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Comparison of Bacteria and Color Removal in Two Surface Waters using Nanofiltration
Citation:
PATTERSON, C. L., A. ANDERSON, R. SINHA, N. MUHAMMAD, AND D. Pearson. Comparison of Bacteria and Color Removal in Two Surface Waters using Nanofiltration. Presented at AWWA WQTC Conference, Seattle, WA, November 15 - 19, 2009.
Impact/Purpose:
To inform the public.
Description:
Small communities typically have small budgets, but big issues to deal with in providing safe drinking water and protecting public health. Communities in remote locations are frequently faced with elevated levels of naturally-occurring organic matter (NOM) that combine with chlorine to form disinfection byproducts (DBPs). Additional treatment for removal of DBPs is often necessary to avoid non-compliance with the requirements of the Safe Drinking Water Act (SDWA). EPA conducted treatability studies on two surface waters in Ely, Minnesota with the Minnesota Department of Health (MDH) and in Cincinnati, Ohio at the U.S. EPA Test and Evaluation Facility. The surface waters were tested for removal of organic matter to determine their potential for disinfection byproduct formation. In collaboration with 4Membrane Systems Specialists, Inc. (MSS) (Formerly ITT Corporation (ITT) and FB Leopold Company), pilot-scale nanofiltration systems were shipped to MDH and EPA for studies on Fall Lake water in Ely, Minnesota and Mill Creek wastewater in Cincinnati, Ohio. ITT’s Fyne Process was tested using two nanofilters made of polyethersulfone and cellulose acetate. The system uses a tubular membrane with the ends connected to effectively form a single continuous membrane. The system requires no pretreatment of the feed water other than a coarse (3mm) screen to prevent large solids from entering the system. The lake water is fed into the inside of the membrane tube and the filtrate is forced out, through the membrane into the membrane housing outlet. The process uses a physical foam ball cleaning technique to minimize the use of chemical cleaners. A foam ball scours the inner tube wall of the nanofilter membrane to reduce pressure drop and to maintain system flow. Organic matter is flushed to drain as the foam ball passes through the inside of the tube. Fall Lake water and diluted Mill Creek wastewater were spiked with Bacillus Subtilis, an aerobic spore used as a surrogate for bacteria, to determine filter removal efficiencies. The effectiveness of the nanofilter membranes in producing drinking water was also gauged by measuring the turbidity, color, and particle counts at the system inlet and outlet. Tests were conducted in two modes of operation; with reject water recycled to the system inlet and in a dead-end mode. Samples were analyzed at EPA’s Biosafety Lab in Cincinnati, Ohio. This paper summarizes the capabilities of the Nanofilter membranes for removal of bacteria and color in surface waters.