Coliphages and enteric viruses in the particulate phase of river water

The present study was undertaken to determine if indigenous enteric viruses and coliphages are free or associated with suspended particulate matter in natural waters. River water was filtered on filters of decreasing porosities (100-0.25 micron) that were pretreated with detergent to eliminate viral adsorption while retaining particulates. This filtered water was refiltered in virus-adsorbing conditions to retain free viruses. The virus-adsorbing filter retained most of the enteric viruses (77.4%) and coliphages (65.8%), which indicated that these viruses were probably free or associated with particles with a diameter of less than 0.25 micron. These observations are important because in water treatment plants small particulates are often the most difficult to eliminate.