Section Four
WASTE MANAGEMENT
A. TOXICITY, ENVIRONMENTAL IMPACT
27    IMPACT OF TOXIC INTERACTION OF ORGANIC AND
INORGANIC FLOCCULANT/COAGULANT AIDS ON
WHOLE EFFLUENT TOXICITY TESTING
Douglas J. Fort, Director of Laboratory Services
Enos L. Stover, President
Stover Biometric Laboratories, Inc.
Stillwater, Oklahoma 74075
INTRODUCTION
Wastewater discharge criteria under the National Pollutant Discharge Elimination System
(NPDES) permit program are becoming much more stringent due to the current state of our water
resources. Within the last three years, most states and/or U.S. Environmental Protection Agency
(EPA) regions have adopted narrative water quality criteria requiring various forms of Whole Effluent Toxicity (WET) testing as a component of the NPDES discharge criteria. Today toxicity control,
which is often regulated through costly and time-consuming Toxicity Reduction Evaluation (TRE)
programs, is one of the most difficult problems that must be addressed by NPDES permittees. WET
may be the result of a myriad of different sources, including unidentified wastewater contaminants
discharged to Publicly-Owned Treatment Works (POTWs) or the result of manufacturing processes
used by direct industrial dischargers. Toxicity, however, may also be the result of the use of chemical
additives, such as coagulant aids, that are either refractory materials not degraded in the treatment
process or toxic degradation products of these additives. In a previous report by Fort et al.,1 toxico-
logical comparisons were made between cationic polymers and commonly used inorganic coagulant
aids, including ferric chloride (FeCl3) and alum (A12(S04)3) based on results obtained by other
investigators.2"5 Differences in toxicity due to the type of treatment application were also evaluated.
Results from the study clearly demonstrated that the series of cationic polymers tested were dramatically more toxic to Ceriodaphnia dubia on an equimolar basis than either FeCl3 or A12(S04)3. The
potential for toxicity problems with both types of flocculant/coagulant aids, particularly the cationic
polymers, when used in final effluent polishing was found to be more problematic than when used in
secondary clarification.
Because polymers and inorganic coagulant aids are commonly used in conjunction with one another
for wastewater treatment, an assessment of potential interactions between the two types of additives
was warranted. Thus, joint-compound interaction studies with both the polymer and FeCl3 or
A12(S04)3 were conducted to determine the effect of co-treatment on WET. Results from these studies
are presented in this paper. Results clearly demonstrated that the toxicity of these additives during
combined treatment was much more dramatic than for each compound individually and that individual toxic assessment would not account for the total magnitude of toxicity induced during combined
treatment.
48th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
279