Evaluation of bioaerosol components, generation factors, and airborne transport associated with lime treatment of lead-contaminated sediment for beneficial use purposes

Existing technical guidance from public health and occupational safety agencies typically focus on potential chemical exposures more so than potential biological agent exposure during contaminated sediment management activities. A physical model of a contaminated sediment treatment and airborne transport process, and an experimental protocol were developed to evaluate the effectiveness of lime treatment to reduce the physiological and environmental availability of lead, identify specific components (bacteria, fungi, cell structural components, and particulates) of a bioaerosol that may be generated from such a treatment process, and the key reaction variables (amount of lime addition, rate of lime addition, mixing energy supplied) that effect the amount of bioaerosol components that may be generated. Lime treatment of a sediment contaminated with heavy metals, petroleum-based organics, and microorganisms increased the sediment pH and solids content of the sediment, but increased the bioaccessibility of lead in the bloodstream as measured by an in-vitro laboratory method. Lime treatment reduced the amount of endotoxin in the sediment, but the effects of lime treatment on beta-d glucan could not be determined. Lime treatment reduced the number of water-extractable bacteria in the sediment from approximately 106 CFU/ml to less than 103 CFU/ml and reduced the number of water-extractable fungi from approximately 10 6 CFU/ml to less than 103 CFU/ml within 14 days. The temperature of the sediment was linearly related to the amount of lime added. Bacteria were aerosolized during the treatment trials, suggesting that public health and occupational safety agencies should consider such exposure. There was no evidence of aerosolization of fungi above the detection limit during the treatment trials, most likely due to either their larger particle size that could not be collected by the impingers, or their particular growth stage. Non-biological particulates, endotoxin and beta-d glucan were not detected in air samples during the treatment trials. The amount of lime added to the reaction and the mixing energy supplied to the reaction significantly effected the aerosolization ratio of bacteria (amount of aerosolized bacteria divided by amount of bacteria in untreated sediment) from the reaction beaker. For the majority of the treatment trials, an increase in the mixing energy input increased the aerosolization ratio. For the majority of the treatment trials, an increase in the amount of lime added decreased the aerosolization ratio. The rate of lime addition did not significantly effect the aerosolization ratio of bacteria.