Using Embedded Sensor Networks to Monitor,Control,and Reduce CSO Events: A Pilot Study

Each year in the United States, combined sewer overflow (CSO) events result in the release of 850 billion gallons of untreated wastewater into lakes and rivers, causing drinking water contamination, human illness, animal and fish kills, and eutrophication. This paper examines the ability of an embedded sensor network to reduce the frequency and severity of CSO events by maximizing the existing storage capacity in the combined sewer system (CSS). This novel network system is called combined sewer overflow network (CSONet). CSONet uses data gathered from a distributed network of sensors to provide decentralized, distributed, real-time control of the CSS's storage capacity using automated valves called smart valves. One pilot CSONet was deployed in South Bend, IN, during the summer of 2005. It controlled the storage of storm water runoff in a large retention basin using level data from sensors within the basin and at the CSO outfall, 3.2 miles away. Once there was no longer a threat of a CSO event, CSONet automatically released the stored water into the CSS and prepared for the next storm. Before the CSONet was in place, the basin was very ineffective during small and medium storm events. The basin can now store all of the water that enters it during most storm events, preventing an equal volume of wastewater from overflowing into the St. Joseph River. Further work is being done to expand CSONet to handle in-line storage, smart valves in series, and predictive control.