Real Time Savings: Using High Density Real Time Monitoring and Control to Optimize South Bend, IN's CSO System

摘要

The goal of a real time control (RTC) system is to prevent combined sewer overflow (CSO) discharges by optimizing the existing collection system. RTC systems use data from real time monitoring (RTM) sites in the combined sewer system (CSS) to provide a snapshot of the current conditions throughout the CSS. The RTC system analyzes this data to determine how storage and conveyance throughout the CSS can be optimized through the adjustment of valves, pumps, etc., which are then adjusted accordingly. Since rainfall varies spatially and temporally during storm events, the RTC approach enables the CSS to continually adapt itself in response to current storm conditions, making the existing system behave more effectively and reducing CSO discharges. RTC systems are made more accurate and efficient when used in conjunction with an extensive RTM system. The RTM system enables engineers to use real data from real storm events (rather than simulated data from simplified events) to fully characterize the CSS, identify its inefficiencies, and design an effective RTC strategy. This system can then also be used to enhance preventative maintenance practices, prevent unpermitted overflows, and diagnose problems.The City of South Bend, IN has implemented the CSOnet® RTM and RTC system throughout its CSS. The CSOnet® system utilizes a network of computerized manhole cover monitoring points and embedded computer control points to implement RTC in a distributed fashion. In this approach, all of the monitoring and control points communicate with each other via radio and cellular connections, and all control decisions are made by the equipment in the field, rather than by a central computer. Moreover, because all of the points communicate with each other, the associated control strategy can also globally optimal. Furthermore, since this system does not require a central computer and makes all of its decisions in the field, this system is perfectly scalable and less expensive than other options.South Bend has installed 110 CSOnet® monitoring locations throughout its CSS, making it the most densely monitored sewer system in the country, if not the world. This monitoring system has drastically improved the City's preventative maintenance and dry weather overflow prevention systems (27 occurred in 2008, 10 in 2009, and a goal of zero in 2010), preventing fines and improving worker productivity. Using data from its extensive RTM system, the City is able to graphically replay real storms, allowing the City's engineers to easily and effectively identify and characterize the existing CSS's inadequacies. The City has already implemented four RTC sites to address these inefficiencies, and is currently installing nine more. It is estimated that these control sites will reduce the amount of CSO discharge by 23% (or over 210 MG) annually, negating the need for a deep tunnel. Furthermore, the City estimates the CSOnet® RTM and RTC system will reduce the cost of its CSO abatement plan by $110-$150 million.