P1-179 Emission and Deposition of Bioaerosols Generated during Mechanical Handling (Mixing) of Composts

Sunday, July 26, 2015
Exhibit Hall (Oregon Convention Center)
Tong (Nancy) Liu, Center for Food Safety and Security Systems, University of Maryland, College Park, MD
Patricia Millner, U.S. Department of Agriculture-ARS, Beltsville, MD
Shirley Micallef, University of Maryland, College Park, MD
Robert Buchanan, University of Maryland, College Park, MD
Introduction: Produce in fields that are in close proximity to concentrated animal feeding operations (CAFO) can become contaminated through airborne transport and deposition of manure with fecal pathogens. It is unclear to what extent fecal pathogens in animal manures are aerosolized, transported, and deposited by air during mechanical operations conducted during compost production.

Purpose: An experimental study was conducted in Beltsville, MD, to determine the emission and deposition of bioaerosols generated during feedstock mixing and windrow turning, common mechanical handling operations in composting processes.

Methods: Bioaerosols generated during mixing/turning of dairy manure solids (DMS, compost feedstock) and 2-week-old DMS-compost windrows were collected 3 m downwind of materials handling operations using 6-stage Anderson Impactors and SpinCon air samplers, operating at 28.3 l/min and 450 l/min, respectively; 30 samples from two experiments were analyzed. Samples (n = 14) of basil leaves from plants exposed to bioaerosol deposition at 3 m downwind were collected. Total aerobic bacteria (tAB), fecal coliform and E. coli concentrations were determined by conventional plating and MPN procedures.

Results: Populations of tAB, coliforms, and E. coli in for dairy solids and composts were not significantly different (P > 0.05). Airborne tAB concentrations were 4.29 and 6.39 log CFU/m3 and E. coli were 0.133 and 1.52 MPN/m3 during mixing and turning of DMS and compost, respectively. Particle-size distribution of tAB was not significantly different (P > 0.05) from that for composts. Both coliforms and E. coli were primarily associated with coarse particles (> 2.1 µm). Calculated deposition of E. coli on basil leaves at 3 m downwind = -3.48 and -4.31 log MPN cm-2·s-1, for DMS and compost, respectively.

Significance: These data will be useful in atmospheric dispersion modeling to predict, refine, and validate projected downwind concentrations of bacterial aerosols generated during dairy manure solids handling and composting operations under a variety of atmospheric conditions across various terrain.