Molecular Characterization and Transformation of Dissolved Organic Matter in Refinery Wastewater from Water Treatment Processes: Characterization by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

A set of wastewaters sampled in a stream-by-stream flow of the process in a refinery wastewater treatment plant were characterized to investigate the molecular composition and transformation of dissolved organic matter (DOM). The samples were separated into organic and aqueous phase DOMs by solvent extraction and solid phase extraction (SPE). Volatile and semivolatile compounds in the organic phase were characterized by gas chromatography–mass spectrometry (GC-MS); DOMs in the organic and aqueous phases were characterized by negative ion electrospray (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The aqueous phase DOMs exhibited a more complex molecular composition than other complex mixtures investigated by far, in which there were totally 76 compound class species identified in a single mass spectrum. Refinery wastewater DOMs have lower values of double bond equivalent (DBE) and O/C ratio than those of natural organic matter (NOM) in fresh and marine waters. The organic phase DOM occupied the major TOC value, but was liable to be degraded in the biological process. Some humic-like substances presented in the aqueous DOM were found resistant to the treatment processes by the ESI FT-ICR MS based semiquantitative results.