Bacterial Air Polution from Sewage Treatment Plants

The research reported here was undertaken to obtain data on the numbers and types of bacteria emitted into the air from activated sludge and extended aeration sewage treatment plants and to evaluate the fate of these airborne bacteria in the air. The mean bacterial emission rate was 440 bacteria per square meter per second. Volumetric concentration of the airborne bacteria was depleted primarily by atmospheric diffusion and by die-off. Deposition of the bacteria to the ground was less important. The average half-life of the bacteria was 14 seconds. Under average conditions the initial bacterial concentration was reduced by 90% at 100 feet downwind of the source. Of the bacteria collected and cultured on trypticase soy agar, only 5% belonged to the Enterobacteriaceae, and these were primarily Klebsiella, Aerobacter, and Escherichia.