Part of Metals and Related Substances in Drinking Water Set - buy all five books together to save over 30%! Visit:http://iwapublishing.com
The Best Practice Guide on the Control of Lead in Drinking Water brings together, for the first time, all of the regulatory, health, monitoring, risk assessment, operational and technological issues relevant to the control of lead in drinking water. Its focus is Europe and North America and the Guide benefits from the input of an international research network involving 28 countries. A large range of illustrative examples and case studies are provided. The Guide will be of interest to scientists, engineers, regulators and health specialists who are involved in the provision of safe drinking water.
The reader will gain a comprehensive understanding of how to assess lead in drinking water problems, both in the water supply systems that serve a City, Town or rural area and at individual properties, dependent on their knowledge of pipe-work circumstances and water quality. Options for corrective action are outlined and their strengths and weaknesses explained, with information on costs and environmental impact. The reader should then be able to develop a strategy for controlling lead in drinking water in their area, establish an appropriate monitoring programme, select the right combination of corrective measures, and define the level of risk reduction that will likely be achieved.
The Best Practice Guide provides a succinct compilation of the wide range of issues that relate to lead in drinking water, at a time when the regulations are under review in both Europe and North America. It will also be very relevant to all those implementing the Protocol on Water and Health, as lead in drinking water has recently been adopted as one of the key issues requiring assessment, improvement planning and reporting.
The key features are:
- For the first time, all the complex inter-related aspects of lead in drinking water have been brought together.
- The detailed explanations given on sampling and monitoring should avoid mistakes being repeated.
- The information on optimising corrective treatment measures is the most comprehensive to date.
- The Best Practice Guide will facilitate the protection of water consumers from lead contamination and reduce associated health risks.
This Guide is one of a series produced by the International Water Association’s Specialist Group on Metals and Related Substances in Drinking Water. It is a state-of-the-art compilation of the range of scientific, engineering, regulatory and operational issues concerned with the control of lead in drinking water.
Download the free Guide for Small Community Water Suppliers and Local Health Officials on Lead in Drinking Water at:http://iwapublishing.com/books/9781843393801/guide-small-community-water-suppliers-and-local-health-officials-lead-drinking
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Read an Excerpt
Sources of lead in drinking water
1.1 Water resources
With rare exception all source waters have relatively low lead. Ground-waters generally have very low lead and river waters sometimes contain detectable lead from industrial discharges or acidic mine drainage. However, even in these cases, much of the lead is removed by water treatment.
1.2 Distribution systems
The water mains used to distribute drinking water have normally been constructed from cast-iron, ductile iron, asbestos cement and, more recently, from plastics (for example, MDPE: medium density polyethylene). Leaching of lead from these materials does not normally occur. Very exceptionally, lead water mains have been used to distribute drinking water. The only known occurrences are in Ireland where their replacement has high priority (Devaney, 2009).
1.3 Lead pipe service connections
The connection between the water main and the buildings where drinking water is consumed (houses, apartments, institutional buildings and industrial premises) was commonly made using a lead, lead-lined or lead-alloyed service pipe in many countries up until the early 1980s. Lead pipes were used because of their resistance to corrosion (compared to iron) and their malleable nature which minimised fracture and leakage under changing ground conditions.
Lead service pipes often supply a single building, in which case the internal pipe diameter is commonly 12 mm. Larger pipe diameters, up to 38 mm, are used for connections to multiple dwellings such as apartment blocks. Intermediate diameters are used for shared connections to a small group of dwellings. The length of the lead service pipe is dictated by the location of the water main and the depth of property frontage. The typical length in an urban/suburban environment will be between 5 and 100 metres. In rural environments, lengths up to 300 metres have been encountered.
Lead pipe "pig-tails" and "goose-necks" were also used to join other pipe materials, but the lengths involved should be limited to a few metres.
1.4 Domestic lead pipe-work
Lead pipes were also used extensively within buildings to convey drinking water to points of use. However, it is likely that their use was largely superseded by copper piping from the 1950s. In some countries the lead pipes within domestic dwellings have been gradually replaced by copper or plastic during refurbishment, particularly in the modernisation of kitchens. However, in some countries it was common practice to bury internal pipes within walls and their replacement has occurred much less. The variable configuration of pipe-work at a single dwelling is illustrated by Figure 1.1.
