Section Two
TOXICITY REDUCTION
6    IMPACTS OF ORGANIC AND INORGANIC
FLOCCULANTS/COAGULANT AIDS ON WHOLE
EFFLUENT TOXICITY TESTING
Douglas J. Fort, Senior Toxicologist
Enos L. Stover, President
Marty D. Matlock, Laboratory Director
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. Several investigators have evaluated the
acute toxicity of flocculating polymers to aquatic organisms (1-4), but none have made specific-
toxicological comparisons between the polymers and commonly used inorganic coagulant aids, such
as ferric chloride (FeCl3) and alum (AI2(S04)3). In addition, of the studies conducted to date, none
have evaluated differences in coagulant aid toxicity due to the type of treatment applications used.
This paper describes the acute toxicity of both organic flocculants (polymers) and inorganic coagulant aids (A12(S04)3 and FeCl3) to the commonly used WET test species Ceriodaphnia dubia. Comparisons are made between the relative toxicity of four cationic polymers and A12(S04)3 and FeCl3.
Because cationic flocculating polymers are often used in conjunction with inorganic coagulant aids in
wastewater treatment, cationic polymers were used exclusively in this study. Differences in toxicity
due to the type of treatment application were also evaluated. More specifically, testing was conducted
to simulate the potential toxicological effects of using the various organic and inorganic coagulant
aids in either secondary wastewater clarification or in final effluent polishing. Results from this study
clearly demonstrate that both the type of flocculating agent used and the type of treatment application
strongly influence toxicity.
INVESTIGATIVE PROGRAM
A schematic overview of the Investigative Program Approach is presented in Figure 1.
Materials
The four organic flocculating polymers, labelled at random I-IV, were obtained from three different commercial vendors (Chemlink, Malvern, PA; Nalco, Naperville, IL; and Cyanamid, Wayne,
NJ). Commercial-grade FeCl3 and A12(S04)3 were obtained from Fisher Scientific (Houston, TX).
Salts used to prepare the reconstituted dilution water used in this study were obtained from Sigma
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
41