Physicochemical mechanisms responsible for the filtration and mobilization of a filamentous bacteriophage in quartz sand

This study examines the influence of pore water chemistry on the filtration and physicochemical properties of a male-specific filamentous bacteriophage isolated from chlorinated effluent of the San Jose Creek Water Reclamation Plant in Los Angeles County, California. The isolate belongs to a class of bacteriophage that are naturally present in sources of sewage, and hence may be an indicator of fecal contamination in groundwater. Furthermore, there is some evidence that this class of bacteriophage are mobilized in the subsurface following rainfall events, although the mechanism responsible for this process is not yet clear. Using a model filtration system consisting of packed columns of quartz sand, we found that the filtration of this isolate was strongly dependent on the concentration and valence of the dominant cation in the pore fluid. In one set of experiments involving columns 19 cm in length, virus retention in the column increased from 0% to 99.999% when the electrolyte composition of the pore fluid was changed from 10 mM NaCl to 10 mM CaCl2. With one exception, filtration efficiencies calculated from the column experiments were inversely proportional to the electrophoretic mobility of the virus, implying that electrostatic interactions between the virus and the quartz surface dominate the filtration dynamics of this particular bacteriophage. From a practical perspective, these results indicate that small changes in the hardness and total dissolved solids of pore fluids - as might occur following a rainfall event - can dramatically affect both the filtration and mobilization of filamentous bacteriophage in subsurface systems. (C) 1998 Elsevier Science Ltd. All rights reserved.