Taking lead service pipes and internal lead pipe-work together, the extent of occurrence varies nationally, in Europe, from <5 to 50% of domestic dwellings (see Section 5.2) and it is possible that in the older districts of many Cities and Towns, the percentage of dwellings with a lead pipe might be much higher, possibly up to around 90%. "Legacy" lead can also be present in non-lead domestic or institutional pipework (such as old galvanized steel or copper). Lead can accumulate in the pipe scales or pipe-work sediments for decades of exposure to upstream lead sources, even those releasing relatively low concentrations of lead into the water.
1.5 Brass fittings containing lead
Brass fittings have been used very commonly in conjunction with copper pipe-work, as elbows, connectors and valves. Brass manifolds have also been used to distribute drinking water to a group of dwellings from a single mains connection. Water meters, pressure control, and flow control devices have historically also been commonly made from leaded brasses. In the US, there is a relatively small number of brass service lines reported, primarily in the northeast and midwest areas. They were apparently mostly installed in a block of time over the later 1920's, though records are very poor about this.
Brass is an alloy containing copper, zinc and lead, the latter component conferring better machining qualities. Brass is considered to be "lead-free" in the US if the lead content is <8%. New brass alloys with minimal lead contents, or those certified against recent stringent leaching standards in the US and Canada, should not pose problems with lead leaching. However, there are recent examples of very high lead contents (80%) at the internal surface of brass manifolds, albeit with a general lead content of around 7%, presumed to be due to poor moulding. In this situation, lead leached to 800 µg/l after 8 hours water contact and 1,600 mg/l after 16 hours water contact (Hepple, 2008).
1.6 Galvanic corrosion of solders containing lead
Solder has also been used very commonly in the jointing of copper pipe-work. If the solder contains lead and if the solder is exposed to water flow at the joint, sacrificial corrosion of lead can occur as a consequence of galvanic (electro-chemical) effects. The use of lead-containing solders was banned in Europe and North America from the early to mid-1980s.
Galvanic corrosion can cause high, and often erratic, concentrations of lead to leach into drinking water. Lead leaching even from very old solder that has been well-passivated, can spike dramatically in response to certain changes in water treatment that affect galvanic corrosion. These changes generally involve treatments that increase the chloride to sulphate mass ratio of the water (Edwards and Triantafyllidou, 2007) including changes in coagulant from ferric sulphate or alum to ferric chloride or polyaluminum chloride (Renner, 2006), chloride based anion exchange, and desalination. In rare cases the lead can remain high for the long term.
Low pH and aggressive anion gradients in the proximity of wrapped solder joint galvanic connections can also locally mobilize high concentrations of dissolved and particulate lead.
Historically, some plasticizers associated with plastic pipes contained lead and leaching of lead into drinking water was found to be possible. Such plasticizers are not now used and while the problem is detectable it is not associated with high level lead leaching.
1.8 Soluble and particulate lead fractions
The principal mechanism for lead leaching from lead pipes to drinking water is the dissolution (or sloughing) of the corrosion film that forms on the inside surface of the pipes. The most common initial oxidation product of lead metal, divalent lead oxide, rapidly converts to lead(II) carbonate or lead(II) hydroxy-carbonate compounds in the presence of carbonate or bicarbonate ions in the water. Divalent lead carbonate and hydroxycarbonate solid phases have low solubility, dependent upon the pH, alkalinity and temperature of the water. However, equilibrium solubilities may easily exceed 0.1 mg/L at even circumnerutral to slightly basic pH, and thus greatly exceed modern day drinking water lead standards. Figure 1.2 illustrates the importance of pH in determining lead concentrations, particularly for low alkalinity waters. The interrelationships amongst pH, alkalinity, dissolved inorganic carbon (DIC), and orthophosphate with respect to plumbosolvency have been extensively studied and reviewed, and the results have been shown to be highly reliable in predicting treatment targets and strategies for plumbosolvency in the pH range of approximately 7 to 9.5 (Schock, 1989; AWWARF, 1990; Schock et al., 1996; Schock and Lytle, 2010). However, it should be appreciated that pH elevation alone will often not meet the modern-day standards for lead in drinking water in many water supply zones, particularly if high numbers of lead service lines are present.
