Evaluation of airborne Actinomycetes at waste application facilities

Abstract

This study aimed to evaluate airborne meso–and–thermophilic actinomycete concentrations and their types at a wastewater treatment plant and a biosolid landfill, in Egypt. Air samples were collected at 200m upwind, and onsite and 300m downwind by using liquid impinger sampler, calibrated to draw 12.5L/min, for 20 minutes. The concentrations ranged between 0.0–7 360CFU/m3 for mesophilic, and 106–586CFU/m3 for thermophilic actinomycetes. Airborne actinomycete concentrations exceeded the suggested occupational exposure limit value of 100CFU/m3. No significant correlations were found between actinomycete concentrations onsite and 300m downwind distance. At the biosolid landfill, upwind thermophilic actinomycetes significantly differed (p<0.05) from onsite and 300m downwind. A total of 40 and 69 airborne actinomycete isolates belonging to 8 genera were identified at the wastewater treatment plant and biosolid landfill. Streptomyces were the dominant actinomycete species. Streptomyces diastaticus, Pseudonocardia compacta and Catellatospora ferruginea were only detected at the biosolid landfill site. Meso–and–thermophilic actinomycetes positively associated with relative humidity, and wind speed positively correlated with onsite thermophilic actinomycetes (r=0.65) at the biosolid landfill. Temperature showed negative effect on survivability of mesophilic actinomycetes (r=-0.8) onsite of the wastewater treatment plant. Waste application facilities increase actinomycete concentrations onsite which may consequently deteriorate air quality in the nearby areas.