TOXICITY OF WET LIMESTONE SCRUBBER SLUDGES,
ASH POND SLUDGES AND EFFLUENT WASTES FROM
A COAL COMBUSTION PROCESS
Eric L. Morgan, Associate Professor
Tennessee Technological University
Cookeville, Tennessee 38501
Timothy C. Yehl, Shift Operator
Waste Treatment Plant
Piscataway, New Jersey 08854
Richard C. Young, Aquatic Toxicologist
Tennessee Valley Authority
Muscle Shoals, Alabama 35660
Biological impacts of point-source municipal and industrial effluents vary according to
the effluent's toxic composition and concentration. Similarly the receiving stream's water
quality and capacity to assimilate stressful events play an important role in regulating the
ecological community established. Additive and combined effects among discharges and
stream constituents, interrelationships, and interactions of the stream biota and the interplay of biota and those constituents by which we measure the physical-chemical water
quality all combine to influence ecological quality of water systems. In attempts to better
evaluate the influence of multiple factors in "real world" environments, novel aquatic test
procedures are currently being developed and implemented in chemical hazard assessment
schemes.
The advanced approach to chemical impact assessment on representative ecological
components is to evaluate the effect and fate of chemicals in interactions between groups
of different types of organisms subjected to an array of environmental conditions. Past single
species toxicity tests employing only one type of organism lacks the predictive capability
found in multispecies test protocols developed for chemical hazard assessment. Several test
systems are currently being evaluated and are becoming available: algal competition, preda-
tion by fish, mixed flask cultures, periphyton communities, sediment cores and pond microcosms [ 1 ]. Additional systems being screened for their potential incorporation into hazard
assessment plans are: zooplankton-zooplankton predation tests, fish-zooplankton predation
tests, parasitism, zooplankton-algae grazing tests, pelagic microcosms and model streams.
Presently, a reasonable approach to chemical hazard assessment of industrial or municipal
waste is a combination of multispecies and single species toxicity tests at site-specific locations and in simulated laboratory studies. Following this approach, single species toxicity
tests and a multispecies "simplified" test were executed during 1981 to assess the impact
of complex chemical wastes discharged from a coal fired steam plant.
The limited reuse of solid coal combustion ash waste by industries and municipalities,
less than 20% of total produced, is creating a potentially huge waste disposal problem. Ash
waste has been employed by industry as a base material for road beds, concrete mixing,
cement making, ceramics, and other products. Potential uses for ash are: (1) precipitation
of phosphates from municipal wastewater; (2) reclamation of wastelands from coal-strip
mining operations; (3) improvement of the agronomic properties of soils in selected instances; and (4) precious metal recovery from waste ash [2,3]. Typically, in attempts to
manage this "high volume" waste, 70% is sluiced to disposal ponds with the remainder
trucked to storage areas [4]. Effluent waters from the disposal ponds and leachates associated with ash materials are matters of particular concern to management alternatives.
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