Toxicity Screening of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) Hydrocarbons in Groundwater at Sour-Gas Plants

Abstract

In this paper a toxicity-based approach was used to assess the quality of groundwater samples collected from gas plants in western Canada. The gas plants selected were typical of plants currently in operation and represent a cross-section of hydrogeological conditions and of the sweetening processes in use. The focus was on the levels of benzene, toluene, ethylbenzene and xylene (BTEX) group of hydrocarbons as indicator compounds for monitoring the degree of bioremediation and bioventing at the sites. Toxicity tests included bacterial luminescence (Microtox®), daphnia mortality, fathead minnow mortality and lettuce seedling emergence. In general, the concentration of BTEX was a good indicator of the toxicity of the groundwater. However, approximately 5% of the samples were observed to be toxic although the concentrations of BTEX were low (< 1 μg/L). Based on the laboratory results, the remediation of BTEX in groundwater at the sour-gas plants is expected to correlate well with the removal of acute toxicity to selected aquatic organisms.