Carbon filtration: A solution for PFOA and PFOS in private water supplies

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Posted on October 17, 2018

shutterstock_114598543.jpgPerfluorchemicals (PFCs), like PFOA and PFOS, are being discovered in groundwater sources throughout North America and causing widespread public concern over the safety of drinking water especially for private water well users.  Carbon filtration, mostly point-of-entry (POE), is commonly the solution but as with any water treatment, it is important to understand the pros and cons of this approach. 

PFCs are a large group of man-made compounds that have been used since the 1960s to make consumer products. PFCs can repel both water and oil, so they are put into products like non-stick cookware, fast food wrappers, stain-resistant clothing and carpeting, and water-proof foot-ware. Two PFCs which were very commonly used, perfluorooctanoic acid (PFOA) and perfluorooctane sulfanate (PFOS), have essentially been banned in the U.S. for more than a decade. Yet they are now being found in the soil and water supplies serving areas surrounding former manufacturing sites. Why now? The first reason is that these are very stable chemicals that can persist in soil and water for long periods of time. Secondly, at both the federal and state level, they have been classified as emerging contaminants, meaning there is recognition of their potential threat to human health. But, for the most part, binding environmental and health standards are lacking. Regulations, however, are catching up. Contamination sites are being discovered, especially as residential developments extend beyond city limits, and testing of public and private water supplies is becoming more and more common.

Whether or not a public water sample warrants a health advisory is largely dependent on jurisdiction, with some states targeting levels as low as 14 or 20 parts per trillion (PPT) while the current Health Advisory level established by the EPA is 70 PPT. Where there is an option to do so, public water utilities will blend supplies, like from two different wells, in an effort to dilute the contamination levels. But where that is not achievable, they are turning to large-scale carbon filtration systems.

Private well owners can turn to bottled water or install a home water treatment system including carbon filtration*. Typical household units will use granulated activated carbon (GAC) filters, either at a single tap (point-of-use or POU) or installed on the main water line supplying the whole home (point-of-entry or POE). The decision will depend on the level of PFCs detected. Carbon is an extremely effective means of removing organic compounds like PFCs, as they adsorb or “stick” to the carbon granules. However, those granules have a very irregular, creviced surface where any microorganisms in the water will flourish, feeding on nutrients in the water and other particles adsorbed by the carbon. This bacterial growth will plug and coat the activated carbon, which overtime will reduce the effectiveness of the filter and could introduce bacteria into your drinking water. As with any water treatment system, proper maintenance is key. Following the recommended schedule for replacing filter cartridges in POU/POE units and filter beds in non-back washable carbon tanks will minimize the risk of breakthrough contamination. Unfortunately, it’s not always easy to recognize when a carbon filter needs attention. There are no alarms, and unless contaminants can be smelled or tasted (which bacteria and PFCs cannot), only water testing will predict when breakthrough is likely to occur.

Installing an ultraviolet (UV) unit as the last stage in the treatment train is an easy and effective way to protect against shutterstock_400659769.jpgbacterial breakthrough. Including disinfection on groundwater supplies should always be considered essential. It is especially prudent after carbon units of the size and scope being employed to reduce PFCs.

If you have concerns about your water supply, even if you are not on a private well, consult a water treatment specialist. They will be able to assist in interpreting water test results and determine the right approach to protecting your water.


*Reverse osmosis is another technology that can be used to remove PFCs.