Arsenic is a contaminant that creates known health risk to humans when consumed. The two main conditions that determine the behavior of arsenic in water are its oxidation state or valency and the pH of the water. Normally, aerated surface waters contain arsenate (As V) while the reductive well waters contain arsenite (As III) due to low oxygen levels in most ground water sources.
How Arsenic contaminates our Drinking Water?
Arsenic exists naturally in nature in areas with natural deposits of metalloids and in areas where ancient rock formations are present. It enters ground water sources through soil erosion from man-made activities using some as wood preservative, petroleum production, semi-conductor manufacture or due to misuse of animal feed additives and arsenic-containing pesticides. Since soluble arsenic is tasteless and colorless, a chemical water analysis is needed to detect its presence in any water sources because it poses a level of risk to human when consumed.
Arsenic exists in two valency forms known as Arsenic III (Arsenite) and Arsenic V (Arsenate) of which a chemical analysis called speciation is needed to identify what valency form is present in a water sample.
In private wells that are susceptible to Arsenic contamination, the substance can easily react with other elements in the oxygen-depleted environment of most ground water sources to form inorganic as well as organic compounds; the inorganic by-products are considered more toxic than the organic forms.
The inorganic forms of Arsenic exist in potable water sources in two valency forms known as Arsenic III (Arsenite) and Arsenic V (Arsenate) of which a chemical analysis called speciation is needed to identify what valency form is present in a water sample.
Arsenic that exists in the valence form of Arsenic III (Arsenite) is not easily removed from water unlike when it exists as Arsenic V (Arsenate). An oxidation process is required to change Arsenic from As III to As V which can be accomplished using chlorination or with ozone.
What Are the Regulations Around Arsenic in Tap Water?
Arsenic when consumed poses a level of risk to humans which is why the amount of arsenic present in water is governed by multiple government agencies.
The most recognized arsenic regulation around the world is the U.S. EPA’s Maximum Contaminant Level (also known as MCL). According to the standard set by the government agency which aligns with most health authorities around the globe, municipal water systems must legally limit their drinking water arsenic levels to less than 10 ppb (parts per billion).
Private well owners have the sole responsibility of ensuring that the level of arsenic in their water is at safe levels and this will require periodic testing at an accredited laboratory.
At Aqtros Water, we can have your water tested at one of our accredited affiliate laboratories if you need to determine the arsenic level in your water sample.
How can Arsenic be removed from Drinking Water source?
It is important for consumers to know that Arsenic cannot be removed from water by simply boiling it when you get a boil water advisory announcement. When water is boiled, some of the water molecules is evaporated and this will simply increase the concentration of the arsenic in the water.
There are several water filtration systems that are designed specifically for arsenic removal to achieve safe drinking water. Some of the techniques are discussed below:
- Anion exchange resins: This process involves the use of premium anion resins to initiate an anion (or ion) exchange process to trap arsenic in a media bed. The media will require periodic backwashing and regenerations when it is saturated with arsenic. Most anion resin beads used in most system will need to be replaced once every six to eight years.
- Reverse osmosis systems: The water will need to flow through multiple filtration phases which includes an activated carbon filter and a semi-permeable membrane. The reverse osmosis membrane used for Arsenic removal must have third-party certifications for arsenic removal and most NSF certified reverse osmosis membranes can remove up to 99.99% total dissolved solids, including arsenic.
- Distillation: This process involves boiling water in a controlled chamber and allowing the steam to condense leaving all the impurities including arsenic behind to be removed. High purity waster is achieved through distillation and the condensate is collected in a separate chamber for use.
- Activated alumina filters: These filters use an activated alumina filtration media to adsorb arsenic from the water as it flows through it. For effective arsenic removal, a power oxidant such as hydrogen peroxide or chlorine is needed to convert arsenic from Arsenic III to Arsenic V for it to be easily adsorbed.
- Manganese Greensand Plus Filters: Most filtration system that have Manganese GreensandPlus media have filtration and oxidation capabilities which allow Arsenic, Hydrogen sulphide and Iron to be removed but for the best arsenic removal, an oxidation pretreatment using chlorine or ozone will ensure all arsenic is completed remove from the water sample.
- Kinetico Arsenic Guard with UltrAsorbTM Filtration media: These filters use Kinetico patented UltrAsorbTM Filtration media to remove Arsenic completely from water. Our Kinetico Arsenic Guard filtration system requires chlorine pretreatment for all Arsenic III to be fully converted to Arsenic V to be effective in removing all Arsenic in the water, making it safe to use.
