Madison, Wisc.-A new study published in the November?ÇôDecember issue of the Journal of Environmental Quality investigated levels of microorganisms in air immediately downwind of biosolids being land-applied, and found risks of aerosol-borne infection for workers are generally low, at less than 1 or 2 percent per year. The authors reported that more than 300 air samples were collected at various locations where coliform bacteria, coliphages, and heterotrophic plate count (HPC) bacteria were enumerated. Concentrations of coliforms relative to Salmonella and coliphage relative to enteroviruses in biosolids were used during this study, along with levels of coliforms and coliphages measured in air. The HPC bacteria were ubiquitous in air near land application sites whether or not biosolids were being applied, and concentrations were positively correlated to windspeed. Coliform bacteria were detected only when biosolids were being applied to land or loaded into land applicators. The conclusion was that risks from aerosolized microorganisms at biosolids land application sites appear to be lower than those previously found at wastewater treatment plants.
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