Monitoring biodegradation of VOCs using high-speed gas chromatography with a dual-point sampling system

A new sampling system has been designed and interfaced with high-speed gas chromatography (HSGC) to monitor and assess the performance of a trickle-bed bioreactor designed for the removal of volatile organic compounds from air. A portion of a gas stream containing styrene and toluene was sampled both before and after passing through the bioreactor by means of a dual-loop sampling system. With a frequency of as high as 2 per minute, treated and untreated samples were alternately transferred on-line to the cryofocusing injection system of a HSGC and analyzed. This analytical system generated data with less than 2% relative standard deviations for standard samples, and residual contamination of subsequent analyses from a highly concentrated sample (2,000 microg/L) was not observed. A bench-scale bioreactor with a fiber mat support was used in these studies, resulting in residence times for analytes in the bioreactor of as little as 1 s. Rapid monitoring of this system detected subtle changes in the concentration of analytes with 30 s temporal resolution. Measurements showed a statistically significant increase in the removal of styrene from 22% to 27% when water was sprayed over the immobilized bacteria for 30 min. Overall, the bioreactor removed styrene from the air stream with a specific elimination capacity of 1,700 g of styrene (m3 of biocatalyst)-1 h(-1) at a space velocity of 3,400 h(-1).