PRETREATMENT AND BIOLOGICAL TREATMENT OF
FIXED-BED COAL GASIFICATION WASTEWATERS
Charles Moretti, Graduate Student
Ronald D. Neufeld, Associate Professor
Farrukh Ali, Graduate Student
Department of Civil Engineering
University of Pittsburgh
Pittsburgh, Pennsylvania 15261
Coal gasification involves the reaction of coal with steam and air or oxygen at elevated
temperatures to produce synthesis gas (CO and H2). Synthesis gas may be further upgraded
to produce methane, or an array of liquid and waxy substances via "tack-on" indirect liquefaction techniques. Thus, gasification is also an integral step in all indirect liquefaction
processes. While much research has been conducted in coal conversion technology and in
gross environmental assessment, little research has been conducted to date in the areas of
environmental control technology development as directed toward the synfuels industry.
The objective of ongoing research at the University of Pittsburgh is to develop a linkage
of unit operations that can effectively and rationally treat fixed-bed goal gasification wastewaters. Approximately 1400 gal of wastewater from the raw gas quench of the Morgantown
Energy Technology Center stirred-fixed bed coal gasification facdity was utdized in this
research. This gasification facility shares many features with a pressurized version of the
commercially available Wellman-Galusha-type low-Btu system.
The specific experimental goals developed in support of research objectives were:
1. to develop a pretreatment process capable of preparing the wastewater for subsequent
biological treatment;
2. to demonstrate and develop treatment techniques to enable such biological oxidation
in a stable fashion at hydraulic detention times of one day; and
3. to develop biokinetic constants and other necessary parameters for the biological
system and pretreatment system as would be required for commercial scaled waste-
treatment systems.
PRETREATMENT TRAIN
Due to the high ammonia and oily substance level of raw gasifier wastewaters, a pretreatment technique was required prior to biological oxidation. The phdosophy of design
approach was to remove both inhibitory levels of ammonia as well as to maximize removals
of "nonbiodegradable" trace organics in a fashion that would permit generation of biofeed
of a reasonably consistant composition.
Table I lists a chemical characterization of three different shipments of METC gasifier
wastewaters. Shipment No. 1 was an aged sample, being produced about 1 year prior to
analysis and stored in 55-gal drums outdoors. This sample contains high levels of organics
as evidenced by COD and TOC values, but relatively low phenol values, indicating that polymerization possibly occurred during the aging process.
Shipments 2 and 3 are considered "typical" wastewaters resulting from two different sets
of gasification  runs. The significance of the compositional difference between these two
121