Analysis of Volatile Organic Compounds in Industrial Wastewater using the Solid Ceramic Dosimeter

Abstract

By reason of the use of abundant of chemicals in industry and daily human life, a plenty of organic compounds have been detected in environmental systems. Among them, Volatile Organic Compounds (VOCs) are dangerous substances found in most environments. VOCs are also found in the aquatic system because of their solubility in water. Thus, monitoring of VOCs contamination in groundwater and industrial wastewater should be performed often. Since VOCs are volatile, grab sampling of VOCs is a high probability that losses of pollutants will occur during the sampling and transportation processes. In addition, new sampling techniques are needed because of the high likelihood of contamination of VOCs from oil spills and chemical exposure accidents. The passive sampling method was introduced to compensate for the drawbacks of the grab sampling mentioned above. Passive samplers can determine the average exposure concentration during a given period of installation in the environment. One of the passive sampler types, the solid ceramic dosimeter, is a device that can adsorb gas phase VOCs in the water. In the nonporous surface of the solid ceramic dosimeter, the VOCs in the water are vaporized into the gas phase and the vaporized VOCs are adsorbed to the adsorbent in the ceramic tube. However, the study of the solid ceramic dosimeter is insufficient compared to other kinds of passive samplers. Therefore, more laboratory experiment and field tests are needed. We conducted laboratory calibration experiment and stability test of the solid ceramic dosimeter. The mass accumulation of target 14VOCs with a range of Henry’s law constants (H; 0.017 to 0.822 at 20℃) in a 2 to 100 μg/L were increased linearly with time in the sampler. The absorption rate of VOCs was related with Henry’s law constant. The diffusivity (diffusion coefficient in the solid ceramic wall, Dceramic) of 14VOCs was calculated by the diffusion equation according to the Fick’s first law. Average Dceramic value was 1.02 × 10-9 m2 /s, which was 7 times higher than that of the previous study. Results of calibration experiment in laboratory can be applied to deployment of the ceramic dosimeter in the aquatic environment to monitoring for VOCs contaminant. The passive sampling was accomplished in a petrochemical plant complex in South Korea with industrial wastewater reservoir. We deployed 3 sets of samplers for each time periods. With total 7 days of deployment, chloroform, ethylbenzene and toluene were detected by both passive sampling and grab sampling in a same level of VOCs concentration. Since the concentration derived from passive sampling means time-weighted average VOCs concentration (TWA conc.), it is a more effective method than grab sampling in terms of VOCs monitoring.