Novel Fluidic Control System for Stacked Rapid Sand Filters
Publication: Journal of Environmental Engineering
Volume 139, Issue 7
Abstract
Infrastructure for water treatment faces numerous challenges around the world, including the high failure rate of digital, electronic, pneumatic, and mechanical control systems due to their large number of components and their dependency on proprietary parts for repair. The development of more efficient, reliable, easily repaired water treatment controls that rely on simple fluidics rather than on complex systems has the potential to significantly improve the reliability of drinking water treatment plants, particularly for cities and towns in developing countries. A stacked rapid sand filter (SRSF) has been proposed as a more robust and sustainable alternative to conventional rapid sand filters because each filter can backwash at the same flow rate used for filtration without requiring pumps or storage tanks. While the concept of this filter has been demonstrated in previous studies, this paper presents a novel control system for the SRSF based on fluidics that eliminates the need for mechanized controls. The water level in the filter is regulated by a siphon pipe, which conveys flow during backwash and which contains an air trap to block flow during filtration. The state of the siphon pipe and the ensuing state of the filter are controlled by one small-diameter air valve. This fluidic control system was tested in pilot-scale experiments, which demonstrated its ability to set the mode of operation of the filter and served as the basis for the derivation of design equations. In addition, the first full-size SRSF was built at a municipal water plant in Honduras using this fluidic control system, which provided a full-scale demonstration of its effectiveness. This simple and robust control system shows promise as part of a sustainable rapid sand filtration process.
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Acknowledgments
The authors thank Maysoon Sharif, Andrew Hart, Andrew Sargent, Sara Coffey, Min Pang, Ziyao Xu, and Alli Hill at Cornell University for their support of the research and design process, along with Sarah Long, Daniel Smith, Antonio Elvir, Roger Miranda, Jacobo Nuñez, and Arturo Diaz at Agua Para el Pueblo in Tegucigalpa, Honduras for their work on this project in the field. We are also grateful to the members of the Támara municipal Water Board and to water plant operator Antonio Cerrato, who put significant time and resources into the first full-scale SRSF implementation. The laboratory work described in this paper was funded by grants from the U.S. Environmental Protection Agency P3 program, and the construction of the full-scale SRSF was financed by the Sanjuan Foundation and the Támara Water Board.
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Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 139 • Issue 7 • July 2013
Pages: 939 - 946
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Jun 24, 2012
Accepted: Jan 29, 2013
Published online: Jan 31, 2013
Published in print: Jul 1, 2013
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