Arsenic in well water has recently become a hot topic for some lower Fairfield County towns such as Weston, Wilton, and Redding. The discovery of arsenic - even at trace levels - can be unsettling. In reality; any private well in CT (or the world for that matter!) is susceptible to arsenic contamination. Arsenic is a semi - metallic, naturally occurring element and is colorless, odorless and tasteless when dissolved in water.
Arsenic in well water most often occurs as a result of the erosion or weathering of arsenic rich minerals. However, there are instances of groundwater contamination due to human activities such as mining and pesticide / herbicide application.
The original maximum contaminant level (MCL) of .050 mg/l was first established because prior to 1975, .050 mg/l was the lowest level of detection for arsenic (LLD) possible. Testing capabilities have since improved and in 2000 the president signed Public Law 106-337 to issue a deadline for lowering the arsenic MCL. The final mandate took effect January 23, 2006 at .010 mg/l.
Acute arsenic poisoning (exposure to higher concentrations over a short time frame) typically results in nausea, diarrhea, and stomach pains (much akin to food poisoning). Left untreated - it can be fatal. Chronic arsenic poisoning (continual exposure to low concentrations over a long period of time) symptoms are less dramatic. With sufficient duration of exposure; the results can be just as lethal. Arsenic poisoning has been linked to bladder, skin, liver, and lung cancers as well as skin lesions and ulcers. Visit; www.insmalldoses.org to learn more about arsenic in well water and the long term affects of exposure to even low concentrations of arsenic.
Removal options for arsenic in well water include ion exchange, reverse osmosis, coagulation / filtration, and arsenic - selective adsorbent medias or resins. Arsenic in well water is most commonly present in two main forms (species); arsenite (As III) and arsenate (As V). When considering removal options for arsenic in well water...it is important to verify how much arsenite (As III) and arsenate (As V) are present. Arsenite (As III) is considerably harder to remove, however, it is not uncommon to find both species present simultaneously in the same water supply.
Having a clear picture of overall water quality is essential because the presence of other contaminants can negatively impact the performance of the various arsenic removal technologies. Note that arsenic (AS) is positioned directly under phosphorous (P) on the Periodic Table of Elements. Arsenic and phosphorous are in the same chemical family. This close relationship lends itself to phosphates competing with arsenic for space on removal medias.
Water chemistry is critical to effective arsenic removal from well water. Start with a basic arsenic and potability test. If there is an arsenic presence;the next step is an arsenic speciation test that also checks silica, vanadium, and phosphates. After considering the jobsite conditions, size and demand of the home; a choice of appropriate technology can be made. Follow up testing is another crucial component of an effective arsenic removal and monitoring program.
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