Detoxification of a mixture of aliphatic chlorinated hydrocarbons in a fixed-bed bioreactor: Continuous on-line monitoring via an attenuated total reflection-Fourier transform infrared sensor

A methanogenic microbial community immobilised on an inert carrier was accl imated to a mixture of chlorinated aliphatic hydrocarbons in a bioreactor u sed for their detoxification. The mixture contained trichloroethylene (TCE) , tetrachloroethylene (PCE), carbon tetrachloride (CT) and hexachlorobutadi ene (HCB). An attenuated total reflection-Fourier transform infrared (ATR-F TIR) optical sensor was developed for continuous on-line measurements of th e toxic compounds in the dechlorinating bioreactor. The sensor consisted of an ATR internal reflection element (IRE) coated with an extracting polymer which was continuously enriched with the toxic compounds. The bioprocess w as monitored through the sensor, which was coupled permanently to the biore actor, over a period of three days of continuous operation. The sensor trac ked the progression of absorbance spectra over time in a non-invasive manne r. The concentration of organochlorine compounds in the bioreactor was pred icted from the absorbance spectra using a partial least squares (PLS) calib ration model which was developed for all components simultaneously. The acc uracy and reproducibility pf this ATR-FTIR sensor was tested by checking th e spectra-based concentration values of the toxic analytes in the bioreacto r effluents against off-line gas chromatography (GC) measurements. This nov el sensor is useful for routine continuous on-line monitoring of the dechlo rinating bioreactor. (C) 1999 Published by Elsevier Science Ltd on behalf o f the IAWQ. All rights reserved.