Mass transfer of volatile organics from large open basins

Controlling the volatilization of organic compounds from treatment works is becoming increasingly important as the definition of industrial categorical Standards for air emissions by the EPA draws nearer. In this light, specific volatilization rates of several volatile organic compounds (VOC's) contained in multimillion gallon retention (''equalization basins'') and settling (''primary clarifier'') basins were measured using a flux chamber technique, a method used by the EPA for emission measurement. In this method, the liquid surface within an enclosing chamber is swept with air at a measured rate and the gas is analyzed. The mass transfer coefficients derived from these VOC vaporization rates were equal for the primary clarifier and the equalization basins. Factors were estimated to correct for the different ambient wind conditions to which these basins are exposed. Also it tons determined that the rate of volatilization of VOC's with low Henry's law constants may be underestimated by the measurement. This is a result of the gas-phase resistance being dominant under the test conditions and the liquid-phase resistance being dominant under normal ambient conditions, and of the assumption that the liquid-phase resistance remains unchanged under both test and ambient conditions, The particular organics studied were acetone, methyl ethyl ketone, methyl isobutyl ketone, isopropanol, methanol and toluene.