Investigation of quaternary ammonium silane-coated sand filter for the removal of bacteria and viruses from drinking water

• Published in: Journal of applied microbiology 2012-11, Vol.113 (5), p.1196-1207
• Main Authors: Torkelson, A.A., da Silva, A.K., Love, D.C., Kim, J.Y., Alper, J.P., Coox, B., Dahm, J., Kozodoy, P., Maboudian, R., Nelson, K.L.
• Format: Article
• Language: English
• Subjects: Adenoviridae - isolation & purification; Adenovirus; Bacteria; Biological and medical sciences; Drinking water; Drinking Water - microbiology; Escherichia coli; Escherichia coli - isolation & purification; filtration; Filtration - methods; Fundamental and applied biological sciences. Psychology; household water treatment and safe storage; Humic Substances; Levivirus - isolation & purification; Microbiology; MS2 coliphage; Poliovirus; Poliovirus - isolation & purification; Quaternary Ammonium Compounds - chemistry; quaternary ammonium silane; Silanes - chemistry; Silicon Dioxide - chemistry; Viruses; Water Purification - methods; Water Quality; Water treatment
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2012.05411.x

Aims To develop an anti‐microbial 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 micro‐organisms under different water quality conditions. The anti‐bacterial properties were investigated by visualizing Escherichia coli (E. coli) attachment to coated media under fluorescence microscopy combined with a live/dead stain. A 9‐cm columns with a filtration velocity of 18 m h−1 achieved log10 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 log10 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. Escherichia 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 micro‐organisms and natural organic matter and low removal of viruses PRD1 and Adenovirus 2. Significance and Impact of the 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.