Equilibrium Environmental Inc.
March 2022
Abstract
The Canadian Council of Ministers of the Environment (CCME, 2011) provided an updated Water Quality Guideline (WQG) for chloride (from 230 to 120 mg/L for the long-term exposure), applicable to freshwater aquatic life species. In the 2011 derivation, the CCME also identified water hardness as an important factor modifying the toxicity of chloride to aquatic life. As a result of limitations with the longterm dataset, a hardness-derived guideline was not established in 2011. Long-term hardness-toxicity data were either not available or did not meet the minimum data requirements for hardness-adjusted water quality guidelines at the time based on the methods of Stephen (1985). Due to existing data limitations, the Petroleum Technology Alliance Canada (PTAC) commissioned a multi-year study in order to generate additional toxicity information for species sensitive to chloride toxicity, and data analysis on the topics described above, with a focus on water hardness.
20-RRRC-03