Gas Permeable Membrane Selection Methodology for Wastewater Treatment and Resource Recovery

Abstract.

The use of gas-permeable ePTFE (Teflon) membranes in wastewater treatment and resource recovery has become a research topic but many of these membranes vary widely in specifications, characteristics, and performance. Further, these studies do not justify the specific membrane selection but simply describe performance of one membrane material. Operational considerations such as flowrate, permeability, pressure differences, and flux rate are impacted by manufacturing details and material properties. We describe three procedures that will test the performance of ePTFE membranes in pressure, flow, and flux under conditions specific to the application of interest—ammonia recovery from swine wastewater. We apply these procedures to select the material density and wall thickness of tubular membranes that will be suitable for a specific ammonia recovery reactor design. Tests included maximum hydrostatic pressure, the relationship between gas flow and applied pressure, and ammonia flux rate. Results revealed a small difference in NH₃ transfer rates among different membranes, leaving the membrane selection to rely on results of membrane durability and handing which are different for specific applications. These tests were successful in determining the optimal membrane for ammonia recovery in swine wastewater and can be modified for other applications of interest. Funding for this project was provided by NRCS CIG Award Number 69-3A75-12-183.