TIE for cyanides in groundwater at a former coal gasification plant

Groundwater remediation efforts are underway at a former coal gasification plant site in British Columbia because the concentrations of cyanide and other substances were found to exceed aquatic life guidelines. Hemmera and Nautilus Environmental examined whether that groundwater was toxic to a variety of sensitive marine aquatic life species, and whether cyanide was the primary toxicant. Untreated groundwater containing cyanide, weak acid dissociable cyanide and free cyanide was tested for toxicity on bivalve larval survival, kelp zoospore germination, sea urchin gamete fertilization, and larval topsmelt survival and growth. The untreated groundwater was found to be toxic to kelp zoospores and sea urchin gametes, but relatively non-toxic to bivalve larvae and topsmelt. The following 4 toxicity identification evaluation (TIE) treatments were conducted on site groundwater: (1) acidification/aeration of the sample, (2) filtration of the sample through anion exchange media, (3) filtration of the sample through activated carbon, and (4) exposure of the sample to UV light. Both the cyanide concentration and the toxicity to kelp decreased considerably when the anion exchange treatment was applied. The results suggest that the toxicity may be attributed to cyanides in the groundwater. The information obtained from this study will be used to plan excavation water treatment strategies during site remediation as part of an ecological risk assessment for the site.