On-line biodegeradation monitoring of nitrogen-containing compounds by membrane inlet mass spectrometry

Abstract

Membrane inlet mass spectrometry (MIMS) has been developed for the on-line monitoring of compounds in a continuous stirred tank bioreactor (CSTB) used to simulate a wastewater treatment plant (WWTP). A mixture of four industrially relevant nitrogen-containing volatile and semi-volatile compounds was fed to a 3 dm3 CSTB with a hydraulic retention time (HRT) of 24 h. In-membrane preconcentration/thermal desorption was used for the on-line monitoring of semi-volatile compounds (n-methylpyrrolidinone and tetramethylethylenediamine), while volatile organic compounds (3-bromopyridine and 2-chloro-5-trifluoromethylaniline) were determined by continuous infusion through the membrane. Quantification of the four compounds was achieved by MS. The CSTB was run for 160 h and, after reaching steady state, n-methylpyrrolidinone showed removal to levels below the limit of detection, while there was partial biodegradation of 2-chloro-5-trifluoromethylaniline and 3-bromopyridine. There was no evidence of significant biodegradation for tetramethylethylenediamine. Intermediates in the metabolite pathways of 2-chloro-5-trifluoromethylaniline and 3-bromopyridine were identified by MIMS, gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS). COD was measured offline, and results agreed well with MIMS, although COD data did not provide information on the removal of the individual compounds. © 2003 Society of Chemical Industry.