Water & Wastewater Treatment

WWT November 2019

Water & Wastewater Treatment Magazine

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Page 30 of 47

Databank The performance of England's water companies declined slightly in 2018, with Compli- ance Risk Index (CRI) and Event Risk Index (ERI) scores both rising. The latest Drinking Water report, covering 2018, showed compliance with the EU Drink- ing Water Directive across England remains extremely high at 99.95 per cent. With standards remain- ing at similar standards over a prolonged period, the Drinking Water Inspectorate is now using the CRI and ERI to provide further insight into performance. The CRI is designed to allocate a numerical value to risk, assigning a figure to the significance of the failing parameter, the proportion of consumers potentially affected and the quality of the com- pany's response. In 2018, for companies wholly or mainly in England, the CRI in 2018 was 3.86, rep- resenting a marginal increase on 2017, which was 3.62. In England, failures of samples to meet EU, national and indi- cator standards taken at treat- ment works, service reservoirs and taps all contribute to the national CRI score. Companies wholly or mainly in Wales saw an in- crease in CRI, hitting 4.15 from 2.63 in 2017. Across England and Wales, the ERI score rose to 783 from 241. While CRI in- dicates the risk that a water quality event will occur, ERI is used to produce a mean- ingful measure to quantify risk to the consuming public when there is an incident. The DWI said this figure was largely due to detec- tions of Cryptosporidium at Knapp Mill Works (Bourne- mouth Water), and at works serving large populations in London (Hampton and Coppermills operated by Thames Water) and repeated coliform detections at Testwood works (Southern Water). "This does not reflect an overall increase in the num- ber of events contributing to ERI since the total number of events in 2018 was 532, well within the normal lim- its of event numbers since 2014," DWI chief inspector Marcus Rink said. For the Wales-based companies specifically, ERI improved, falling to 32 from 55 in 2017. DRINKING WATER QUALITY 3.86 The CRI score for companies in England in 2018, rising from 3.62 in 2017 99.95% Public water supply compliance with the EU Drinking Water Directive in 2018, falling 0.01 per cent from the 2017 figure 783 The ERI score for companies in England in 2018, rising from 241 in 2017 Compliance Risk Index (CRI) and provisional Event Risk Index (ERI) figures for 2018 Number of microbiological tests failing to meet standards for water companies in England in 2018 CRI ERI Affinity Water 5.18 135.94 Anglian Water 2.09 9.1 Bournemouth Water 1.56 1590.82 Bristol Water 0.75 22.54 Cambridge Water 1.25 0.42 Dwr Cymru Welsh Water 4.31 34.46 Essex & Suffolk Water 2.12 2.04 Hafren Dyfrdwy* 0.5 0.1 Northumbrian Water 2.43 16.67 Portsmouth Water 1.78 11.76 SES Water 0.01 10.76 South East Water 3.39 51.89 Southern Water 11.59 5499.87 South Staffs Water 16.71 75.2 Severn Trent Water 8.4 238.2 South West Water 1.94 235.31 Thames Water 1.95 2727.22 United Utilities 2.26 90.33 Wessex Water 0.87 35.05 Yorkshire Water 1.9 57.2 Source: DWI www.wwtonline.co.uk | WWT | NOVEMBER 2019 | 31 E.coli 5 DRINKING WATER QUALITY * Hafren Dyfrdwy data only covers July-December period Source: DWI Source: DWI Coliform bacteria 56 Clostridium perfringens 21 Turbidity 22

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