Pipe scales release hazardous metals into drinking water
Michael Schock et al .
Mineral deposits inside drinkingIn recent years, corrosion withantimony was 27 ppb and rising. At water pipes can contain high levels in the distribution system has the time, the water at the treatment of hazardous metals, including arbeen blamed for high lead levels in plant met regulatory standards. senic, cadmium, and mercury, and Washington, D.C., drinking water; In Park City, changes in the the metals can contaminate tap high levels of arsenic, lead, and anflow rate caused the contaminawater when they are disturbed, actimony in Park City, Utah, drinking tion, says Scanlan. Similar changes cording to new research published water; and high levels of radon in can occur during high-demand in ES&T (pp 4285–4291). But curwater from systems in Iowa, Minperiods, for instance in the mornrent water-quality regulations miss nesota, and Florida. Apart from ing as households wake up or in such disturbances, the evening when because they call for people come home monitoring at the from work. Abrupt treatment plant bechanges in water fore the water enters chemistry as a result the distribution sysof a water treatment tem pipes. change can also reU.S. EPA corrolease contaminants, sion chemist Miaccording to Schock. chael Schock and These changes can colleagues analyzed potentially cause unlead pipe scales from detected, long-term 26 water systems intermittent expoand found unexsure to contaminants pectedly high accuin tap water. mulations of many “It is clear that hazardous metals. consumers are some The scales had arsetimes drinking water Pipe scales concentrate many different metals, often in different layers. Here, a crumbly outer layer (L1, inner L1) rich in manganese, iron, and alunic concentrations containing levels of minum overlays whitish and gray lead carbonate layers (L2, L3). as high as 426 parts contaminants that per million (ppm), are orders of magnimercury as high as 2 ppm, barium Washington, D.C., at the time of tude higher than those detected in as high as 2900 ppm, vanadium as the contamination, all of these syswater leaving the treatment plant,” much as 20,000 ppm, and cadmitems met water safety standards. says Marc Edwards of Polytechnic um up to 308 ppm. Mobilization of It is impossible to say how comInstitute and State University. these scales would cause drinking mon or significant such disturEPA could take action on this iswater at the tap to exceed federal bances are, because contamination sue as part of the ongoing review of water-quality limits. At the time that occurs within the distribution the Total Coliform Rule. An issue of sampling, almost none of the system isn’t monitored, according paper by consulting firms HDR Enutilities were in violation of waterto Rich Valentine, a University of gineering and Environomics indiquality regulations. In a few cases, Iowa engineer whose ongoing work cates that the problem is significant. lead and copper, the only inorganic is generating similar results. EPA’s Office of Water did not recontaminants currently monitored Contamination from water sysspond to ES&T queries for this story. at the tap, exceeded regulatory tems can be extreme, says former The experts contacted by ES&T standards. Utah Department of Environmenhave differing opinions about op“Our work shows that when cortal Quality chemist Larry Scanlan, tions for proceeding on this issue. rosion impacts water quality, it isn’t who investigated consumer comSome say that contaminants should just about the metal that makes up plaints in Park City, Utah, in 2000. be monitored at the treatment plant the pipe. Other metals can be mobiAfter determining that the source of and within the distribution system. lized as well,” says Schock. The recontamination lay within the disOthers say that with more research search is important, says engineer tribution system, Scanlan and colit should be possible to determine Vernon Snoeyink at the University leagues sampled drinking water at which water systems are vulnerof Illinois, because “it should open a fire hydrant and found that after able to such problems and then to people’s eyes to what may be lurk10 minutes of flushing, the drinkfocus attention there. All agree that ing in the water distribution sysing-water lead levels were 1370 the problem is real and currently igtem. Schock’s results could be the parts per billion (ppb) and rising, nored by water regulators. tip of the iceberg,” he adds. arsenic was 151 ppb and rising, and —REBECCA RENNER June 15, 2008 / Environmental Science & Technology ■ 4241
