Model enteric viruses were concentrated from seeded samples of raw, finished and granular activated carbon (GAC)-treated waters and from GAC-treated waters supplemented with humic or fulvic acid or bentonite clay particles by adsorption to electropositive (Virosorb 1MDS) filters at pH 7.5 or electronegative (Filterite) filters at pH 3.5 with and without 5 mM added MgCl2, followed by elution with 0.3% beef extract in 50 mM glycine at pH 9.5. Natural particulates in raw and finished waters had little effect on virus concentration efficiencies. Soluble organic compounds reduced virus adsorption efficiencies from both raw and finished waters compared to GAC-treated water, but the extent of interference varied with virus type and adsorption conditions. Humic and fulvic acids caused appreciable reductions in poliovirus adsorption and recovery efficiencies with both types of filters. Fulvic acid caused greater reductions in virus recovery with Virosorb 1MDS filters than with Filterite filters. Fulvic acid interference with virus recovery by Filterite filters was overcome by the presence of 5 mM MgCl2. Although humic acid reduced virus recoveries by both types of filters, its greatest effect was on virus elution and recovery from Filterite filters. Bentonite clay enhanced poliovirus retention by both filter types as much as 8-fold. However, the presence of clay often interfered with elution of retained viruses from both filter types. Under some conditions, overall virus recoveries were considerably lower from water with clay than from clay-free control water. The results of this study suggest that high concentrations of soluble organic matter such as humic and fulvic acids and suspended solids such as bentonite clay may interfere somewhat with virus recovery by filter adsorption-elution methods.
Influence of water quality on enteric virus concentration by microporous filter methods.
