Water & Wastewater Treatment

8 | DECEMBER 2015 | WWT | www.wwtonline.co.uk Comment Customer awareness call over lead in water Section 20 of the Water Supply (Water Quality) Regulations, the Drinking Water Inspectorate has enforced legally binding undertakings on water suppliers to dose water in supply zones where sampling showed it was necessary. However, these measures are less effective at meeting the newly-reduced limit for lead. Concern about human exposure to lead in the environment resulted in the maximum amount of lead in drinking water being reduced from 50 micrograms per litre (μg/l, parts per billion) in 1990, to 25μg/I in 2004, to 10μg/l from 2014. Water suppliers have removed many of their lead communication pipes and encourage their customers to replace lead pipes within premises for which they are responsible. In England and Wales, this has significantly reduced the numbers of failed samples taken as part of the statutory sampling programme: there were 84 failed samples in 2014, just 0.68% of the samples tested. This compares to 123 failures in 2004, with the reduction achieved despite the more stringent standard applied today. Nevertheless, other sources of lead have proved problematic. In the 1980s Water Supply Byelaws prohibited lead-based solder used on pipework supplying water for cooking, washing, drinking or food production purposes. Yet water suppliers continue to find lead solder used, with the latest examples in schools, children's nurseries and houses with recent plumbing work. Water suppliers and the Water Regulations Advisory Scheme publicise the ban on lead solder and have recently worked nationally with housebuilders to inform their plumbers. To assist in manufacturing water fittings, brass alloys contain up to 2% lead which in some cases has dissolved into water passing through them. Research is being undertaken to eradicate this, although with normal use the amount of lead diminishes to insignificant concentrations over a few weeks to months. Lead accumulates in the body and swallowing it over a prolonged period can cause severe lead poisoning. Illegal use of lead solder has been a particular cause of lead poisoning. Lead can permanently impair mental development in children's nerves and brains, so those most at risk are children, babies and pregnant women. If excess lead is found in buildings to which the public have access, the water supplier can enforce the removal of lead pipes or solder. Where lead solder has been used illegally for recent work, affected joints can be replaced at the installer's cost. However, faced with meeting the cost of lead pipe replacement, a typical private householder's response is "I've lived here for years and it hasn't done me any harm". In conclusion, despite the successful efforts of water suppliers to reduce exposure to lead for which they are responsible, people are still consuming lead in their drinking water. Further efforts are needed to prevent installers using lead solder and to encourage premises owners to replace their lead pipes. Dr Steve tuckwell TEChniCal aDvisER WRas While lead has been largely eliminated from public water supplies, problems with customer- side pipes remain S ources of water used for public supply contain extremely low concentrations of lead; yet in 2014 in England and Wales, 16 out of 22 public water suppliers found lead in excess of the permitted amount in customers' tap samples taken for statutory water quality monitoring. Customer-owned pipes and plumbing caused over 80% of these cases, where lead had been used for pipes, lead-based solder for making joints on copper pipes or in some brass fittings. Until the 1970s, lead was used in some areas for communication pipes connecting premises to water mains and for the supply pipes within premises. Installation of new lead pipes was prohibited in the 1986 Model Water Supply Byelaws, but existing legally installed lead pipes were allowed to continue in use. Depending on the chemistry of the water, lead may dissolve from the pipe wall resulting in excess amounts in the supply. Lead can dissolve not just in so¥ acidic water typical of upland areas of the South West, parts of Wales, Scotland and the north of England, but also in hard waters. Two thirds of samples which failed in 2014 came from the southern part of England, where hard waters predominate. The amount of lead dissolving into water can be reduced by making so¥ acidic water supplies more alkaline, and by controlled addition of phosphate in hard water supplies. Using

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