| All pulp and paper mills in Canada are required to conduct regular toxicity testing under the federal Pulp and Paper Effluent Regulations. According to the regulations, toxicity testing must be conducted weekly for Daphnia magna (daphnia) and monthly for Oncorhynchus mykiss (rainbow trout). A test failure is designated by greater than 50% mortality in daphnia or trout in 100% effluent concentration for a 48 or 96 hour period; respectively. Diagnosing the specific cause of toxicity is a difficult process, as there are often many contributing factors. During this study, previous toxicity events (January 2002 to December 2006) were examined using a three phase methodology to provide a basis for investigations of future toxicity events. The three phase methodology included: graphical representation of the primary growth parameters versus toxicity data to identify trends, multiple regression analyses to identify correlations between these variables, and a review of mill and wastewater treatment plant operating records. During this period, toxicity episodes were attributed to various sources; specifically: low dissolved oxygen, high temperature, nitrogen deficiency, denitrification, high total suspended solids, dramatic swings in BOD loading, high hydraulic flows, chemical releases from the mill, and septic material entering the system during mill shutdowns and while bringing the equalization (EQ) basin into service. In conclusion, the three phase methology was developed to assist in the investigation of future toxicity events at the Pine Falls facility. The methodology will be added to the wastewater treatment facility operating procedures. |
