow recognised methods of analysis such as those published by the Standing Committee of Analysts (SCA) or use equivalent methods. This is to provide public reassurance that the robustness and integrity of water company results is beyond question. Our final role is to investigate consumers' complaints and incidents that affect or could affect drinking water quality. Investigations of incidents can lead to water companies being prosecuted”.

To protect public health there are microbiological standards which have to be met at each treatment works and treated water service reservoir or tower. Microbiological tests are also undertaken on consumer tap samples. The significance of individual test results for each microbiological parameter at each location varies and a single positive result does not necessarily mean that water is unsafe to drink. Each of the standards is listed below:
• Escherichia coli and Enterococci are bacteria present in the gut of warm blooded animals. They should not be present in drinking water and, if present, immediate action is required to identify and remove any source of faecal contamination that is found. The standard is 0 per 100ml.
• Cryptosporidium is a parasite that causes severe gastroenteritis and can survive disinfection by chlorine. In the UK continuous monitoring is undertaken at works classified by the company as being at significant risk. The treatment standard for these works is <1 oocyst per 10 litres.
• Clostridium perfringens is a spore forming bacterium that is present in the gut of warm blooded animals. The spores can survive disinfection by chlorine. The presence of spores in drinking water indicates historic contamination that requires investigation. The standard is 0 per 100ml.
• Coliform bacteria are widely distributed in the environment often as a result of human or animal activity but some grow on plant matter. Their presence in a water supply indicates a need to investigate the integrity of the water supply system. The standard is 0 per 100ml.

Each year as part of its remit, the DWI publishes an annual report of its activities which gives a comprehensive overview of the safety of tap water within England and Wales. The Inspectorate’s latest report revealed that in England, 99.94% of more than 1.8 million tests carried out in 2005 met all the national and European health based standards. In Wales 99.92% out of more than 140,000 tests met the standards. New and more rigorous drinking water standards came into force on 1 January 2004 and reset the baseline for assessing and judging drinking water quality in the UK and across Europe. The latest year figures for public water supplies in England and in Wales put the safety of our drinking water beyond question.
To coincide with the new standards the Inspectorate now publishes its report in a new style that looks at drinking water quality on a regional basis as John outlines. “This was because the overall quality of drinking water is so high that it is more relevant to look and see where in the country there is still a need for further improvement. The report has adopted a radically different approach in terms both of its design and its content as it includes changes which reflect the views of local authorities, reports at a community level, revealing the disparities that can exist within a region and focuses on the consumer’s experience, not just on meeting scientific standards. It also includes new compliance and other performance-related indices and full details of all incidents reported and action taken. The Inspectorate thinks that its annual report is the most comprehensive information on everything involved in the management of the safety and quality of public water supplies to be openly published anywhere in the world.”

Dr Gray appreciates that consumers’ experience of tap water quality does indeed vary across the country, but there is a sound basis for this. “Consumer expectations are higher than ever and those who intermittently receive discoloured or bad tasting water rightly want something done about it. The permanent remedy to these aesthetic quality problems is appropriately targeted water company distribution and maintenance strategies. In our report we give details of the improvement programmes that the Inspectorate is requiring of water companies over the next five years. Ensuring the safety and good quality of drinking water is a never ending task of constant vigilance by many and drinking water quality cannot be judged solely by a single compliance number that relates to tests done in a laboratory. Some of the regulations address specific aspects of drinking water safety. For example, there is a legally enforceable treatment standard for the parasite, Cryptosporidium ,a requirement to adequately treat and disinfect water supplies, and controls over the use of chemicals and materials of construction used in public water supplies. Our role here is to provide guidance to water companies on how these requirements can be met. We carry out independent technical audits of water company records and sites to ensure their operational and management procedures are robust and appropriate’. 

Apart from his day to day Inspectorate activities Dr. Gray also represents the Inspectorate in matters of national emergencies which affect drinking water supplies and the wider environment, and is heavily involved in national security issues affecting the water industry including directing associated research. “During 2005 the Inspectorate continued to work in partnership with non-Governmental bodies and research organisations, both in this country and overseas, to ensure that it is up-to-date with relevant technology and research. The Inspectorate has been involved in a number of groups to develop new water industry operational protocols and to update existing ones. Our Inspectors also regularly take part in major exercises designed to test emergency responses”. Despite its relatively short existence, Dr Gray, who in January 2007 is set to finally take a very well earned retirement from his post at the DWI, is proud of the organisation’s achievement to date, but realises there is still much work to be done to ensure tap water quality remains as high as possible. “The Inspectorate has worked hard since it’s creation in 1990 to establish itself as the foremost authority on water quality and its regulation. Although we have had major success in improving the quality of drinking water supplies to consumers in England and Wales, we recognise that there are still opportunities to enhance even further the quality of drinking water supplies. Furthermore, the protection of public health is an issue which will remain at the forefront of the Inspectorate’s activities”.

By Barry Hill. Barry has worked within pathology for over 30 years and specialises in the discipline of blood transfusion & haematology. A former member of the IBMS Blood Transfusion Special Advisory Panel, he is also a prolific freelance writer of short medical articles for a wide range of medical & scientific based publications.