In October 2018, the Regina Wastewater Treatment Plant experienced a unique effluent quality event. The event resulted in a substantial shift in biological populations, and the degradation of the effluent quality, including Total Phosphorus, E. coli, and Total Suspended Solids. This presentation highlights the investigative process used to determine the cause of the event and its immediate impacts within hours, weeks and months. As part of the investigation into the event, 13 different process functions were analyzed. The investigative measures taken were necessary to provide EPCOR's client, the City of Regina, with a comprehensive report explaining why the event impacted the final effluent quality. Throughout the investigation, extensive laboratory data was collected and analyzed, literature reviews were conducted and outside experts were consulted. During the investigation, it became apparent that there was insufficient experience and published information available regarding a large scale events within a biological nutrient removal plant. Other than hearsay information, we did not find any precedent for an event like ours. To determine the cause and impact of this event, we were required to complete extensive research using information from multiple technical and research sources. In conclusion, each individual reaction to the event was thoroughly understood and was significant enough to draw the firm conclusion of zinc toxicity.
