The knowledge of arsenic as a poison goes way back to the time of Hippocrates, (460 – 370 BC). Purportedly Nero used arsenic to poison his stepbrother to get the top spot as Emperor of Rome. In the seventeenth century arsenic acquired the nickname “inheritance powder”, namely because wives were poisoning their wealthy husbands for their money. Even Hollywood was enamored with arsenic. A famous (still famous) movie called Arsenic and Old Lace appeared in 1944 starring Cary Grant. In this movie two kindly sisters were administering this poison of choice to bachelors to rid them of their “suffering due to loneliness”. And why shouldn’t arsenic be the poison of choice? After all it is, in fact, odorless and tasteless. Of course once a chemist discovered a method to detect arsenic in corpses, arsenic’s use as an effective, undetectable poison, greatly diminished in the seventeenth century, as word got around that you better try another strategy to become a rich widow.
From our perspective, we sure don’t want arsenic in our drinking water. The EPA (Environmental Protection Agency) has set the Maximum Contaminant Level (MCL) at 10 ppb (parts per billion), the enforceable regulation for arsenic. They (the EPA) also have a non-enforceable health goal which is concerned with exposure over a lifetime and possible health risks. This is called the Maximum Contaminant Level Goals (MCLG) and this is ZERO for arsenic. It should be noted that the EPA regulates public water sources but not well water. However, the EPA does recommend that well water should be tested on a regular basis for contaminants.
Regarding the effects of arsenic poisoning, for over a 50 ppb concentration in drinking water, skin lesions and cancers (lung, kidney, bladder, and skin) can arise. We will concern ourselves in this article with the inorganic species AS(III), called arsenite, and AS (V) called arsenate. Arsenite is fifty times more toxic than arsenate, increasing the probability of developing diseases attributed to arsenic.
So, how do we rid ourselves of arsenic in our drinking water? It’s a two-step process. First, we must convert the nasty soluble arsenite to arsenate. (Soluble means than the arsenite is easily dissolvable in water). This is accomplished using a chemical process called oxidation. There is a more arsenite than arsenate in groundwater that has about a neutral pH (neither acidic nor alkaline). Oxidation occurs by using ozone, chlorine, or potassium permanganate for fast and effective conversion of the arsenite to arsenate.
Next step is the removal of the arsenate from the water via techniques such as adsorption, ion exchange, use of membrane technologies like reverse osmosis (RO), or coagulation. Adsorption uses solids to remove the arsenic. Ion exchange works on the same principle as a water softener. The RO can be either POU (Point Of Use) or POE (Point Of Entry), with POU being usually an under the kitchen sink Installation for residential use. When considering buying hardware to remove arsenic the consumer must decide if they want a water treatment unit that converts the arsenite to arsenate and also then removes the arsenate. Or, maybe buy two separate units: one to do the conversion and one to remove the arsenate. The decision is of course dependent upon total price and space available for the water processing gear. Oh, one more thing, please be aware that the effectiveness of the water treatment hardware is usually dependent upon the pH of the water. So, make sure you ask the right questions before any purchases. For example, you need to know if you first have to adjust the pH, which involves acquiring additional hardware.
The overarching recommendation here is to first get your well water tested, particularly if you are aware of other locations in your neck of the woods that have a confirmation of the presence of arsenic.
– By Steven G. Karr PhD