Safeguarding supplies from catchment to tap

Water companies are implementing a new management system to help them deliver top-quality drinking water, all day every day. Philip Lightowlers talks to firms and the Drinking Water Inspectorate to discover how the plans will work

In the early hours of Sunday morning, 22 July, Severn Trent Water found its water supplies to the Gloucester and Cheltenham areas facing an unforeseen threat. Rising floodwater from the swollen rivers Severn and Avon threatened the company’s Mythe treatment works in Tewkesbury.

The site had to be evacuated and shut down as the flood waters rose to a metre deep across the works. The full effects took a day or two to materialise, but by Wednesday 340,000 people were without tap water. This was a disruption of supply on a scale not seen since the Second World War.

Suddenly the company found itself running a logistics business, organising water deliveries with whatever materials it could borrow, hire or beg for the purpose.

The treatment works, said Severn Trent’s Andrew Marsh, was not on a flood plain – a doubtful assertion – and was 30 feet above the normal level of the river. “We put the risk at just one in a thousand. There are many, many Mythes in the industry.”

The works, to the north of the town at the confluence of the two rivers, dates from the 1880s but has been rebuilt several times. In its current incarnation it was built to withstand the record floods of 1947.

Although the company had contingency plans for emergency supplies, these were overwhelmed by the scale of the problem. Some customers in nearby Tewkesbury could be supplied by another treatment works, but many more in and around Cheltenham and Gloucester were left with only bottled drinking water and emergency bowsers.

The incident was a wake-up call for utilities everywhere to assess the security of their key infrastructure assets. But for water companies in particular, the flooding came at a time when regulation of the industry is changing in a way that will oblige firms to be more aware of all threats to their supplies – including pollution, accidents and even terrorism.

Water safety plans
From 2008 the Drinking Water Inspectorate (DWI) will require companies to implement water safety plans (WSPs) for all water supplies. Firms must look at entire supply systems to identify hazards and prioritise safety improvements.

WSPs were introduced in the World Health Organization’s 2004 Guidelines for Drinking-water Quality, the third edition of the bible promoting global standards for safe supplies.

Earlier versions of the guidelines mainly comprised discussions on microbiological safety and appropriate limits for metals, organic pollutants and disinfection by-products. The latest edition prefaces these guidelines with a discussion on how best to ensure the delivery of safe water – through WSPs.

The plans are nothing less than a full risk assessment of water supply systems from source to tap. The planning process requires all potential risks to be assessed and actions to be prioritised depending on the probability and consequences of failure.

Chivvying and encouraging water companies to implement the water safety plan approach has fallen to the DWI’s David Drury, its water science and strategy advisor.

WSPs are, Mr Drury says, “a very simple idea and nothing intrinsically new to a well-run water company”. They are similar to hazard analysis and critical control points (HACCP), used in the food and pharmaceuticals industry as a systematic and preventative approach to product safety. Where the water industry differs from food processing, however, is that water treatment is continuous and not a batch process. Water cannot be recalled once it leaves the treatment works.

They key point about HACCP and WSPs is that they analyse quality assurance within a company’s operations and procedures and do not assess quality at the end of the production process.

This is a break with tradition for the DWI, which for many years focused annual reports on documenting the water industry’s progressive increase in compliance with a barrage of quality tests required by EU and national legislation.

The level of samples taken in water supply systems passing quality standards (known as mean zonal compliance) exceeded 99% in 1994 and has edged ever closer to 100% in following years, reaching 99.96% in 2006, according to the DWI’s latest report.1 Impressive as this seems, the DWI recognises this is not the whole story when it comes to customer perceptions of tap water quality.

“Endpoint compliance can hide an awful lot of problems,” Mr Drury acknowledges. The DWI must take a broader view of performance including monitoring the number of customer complaints that companies receive and the number of so-called “events potentially affecting water quality” they report.

It is after all not compliance with random samples that make customers notice, but unacceptable deviations from the norm which dent their trust in tap water supplies.

Drinking water reporting, in short, has changed. Although compliance is still reported, the emphasis is often local and incidents occupy a prominent position.

Not a good year
Mr Drury concedes that 2006 was “not the best year” for water companies in terms of their achievement. The DWI’s report complains that the number of ‘events’ reported increased from 369 in 2005 to 404 the following year. These may include anything from outbreaks of cryptosporidiosis – a stomach bug often linked to tap water – to minor reports of unusual colour, taste or odour.

One of the DWI’s roles is to examine such ‘events’ and decide whether they are serious enough to be classed as ‘incidents’. Incidents are investigated by the inspectorate and may result in prosecution. A recent example resulted in almost 2,400 complaints to South West Water about an oily taste in water supplied in Exeter in February 2006.

