Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/904738
14 | DECEMBER 2017 | WWT | www.wwtonline.co.uk Water companies make progress on risk-based drinking water approach James Brockett reports from Birmingham W ater companies are making progress towards a risk-based approach for drinking water quality rather than merely focusing on compliance, but more work remains to be done, delegates heard at the WWT Drinking Water Quality conference. Speakers at the Birmingham event, presented in association with Northumbrian Water, discussed how the Drinking Water Inspectorate has worked with water companies to introduce the Compliance Risk Index (CRI) as a replacement to the commonly-used regulatory measure of mean zonal compliance (MZC). The new index measures not only the frequency and location of compliance failures, but the The talk: Events significance of these failures in terms of their effect on customers; it also takes into account the cause of failures, the water company's ability to control this cause and how effectively it manages an incident that occurs. "The new compliance risk index is a positive development, which is helping us gain a greater understanding of the whole picture of what we are doing and the risks that are involved at every stage," Northumbrian Water chief executive Heidi Mottram said in her opening address to the conference. "As water companies, we will all be striving to be at the top of that index, but over time, the aim is that we will continue to raise the bar on water quality and risk reduction for the whole industry." DWI Chief Inspector Marcus Rink said that while mean zonal compliance in England and Wales stood at 99.96% in 2016 and this was vastly better than 20 years ago, performance has reached a "plateau" over the last dozen years. He highlighted that there were 150 serious incidents last year which required in depth investigation, and that it was important to analyse what went wrong in each of these cases to minimise the risk of their reoccurrence. "It wasn't just chance that these incidents occurred," said Rink. "In each case something has gone wrong with either people, processes or technology." Inadequate or incorrect risk assessments were o™en to blame, he added. Incidents which he cited as examples included the chlorine contamination at Severn Trent's Castle Donington Reservoir in March 2016, which followed a flow control failure; and an incident at SES Water's Elmer Works in February 2017 which saw sodium hypochlorite mistakenly put into a storage tank meant for ferric sulphate, resulting in the release of dangerous chlorine gas and the works being evacuated. Later the conference heard from Clair Dunn, Water Quality Risk and Optimisation Manager at Anglian Water, about the operational risk assessment process Anglian carries out when it is looking to make changes in its processes. Anglian has carried out more than 100 such assessments so far in AMP6, ensuring that efficiency measures taken which save energy, chemicals and money do not add to operational risk. The company has also worked to develop 'process safety' procedures at some sites which are more commonly used in the oil and gas and nuclear sectors. The conference also heard from Aidan Marsh, Flow Cytometry Project Leader at Northumbrian Water, about how advances in flow cytometry – a technique which counts the total number of bacteria in a water sample and establishes whether they are living or dead – is set to enable a more optimised approach to the use of chlorine and other disinfectants. The method gives much more information than the current most commonly used testing technique, heterotrophic plate counting, and the results are available in near real-time rather than having to wait for lengthy lab analysis. This means that the amount of chlorine used for disinfection can be more responsive and there could be a seasonal variation in chlorination to match the likely risk in service reservoirs, for example. Finally, the conference also heard