Development of Antimicrobial Surfaces on Silica Media to Enhance Bacteria and Virus Removal and Inactivation During Filtration
Abstract:We report on progress made in the development of a novel point-of-use filtration medium coated with a quaternary ammonium compound (QAC). QACs are surfactants that have been studied previously as effective antiseptics and disinfectants against bacteria and viruses. In our study, a silanized QAC, containing a positively charge nitrogen group surrounded by 4 organic substituents, was covalently bonded to silica sand and evaluated as a filtration medium. Columns of the coated silica sand were challenged with several types of microorganisms in varying water quality. These columns were shown to cause up to 6-log removal (99.9999%) of Escherichia coli, 4-log removal (99.99%) of MS2, 1-log removal (90%) of PRD1, and 1.95-log removal (∼99%) of poliovirus under the conditions tested. As expected based on filtration theory, removal increased with an increase in column length and decrease in velocity. Removal decreased over the course of an experiment, however, due to fouling by cell residues. Furthermore, reduced source water quality, represented by the presence of 20 mg/L of natural organic matter (NOM), quickly caused column fouling. A prefilter of iron oxide coated sand or activated carbon placed before the QAC-coated media effectively removed the NOM, allowing column removal of bacteria or viruses to return to that observed in source water without humic acid. Currently, work is in progress to demonstrate evidence of inactivation of bacteria and viruses after exposure to QAC-coated surfaces. Previous results from a live/dead stain have shown E.coli to be membrane permeable following exposure. Ongoing experiments have been planned to determine the long-term effectiveness of a QAC-coated media and investigate the inactivation mechanism of bacteria/viruses.
Document Type: Research Article
Publication date: 2011-01-01
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