Water & Wastewater Treatment Magazine
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In the know Digging deeper: Pipes and pipelines 32 | NOVEMBER 2016 | WWT | www.wwtonline.co.uk could significantly reduce the propensity of any water supply to reduce plumbosolvency to the point at which 10 micrograms per litre could generally be achieved. However this would not be the case if significant amounts of particulate - rather than soluble - lead were present. On those occasions where water sources were changed due to supply constraints or cost optimisation, the changes in water chemistry could result in significant release of particulate lead along with iron and manganese from the pipe wall. Barrier techniques The people of Flint, Michigan and Sebring, Florida have recently been exposed to elevated lead levels in their drinking water due to short-term changes in the water chemistry. The only long-term solution is to stop drinking water coming into contact with lead, either by removing any lead pipe and lead-based solder, or by creating an impermeable barrier of epoxy or other polymeric lining. Since North West Water's early work, patents on lining lead service pipes and associated communication pipes, or extracting the lead pipe from the ground and simultaneously inserting a new polyethylene pipe, have expired. The selection of the lowest whole-life cost solution, that meets the customer's need, remains the objective. As a member of the AWWA advisory panel I have seen the development and commercialisation of those techniques advocated back in 2001 become viable solutions. Unfortunately they have not been as widely accepted by utility operators or their contractors as they could have been. The implications for customers' health and child development can be seen with incidents such as Flint, and are most probably happening on a smaller scale in any country with lead supply pipes. Technology performance There have been significant availability and commercial improvements in techniques for pipe cleaning and lining over the last 15 years. This includes the ability to rehabilitate smaller diameter pipes. Improvements in pipe-bore cleaning techniques mean that the interior walls of supply pipes can now be prepared for lining to a higher standard. This means cheaper operational costs for utilities. Improvements in resin compounding mean better adhesion and improved curing times during epoxy pipelining installations. This results in a more homogenous lining than those trialled by the AWWA in 1999/2000. The capability to line smaller lead communication pipes at the same time as the customer's supply pipe means a much more efficient programme of works with less risk of unplanned activities or damage to customer's internal decoration, fixtures and fittings. For example, Serline by Aquam demonstrates these efficiency improvements and can now be shown to deliver the improvements in lead reduction expected by customers. Reducing risk A lead-reduction strategy should consider the risk ratio and cost benefit of a lead pipe replacement and lining programme targeted at private housing stock as well as public premises where high risk customers use a particular building, for example, nursery schools, ante-natal clinics, GP and midwifery practices. A lead-reduction programme of domestic properties with the highest public health risk, for example, where pregnant women and young children are resident, would start with detailed analysis to identify the likelihood of there being a complete lead service pipe in place. This would take account of property type, age and other factors. Analysis of water quality by water supply zone is unlikely to be sufficient to identify individual properties at risk in specific streets or postcode areas. An inspection of boundary stop-taps and possibly internal plumbing inspections would identify actual properties with lead pipes that are owned by the public utility company and need to be replaced or epoxy-lined. Graphic showing cut-out of three stages of pipelining Impediments - site Impediments - pipe condition Customer impact Mobility/space constraints Open trench replacement Yes (surface) No High (traffic, noise) Yes Replacement on new route Yes (utilities, soil) No Moderate (traffic) Yes Replacement along existing route Yes (soil) yes (bends, encrustrations) Moderate (traffic) Yes Slip-lining No Yes (bends, encrustrations, hydraulic capacity) Low Yes Pipe coating No Yes (structural, encrustrations) Low (curing time only) No