Characterization of Major and Minor Organic Pollutants in Wastewaters from Coal Gasification Processes

Abstract

In order to investigate the feasibility of anaerobic biological treatment for wastewaters generated from thermal gasification processes of coal, a characterization program was implemented whose major effort consisted in the elucidation of specific organic constituents contained in the wastewater. Solvent extraction in acid and base conditions followed by glass capillary gas chromatography in combination with several detectors (i.e., FID, NPD, and MS-DS) were employed for the investigation of major and minor “extractable” organic constituents. Direct aqueous injection on a polar glass capillary column (i.e., OV-351) was used for the major “nonsolvent extractable” organic constituents amenable to GC. The identity of 28 organic compounds was confirmed by comparison with pure standards. Phenol, the three cresol isomers, 5,5-dimethyl-hydantoin and 5-methyl,5-ethylhydantoin were identified as major wastewater constituents. Several substituted phenols (e.g., methyl, dimethyl, trimethyl, methylethyl, hydroxy and methoxy), pyridines, anilines, quinolines, PAHs, dibenzofuran and aldehydes were either confirmed or tentatively identified as minor wastewater constituents. Although the organics identified did not account for the total organic content, which implies the presence of still unidentified highly polar compounds, the information was utilized to set a data base for monitoring the biological treatment operations. Process monitoring data indicated that several organics (i.e., 5,5-dimethyl-hydantoin, 5-methyl,5-ethylhydantoin, o-cresol, m-cresol and p-cresol) were only partially removed by the treatment process employed.

Key Words:

• Characterization of coal gasification wastewater
• polar and non-polar WCOT
• direct aqueous injection analysis