Assessment of a Point-of-Use Ultrafiltration System for Turbidity and Microbial Pathogen Removal

U.S. EPA's Office of Research and Development has been evaluating the performance of point-of-use (POU) devices designed for use in homes and small businesses for many years. In collaboration with the University of Cincinnati, a series of pilot-scale tests were conducted on a Matrix Membranes ultrafiltration (MMUF) system at the U.S. EPA Test and Evaluation Facility in Cincinnati, Ohio. The MMUF system operates at a low flow rate (< 2 gpm) and feed pressure (< 30 psi). The polyethersulfone (PES) membrane (2" x 21") is designed for high flux rates with inside-out operation. Membrane integrity tests require the injection of compressed air (10 psi) into the closed system to check for breakthrough or air bubbles in the membrane. The MMUF system requires back-flushing when the filtrate flow drops 25%. The chlorine resistant membrane consists of 500 hollow fibers with 0.8 mm inner diameter and 1.50 mm outer diameter and contains 5.67 square feet of filter surface area. The membrane is cleaned with chlorine (2–200 mg/L) at pH 11 using sodium hydroxide. The membrane has an average pore size of 0.2 μm and a Molecular Weight Cut-off of 100,000. The research study evaluated removal of turbidity (2, 5, and 10 ntu) and microbial surrogates (3 micron polystyrene latex (PSL) beads, MS-2 bacteriophage, and E. coli). Other parameters of interest included system flux, runtime, raw water characteristics, and operating cost. Results are summarized and presented on turbidity and microbial removal efficiency.