MASS-TRANSFER OF VOLATILE ORGANICS FROM LARGE OPEN BASINS

Controlling the volatilization of organic compounds from treatment wor ks is becoming increasingly important as the definition of industrial categorical Standards for air emissions by the EPA draws nearer. In th is light, specific volatilization rates of several volatile organic co mpounds (VOC's) contained in multimillion gallon retention (''equaliza tion basins'') and settling (''primary clarifier'') basins were measur ed using a flux chamber technique, a method used by the EPA for emissi on 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 ra tes were equal for the primary clarifier and the equalization basins. Factors were estimated to correct for the different ambient wind condi tions 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-pha se resistance being dominant under the test conditions and the liquid- phase resistance being dominant under normal ambient conditions, and o f the assumption that the liquid-phase resistance remains unchanged un der both test and ambient conditions, The particular organics studied were acetone, methyl ethyl ketone, methyl isobutyl ketone, isopropanol , methanol and toluene.