Polyfluoroalkyl substances (PFAS) are a group of man-made chemicals that includes PFOA, PFOS, and many other chemicals. PFAS have been manufactured and used in a variety of industries around the globe, including in the United States since the 1940s. PFOA and PFOS have been the most extensively produced and studied of these chemicals. Both chemicals are very persistent in the environment and in the human body – meaning they don’t break down and they can accumulate over time. There is evidence that exposure to PFAS can lead to adverse human health effects.
The EPA is developing rules to limit discharge of these chemicals into the environment. The proposed rule calls for no more than 40 parts per trillion (ppt) in any discharge permit. The molecular weight of PFOS and PFAS are about 500 Daltons. The chemicals are large in comparison to regular dissolved inorganic salts such as Sodium and Chloride. Reverse Osmosis (RO) membranes have a molecular weight cut off of less than 100 Daltons and can easily reject very high percentages of these chemicals. Nanofiltration (NF) membranes can have a molecular weight cut off size from 100 to 1000 Daltons. So with the right size NF membrane, these chemicals can be rejected as well.
New Logic has experience with both PFOS and PFOA chemicals including two full-scale installations and several pilot tests. We conducted a pilot test for an American waste and environmental services company in North America. The facility accepts and treats a wastewater contaminated with firefighting foam, some fine suspended solids, and other contaminants. The compounds in the wastewater that are of highest concern are a collection of polyfluorinated compounds (PFOS). The VSEP would treat the effluent so that the permeate could be discharged while the VSEP concentrate would be solidified in a landfill. We tested both NF and RO membranes.
A RO membrane was used to filter the PFOS wastewater with an average flux of 23.0 GFD at 88.1% permeate recovery, operating at 500 psi and 25°C. A summary of the flux and recovery results and analytical information is shown below. The RO membrane was able to produce treated water with non-detect levels of PFAS materials.
In 2004 New Logic installed a full-scale system to treat a waste stream containing non-ionic surfactant, PTFE solids, PFOA, and other unreacted fluorinated monomers. The system operates with a flux rate of 16 GFD at 500 psi and 25ºC using a RO membrane. The RO permeate has 0.0% total measurable solids and very low conductivity. The 20% volume left as concentrate is sent to an incinerator for disposal.
In 2013 New Logic installed a four module VSEP RO system for a company that manufactures fire extinguisher and fire suppression chemicals. Groundwater contamination occurred resulting in levels of PFOS, arsenic salts, and herbicide materials. A groundwater remediation plan was activated and groundwater was pumped out to be treated by the VSEP system. The four module VSEP RO system processes 156 gpm of the contaminated groundwater and produces 80% of that volume as RO permeate. The remaining concentrate is hauled and treated for zero discharge.
The category of PFAS polyfluorinated materials covers a wide range of chemicals. PFOS and PFOA are only two of many. A recent pilot test was conducted testing for the entire range of PFAS materials. The table below shows the results of analytic testing measuring in parts per trillion (PPT or ng/L)
If you have PFAS challenges, consider VSEP.
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