Low-pressure volume retarded osmosis for removal of per- and polyfluoroalkyl substances

Forward osmosis is an energy efficient process that is capable of recovering high-quality water from secondary wastewater treatment. However, regeneration of the draw solution (DS) is a problem that needs to be addressed. Herein, we developed and optimized a one-step process that does not require additional treatment for the DS. This process, called pressure assisted-volume retarded osmosis (PA-VRO), utilizes naturally occurring pressure with the aid of a small inlet pressure (< 1 bar). Poly(styrenesulfonate) was employed as the DS, for its high solubility in water and large molecular size (∼70,000 Da). Accordingly, real wastewater was employed as the feed solution for 48 h to remove perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) through PA-VRO. The rejection rates for PFOA/PFOS and poly(sodium-4-styrenesulfonate) (PSS) were observed to exceed 98%, after 24 h and 99%, after 48 h. Moreover, there were no traceable amounts of PFOA/PFOS in the DS, and hence the detected concentrations of PFOA and PFOS can be attributed to the residuals from the equipment. Therefore, this well-optimized PA-VRO process can be utilized for potable water production from treated wastewater.