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5B a - RA/ Ranking and Chemical Specific (TUP/200) Wastewater treatment polymers: a real or perceived risk to aquatic organisms? Liber, Karsten1, de Rosemond, Simone1, Wilson, Anne2, 1 Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada2 Environmental Protection Branch, Environment Canada, Yellowknife, NT, Canada ABSTRACT- Polymers such as coagulants and flocculants have been used within water and wastewater treatment facilities since the mid-1950s to clarify potable water, industrial effluents and municipal wastewater, thicken and de-water sludge, and aid in the filtration of primary and digested sludge. The primary function of these polymers in water clarification and sludge de-watering processes is to destabilize colloidal suspensions and induce particle flocculation. Residual wastewater treatment polymers in effluents were initially thought to be of little toxicological concern to aquatic organisms due to their high molecular weight (>104) and the propensity for these compounds to bind to suspended solids. However, recent research using a weight-of-evidence approach has demonstrated that effluents containing wastewater treatment polymers can be acutely and chronically toxic to aquatic organisms at concentrations as low as 4 ug/L. The present problem is that current Toxicity Identification Evaluation (TIE) procedures are unable to clearly identify and confirm polymers as the toxic component in effluents. In addition, there are no routine analytical detection methods available that are selective and sensitive enough to detect polymers in wastewater effluents at concentrations that are toxic to aquatic organisms. Furthermore, very little information exists on individual polymer formulations with regard to toxicity to aquatic organisms, environmental persistence, and degradation pathways. Therefore, in order to determine if wastewater treatment polymers pose a real risk to aquatic organisms, data quantifying the degree of toxicity to exposed organisms must be generated, the environmental fate of polymers and their degradation products must be determined, and adequate analytical detection methods need to be developed. These needs are discussed within the context of data available for a diamond mine operating in Canada's far north. Key words: effluents, polymers, risk assessment, aquatic organisms |
