Drinking water quality technical background
The approaches adopted by water companies to ensure the quality of drinking water varies considerably depending on many different factors.
Drinking water in the UK is derived from a number of different sources, including underground aquifers, rivers and upland storage reservoirs. The greatest concern for water supplies is still the danger of pathogenic microorganisms that can come from a number of different sources. Our water suppliers use a range of barriers (the multiple barrier approach) and disinfection techniques against such microorganisms within a rigorous testing and treatment regime.
Raw water sources
All water will contain natural minerals, such as calcium and magnesium, which dissolve from rocks through which the water passes before being abstracted for supply. The actual amounts and compositions of the mineral salts will vary from place to place. These minerals contribute to the taste and natural character of local drinking water.
Because water is a very good natural solvent, depending on the water source and other factors, various other substances can also be present in very small quantities. These can derive:
- from natural organic matter from the breakdown of plants and organic matter in soil found in the source water, particularly for surface waters
- from pollution
- as a result of the treatment and distribution process itself
- due to interaction with plumbing systems in buildings.
Water suppliers assess the risks of different contaminants being present in drinking water and take action to ensure that the safety of water is guaranteed at all times.
How is the quality of drinking water assured?
It is the job of water suppliers to manage the quality of drinking water and ensure that it is safe and pleasant to use for all domestic purposes. However, water quality experts agree that, where possible, management of drinking water quality is best achieved through partnerships between all those with responsibilities that affect the various stages of the water supply process from source to tap.
As well as water suppliers this includes:
- governments, health authorities, local authorities and regulatory agencies
- environmental protection agencies
- industry, agriculture and others that can cause pollution or inadvertent damage to infrastructure
- house builders, plumbers and suppliers of plumbing fittings
- house and building owners.
To provide a framework for these partnerships and to further enhance the protection of drinking water quality, the WHO and other expert bodies developed the Water Safety Plan (WSP) approach. This retains the use of water quality standards but manages drinking water quality on a more holistic and systematic basis, in which all potential risks to water quality, from source to tap, are identified and addressed. In fact, such an approach has been used in the UK for some time, and Water UK members are actively working with other organisations, locally and nationally, to further develop, refine and formalise the Water Safety Plan (WSP) framework.
Water suppliers are at the heart of the developing Water Safety Plans, focusing on the aspects under their control - particularly water treatment and distribution through the supply network. However, as outlined above, to be fully effective it is essential that all those concerned with drinking water quality play their part.
It is particularly important that regulators and environmental protection agencies responsible for preventing pollution of water resources do more to protect and improve the quality of our raw water. This is a requirement (under Article 7, relating to dangerous substances) of the EU Water Framework Directive (WFD). The UK water industry strongly supports such a preventative approach and is working closely with the various authorities and initiating work with farmers and other stakeholders to develop catchment approaches to protect drinking water sources from pollution.
Water in buildings
Deterioration in water quality can occur after the point of delivery to consumers due to the condition and operation of the plumbing systems within buildings. This is why it is so important that all plumbing systems are designed, installed and maintained in ways that avoid such risks. Although the plumbing systems in buildings are not the responsibility of water suppliers, the water suppliers will usually provide advice to customers. Water UK requires that any plumbing work is carried out by a trained and competent plumber.