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- Title
Arsenic treatment considerations
- Authors
Edwards, Marc; McNeill, Laurie S.; Clifford, Dennis; Chen, Hsiao-wen; Frey, Michelle W.
- Abstract
Arsenic is bad medicine. It is classified as a human carcinogen, andit must be reduced to low concentrations in drinking water. The maximum contaminant level (MCL) mandated for arsenic in drinking water isnow 50 5g/L; the revised MCL goal is expected to be considerably less than that-2-20 5g/L. A lower arsenic MCL will mean that some utilities may need to modify their treatment process. What's the best way to do this? The 'best way'-i.e., the lowest-cost effective method-depends on the particular circumstances of individual treatment plants. Characteristics of both the influent (type of arsenic present, parameters such as hardness and pH, and other compounds in the water) and the effluent (toxicity of residuals) must be considered. Results of theNational Arsenic Occurrence Survey show that groundwater tends to contain more arsenic than surface water; that an average of more than athird of arsenic is in particulate form and removable by filtration;and that of the two most common arsenic species, arsenate is easily removed and arsenite-the more toxic form-is much less abundant. Surface water with high concentrations of arsenic tends to contain higher concentrations of chloride, sulfate, and total dissolved solids. High-arsenic groundwater, in contrast, tends to contain higher concentrations of iron and manganese. The least expensive way to remove arsenic, by a wide margin, is to modify conventional treatment (coagulation, lime softening, or Fe-Mn removal); the most expensive way is to usereverse osmosis. But the most cost-effective process that reduces all constituents of concern and produces a residual that is easily disposed of must be determined site by site.
- Subjects
DRINKING water; METHODOLOGY; SEWAGE purification
- Publication
Journal: American Water Works Association, 1999, Vol 91, Issue 3, p74
- ISSN
0003-150X
- Publication type
Article