Sewer odour generation and mitigation in Edmonton's sewer systems

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The City of Edmonton has been experiencing severe sewer odour issues and related pipe corrosion problems due to the generation of hydrogen sulfide (H2S) in its sewer systems. When anoxic conditions prevail in a sewer system, sulfate present in the wastewater is reduced to sulfide by sulfate-reducing bacteria residing in the biofilms on the pipe walls and bottom sediments. The dissolved H2S in the sewage can emit into the sewer head space, escape to the ground through manholes, vent pipes, pump stations, etc., and cause odour complaints. H2S in the sewer head space can also be oxidized to sulfuric acid and cause sewer pipe corrosion. To assist the City of Edmonton in developing and assessing its sewer odour control strategies, fundamental research is proposed to investigate the generation and emission of H2S, potential structural and operational improvements in H2S control, and optimal chemical treatment methods. The City's deep sewer system is believed to be a leading cause for generating excessive flow turbulence and significant H2S emission from the sewage. The H2S emission mechanism at drop structures will be studied as well as the potential of using drop structures for air treatment and oxygenation. The solid deposition/erosion process will be studied, and sewer cleaning methods will be examined for their potential to control H2S generation at sewer biofilms and bottom solids. Structural and operational improvements at pump stations will also be investigated to prevent excessive solids accumulation. As the final defense, chemical treatments will be studied to understand how they work on biofilms and control H2S generation. The effects of various chemicals on biofilms and sewage liquid will be examined to obtain optimized chemical treatment methods. The results of this study will help the City of Edmonton develop and implement innovative, cost-effective odour control/mitigation strategies and assist other municipalities in their sewer odour prevention and corrosion control efforts. The proposed study will train 3 PhD students, 2 MSc students, 2 Postdoctoral fellows and 1 undergraduate student.