June 4, 2008

Engineers design 'brain' of smart sewage-control network

Wireless sensor network
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The system will use a citywide network of 105 manhole-mounted sensors and "smart valves" to automatically hold back the flow of rainwater and sewage in existing sewer system pipes and retention basins until the storm has passed.

"To our knowledge, this monitoring system will be the first of its kind in the world because it will be the largest wireless sensor network in a permanent, industrial setting," said Luis Montestruque, CEO of EmNet, founded in 2004 and located in Granger, Ind.

The system, called CSOnet, consists of numerous computer chips that communicate with each other over a wireless radio network. These microcomputers are embedded in the city sewer system and are connected to flow sensors, pressure sensors and valves in a network that works in a cooperative manner to control storm runoff, Montestruque said.

Such "embedded wireless sensor networks," or EmNets, also could be used in hundreds of cities around the world faced with similar sewage-overflow problems, he said.

Sensors are mounted on the undersides of manhole covers and will have to perform in an urban setting full of interference sources, said William Chappell, a Purdue assistant professor of electrical and computer engineering who helped design the sensor technology.

"The sensors must be made to operate in harsh conditions and adapt dynamically to changes in the wireless system, such as interference or the presence of parked or moving cars," Chappell said. "And the system will need to broadcast sensing data generated underground to a network that operates above ground in a challenging environment."

The system is expected to be fully functional next summer, with work progressing in stages as the system evolves to increase its monitoring capabilities, said Gary Gilot, South Bend's public works director.

Research to develop the system began in 2004 under the direction of Jeffrey W. Talley, an associate professor of civil and environmental engineering at Notre Dame. Talley led a team of project participants at Notre Dame, Purdue, the city of South Bend and EmNet that in 2005 deployed a small prototype of the CSOnet system in the city. EmNet later took over the project to expand the earlier prototype into a citywide system.

The technology is an example of a "cyberphysical system," or a network of computers tightly integrated with sensors and motorized controls, said Michael Lemmon, a Notre Dame professor of electrical engineering.

Such systems are currently being proposed for use in various applications, including control of the national power grid, automated manufacturing, air traffic control, homeland security and material distribution for industrial supply chains.

"There are many sensor networks in operation around the world, but few attempt to do active control, and that's one of the innovative aspects of this project," said Lemmon, who is leading work to develop and test computer algorithms that enable CSOnet to control storm runoff in an optimal manner.

Saurabh Bagchi, a Purdue assistant professor of electrical and computer engineering, has developed critical software, called middleware, for the system. The software allows the sensors to talk to each other in an "ad-hoc mesh network."

"The ad-hoc part means there is no need for preexisting infrastructure," Montestruque said. "It doesn't rely on a cell phone tower or telephone lines for the wireless portion of the communication to work. The mesh part means that between every two devices there are a number of different paths for it to communicate, bypassing interference and obstacles."

The adaptive capability made possible by the middleware is similar to how a human brain reroutes signals around damaged nerve cells, said Bagchi, whose work is affiliated with Purdue's Center for Wireless Systems and Applications.

"Networks need to be reliable, which means you don't want to have one single point of failure," Bagchi said. "This is particularly important because we are dealing with devices that are prone to failure. They are affected by changing seasons and environments."

Unlike other wireless systems, the network does not require a command center and can be reprogrammed wirelessly from a remote location. Information from the sensors will be relayed to a server operated by EmNet.

The sensor data will be used to monitor hydraulic conditions in the sewer system, indicating when excess runoff and raw sewage are about to overflow. Then valves will divert the flow into temporary storage sites.

The sewage will be selectively released later so that it flows into the treatment plant when capacity is available, preventing the waste from being dumped into Indiana waterways, including the St. Joseph and Wabash rivers.

Cities that have combined storm and sanitary sewers are often overloaded during major storms, forcing municipalities to divert this "combined sewer outflow" into waterways to prevent sewage from backing up into homes and businesses.

More than 700 cities around the United States and 100 Indiana cities have combined storm and sewer systems, Montestruque said.

"And many more cities are affected in Canada and Europe," he said. "People using lakes and rivers for recreational purposes can get sick, most likely because of sewage contamination, which contains large E. coli counts. Not just E. coli, but all sorts of chemicals, metals and industrial waste. Raw sewage is very toxic. It's going to take an estimated $50.6 billion to solve the problem in the United States alone. The amount of sewage dumped into rivers, lakes and the oceans by combined sewer overflows is equivalent to the water carried into the Gulf of Mexico by the Mississippi River in one week. That's 850 billion gallons per year."

Cities are fined for failing to meet U.S. Environmental Protection Agency standards. It is estimated that $4 billion will be needed to bring Indiana within federal guidelines over the next few years, Montestruque said.

The system being developed for South Bend will control flows at about 20 locations in the city sewer system. Algorithms developed by Lemmon allow each of these locations to make flow-control decisions in a manner that requires only information from neighboring points, an approach that assures optimal control of storm-water flows while greatly reducing the amount of information that must be exchanged between different locations in the system.

"This results in a control algorithm that is very efficient in its use of communication resources, or bandwidth," Lemmon said.

Gilot likens the concept to modern traffic signal controls that adjust signal timing in response to changing traffic flow and demand.

"We are going to apply that same kind of logic to sewers," Gilot said.

Talley, an environmental engineer, also is developing a technique of using ultrasound to clean water diverted to temporary holding facilities. The method works by bombarding water with high-frequency sound waves, producing bubbles that implode, generating high heat that purifies water.

The ultrasonic method may eventually be incorporated into the system. Water cleaned using the ultrasonic method would be released directly into waterways, reducing the need to later route water to the municipal wastewater treatment facility.

Writer: Emil Venere, (765) 494-4709, venere@purdue.edu

Sources: Luis Montestruque, (574) 360-1093, lmontest@heliosware.com  

William J. Chappell, (765) 494-6225, chappell@ecn.purdue.edu  

Saurabh Bagchi, (765) 494-3362, sbagchi@purdue.edu

Michael Lemmon, (574) 631-8309, lemmon@nd.edu

Jeffrey W. Talley, (574) 631-5164, jtalley1@nd.edu

Gary Gilot, (574) 235-9251, ggilot@southbendin.gov

Purdue News Service: (765) 494-2096; purduenews@purdue.edu

Note to Journalists: Montestruque is pronounced monn-tess-TRUE-keh

PHOTO CAPTION:
Purdue electrical and computer engineering doctoral students Rajesh Krishna Panta, from right, and Jin Kyu Koo discuss software needed for a wireless sensor network in South Bend, Ind., to prevent raw sewage from overflowing into waterways, especially from surging runoff during storms. The software must be loaded into antenna-equipped miniature computing nodes to control a citywide network of 105 manhole-mounted sensors and "smart valves." The system is designed to automatically hold back the flow of rainwater and sewage in existing sewer system pipes and retention basins until the storm has passed. The stored water would then be released in a controlled manner for subsequent treatment by the city's wastewater treatment plant. (Purdue News Service photo/David Umberger)

A publication-quality photo is available at https://www.purdue.edu/uns/images/+2008/bagchi-wirelessnetwork.jpg

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