Liping Pang, Susan Lin, Erin McGill, Joanne Hewitt, Chris Nokes (Institute of Environmental Science and Research)
Annabelle Tham (Institute of Environmental Science and Research, University of Otago)
Vernon Ward (University of Otago)
Household drinking-water treatment of non-reticulated water supplies relies largely on point-of-use (PoU) filters. Source waters of non-reticulated water supplies are often microbially contaminated but little is known about human enteric virus reductions in these filters. We evaluated reductions of human rotavirus, adenovirus and norovirus in 10 commonly used activated carbon, polypropylene and polyester microfilters (cartridge 25.4 cm long, 7 cm in diameter) with pore sizes of 0.2–5 m. Replicate virus challenge tests were conducted on each filter using chlorine-free tap water under a constant flow rate of 1 L/min.
Virus reductions, expressed as log10 reduction values (LRVs), in the carbon filters (LRVs=1.17–6.0) were significantly greater than those in the polypropylene (LRVs=0.02–0.54) and polyester (LRVs=0.00–0.73) filters (P≤0.0001). Virus reductions in the polypropylene and polyester filters did not differ significantly (P>0.24). In most of the filters investigated, the norovirus and adenovirus reductions were similar (P>0.49). Compared with the norovirus and adenovirus reductions, the rotavirus reductions were significantly lower in the carbon filters (P≤0.009).
All the filters tested failed to meet the “protective” rotavirus reduction level (LRVs ≥3 log10) required for household drinking-water treatment (WHO, 2011). Our findings highlight a critical need for additional water treatment when using PoU microfilters, for example, water boiling or ultraviolet radiation, or the use of effective surface-modified filter media to prevent drinking-waterborne infections from enteric viruses.