Airborne coliphages from wastewater treatment facilities

The emission (from wastewater treatment plants) of airborne coliphages that form plaques on two strains of Escherichia coli was investigated. Two activated-sludge and two trickling-filter plants were studied. Field sampling procedures used large-volume air samplers with recirculation devices. Coliphages were enumerated by a most-probable-number (MPN) procedure. Temperature, relative humidity, windspeed, and presence of sunlight were monitored. Concurrent samples of sewage were taken during each air-sampling run. Average coliphage levels in the airborne emissions of trickling-filter beds and activated-sludge units were 2.84 X 10(-1) and 3.02 X 10(-1) MPN/m3, respectively, for all positive observations, and sewage liquor concentrations from the sources were 4.48 X 10(5) and 2.94 X 10(6) plaque-forming units/liter, respectively, depending upon the E. coli host used for assay. This work establishes minimal airborne-coliphage concentrations from the plants studied. The procedures employed will be useful in evaluating the animal virus levels in these emissions.