Laboratory and Field Evaluation of a Nanofilter Membrane to Remove Disinfection Byproduct Precursors and Microorganisms from Lake Water Sources Used for Drinking Water

Small community systems that use surface water as a source of drinking water are frequently faced with elevated levels of naturally-occurring organic matter (NOM) that are not removed by conventional filtration methods. These residual levels of NOM can then combine with chlorine used for disinfection and create disinfection byproducts (DBPs) that could potentially exceed the regulatory limit for various DBPs. Additional treatment for removal of these DBP compounds may be required for compliance with the requirements of the Safe Drinking Water Act (SDWA). The formation of DBPs can be prevented by removing NOM which act as DBP precursors. This paper presents the results of experiments conducted on two nanofilter membrane systems with a patented method for cleaning the membrane using a foam ball. The tests were conducted at the U.S. EPA Test & Evaluation (T&E) Facility (using dechlorinated potable water with the addition of humic acid to simulate NOM) and at a field site using lake water. The treatment system uses a tubular membrane with the ends connected to effectively form a single, long, membrane. A foam ball is periodically passed through the inside of the membrane by reversing the flow direction to scour the membrane surface and remove accumulated organic matter capable of fouling the membrane surface. This organic matter is then discharged by back-flushing the membrane. The effectiveness of the system in producing drinking water was gauged by measuring the turbidity, color, and organic content of the system inlet and outlet. Tests were also performed using the aerobic spore Bacillus subtilis (B. subtilis) as a surrogate for bacteria removal and MS2 bacteriophage as a surrogate for virus removal.