Airborne coliphages from wastewater treatment facilities

Abstract

The emission (from wastewater treatment plants) of airborne coliphages that form plaques on 2 strains of Escherichia coli was investigated. 2 Activated sludge and 2 trickling filter plants were studied. Field sampling procedures used large volume air samples 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 MPN/m3, respectively, for all positive observations, and sewage liquor concentrations from the sources were 4.48 x 105 and 2.94 x 106 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.