Wastewater treatment polymers identified as the toxic component of a diamond mine effluent

Abstract

The Ekati Diamond Mine, located approximately 300 km northeast of Yellowknife in Canada's Northwest Territories, uses mechanical crushing and washing processes to extract diamonds from kimberlite ore. The processing plant's effluent contains kimberlite ore particles (< or =0.5 mm), wastewater, and two wastewater treatment polymers, a cationic polydiallydimethylammonium chloride (DADMAC) polymer and an anionic sodium acrylate polyacrylamide (PAM) polymer. A series of acute (48-h) and chronic (7-d) toxicity tests determined the processed kimberlite effluent (PKE) was chronically, but not acutely, toxic to Ceriodaphnia dubia. Reproduction of C. dubia was inhibited significantly at concentrations as low as 12.5% PKE. Toxicity identification evaluations (TIE) were initiated to identify the toxic component of PKE. Ethylenediaminetetraacetic acid (EDTA), sodium thiosulfate, aeration, and solid phase extraction with C-18 manipulations failed to reduce PKE toxicity. Toxicity was reduced significantly by pH adjustments to pH 3 or 11 followed by filtration. Toxicity testing with C. dubia determined that the cationic DADMAC polymer had a 48-h median lethal concentration (LC50) of 0.32 mg/L and 7-d median effective concentration (EC50) of 0.014 mg/L. The anionic PAM polymer had a 48-h LC50 of 218 mg/L. A weight-of-evidence approach, using the data obtained from the TIE, the polymer toxicity experiments, the estimated concentration of the cationic polymer in the kimberlite effluent, and the behavior of kimberlite minerals in pH-adjusted solutions provided sufficient evidence to identify the cationic DADMAC polymer as the toxic component of the diamond mine PKE.

A Mobile DNP Polarizer for Clinical Applications

“…Although poly(DADMAC) itself has been shown to be toxic towards aquatic organisms [22], many natural water-soluble polyelectrolytes could be spinlabeled and used as nontoxic polarizing agents (e.g., polysaccharides or chitosan derivatives). Furthermore, one can devise schemes to extract spin-labeled polyelectrolytes from the solutions before injection by using them as a fixed polyelectrolyte gel matrix (similar to the system in ref.…”

Ecotoxicological assessment of flocculant modified soil for lake restoration using an integrated biotic toxicity index

“…The adding of soil could reduce toxicities of chitosan and cationic starch by one to two orders of magnitude. Some reports indicated that clays could effectively reduce the acute toxicities of cationic polymers to aquatic organisms (de Rosemond and Liber, 2004). Goodrich et al (1991) also found that the biotic toxicity of cationic polymer was reduced 33-to 75-fold at higher humic acid concentrations (Goodrich et al, 1991).…”

Transfer and degradation of polyacrylamide-based flocculants in hydrosystems: a review

“…High molecular weight PAMs can be modified to develop non-ionic, anionic, or cationic properties for specific uses (Scott et al, 1996). However for environmental applications which are described in this article, anionic PAMs are preferred because of their extremely low aquatic toxicity compared to cationic forms (Hamilton et al, 1994;de Rosemond & Liber, 2004;Liber et al, 2005). Common anionic…”

“…The use of flocculants enables to increase the recycling rate of process water and to decrease sludge volumes and thus the surface of settling ponds. Those ponds are open systems with possible exchanges into the near aquatic environment (water percolation towards soils and aquifers, water seepages in natural streams or rivers…), which can lead to the dissemination of flocculants into surface and groundwaters (de Rosemond & Liber, 2004;Liber et al, 2005). The question of flocculants safety is now arising as a new key-environmental issue.…”