CONCENTRATION AND BIOTOXICITY ASSAY OF DILUTE AQUEOUS-SOLUTIONS OF VOLATILE CHLORINATED ORGANICS USING SUPERCRITICAL-FLUID EXTRACTION

Chlorinated volatile organic compounds (VOCs) were extracted from dilu te aqueous samples into methanol to provide sufficient concentration f or bacterial toxicity measurements. Using equipment designed to preven t loss of volatiles, standards and biological reactor effluents were f iltered, adsorbed onto XAD-2 resin, extracted using supercritical carb on dioxide, and cryotrapped in liquid nitrogen with methanol as a keep er solvent for toxicity measurements using the Microtox bioassay syste m. The levels of 15 VOCs were increased 7-36 times in the methanol con centrates over the aqueous concentrations which ranged from 5 to 100 m u g/L. Mass recoveries averaged 76%. Using this system, the effluent o f an anaerobic bioreactor treating a complex mixture of chlorinated or ganics was found to be significantly less toxic than the influent (46% less), but the toxicity of the total organic halide fraction increase d by 80%.