The Emission Rate, Biological Characterization, and Transport of Aerosols Emitted During the Disk Incorporation of Class B Biosolids
Biosolids contain metal, biotoxin, and pathogen concentrations that are greater than the agricultural soils to which they are applied. Once applied, biosolids are incorporated into soils by disking and this process generates aerosols that may be a health hazard to workers and nearby residents. Field studies at a Central Arizona biosolids land application site were conducted to characterize the physical, chemical, and biological content of the source aerosols produced during biosolids disking and to validate a model for the off-site transport of these aerosols. Source aerosol concentrations and calculated emission rates reveal that disking is a substantial source of biosolids-derived aerosols. Biosolids disking emitted between 9.91 to 27.25 mg biosolids s-1 and these rates were greater than previously measured emission rates produced during the spreading of dewatered biosolids or the spraying of liquid biosolids. While source PM10 concentrations emitted during biosolids disking averaged 1.5 mg m-3, comparisons with source PM10 concentrations produced during the disking of fields that did not have biosolids amendments revealed that adding biosolids to dry soils increased the moisture content and reduced the total PM10 emissions by at least three times. Using real-time PM10 concentration downwind field measurements, a Gaussian plume model for predicting off-site transport of aerosolized biosolids was validated.