Section Nine
RESPIROMETRY AND EFFLUENT TOXICITY
64   JOINT TOXIC ACTIONS OF ORGANIC
FLOCCULATING POLYMERS: IMPACT ON WHOLE
EFFLUENT TOXICITY TESTING—PART 3
Douglas J. Fort, Director
Research & Technical Services
Enos L. Stover, President
THE STOVER GROUP
Stillwater, Oklahoma 74076
INTRODUCTION
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 National Pollutant Discharge Elimination System (NPDES) discharge criteria.
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 municipal wastewater treatment plants 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
previous reports by Fort et al.' and Fort and Stover,2-3 toxicological comparisons were made between cationic polymers and commonly used inorganic coagulant aids, including ferric chloride
(FeClj) and alum (A12(S04)3) based on results obtained by other investigators.4-'' Differences in
toxicity due to the type of treatment application were also evaluated. Results from these studies
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)V 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
FeClj or A12(S04)3 were conducted to determine the effect of co-treatment on WET. Results
from these studies 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.
Combinations of flocculating polymers with different physical/chemical characteristics (i.e.,
chemical structure, molecular weight, hydrophobicity, molar refractivity, and charge density) are
also commonly used in wastewater treatment. Thus, as the third phase of the previously described studies, joint-polymer action studies with several polymer mixtures were performed.
Polymers used in these studies included cationic polyquaternary amine (PQA), cationic
epichlorohydrin/dimethylamine (EPI/DMA), anionic polyacrylamide (A-PAM), and non-ionic
polyacrylamide (N-PAM) polymers. Results from these studies are presented in this manuscript.
50th Purdue Industrial Waste Conference Proceedings. 1995, Ann Arbor Press. Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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