Organic chemicals and microbial facies of liquid aerosols from a wastewater treatment plant

Microbial facies and organic chemicals, extractable with methylene chloride , in liquid aerosols produced by the aeration tanks of the Baciacavallo was tewater treatment plant (Prato) were determined from December 1995 to Octob er 1996. Chemical analyses pointed out the presence of aliphatic and aromatic hydroc arbons, polyciclic aromatic hydrocarbons (PAH,), aliphatic aldehydes, phtha lates and degradation products of nonylphenol polyethoxylates. The aerosol composition seems to be closely related to the waste compositio n with the exception of volatile compounds which were transferred directly from water to air in the gas-phase. The results of the microbiological anal yses demonstrated that the number of microorganisms of various species was low with respect to what was expected considering the high concentration of bacteria in the wastewater. A comparison of the chemical and microbiological data indicated a possible correlation between the trends of the total viable count and the sum of the concentrations of nonylphenols (NP) and their mono and diethoxylate deriva tives (NPEO1 and NPEO2). There are significant differences between the chemical composition of these aerosols and the particulate matter taken from the Prate urban centre whic h indicated nonylphenols as "markers" of the sewage treatment plant emissio n.