On January 22, 2001, the US EPA published a final Arsenic Rule in the Federal Register that revised the MCL for arsenic at 10 parts per billion. Two months later, in March 2001, the effective date of the rule was extended to provide time for the National Academy of Science to review new studies on the health effects of arsenic and for the National Drinking Water Advisory Council to review the economic issues associated with the standard. After considering the reports by the two review groups, the US EPA finalized the arsenic MCL at 10 parts per billion in January 2002. The final rule requires all community and nontransient, noncommunity (NTNC) water systems to achieve compliance with the rule by February 2006. Adsorptive media processes are capable of achieving that level.
How our system removes arsenic
Electric City uses the ATEC process which is an oxidation/filtration process wherin arsenic binds to iron oxide solids in the water and the arsenic-iron precipitate complex is filtered out. As the percipitate builds up in the filter, a backwash is required to remove buildup.
The first step in the process is to oxidize arsenic from its +3 state, called arsenite, to its +5 state called arsenate. Arsenate is more easily removed through this process. An oxidant (sodium chloride) is used to oxidize the arsenic. The addition of the oxident also oxidizes any iron and manganese in the water to precipitates that are filtered out.
The oxidized arsenic will bind to the iron oxide precipitate and the bound arsenic will be removed from the water by the filter media. Since there is insufficient amounts of naturally occuring iron in Electric City well water to successfully remove the arsenic, ferric chloride is added to the water.
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