Citation:

Herrmann, R., R. Grosser, D. Farrar, AND B. Brobst. Field Studies Measuring the Aerosolization of Endotoxin During the Land Application of Class B Biosolids. AEROBIOLOGIA. Springer, New York, NY, 33(3):417-434, (2017). https://doi.org/10.1007/s10453-017-9480-8

Impact/Purpose:

The work presented here is one attempt at reducing the unknowns in biosolids endotoxin anaylsis by comparing the efficiencies of various air sampling devices, contribution of wind speed to endotoxin recovery, examining the timing of the particulate plume, as well as comparing land application of various biosolids sources at different sites. This information is of interest to Regional and Program Office decision makers, States, and local affected communities.

Description:

Endotoxin is a component of the cell walls of Gram-negative bacteria and is known to be present in biosolids. Endotoxins have been shown to be a potent stimulator of the innate immune response causing airway irritation and shortness of breath. Class B biosolids are routinely applied to agricultural lands in the US to enhance soil properties and can be used as an alternative to chemical fertilizers. This study investigated the aerosolized endotoxin produced during the land application of Class B biosolids from various wastewater treatment plants on agricultural land and a concrete surface at two sites in Colorado, USA. Aerosolized endotoxin was captured using HiVol sampler fitted with glass fiber filter, polycarbonate filter cassette (both open and closed), and BioSampler impinger air samplers. Endotoxins were also measured in the bulk biosolids to allow for correlating bulk biosolids concentrations with aerosol emission rates. Endotoxin concentrations in biosolids, impinger solutions, and filter extracts were determined using the kinetic Limulus amebocyte lysate assay. Aerosolized endotoxin concentration was detected from all sites with levels ranging from 0.5 to 642 EU/m³. The four types of sampling apparatus were compared and the HiVol and open-faced cassette samplers used produced higher TWA measurements (EU/m³) than the impinger and closed cassette samplers. Ambient wind speed at the sites was found to be the variable best describing the results with an optimal wind speed estimated at 5 m/s. It is argued that HiVol air samplers are a particularly reliable approach and subsequent analyses relating TWA measurements to wind speed and biosolids characteristics were based on the measurements collected with those samplers.

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