Evaluation of airborne Actinomycetes at waste application facilities

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 200 m upwind, and onsite and 300 m downwind by using liquid impinger sampler, calibrated to draw 12.5 L/min, for 20 minutes. The concentrations ranged between 0.0–7 360 CFU/m3 for mesophilic, and 106–586 CFU/m3 for thermophilic actinomycetes. Airborne actinomycete concentrations exceeded the suggested occupational exposure limit value of 100 CFU/m3. No significant correlations were found between actinomycete concentrations onsite and 300 m downwind distance. At the biosolid landfill, upwind thermophilic actinomycetes significantly differed (p < 0.05) from onsite and 300 m 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.