Use of Air Circulation Pipes in Deep Dropshafts for Reducing Air Induction into Sanitary Sewers
Publication: Journal of Environmental Engineering
Volume 142, Issue 4
Abstract
Falling water in dropshafts can induce large amounts of air into the airspace of sewers, and the subsequent release of the pressurized air can cause sewer odor concerns. The construction of a vertical airshaft that is connected to a dropshaft via pipes is expected to circulate the air and reduce air induction into sewers. In this study, two deep dropshafts with drop heights of 24 and 11 m were retrofitted sequentially with air circulation pipes in a sanitary sewer system. Air pressure inside the sewer line and air flow rates inside the air circulation pipes were monitored in 2006–2011. The results show that the retrofits reduced the manhole air pressure by about 10–47%. Air pressures in the manholes and the dropshafts, as well as air flow rates in the air circulation pipes, were noticed to have diurnal patterns, which appeared to relate to wastewater discharge and air pipe elevation. Overall, the ratios of air flow rate to water flow rate were found to be and for the two dropshafts, which are several times larger than those reported for laboratory dropshafts without air circulation pipes. Sewer air was indeed circulated via air pipes in the first dropshaft, while no circulation was observed most of time in the second dropshaft because the air was directly pushed downstream by the upstream dropshaft.
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Acknowledgments
The authors are thankful to the Natural Sciences Engineering Research Council of Canada (NSERC) and the City of Edmonton for their financial support.
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Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 142 • Issue 4 • April 2016
Copyright
© 2015 American Society of Civil Engineers.
History
Received: Oct 14, 2014
Accepted: Sep 2, 2015
Published online: Dec 28, 2015
Published in print: Apr 1, 2016
Discussion open until: May 28, 2016
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