The wastewater treatment plants (WWTPs) of three representative petrochemical plants in southern Taiwan were sampled to investigate their VOC emission characteristics. Generally, emissions decline along the process flow, while the VOC concentration accumulates to as much as around 2400 mg/m3 (as total hydrocarbons) at several closed vessel vents during the primary treatment. VOC emission rates (g/s) and fluxes (g/m2 hr) exhibit a similar trend of reducing concentrations in the WWTPs. From the field analysis data, VOC emission potential is best indicated by the concept of emission flux rather than concentration or emission rate. The Water 8 emission model version 4, developed by the U.S. EPA in 1995, was used to simulate the emission rate. The output results were compared to the calculated VOC liquid-gas mass equilibrium based essentially on the saturated gas concentration of the individual VOC components in wastewater. The comparisons clearly identified the proposed mass transfer approach using as a reliable timesaving alternative to Water 8, which requires numerous input parameters and water analysis data.
Journal of Environmental Science and Health Part A 38(11),2521-2535