Biological removal of organic constituents in quench water from a slagging, fixed-bed coal-gasification pilot plant

This study is part of an effort to assess the efficiency of activated-sludge treatment for removal of organic constituents from high-Btu coal-gasification pilot-plant quench waters. A sample of raw-gas quench water was obtained from the Grand Forks Energy and Technology Center's pilot plant, which employs the slagging, fixed-bed gasification process. The quench water generated in the processing of Indian Head lignite was pretreated to reduce ammonia and alkalinity, and then diluted and subjected to long-term biological treatment, followed by detailed characterization and analysis of organic constituents. The pretreated (influent) and treated (effluent) samples were extracted using a methylene chloride, pH-fractionation method to obtain acid, base, and neutral fractions, which were analyzed by capillary-column gas chromatography/mass spectrometry (GC/MS). Over 99% of the total extractable and chromatographable organic material in the influent acid fraction was composed of phenol and alkylated phenols. Biological treatment removed these compounds almost completely. Major components of the influent base fraction were alkylated pyridines, anilines, aminopyrroles, imidazoles and/or pyrazoles, diazines, and quinolines. Removal efficiency of these compounds ranged between 90 and 100%. The influent neutral fraction was composed mainly of cycloalkanes, cycloalkenes, naphthalene, indole, acetophenone, and benzonitrile. Alkylated benzenes were generally absent. Removal efficiencies of these compounds were generally very good, except for certain alkylated cycloalkanes and cycloalkenes. Results are compared with those of a similar study on HYGAS coal-gasification quench water