In some water supply areas, problems are experienced with the corrosion of old cast-iron water mains, such that iron (red-water) discolouration can become an aesthetic problem with iron concentrations exceeding several parts per million (mg/l). In such cases, the loose iron corrosion deposits can settle within a lead pipe and absorb lead; it is likely that this absorption enhances lead dissolution from the lead corrosion deposit as the equilibrium concentration for the dissolved lead is given less opportunity to be realised. Any disturbance of the loose deposits, such as the scouring effect of high flow, can cause elevated concentrations of lead in the drinking water. As an approximation, lead concentrations can double as a consequence of the interaction with loose iron deposits. Particulate lead may also arise from the physical sheer of pieces of the lead corrosion deposit from within the lead pipe, as a consequence of physical damage (as can occur in partial lead pipe replacement). Vibration from heavy road traffic might also cause pieces of the lead corrosion deposit to sheer. There is some evidence (Cardew, 2009) that the lead corrosion deposits are less stable physically in areas with low alkalinity and organically coloured waters, and that ortho-phosphate dosing has improved stability with associated less occurrence of particulate lead.
There is strong evidence that natural organic matter, particularly the humic and fulvic acids associated with colour, increases the dissolution of lead from lead pipes (Cardew, 2009) by up to ten times (Hayes and Skubala, 2009a). This can be explained by chelation of the lead by the poly-anionic organic matter. In consequence, ortho-phosphate doses must be higher for reducing lead dissolution in waters which have an appreciable organic content (> 3 mg/l TOC). Organics from sewage effluent and algae can also increase lead dissolution.
2.1 World Health Organization guidelines for drinking water
The third edition of the World Health Organization's (WHO, 2004) Guidelines for Drinking Water (and subsequent revisions) includes a guideline for lead and recommendations for drinking water safety planning, both of relevance to this Best Practice Guide (the WHO guidelines also extend to many other aspects of drinking water). Drinking water safety planning is strongly advocated in the Bonn Charter (IWA, 2004).
WHO guideline for lead in drinking water
The toxicity of lead is well established and the WHO has established a provisional tolerable weekly intake of 25 µg/kg body weight (equivalent to 3.5 µg/kg body weight/day). Using the weight of an infant of 5 kg, a consumption of drinking water of 0.75 litres/day and an exposure contribution of 50% from drinking water, WHO has established a guideline value of 10 µg/l for lead in drinking water (WHO, 2004), as a weekly average concentration.
The way in which this guideline value should be implemented is not specified. However, it is generally assumed that this guideline value applies at individual dwellings and to their individual occupants, as it is aimed at health protection.
The Bonn Charter
The Bonn Charter for Safe Drinking Water was published in September 2004 by the International Water Association. Its goal is "good safe drinking water that has the trust of consumers". It is aimed at all stakeholders from governments to consumers and sets out the principles of an effective framework for managing drinking water quality and the responsibilities of key parties.
Its key principles are:
(1) Management of the water supply chain must be holistic.
(2) Systems to ensure drinking water quality should not only be based on end-of-pipe verification and should incorporate risk assessment and risk control.
(3) Close cooperation is required between all stakeholders.
(4) Communication between stakeholders should be open, transparent and honest.
(5) Roles and responsibilities must be clearly defined.
(6) Decisions about standards should be transparent.
(7) Water should be safe, reliable and aesthetically acceptable (albeit standards may vary regionally and over time).
(8) The price of water must not be prohibitive in meeting fundamental domestic needs.
(9) Assurance methods should be based on "best science" and be sufficiently flexible to meet different regional situations.
The Charter proposes a framework for the delivery of safe and reliable drinking water, incorporating the development of water safety plans and the measurement of drinking water quality against relevant standards. The framework is illustrated in Figure 2.1.
