MUTAGENICITY AND TOXICITY OF TREATED AQUEOUS EFFLUENTS
FROM COAL CONVERSION PROCESSES
J.I. Brand, Development Engineer
J.A. Klein, Group Leader Chemical Technology Division
B.R. Parkhurst, Research Associate Environmental Sciences Division
T.K. Rao, Research Associate Biology Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830
INTRODUCTION
The task of developing rational treatment systems for complex and varying wastewaters
from coal conversion processes necessarily must reflect both technical and regulatory considerations. These wastewaters are highly variable, both between conversion processes and
for differing operating conditions within the same process. These wastes are also sufficiently
complex and different from the more common industrial and municipal wastes to necessitate
modification of standard wastewater analytical techniques [1]. FinaUy, the anticipated
discharge standards to be met are only tentative.
At Oak Ridge National Laboratory (ORNL), experimental treatment of a variety of
these wastes has been successful in cleaning these waters so that anticipated regulations
for the discharge of conventional poUutants such as total organic carbon (TOC) and phenols
are met. However, since these wastes are known to be unusual, meeting standards designed
for conventional industrial wastes does not necessarily ensure that the hazardous nature of
these wastes is adequately reduced, nor does it ensure that some unexpected hazards are
not introduced as artifacts of the treatment scheme. In addition, in any waste, the presence
or absence of specific chemical species may not indicate the biological activity of the waste.
Thus, specific wastewaters were selected for exploratory studies of their biological impact,
as measured in a laboratory setting by short-term mutagenicity and acute toxicity assays.
These bioassays were performed on the wastes before and after treatment, as weU as at
selected intermediate points within treatment schemes typical of those which have been
purposed for coal conversion waste treatment. WhUe biological tests of this nature are often
more complicated and time consuming than simple chemical assays, the information obtained
can be quite valuable in the development and evaluation of treatment processes.
EQUIPMENT
Bench-scale facdities at ORNL for the treatment of aqueous effluents from coal conversion processes include a number of individual unit operations which can be operated in a
variety of configurations and combinations depending on the physical and chemical characteristics of the specific waste being treated. The current configuration is shown schematicaUy
in Figure 1. The major components of the system are the primary treatment, performed
in the stripping column, secondary treatment performed in the biological oxidation units
and polishing, which is intended to remove refractory organics, performed in the ozonation
and the sorption systems.
If ammonia and hydrogen sulfide were present, the wastes were stripped using a nominal
2-in. (5-cm) diameter column fdled with 1/2-in. (1.3- cm) Berl saddles with a total packing
depth of 1.2 meters. This column could be used for either air or steam stripping.
Biological oxidation of phenolics has been extensively studied at ORNL in both fluidized
beds and continuously stirred activated sludge tanks [2-4]. In this study, the fluidized bed
reactors had an active bed volume of 2.5 liters; the activated sludge tanks had a nominal
volume of 3 liters. Either type of reactor could be operated in paraUel or in series with
others of the same type and could be operated in either batch or continuous modes.
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