Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | APRIL 2019 | 15 people do this each year. For example, Thames Water plans to replace 53,840 lead communication pipes in the five years of AMP7, but only expects 5,500 of these to be as a result of a request by the householder. Unsurprisingly, water companies are focusing their proactive replacement programmes on high-risk areas and places where children and vulnerable people are drinking the water. Thames, for example, has undertaken that there will be no lead communication pipes at schools or nurseries in its region by the end of AMP7. Where there is a proactive replacement of communication pipes, efforts can then be made to persuade customers to also replace their own pipes. Renovating lead supply pipes by trenchless means, using techniques such as slip lining, avoids the cost and disruption associated with full replacement and can be an option in inaccessible locations or for cash-strapped householders. However, some in the industry are cautious. "Removal and replacement is the only certain way to eliminate the risk of lead in drinking water," says Philp. "Lining has a role to play, but one factor is that lining is not very efficient for reactive, single pipe interventions. The life and efficacy of the lining over the complete length of supply pipes impacting water quality, a legislative change might be needed under which water companies would adopt supply pipes – as happened in the case of private drains and sewers. However, this would be a massive and costly exercise, requiring water companies to gain access to customer homes. Another legislative option would be to require lead pipes to be replaced when a house is sold, but politicians might think twice before passing such a law because of its likely effect on house sales. In the meantime, Ofwat has upped the pressure on water companies as part of PR19 by setting a common performance commitment of 100% drinking water quality compliance, meaning that any water quality failures could quickly result in financial penalties. The move is unlikely to encourage water companies to turn off the orthophosphate any time soon. "The use of orthophosphate does appear to have been successful, but it doesn't prevent all lead failures," says Paul Millard, Technical Manager at WRAS. "In addition, the benefit of the treatment stops as soon as the dosing stops, so it must be continued indefinitely unless the lead pipes are replaced. Ultimately, it isn't the most sustainable approach, but can be useful as a protection method until a more permanent solution can be achieved." pipe is also not fully understood." Tightening standards One development which might provide a burning platform for further action is the revision of the EU Drinking Water Directive, which is expected to tighten the level of lead from 10µg/l to 5µg/l. On the assump- tion that this would be reflected in domestic legislation (a likelihood, despite Brexit), this would cause the number of water quality failures to shoot up. "Current iterations for the recast of the Drinking Water Directive are considering a 5μg/l limit on lead with a ten-year transition period," wrote DWI Chief Inspector Marcus Rink in the regulator's annual report in July 2018. "If this were to be included in domestic secondary legislation the only permanent long-term solution to the issue of lead in tap water is the removal of lead pipes and fittings, including the communication and supply pipes as well as homeowners replacing lead pipes or fittings. Many or indeed most of the current company strategies are not ambitious enough to consider this forthcoming challenge and may fall short of achieving the future standard." Some commentators believe that to solve the problem of customer-owned supply • LEAD FACTS • The harmful health effects of ingesting lead include damage to kidneys, the circulatory system and the brain. Children and pregnant women are particularly vulnerable. In the UK, the overwhelming route that lead reaches drinking water is from pipework which was installed before 1969, the year when lead pipes were banned • The health risks of lead were demonstrated in an extreme form by the crisis in Flint, Michigan in the USA, when a decision to change the source water for the city in 2014 resulted in rapid corrosion of ageing lead pipes and at least 6,000 children developed health problems. • The World Health Organisation advises that there is no safe level of lead for drinking water. However, the EU Drinking Water Directive currently sets the limit at 10µg/l; a potential revision may soon bring this down to 5µg/l. • Of 11,488 water quality tests conducted in England by the DWI in 2017, there were 70 failures in total against the lead standard (compliance of 99.4%) in public water supplies. Lead was the fourth most frequent cause of quality failures, a er taste & odour, coliforms and iron. • Orthophosphate dosing has long been used by water companies at the treatment stage to stop lead dissolving into the water (reducing plumbosolvency) but this has is not a sustainable solution because of the declining availability of phosphorus-based chemicals and the problems caused by phosphates in wastewater.