The Use of Porifera Membranes for Urea Rejection in Forward Osmosis Systems

Forward Osmosis (FO) systems are used to produce clean water from wastewater due to an osmotic pressure difference across a semipermeable membrane. While it is important to have membranes that can produce high water flux and low salt back flux, it is also necessary for them to highly reject organic and inorganic contaminants present in wastewater. It is of our interest to evaluate membranes that can highly reject urea, the main component in urine, without fouling. Currently, there are no commercially available FO membranes that can reject urea. Porifera, Inc. manufactures high performance FO membranes with open-pore hydrophilic configuration with an excellent rejection layer. Porifera FO membranes have three times higher flux and more than three times lower salt passage than conventional cellulose acetate FO membranes. In this work, deionized (DI) water with urea at ppm level was used as feed, while calcium nitrate (Ca(NO3)2) at a concentration range of 5% to 15% w/w was used as draw solution. The performance of Porifera FO membranes was evaluated terms of water flux rates, salt back flux and urea rejection. Results confirm that Porifera FO membranes have high urea rejection and very low salt back flux.