Technology Update
Existing technologies can remove arsenic, but at a cost of Iowa, who chaired a 1997 committee on arsenic for EPA's Office of Research and Development. Although the 1996 Safe Drinking Water Act Amendments required EPA to propose a new arsenic standard by Jan. 1, the agency is delaying its announcement until early spring, according to a spokesperson. EPA has been evaluating nine potential treatment technologies witii removal efficiencies ranging from 50% to more than 95% (see Table 1). As is typically the case with water treatment, the size of the water treatment facility, as well as the chemistry of its source water and the mix of treatment technologies it already employs, will dictate which new treatment options are most appropriate. In general, it looks as if coagulation treatment with ferric chloride, ferric sulfate, or alum will work very well for large water treatment facilities that must cope with arsenic in the form of As(V), Schnoor said. Scientists in EPA's Office of Drinking Water stress that it is much easier to remove As(V), which is generally found in oxygen-rich surface waters, than As (III), the form of arsenic usually found in groundwater. For that reason, they recommend that water treaters oxidize As(III) to As(V) before TABLE 1 attempting to remove it. Technologies for removing arsenic from The seven novel technologies that EPA is indrinking water vestigating for attacking The performance of arsenic removal technologies varies widely. arsenic require more testing stressed Amit Maximum Kapadi,a an environmenpercent removal Treatment technology tal engineer with EPA's Ion exchange 95 Office of Groundwater Activated alumina 90 and Drinking Water The This spring, EPA is widely expected to propose reducing the levels of arsenic allowable in drinking water. In anticipation, the agency's scientists have identified more than a dozen methods for removing greater amounts of the known human carcinogen from water, including some new technologies. In March 1999, the National Research Council (NRC) published a report recommending that the current standard of 50 parts per billion (ppb) be lowered "as promptiy as possible" because it was not sufficiently protective of public health (ES&T 1999, 33 (9), 188A). This NRC report is expected to form the scientific basis for EPA's new proposal, according to agency literature. Because ingestion of arsenic is associated with cancers of the bladder liver and skin the World Health Organization (WHO) recommends that drinking water contain no more than 10 ppb and Canada's maximum allowable concentration is 5 ppb The maximum contaminant level (MCL) that EPA is likely to propose will be between 2 ppb and 20 ppb, based on the WHO and Canadian studies, according to Jerald Schnoor, Distinguished Professor of Environmental Engineering at the University
Reverse osmosis Coagulation-assisted microtiItration Modified coagulation filtration Modified lime softening Point-of-use reverse osmosis/activated alumina Point-of-entry activated alumina Oxidation/Filtration (including greensand filtration) Source: EPA Draft, 1999.
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ally used for iron and manganese removal, is among the most promising, Kapadia said. Four of the novel technologies are similar
to those being developed for removing arsenic from the highly contaminated wells in Bangladesh because they use iron. Some sound quite promising, like sulfur-modified iron, which is currently undergoing pilot testing in Reno, Nev. The technology has the potential to remove total organic carbon and disinfection byproducts and should be priced competively at $300 per acre-foot, according to its inventor, Pete Santina, who is president of SM,, Inc., of Walnut Creek, Calif. When the proposed standard is announced, it will likely be controversial, Schnoor said. The Natural Resources Defense Council, which has been pushing for a stricter standard, is planning to publish a report critical of the existing standard, called Arsenic and Old Laws, sometime early this year. Most environmentalists feel that, because there are clearly adverse health effects from consuming more than 100 ppb of arsenic, the 50-ppb standard does not provide enough of a safety margin, Schnoor explained. About 2.4 million people in the United States currentiy drink water containing more than 20 ppb of arsenic, said Andrew Schulman, a statistician with EPA's Office of Groundwater and Drinking Water. To date, however, this population has not reported adverse effects from the exposure, Schnoor noted. "That doesn't mean the [health effects] are not tiiere," he stressed. Drinking water providers are concerned about the potential cost of the new technology. The American Water Works Association estimates that meeting an arsenic standard of 10 ppb would affect 2200 water supply systems and could cost $1 billion per year. There are natural geochemical sources of the element around Los Angeles, as well as in Arizona and New Mexico. Some rural wells in Michigan, Indiana, and Maine are also contaminated with arsenic, and the ruling may force a number of waste sites to be re-evaluated Schnoor said.
FEBRUARY 1, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS » 7 5 A
