A new report published by the Drinking Water Inspectorate on drinking water quality in England shows a rise in water compliance failures during 2018.

The annual report Drinking water 2018, the 29th published by the DWI which covers both private and public water supplies, is a record of the work of the Inspectorate in checking that water companies and local authorities have taken the appropriate action to maintain confidence in drinking water quality and to safeguard public health.

In 2018, the figure for public water supply compliance with the EU Drinking Water Directive was 99.95%, a figure which has remained largely unchanged since 2004.

In 2016, the Inspectorate introduced a new measure called the Compliance Risk Index (CRI), a measure designed to illustrate the risk arising from treated water compliance failures. The CRI assigns a value to the significance of the failing parameter, the proportion of consumers potentially affected and the quality of the company’s response. The measure also has been introduced as a common performance commitment for the Periodic Review 2019 by the financial regulator OFWAT.

In 2018, for companies wholly or mainly in England, the CRI in 2018 was 3.86. This is a marginal increase on 2017 which was 3.62. In England, failures of samples to meet EU, National, and indicator standards taken at treatment works, service reservoirs and taps, all contribute to the national CRI score.

"Majority of failures due to just a handful of assets which present majority of risk and contribute greatest to CRI"

According to the DWI. the common link between the majority of these failures is they are due to just a handful of assets which present the majority of risk and contribute greatest to CRI.

In 2018, there were 1,185 failures of EU, National Standards and indicators taken at treatment works, service reservoirs and taps, which all contribute to the national CRI score.

The report shows that the single largest contribution to CRI for the industry remains detections of coliforms at treatment works and service reservoirs, reflecting widespread risk to consumers where there are large populations supplied by treatment works.

The single largest contributing factor to the CRI for coliforms at works was by Southern Water

at Testwood Works, accounting for 30% of the score. According to the report, there were repeated detections of coliforms between February and May 2018 and the situation was treated as an event.

The site is subject to a Notice requiring immediate short-term actions including the replacement of coverings on storage tanks and longer-term refurbishment works due for completion in 2026.

For service reservoirs there were two companies contributing 50% of the CRI for coliforms, Affinity Water, (Harefield Reservoir) and Bournemouth Water, (Sway and Hightown Reservoirs). These sites are subject to recommendations requiring continuing scrutiny of the assets.

The report says:

“Affinity Water remain a focus due to the year-on-year poor performance at service reservoirs, contributing the greatest number of failures at this asset type, in 2018, of all companies.”

Cryptosporidium incidents caused rise in ERI to 783 in 2018 -up from 241 in 2017

In 2017, a new drinking water quality measure - the Event Risk Index (ERI) - was also introduced to illustrate the risk arising from drinking water quality events. Like CRI, it assigns a value to the significance and duration of the event, the number of consumers potentially affected and the quality of the company’s response.

Similar to CRI, Ofwat has also made this measure available as an asset health performance commitment for PR19, if companies wish to be measured by it. The industry ERI in 2018 was 783 and was higher than the 241 recorded in 2017. The figure was due to detections of Cryptosporidium at Knapp Mill Works (Bournemouth Water), and at works serving a large populations in London (Hampton and Coppermills operated by Thames Water) and repeated coliform detections at Testwood works (Southern Water) amongst 46 events classified as serious by the Inspectorate.

In 2018 the DWI completed two successful prosecutions and two Cautions of water companies for events. United Utilities were prosecuted for two separate incidents of inadequate disinfection of water at Sweetloves works and were also cautioned for a similar occurrence at Buckton Castle where consumers were asked to boil their water for a short period.

The second prosecution was for the supply of unfit water from Southern Water’s Cooks Castle service reservoir in the Shanklin area of the Isle of Wight.

Writing to Thérèse Coffey, Parliamentary Under Secretary of State for the Environment, about the publication of the report, Marcus Rink Chief Inspector of Drinking Water commented:

“The event occurred in 2013 and only came to light through investigations by my Inspectors who discovered the event retrospectively as the company had failed to report the matter.”

The final Caution was due to the provision of discoloured water from Seedy Mill works by South Staffs Water.

The Chief Inspector told the Minister that a separate prosecution which finally completed in January 2019 has also been included in the report due the serious nature of the incident, commenting:

“This occurred at South Moor service reservoir (Northumbrian Water). This was an event that should not have happened. Corners were cut in carrying out the work and inadequate scrutiny did not identify this. Consumers experienced water with an unpleasant taste and odour which is likely to have been detected had adequate checks been carried out before the reservoir was put back into service.”

In 2018, the continuing strategy of innovative regulation introduced analysis of recommendations made to companies by the Inspectorate. The basis of the Recommendation Risk index is to build upon the concept of a recommendation as a first level regulatory intervention.

The objective is to encourage companies to take action themselves before the need for formal enforcement action. As part of this, and since 2016, four companies have been identified as being at a higher risk of regulatory failure, namely, Severn Trent Water, United Utilities, Southern Water and Thames Water.

In his letter to Thérèse Coffey, Marcus Rink said:

“As part of progressive and better strategic regulation, we have worked with these companies to formalise a water quality improvement strategy through transformation programmes. The programmes comprise a set of legal instruments that set out agreed actions. I am pleased to report the positive response by the companies to these programmes and the evidenced improvements.”

Click here to download Drinking Water 2018