Drinking water, lead distribution systems

In a more recent Lederal Register notice (EPA 1991d), EPA examined the occurrences of lead in source water and distributed water. By resampling at the entry point to the distribution system, few samples were found to contain lead at levels above 5 pg/L. EPA now estimates that approximately 600 groundwater systems may have water leaving the treatment plant with lead levels above 5 pg/L. Based on several data sets, it is estimated that less than 1% of the public water systems in the United States have water entering the distribution system with lead levels above 5 pg/L. These systems are estimated to serve less than 3% of the population that receives drinking water from public systems (EPA 199 Id). 

Lead levels ranging between 10 and 30 pg/L can be found in drinking water from households, schools, and office buildings as a result of plumbing corrosion and subsequent leaching of lead. The combination of corrosive water and lead pipes or lead-soldered joints in either the distribution system or individual houses can create localized zones of high lead concentrations that exceed 500 pg/L (EPA 1989f). 

Distribution Systems. A substantial amount of contamination of drinking water can occur while the water is in transit to the consumer after treatment. Pipes are made of copper, galvanized iron, asbestos-cement, lead, or plastic, and often polymeric or coal tar coatings are used. All of these are capable of contributing contaminants to the water, especially if the water is corrosive. Lead, copper, cadmium, and polynuclear aromatic hydrocarbons in finished water are primarily problems of water distribution and not source water contamination. Physical deterioration of the distribution system can also permit biological contamination to occur during transit. 

We can thus conclude that the amino acids do not represent a negligible part of the overall residual (10—30%). The amino acid release by filter in drinking-water may present a danger of bacterial proliferation in the drinking-water distribution system, since the carbon source is easily biodegradable. Such a hazard can be minimized by a superchlorination at the end of the treatment. However, previous [12, 13 ] and more recent [14, 15] research has shown that the action of sodium hypochlorite on ctamino acids rapidly leads to the formation of aldehydes and nitriles. Therefore, postchlorination only changes the problem to a more complex one. 

The composition and pH of water also affect the oxidation of lead metal. Modern drinking water treatment is highly effective at removing lead from water before it is pumped to the consumer most water contamination comes from corrosion in distribution systems, that is, lead pipes and lead-based solder (408). Under acidic or neutral conditions in the presence of oxygen, metallic lead is readily oxidized to Pb ", as can be seen from the equations below and from Figure 21 (48, 408, 409). 

Lead usually gets into our drinking water when the water absorbs the toxic element from our household plumbing systems or our water distribution systems. 

Water Distribution Systems Often Account for Lead in Drinking Water... 

Fixtures containing lead can also be a source of contamination, both in our water distribution systems and in our homes themselves. Brass fixtures, such as faucets, can contain up to 8% lead, some of which can leach into drinking water, especially when it has been sitting in contact with the brass for several hours or overnight. 

This procedure will tell you not only how much lead is in your drinking water, but also whether the lead is coming from your own plumbing or from the water distribution system, and how effective letting the water run for a couple or a few minutes is in controlling the amount of lead it contains. 

The major source of high concentrations of lead in drinking water is the dissolution of lead from lead pipes or lead solders used in the distribution system, known as plumbosolvency (Section 3.3.5). In Britain, it is estimated that roughly 7 million households have lead somewhere between the water main and the tap. Many households may thus be exposed to elevated levels of lead in their drinking water (Section 3.3.5). Attention is currently focused on possible remedial actions. 

Isaac, R.A., Gil, L., Cooperman, A.N., Huhne, K.I., Eddy, B., Ruiz, M., et al 1997. Corrosion in drinking water distribution systems a major contributor to copper and lead in wastewater and effluents. Environ. Sci. Technol 31, 3198—3203. 

Schock, M.R., Wagner, I. and Oliphant, R. (1996). The Corrosion and Solubility of Lead in Drinking Water. Internal Corrosion of Water Distribution Systems. AWWA Research Foundation/DVGW Forschungsstelle, Denver, CO, pp. 131-230. 

Corrosion of water distribution piping raises environmental concerns mostly due to the presence of lead, cadmium, zinc, and copper in drinking water. These metals enter the wastewater collection system and eventually accumulate in the sludge and end up in a landfill, on croplands, or other locations, depending on the disposal method. Metals corroded from water piping are the largest source of these contaminants in the wastewater of many communities. 

The water supply system serves a population of around 300,000 people with acknowledged high quahty drinking water. The Utility has 74,000 customer connections of which 26,000 (35%) are lead service lines (LSL), including the privately owned side. Additionally, the Utility provides water supplies to neighbouring Utilities that serve a further 300,000 people. Water is abstracted from a series of reservoirs and treated by rapid sand filtration with conventional chemical treatment before pumping into distribution. 

Lead makes its way into the water supply primarily through the use of old lead water pipes or lead solder in plumbing. Lead in drinking water can be a significant source of human exposure because of the large amounts of water consumed each day and the ready absorption of lead from water. Lead water pipes are common in older housing and the water distribution systems of older cities. The contribution of lead pipes to blood levels is well documented (ATSDR, 1988). Because soft water is likely to corrode metallic surfaces, lead water pipes are a significant source of lead exposure for people in soft water areas. It also appears that the water supply in the nation s public schools contains lead and thus provides an additional source of lead exposure. 

The United States Public Health Services drinking water standards specify a 50 mg/1 maximum for lead, EPA [73] has shown that this limit is only infrequently exceeded in larger United States cities. The presence of lead in drinking water may result from the use of lead materials in the water distribution system. Naturally occurring lead in rocks and soils may be an important source of contamination in isolated instances but lead from industrial wastes represent a local and not a widespread problem. The disposition of lead compounds from gasoline is a major source of lead in water systems [73]. 

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