BACTERIAL AEROSOLS RESULTING FROM SPRAY IRRIGATION WITH WASTEWATER

摘要

Air sampling equipment was selected and adapted for the study of bacterial aerosols generated through land application of treated wastewater by spray irrigation. Preliminary data were obtained on bacteria present in treated and untreated domestic sewage at Army installations. Data were also obtained on survival of enteric bacteria in laboratory aerosols generated from wastewater at various relative humidities. A field study of 3 weeks duration was undertaken to measure aerosol dissemination of bacteria at a wastewater spray irrigation site at Ft. Huachuca, Az, Aerosol densities for the total aerobic bacteria ranged up to 1630 cu. m. at sampling points nearest the aerosol source. Confirmed coliform bacteria represented about 0.5 percent of the total, and of those nearly half were Klebsiella. Densities were greater under conditions of low wind, atmospheric stability and darkness. A mathematical model predicting downwind aerosol densities was developed, based on the dispersion equation of Pasquill and took into account the parameters of the spray equipment used. The model, in conjunction with fluorescein tracer data, was used in deriving an estimate of the fraction of wastewater entering the aerosol state.