Second Drinking Water Quality Conference
Birmingham, November 2017
Mike Waite, FWR Water Supply Co-ordinator
Water & Wastewater Treatment, in association with Northumbrian Water Group, organised this very interesting conference on Drinking Water Quality which I was pleased to attend. It was refreshing to have such a conference away from London! There was so much information presented that it is only possible to give a flavour here but all the speakers' visual material is available
Marcus Rink (Chief Inspector DWI) gave a presentation on the recent DWI Annual Report. With only 0.04% of tests not complying with standards, and no E.coli in any samples from treatment works, the high standard of drinking water in England and Wales is being maintained. Metaldehyde continues to be a cause of failures but numbers are decreasing. Private Water Supplies remain of poorer quality with c. 5% of samples failing, although this is an improvement on c. 10% failures in 2010. Water supply events continue to occur with 8 being significant in 2016. DWI has developed a Compliance Risk Index (CRI) based on WHO principles and in 2016 the national CRI was 4.78. In 1990 this would have been >10,000!
Elise Cartmell (Chief Scientist, Scottish Water) gave an excellent talk on Scottish drinking water. Scottish Water (SW) achieved 99.91% compliance from c.150,000 tests. Of the 131 tests failing, 37 were for coliforms and 23 for iron. Although only 8 were for trihalomethanes, most Scottish sources are peaty and future changes in environmental management are likely to increase the release of organics. SW is seeking to deliver biologically stable water and minimise production of disinfection by-products (DBP) by both additional treatment processes and land management, including restoring peat.
The meeting then broke up into three groups and I participated in the group considering ‘Improving the technical elements of drinking water treatment’. Clair Dunn (Anglian Water) described how AWS had started a project seeking to improve efficiency without adversely impacting on water quality, and identifying assets too critical to fail. In the first year, savings of £586k of OPEX (operating expenses) were achieved including £280k on chemical use and £400k of CAPEX (capital expenditure) was averted. Anglian Water has developed a process of Operational Risk Assessment which looks at the potential cost impact of a circumstance or event, which, when multiplied by the likelihood of it happening, gives the costed risk. A similar risk can be estimated for any proposed solution to a problem and if the solution implies a net cost, then a management decision is needed to determine whether that cost is acceptable. Anglian is assessing all assets to determine whether they are too critical to fail, and assigning a risk score to prioritise action. Their key considerations are containment of an event and whether the site can be recovered before supplies are affected.
Chris Rockley (South West Water) described the decisions leading up to the new Mayflower Treatment Works which has replaced the old Crownhill works at Plymouth. The new works needed to provide a 100% barrier to Cryptosporidium, reduce production of disinfection by-products and be robust and offer savings. He outlined the pilot plant investigations and how, in consequence, the design evolved while being evaluated. The final treatment train begins with suspended ion exchange, the resin being completely recovered and regenerated each cycle, followed by addition of a low coagulant dose to reduce fouling before passing to a ceramic filter. The treatment concludes with GAC and UV disinfection, with a low chlorine dose being applied to maintain quality in distribution.
Paul Weir (Scottish Water) spoke about understanding and managing microbial risk at WTW (water treatment works). Using flow cytometry it was found that total cells leaving the works correlated with rainfall levels with some time lag, and there is a relationship between distribution microbial failures and high numbers of cells leaving the WTW.
The full meeting then heard from Aidan Marsh (Northumbrian Water) who spoke on setting standards in water quality. Bacteriological culture methods take up to three days and detect less than 1% of bacterial cells, whereas flow cytometry in three minutes can detect all cells and determine whether alive or dead, and intact or disrupted. Cells can also be differentiated between HNA (high nucleic acid) and LNA (low nucleic acid) based on fluorescence. LNA cells are likely to be less culturable and resistant to chlorine while HNA cells are likely to be actively growing and chlorine-sensitive. Northumbrian has developed a logarithmic risk score from 1–10 which assists in predicting failures.
Robin Price (Anglian Water) spoke about Anglian’s Shop Window. Anglian Water believes in innovation through collaboration and is aiming to achieve 100% compliant water by chemical-free treatment. They currently have over 100 organisations participating in more than 60 projects. They are liaising with farmers on the impact of their activities and utilising satellite imagery to monitor changes in land use. They are also working with experts and developers to create ‘the house of the future’ which aims to use only 40 l/head/day and will allow suppliers to showcase their products and services. They are also looking at other aspects of distribution, including novel approaches to leak detection. Newmarket has been designated as their ‘shop window’ where it is applying all its innovations.
Dr Ulrich Borders (IWW Water Centre, Germany) then spoke about the value of non-target analysis (NTA) compared with specifically analysing for designated determinands. NTA looks at a range of analytes and then analyses the results for significant features rather than targeting specific determinands such as coliforms. He also discussed the role of Effect-Directed Analysis (EDA) in regards to toxicology. Currently, every possible compound has to be subject to full toxicity assessment whereas with EDA a toxicity test on the water would determine the safety of the supply without considering the potential toxicants.
The final session consisted of three short papers relating to incident management and customer-side risk. Ashlea Lane (Wessex Water (WW)) spoke briefly about the company's
approach to incidents with specific reference to a lead incident. WW has a trigger point above which it will replace lead pipes, including those of the customer. It now has a pro-active programme of lead pipe replacement which has led to better pipe replacement practices such as pipe pulling. When lead has exceeded the trigger level, WW follows up the root cause to see if it could happen elsewhere.
Julie Spinks (WRAS) outlined the role of the Water Regulations Advisory Scheme pointing out that it has no legal powers to ensure that only approved materials and equipment are used in water supply; however, water companies have powers under the Water Fittings Regulations. In a survey, 60% of customers did not know they need to comply with these regulations and 73% did not realise that they were legally responsible if their plumber installs non-compliant fittings. Only 5,530 of the c. 84,000 plumbers in England and Wales are registered as WaterSafe Plumbers. She explained that there is poor awareness among manufacturers, retailers, plumbers and consumers regarding WRAS approval. It is not illegal to sell non-compliant equipment but retailers should tell customers it will be illegal if fitted.
Finally, Luke Montgomery and Marcus O'Ceafarcaigh (Yorkshire Water) spoke of lessons to be learned after an incident involving bacterial contamination of public potable supply (at Thorne and Moorends near Doncaster) in 2016. A food manufacturer reported discolouration of supply and when the main was flushed it was noted that the water was warm and within two hours the discolouration returned. The company carried out sampling and inspected a number of farms, schools and industrial premises. Very high numbers of E.coli were found from a number of hydrants. Attention was focussed on a chicken processing plant and the supply to the plant was cut off. Although the factory had spent £12m on new plant, it had not used qualified plumbers. Although the plant was supplied via a tank with adequate air-break and had a pump downstream feeding the industrial processes, there was a return loop with a closed valve downstream of the pump leading back to the feeder tank. When the pump failed, the valve was unable to prevent process water returning to the tank. Despite the demonstration of 37 contraventions only 4 were presented to the court and it ruled that it could not be proved that the manufacturer caused the contamination: a fine of £2,700 was the only punishment. An important lesson learned was that it is important to be able to delineate the affected area accurately, as on this occasion a number of unaffected customers were advised to boil water. Social media were also useful in disseminating information to the public.