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MODIFYING IRON REMOVAL PROCESSES TO INCREASE ARSENIC REMOVAL
Citation:
Sorg*, T J. MODIFYING IRON REMOVAL PROCESSES TO INCREASE ARSENIC REMOVAL. Presented at AWWA Water Quality technology Conference, Nashville, TN, 11/11-14/2001.
Description:
Iron and manganese are naturally occurring substances that are normally found in insoluble forms in many ground waters in the US. Similar to iron and manganese, arsenic also occurs widely in the earth's crust and is a natural contaminant of many ground waters. Iron and manganese have no known health efects, but can cause aesthetic problems in drinking water when oxidized. Arsenic does have health effects. Under the requirements of the 1974 Safe Drinking Water Act (SDWA), EPA established a maximum contminant levels (MCL) of 0.05 mg/L for arsenic and a secondary maximum contaminant levels (SMCL) of 0.3 mg/L for iron and 0.05 mg/L for manganese. Because arsenic is associated with common iron ores in the natural environment, arsenic and iron frequently occur rogether in ground waters. Concentrations of iron and manganese exceeding the SMCLs are common in Midwest ground waters. To reduce iron and manganese levels to below the SMCLs, mahy water utilities have installed iron/manganese (Fe/Mn) removal treatment systems. Becaue iron is an excellent adsorbent for the removal of arsenic, arsenic in the finished waters generally does not exceed the current arsenic MCL. Now that the arsenic MCL is being lowered by EPA, many of these water utilities have found that the arsenic concentration in their finished water could present a compliance problem, particularly if the arsenic MCL is revised to 0.01 mg/L as proposed. Many published studies have shown that iron coagulation followed by filtration is a very effective mechanism for removing arsenic. New iron based media and modified (with iron) activated alumina media are adsorption media that also utilized the arsenic adsorption capability of iron to treat for arsenic removal. Removing naturally occurring iron from arsenic-laden sources can result in arsenic removal.