Water Filtration and Treatment – Arsenic Removal

Arsenic in drinking water is a big concern and many are looking for water treatment and filtration solutions to remove this harmful contaminant from their well water.

The International Agency for Research on Cancer (IARC) classifies arsenic in drinking water as a known cause of cancer. As a naturally occurring mineral, there are known hot spots throughout the Atlantic Provinces (New Brunswick, Nova Scotia in particular) where drilled wells have levels that exceed the Health Advisory Limits (HAL) of 0.01 mg/L.

Removal Options

For proper removal, it is extremely important that a thorough water analysis be conducted to determine what other contaminants are present in the water. There are many factors that will determine the effectiveness of the arsenic treatment. Variables include:

Type of Arsenic:  Arsenite (As[III]) Vs.  Arsenate (As[V]). Because Arsenite has a neutral charge, standard Ion exchange methods will prove to be ineffective at removing this form of arsenic. Pre oxidation techniques may be used to convert the arsenite to arsenate which in many cases allow for a high conversion and removal rate.

Competing IONs: Most resins have a high affinity for other compounds such as Nitrates and Sulphates, which will reduce the reduction performance of arsenic. In these situations we have found it best to use both ION exchange resin in combination with  Adsorbent Media.

Additional Contaminants: For water supplies with high arsenic levels, the reduction of other present contaminants, such as Iron, Hardness and Manganese, must be considered. These contaminants will drastically affect the ability of ION exchange resin (Anion Resin) and must be removed if the levels are too high. Also, depending on the technology selected, pH must also be considered as it will impact the life expectancy and removal rates of GFO or adsorbent medias.

Testing

Once a system is installed, ensure the water quality is being monitored by frequent testing. Some technologies, if improperly maintained, can cause the post treatment water to have arsenic levels higher than the pretreatment level. For non regenerable media, testing will also indicate when the point of exhaustion has been reached. If using non regenerable solutions only, it is recommended that duplex filters be installed in a Lead-Lag configuration and testing be conducted between the two filters.  

Conclusion

There is much to be considered before choosing a system to treat for Arsenic in drinking water. There are many options and combinations of water filtration equipment for arsenic reduction. Choose a qualified and experienced company that is aware of the many options and can thoroughly explain their recommendation. There is no one size fits all water filtration solution when it comes to treating arsenic. Make sure a water quality guarantee is put in writing and check to see if all equipment and water treatment media is certified by NSF, WQA and UL.