Investigations by the company and the DWI revealed that staff or contractors at one of the company’s sites had filled a 20-litre container used to supply hypochlorite solution for boosting the chlorine level in the water supply mains with diesel oil. The container became mixed up with new hypochlorite containers. Staff failed to spot the broken seal and the content’s unusual smell, so the container was loaded into a dosing system at a water service reservoir and contaminated water supplies to about 6,000 people.

The DWI pressed charges against the South West Water for supplying water unfit for human consumption and the company was fined £20,000 in June after pleading guilty to four charges (ENDS Report 390, p 56 ).

Despite prompt responses from water companies, these kinds on incidents damage customer perceptions of water quality.

More mundane examples of problems that WSPs might bring to light, Mr Drury says, are where a company’s IT systems do not share information, preventing staff accessing key control data, or where on-screen alarm signals scroll out of sight in the control room and are missed by an operator.

In the annual report, chief inspector Professor Jeni Colbourne criticised firms for adopting a “reactive and failure-driven” approach to the maintenance of treated water service reservoirs. The microbiological quality of water leaving reservoirs declined during the year, often because of undetected structural problems.

In one case, Yorkshire Water’s investigation into faecal contamination at a reservoir found a decaying rodent on the floor.

Another worrying trend highlighted in the annual report was companies’ failure to update operating procedures. Firms were not setting and adhering to critical water quality control measures, the DWI found, and staff were not always responding adequately to alarms or customer reports because they did not understand their significance to water quality protection.

WSPs, Professor Colbourne believes, will mean companies show fewer of these kinds of problems and that companies most advanced in implementing them are already seeing a reduction.

Hazard identification
The essential features of a water safety plan are that it considers the whole water supply system from catchment to tap, breaks it down into discrete parts and considers the hazards to each. Typically companies will have at least four compartments: the catchment, treatment works, the distribution system and the customer’s premises.

Catchment risks might include an incident polluting the river or groundwater source or diffuse pesticide inputs from agricultural or other land. Treatment risks might include staff failing to act on high turbidity alarms, allowing poorly filtered water into the mains.

For each hazard, the company must identify control or mitigation measures and where these do not exist, prioritise the gaps using a probabilities and consequences matrix.

The result should be a prioritised list of risks to water supply which can be used to guide expenditure on improvements.

Given this overall plan, the DWI leaves the detail up to companies. “I don’t tell water companies how to do it. It has to come from them,” Mr Drury says. In fact, key differences in organisation are already apparent between companies leading in WSP implementation.

“The best plans are team efforts representing all parts of a company structure,” Mr Drury says. Most parts of the company need to be involved – even security and IT staff – and it is not just about operations. “WSPs need a deep understanding of how a company operates and they can’t be done by an outsider. Consultants can facilitate them, but they cannot carry them out.”

In fact, Mr Drury believes there is a danger of over playing WSPs. New WHO guidelines on the subject are “too long-winded and too detailed”, he says. “I’m concerned that WSPs are being built up into something too complex. They are common sense but they need to be done by the company and within the company.”

Annual audit
In terms of assessing the results, the DWI is not expecting a revolution in companies’ operations. “I would be worried if companies were finding a lot of high risk, serious hazards,” Mr Drury says. “Many will be minor, but as the annual report shows there are still too many ‘incidents’ affecting water quality. And many are due to silly mistakes.”

The DWI annual audits of companies’ WSPs from 2008 will be looking for evidence of a plan and a team responsible for implementing it, Mr Drury says.

Teams will be expected to have toured company sites to gather information. Firms will also have to show documentary evidence of the hazards identified and the identification and prioritisation of any gaps.

Without clear prioritisation through WSPs, the DWI will not support water company applications for funding during the next five-year industry asset management planning round – due to be finalised in 2009. The process sets a tight deadline for companies as 2010-2015 investment plans are likely to have to be submitted to financial regulator Ofwat in 2008. Companies such as Thames Water and United Utilities are already fast-tracking WSPs where they anticipate supplies will require significant improvement.

In the longer term, Mr Drury says the DWI envisages WSPs will drive the protection of drinking water quality “backward into the catchment”, meaning measures will increasingly be introduced to prevent deterioration of drinking water at source rather than relying on remedial treatment.

Reducing pesticide or nitrate inputs, for example, would remove the need for energy- and capital-intensive treatment plant.

It is an ambitious goal, and whether it will ever be possible to retire these installations remains to be seen.

With the uncertainties of climate change and the experience of the Mythe works facing the industry, companies need to focus not just on pollution risks but on the key issue of security of supply.

The DWI’s investigation into what happened in Tewkesbury will be essential reading for companies polishing their WSPs. 

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