55    COUPLED BIOLOGICAL DOWNFLOW FLUID BED
REACTOR TREATMENT OF SYNFUELS WASTEWATER
Charles D. Turner, Associate Professor
Department of Civil Engineering
Chung Seng Ong, Graduate Research Assistant
John R. Gallagher, Research Microbiologist
Energy and Mineral Research Center
University of North Dakota
Grand Forks, North Dakota 58202
INTRODUCTION
Despite the current glut of crude oil on the world market, the oil resource is very limited and by the
turn of the century alternate sources of energy will be replacing oil. Another form of energy, nuclear
energy, is not acceptable to the American public and the solar energy industry is stagnated. Coal, in all
its forms, is the most readily extractable and technologically available source of energy in the United
States. Because of this, the production of synfuels from coal will become a major source of nonelectric power in the United States near the turn of the century.
Synfuels processes, such as the Lurgi dry ash gasification process, produce wastewater with high
concentrations of both organic and inorganic contaminants. These contaminants are difficult to
remove prior to discharge and create operational problems if recycled back into the process. Cost-
efficient production of synfuels can only take place if the technologies for production and waste
management are developed prior to prototype plant construction.
This research involved the application of coupled fluid bed reactors that combine nitrification and
denitrification with organics removal in hydraulically connected anoxic and oxic columns for the
treatment of synfuels wastewater from the Great Plains Gasification Plant (GPGP) near Beulah,
North Dakota. The wastewater contained BOD5 and ammonia concentrations of 1250 mg/L and 1100
mg/L, respectively. The wastewater was treated at the University of North Dakota Energy and
Mineral Research Center where the coupled bed process reduced the BOD5 and ammonia concentrations by 80% or more each. This paper reviews the fundamentals of the treatment process, previous
research, bench-scale equipment, operation and results of the research.
BACKGROUND
Synfuels wastewater that utilizes coal as the process feedstock can be expected to have characteristics related to the chemical makeup and structure of the coal. The specific synfuels process also
regulates wastewater characteristics. Process variables that most affect wastewater composition are
gasifier temperature and pressure. Coal variables include coal rank, such as lignite, subbituminous,
and bituminous and the variability in sulfur, ash and trace metal contents. Each specific process
whether it be Lurgi, Texaco, or KILNGAS, will produce wastewater with distinctly different chemical
characteristics for various coal types and each synfuels process will generate different wastewater
characteristics with the same coal.
Table I shows the COD, BOD5, ammonia, phenol and thiocyanate content of wastewater from
several gasification processes. These values represent characteristics after solvent extraction and
ammonia stripping. Although the values vary widely, high ammonia concentrations are typical of
each wastewater.
By-product recovery reduces organic and inorganic concentrations in the wastewater to the point of
optimizing economic recovery of those products. GPGP utilizes the Phenosolvan for phenol recovery,
Phosam-W for ammonia recovery, and the sulfolin process for sulfur recovery. After passing through
the Phenosolvan and Phosam-W units, the wastewater is termed stripped gas liquor (SGL). The by-
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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