Do our water quality standards demonstrate to the public that their water supply is clean?

Martin Kimber, Christopher Binnie and Hugh Thomas discuss the importance of water quality management to ensure that what’s supplied to consumers is of a consistent standard.

Managing water quality requires careful control throughout the supply system.
Managing water quality requires careful control throughout the supply system.

In most countries, there are water quality standards and associated requirements for sampling and analyses of the public water supply which are intended to ensure that consumers always receive clean water. But do they, and is it realistic to assume they always will?

Meeting the standards

While the frequencies of sampling and analysis for the various quality parameters reflect both their significance in health terms, and the probability of failure, it’s simply impracticable to monitor all parameters of concern all the time.

Compliance with the water quality parameters across the UK is very high, with the failure rate for analyses being less than 0.1%. That is, less than one analysis in a thousand fails to comply with the relevant standard.

Water companies spend a lot of time, effort and money to demonstrate compliance, but there are also occasional water quality incidents resulting in consumers being advised to boil water.

What else are water suppliers doing to minimise the chance of a failure occurring and ensuring public confidence in the public supply?

Minimising failure

Managing water quality is a complex process that requires careful control throughout the supply system – from source to tap.

Much of the investment in water supply systems is aimed at improving the resilience of supplies.

The investment may be required due to: population growth; climate change; deteriorating raw water quality; or other reasons.

This resilience is often achieved by providing an alternative or secondary water source to reduce the likelihood of a supply interruption.

Until recently, new or changing water sources have been introduced without the focus on water quality that the ‘source-to-tap’ water safety planning approach requires.

In 2017, the Drinking Water Inspectorate issued guidance to water companies which stressed the need for risk-based water safety planning through the entire strategic planning and investment cycle, whether these are compliance or customer acceptability.

Meeting consumers demands and expectations

In our digital world, there’s increasing public voice about the quality of the water, and the ability for customers to instantly voice concerns about issues over social media.

This is increasingly a significant factor driving enhancements in water quality, notwithstanding the increasing pressure from customers and the regulator to keep bills low.

So what kind of water quality risks may become of increased concern? In the absence of a crystal ball, informed guesswork is required.

New sources will normally contain contaminants derived from agricultural, municipal or industrial discharges.

Where a new, or alternative, source is brought into use, its chemical characteristics will often differ from the existing source – often leading to customer perception of a deterioration in water quality, whereas in reality there’ll be full compliance with water quality standards.

Any change in the quality of water delivered to consumers is often seen by the consumer as a deterioration in quality – something of a nightmare for suppliers struggling to meet demand where there’s an increasing population and often a reduced resource due to environmental concerns.

Domestic consumers are predominantly concerned with the aesthetic quality of water and, arguably, the hardness of a supply.

Many of the water quality parameters defined by regulations and monitored by sampling and analyses do not affect consumers’ perception of water quality.

Changes in the taste, odour or hardness of the water will generate complaints, whereas a change in, for example, nitrate will be undetectable by the consumer.

Future challenges

In the future, there’s likely to be increasing emphasis on supplying water of a consistent quality, blending waters from different sources to avoid changes that may be undesirable to consumers.

So, while no additional water quality standards may be required, better planning and management of sources is likely to be.

Water safety planning and approaches to managing water quality from source to tap are the focus of Basic Water Treatment, Sixth Edition.

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