Water quality based standards are derived by calculating how much of a given substance can be released while still meeting instream surface water quality objectives (3) . For details please consult the Water Quality Based Effluents Limits Procedures Manual (4) . As an example, Alberta Environment is evaluating the need to set more stringent release limits on BOD for mills releasing to the Athabasca River based on water quality assessments on in-stream dissolved oxygen. These assessments are designed to establish the maximum level of BOD5 that can be released into the river without risking maintenance of the acute.
