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3.1drinking water directive(s)
The drinking water quality standards which must be met by the water authorities are well defined. These are laid down in the existing Drinking Water Directive implemented with some additional national standards and a more prescriptive sampling regime in the Water Supply (Water Quality) (Scotland) Regulations 1990.
A new Drinking Water Directive (98/83/EC) came into force in 1998 with the first, and main, compliance deadline being 2003.1 The new Drinking Water Directive will require to be implemented by new regulations which must also be made by end 2000 but will not come into force until end 2003.
For the broad range of parameters the new Drinking Water Directive will not result in changes to standards. However the structure of the monitoring regime will change with the consequence that it is not possible to judge compliance with the new Directive's standards on the basis of the current monitoring regime. In order to facilitate compliance with the new Directive by the due date transitional arrangements will be made in regulations, to the extent necessary to judge performance against the new Directive's standards (where these are higher) and its new monitoring regime. This will allow the water authorities to put in place the necessary undertakings 2 to achieve compliance when the new Directive comes into full force at the end of 2003.
The revised standards will apply as national standards from 1 January 2001 and the basis of the Annual Water Quality reports will change also at that time. Interim standards for trihalomethanes (THMs) and lead will be replaced by permanent standards by the end of 2008 and 2013 respectively. (See sections 3.1.1 and 3.1.2 for more detail on lead and THMs) In many cases, existing treatment works can only meet microbiological standards through extensive chemical treatment, resulting in THM failures. The Scottish Executive has agreed binding undertakings with the authorities to improve these works, and thus achieve safe water without excessive chemical treatment.
Beyond this programme the cost of compliance with the Directives' standards will be determined by the content of the work to be carried out by the compliance dates. In recognition of the significant amount of work required for lead and trihalomethanes (THMs) more time was allowed in the Directive to achieve full compliance with the requirements for these parameters than for the other parameters.
The water authorities should carry out the necessary investment to ensure that they are properly equipped to meet the requirements of the Drinking Water Directive. The Directive allows for Scottish Ministers to provide derogations for certain chemical parameters, provided no derogation constitutes a potential danger to human health. Any derogations should be limited to as short a time as possible and may not exceed 3 years. Scottish Ministers wish to use these powers as sparingly as possible, but it is recognised that the larger numbers of small rural works in some areas pose a particular challenge. The Directive contains specific exemptions/provisos in respect of THM and Lead.
3.1.1Trihalomethanes
Trihalomethanes (THM) are formed from the reaction between organics present in the source water and chlorine which is added to disinfect supplies. The upland peaty waters which are the typical source water for the majority of Scottish drinking water supplies are rich in both microbiological and organic material. The Drinking Water Directive acknowledges that the public health importance of disinfection outweighs the consequent formation of disinfection by-products. However, it is also considered prudent to minimise the formation of disinfection by-products. THM is the parameter used as a surrogate measure of disinfection by-products where chlorine is used as the disinfectant. The Government's long term objective is that the water treatment provided for all Scottish water supplies should be capable of removing organic material without excessive use of chlorine so that THM is reduced to acceptable levels. The new Drinking Water Directive is formulated to drive the introduction of improved water treatment while recognising, by means of an interim standard, that the final standard cannot be met for some while.
Inside North of
Scotland Water's (NOSWA) Gorthleck Water Treatment Works
(photograph courtesy of NOSWA)
The authorities must aim to comply with the interim standard of 150 µg/l * by end of 2003. In certain circumstances the Scottish Executive may provide a derogation under Article 9 of the Directive. This would provide an additional 3 years for compliance with the 150 µg/l interim standard. Applications for derogations will be treated on a case by case basis.
The interim standard for THM will be replaced by a permanent standard of 100 µg/l by end of 2008. The Government's aim is that all undertakings to comply with the THM standard of the new Directive should be completed by the end of 2006 when the derogations against the 150 µg/l interim standard mentioned above will cease to apply. There will be no derogations against the 100 µg/l long term standard.
The provision of Article 8 of the new Directive concerning the reporting of failures to customers will apply during the period of any derogation authorised by the Scottish Executive.
3.1.2 Lead
Lead is a well known toxin and studies have shown that children may be particularly vulnerable with adverse effects on their intelligence. The body will easily absorb lead from drinking water since much of the metal is in soluble form. The major source of lead in drinking water is from the metal dissolving into the water from the service pipe connecting the house to the main and any lead plumbing within the house. The water authority owns the part of the service pipe up to the stop-cock (usually at the property boundary) and is responsible for any work needed on pipes up to this point. Beyond this point, the pipe work belongs to the owner of the house. The present standard for lead is a maximum of 50 µg/l in any sample at the tap. The new drinking water standards are 25 µg/l to be achieved by end of 2003 and 10 µg/l to be achieved by end of 2013. Value for money considerations will determine where for particular areas, it is appropriate to invest once to meet the higher standards rather than do it in 2 stages.
The new Directive also places an obligation on water authorities to notify both the owners and the occupiers of premises, where failures have occurred, of actions that they can take to limit exposure to lead (pipe removal in the case of owners, pipe flushing in the case of occupiers). This obligation will come into force at the end of 2003 and a substantial effort will be required to enhance water authority IT systems to cope with all the relevant records regarding lead in houses and ownership/occupier details to allow this obligation to be fulfiled.
Typical domestic water service connection
The specific provisions in the new Drinking Water Directive are complex and elements of the provisions concerning a sampling protocol have not yet been determined. The planning assumptions for the purposes of this paper should be based on Departmental guidance issued to water authorities in December 1998.
The interim standard of 25 µg/l will come into force at the end of 2003. In order to meet this standard, authorities should in the first place check that the requirements for water treatment are fully met. This will require two distinct actions.
The permanent standard for lead of 10 µg/l will come into force at the end of 2013. The planning assumption should be that for Scottish waters, water treatment alone is not capable of reliably reducing the uptake of lead into drinking water to below this level. However, a breach of the 10 µg/l limit at a household tap will not be a breach of the Directive's requirements if the water authority can demonstrate that all lead in the relevant supply chain in the water authority's ownership has been removed. The planning assumption should therefore be that substantially all lead communication pipes will need to be removed by the end of 2013. The removal of lead communication pipes is an integral part of the water authorities' mains renewal programmes. Past policy by the water authorities and the former regional councils was not consistent so it is expected that many serviceable, renewed or relined mains still have lead communication pipes. These will need a separate programme of communication pipe replacement by end of 2013.
1End of 2003 means 25 December 2003 to be precise. Reference to end of 2000, 2008 and 2013, also means 25 December of those years.
2 The Scottish Ministers must take enforcement action against a water authority which fails in its duty to supply wholesome water unless the failure is trivial or the water authority is complying with a legally binding undertaking to remedy the matter. These undertakings are reviewed annually.
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