The Charter specifically draws attention to its support of water safety plans as described by the WHO in their 3rd Edition of Drinking Water Quality Guidelines and will provide a foundation for significant improvement in water supply, worldwide. It reinforces the view that effective plumbosolvency control must be holistic.
Drinking water safety planning
The WHO Guidelines (2004) devote an entire chapter to the topic of drinking water safety planning. It is recommended that a risk assessment and risk management approach should be implemented in the design and operation of water supply systems, additional to the verification of water safety by sampling. The risk assessment and risk management approach should extend from "source to tap", that is, the entire water supply chain. This is considered further in Chapter 6 in the context of risk assessment in plumbosolvency control.
The key steps in developing a water safety plan are:
(1) Assemble the development team.
(2) Document and describe the water supply system.
(3) Undertake a hazard assessment and risk characterization.
(4) Prepare a flow diagram to illustrate the system and the risks identified.
(5) Identify control measures.
(6) Define how the control measures will be monitored.
(7) Establish verification procedures.
(8) Develop supporting programmes (e.g.: training, upgrade and improvement, R&D).
(9) Prepare management procedures.
(10) Establish document control and communication procedures.
In the context of plumbosolvency control, drinking water safety planning should focus on:
(1) The extent of occurrence of lead pipes in the water supply system.
(2) The corrosivity (plumbosolvency) of the water supplies to lead, as influenced by pH and alkalinity.
(3) The extent of exacerbation of plumbosolvency by natural organic matter.
(4) The extent of iron discolouration and its potential for particulate lead problems.
(5) The adequacy of controls over brass fittings and solder.
The elements of the water safety plan should also focus on the issues related to lead pipe replacement, including particulate lead, and the potential galvanic effects of partial lead service replacement.
2.2 EU drinking water directives
The first EU Drinking Water Directive (80/778/EC) set a standard for lead in drinking water of 50 mg/l, qualified by the words "in running water". Most Member States interpreted this as meaning that either the standard applied to the water flowing through the distribution network (before contact with lead pipes) or it applied to samples taken after flushing from consumer taps. Unsurprisingly, very few or no problems with lead in drinking water were identified in these Member States.
The two principal exceptions were: (i) the UK, which implemented the standard on the basis of random sampling (see Chapter 3) and found that corrective actions were required in some areas, particularly in areas with low alkalinity water, and (ii) the Netherlands, where wide-spread reductions in plumbosolvency were initiated by pH elevation and centralised water softening.
Presently, the Member States of the European Union have to comply with the second Drinking Water Directive (98/83/EU), which became a legal requirement from December 2003 (unless a derogation applies to a new Member State). It sets an interim standard for lead in drinking water of 25 µg/l and a standard of 10 mg/l that becomes a legal requirement from December 2013. Both standards relate to the average weekly concentration of lead ingested by consumers, the same basis as the WHO guideline value.
The Directive requires:
Article 6(1): that the parametric values set for lead shall be complied with, in the case of water supplied from a distribution network, at the point, within premises or an establishment, at which the drinking water emerges from the taps that are normally used for human consumption.
Article 7(1): that samples should be taken so that they are representative of the quality of the water consumed throughout the year.
Annex I, Note 3 of Part B: that the parametric value applies to a sample of water intended for human consumption obtained by an adequate sampling method at the tap and taken so as to be representative of a weekly average value ingested by consumers; where appropriate the sampling and monitoring methods must be applied in a harmonised fashion to be drawn up in accordance with Article 7(4); and, Member States must take account of the occurrence of peak levels that may cause adverse effects on human health.
Annex 1, Note 4 of Part B: that Member States must ensure that all appropriate measures are taken to reduce the concentration of lead in water intended for human consumption as much as possible during the period needed to achieve compliance with the parametric value.
Excerpted from "Best Practice Guide on the Control of Lead in Drinking Water"
Copyright © 2010 The Authors.
Excerpted by permission of IWA Publishing.
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Table of Contents
Contents: Sources of lead in drinking water; Regulatory background; Sampling and monitoring; Health perspectives; Evidence of problems with lead in drinking water; Risk assessment and health surveillance; Lead pipe replacement and other engineering options; Corrective water treatment; Control of materials;Investigational methods;Economics of plumbosolvency control; Case studies