Industrial operations such as surface mining, road building, and aggregate washing result in high concentrations of suspended particles (Total Suspended Solids; TSS) in surface waters which must be treated prior to discharge into fish-bearing waters. A common industrial practice is to add flocculants to improve the efficacy and speed of TSS sedimentation. A significant environmental issue even small amounts of uncomplexed cationic polymer coagulant/flocculant remaining in treated water is highly toxic to fish at very low concentrations (LC50 ∼ 0.3 mg L-1). Fingerling trout (Oncorhynchus mykiss) were exposed to (1) a cationic flocculant (Water Lynx 800 (WL800), (2) a Clearflow neutralizing polymer (CN369), and (3) a combination of WL800 and CN369 at various ratios with measured LC50 as an index of toxicity. Acute toxicity was entirely reversed by addition of the neutralizing polymer at WL800:CN369 ratios >1:1.5 mg/L. Furthermore, we demonstrate that the proximal mechanism of acute cationic polymer toxicity is hypoxemia due to accumulation of polymer on the gill epithelia rather than gill damage. Exposure of 0.5 mg/L WL800 reduced oxygen consumption by >50% reduction by 12 h and this was accompanied by significantly increased blood, brain, and liver [lactate] and [glucose]. The development of an inexpensive amelioration technique preventing cationic polymer toxicity is a significant advancement in surface and industrial water treatment to prevent cationic polymer mediated fish kills.
Keywords: Amelioration; Cationic polymer; Fish; Flocculant; Hypoxemia; Polyacrylamide; Sediment; Toxicity; Water treatment.
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