Implication of polymer toxicity in a municipal wastewater effluent

The use of cationic polymers as flocculants and coagulant aids to control s uspended solid levels in the water and wastewater treatment industry is wid espread in most developed countries. Today, the most frequently used clarif ication polymers, polyacrylamides, are often proprietary, and little inform ation exists on the ecological impacts of these products. Following standar d U.S. Environmental Protection Agency (U.S. EPA) whole effluent toxicity t esting (WET) protocols, effluent toxicity can be detected via organism resp onse, yet methods to positively characterize cationic polymers in effluents are not provided in U.S. EPA Phase I toxicity identification evaluation (T IE) protocols. Implication of cationic polymer toxicity in a municipal wast ewater effluent was achieved through a series of Ceriodaphnia dubia toxicit y resting with toxicant elimination steps that included extensive effluent characterization and affluent manipulation. Key in the identification was a discrepancy in effluent toxicity with respect to the type of container in which the effluents were stored. All effluent toxicity was lost within 48 h of storage in plastic containers, while on the contrary, affluent toxicity persisted in glass-contained samples for up to 4 weeks of 4 degrees C stor age. A weight-of-evidence approach suggested that the cationic polyacrilami de polymer. Hyperfloc(R), was the primary source of acute toxicity in the e ffluent. Removal of this polymer significantly reduced effluent toxicity. T his study suggests that cationic polymer-related toxicity might not be dete cted if effluent samples are stored in plastic containers.