Investigation of Quaternary Ammonium Silane (QAS)-coated Sand Filter

July 27, 2012 · 0 comments

J Appl Microbiol. 2012 Jul 26. doi: 10.1111/j.1365-2672.2012.05411.x.

Investigation of Quaternary Ammonium Silane (QAS)-coated Sand Filter for the Removal of Bacteria and Viruses from Drinking Water.

Torkelson AA, da Silva AK, Love DC, Kim JY, Alper JP, Coox B, Dahm J, Kozodoy P, Maboudian R, Nelson KL.

Department of Civil and Environmental Engineering, University of California, Berkeley, Berkeley, California, 94720-1710.

AIMS: Develop an antimicrobial filter media using an attached quaternary ammonium compound (QAC) and evaluate its performance under conditions relevant to household drinking water treatment in developing countries.

METHODS AND RESULTS: Silica sand was coated with dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride via covalent silane chemistry. Filter columns packed with coated media were challenged with microorganisms under different water quality conditions. The antibacterial properties were investigated by visualizing Escherichia coli (E. coli) attachment to coated media under fluorescence microscopy combined with a live/dead stain. 9-cm columns with a filtration velocity of 18 m/h achieved log(10) removals of 1.7 for E. coli, 1.8 for MS2 coliphage, 1.9 for Poliovirus type 3, and 0.36 for Adenovirus type 2, compared to 0.1-0.3 log(10) removals of E. coli and MS2 by uncoated sand. Removal scaled linearly with column length, and decreased with increasing ionic strength, flow velocity, filtration time, and humic acid presence. E. coli attached to QAC-coated sand were observed to be membrane-permeable, providing evidence of inactivation.

CONCLUSIONS: Filtration with QAC-coated sand provided higher removal of bacteria and viruses than filtration with uncoated sand. However, major limitations included rapid fouling by microorganisms and natural organic matter and low removal of viruses PRD1 and Adenovirus 2.

SIGNIFICANCE AND IMPACT OF STUDY: QAC-coated media may be promising for household water treatment. However, more research is needed on long-term performance, options to reduce fouling, and inactivation mechanisms.

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