Vol. 38, No. 5
Influence of Fulvic Acid on Bacteriophage Adsorption and Complexation in Soil
RICHARD L. BIXBYt AND DENNIS J. O'BRIEN* Department of Civil Engineering, University of New Hampshire, Durham, New Hampshire 03824
Received for publication 11 June 1979
The effect of fulvic acid,the major fraction of natural soluble organic matter, on the adsorption of MS2 bacteriophage to soil was investigated in controlled laboratory experiments. Batch experiments together with scanning electron microscopy-energy-dispersive X-ray analysis showed that fulvic acid complexed phage, which prevented its adsorption to soil. Phage strongly adsorbed to soil in the absence of fulvic acid. Phagewhich was complexed with fulvic acid was not irreversibly inactivated and could become viable under proper conditions, illustrating the importance of assay and elution procedures in the recovery of virus from aqueous solutions. Viruses are naturally found in wastewater, and their fate once they enter the environment is of concern due to their possible pathogenicity. Land disposal of wastewater is ofimmediate interest as an alternative to more conventional treatment methods. Land filtration of primary and secondarily treated domestic sewage is an effective method of removing organic matter and pathogenic microorganisms (6). Because viruses are negatively charged particles at pH values close to neutrality, sorptive interactions may influence the behavior of viruses in soil. Conflictingresults have been reported concerning the interactions of organic matter, viruses, and soil. Soluble organic matter has been shown to compete with virus for soils, thus leading to decreased adsorption or elution of already adsorbed virus (8). When Wellings et al. (18) detected viruses at 10 and 20 feet (ca. 305 and 610 cm) in monitoring wells near a spray irrigation plot after heavy rains, it wasconcluded that the rainfall resulted in a large increase in the soil-towater ratio which led to increased solubility of portions of the organic layer and thus desorption of attached virus. Schaub and Sorber (13a) noted low virus adsorption by unconsolidated silty sand and gravel when primary effluent was administered. However, Drewry and Eliassen (5) found that virus adsorption by soil generallyincreased with increased ion-exchange capacity, clay content, organic content, and glycerol retention capacity. Robeck et al. (13) recommended that soil have a 0.5 to 1.0% organic content to provide adsorptive capacity. Gerba and Lance (6) found that
t Present address: State of New York, Department of Environmental Conservation, Albany, NY 12233.
the adsorption of poliovirus from primaryeffluent and virus movement through loamy sand were not affected by the higher organic content of primary sewage effluent. An understanding of the interaction of virus with soil in the presence of organics has not been clearly defined, as evidenced by these results reported by previous investigators. There have been attempts to study the effect of organic matter on virus adsorption to more definedsurfaces such as clays and activated carbon (4, 7). According to Carlson et al. (4), virus inactivation by clay was reduced in the presence of albumin and sewage, and virus desorption from clay occurred when sufficient organic matter was present. Gerba et al. (7) found that poliovirus removal from wastewater effluent by carbon was greatly improved by reducing the amount of organics by lime coagulation.Watson and Drewry (17) concluded that competition for adsorption sites with the virus by organic matter was a major factor in the efficiency of activated carbon for virus removal from wastewater. The purpose of this study was to examine the adsorption of MS2 phage by soil in the presence of fulvic acid, the predominant fraction of naturally occurring organic matter in water. The experimental...