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OPTIMIZED REAL-TIME CONTROL OF COMBINED SEWERAGE SYSTEMS: TWO CASE STUDIES
Jacquet, G., E. Villeneuve, M K. Stinson*, AND R Field*. OPTIMIZED REAL-TIME CONTROL OF COMBINED SEWERAGE SYSTEMS: TWO CASE STUDIES. Presented at 2000 Joint Conference on Water Resources Engineering & Water Resources Planning & Management of the American Society of Civil Engineers-Urban Water Resources Research Council sponsored session, Minneapolis, MN, July 30-August 2, 2000.
The paper presents results of two case studies of Real-Time Control (RTC) alternatives evaluations that were conducted on portions of sewerage systems near Paris, France and in Quebec City, Canada, respectively. The studies were performed at real-scale demonstration sites. RTC alternatives use dynamic mathematical modeling and simulations to develop a program for a specific sewerage system to guide operation of automatic regulators when wet-weather flow is approaching. Advanced RTC alternatives also use a radar-based rainfall measurement and forecasting tool. Thus, the function of RTC-based combined sewer management is to assure efficient operation of the system and to maximize storage capacity of the existing sewerage facilities to contain combined sewer overflow (CSO) and there is a cost saving aspect of this function. The first case study was conducted on a site, located northeast of Paris, France, that was a portion of the Seine-Saint-Denis combined sewer network with independent capture from other parts of this network. This site, controlled by six regulators, includes a primary settling and storage facility of 200,000 m3 capacity, which can be operated to either increase settling efficiency of the retention pond or to increase the sewer relief capacity to decrease flood risk. This case study compared two RTC alternatives: the presently used Supervisory Predictive Control, aided by a radar-based CALAMAR system, and, a simulated, Local Reactive Control, without CALAMAR. The Supervisory Predictive Control was shown to be superior.
The second case study was conducted on a site in Quebec, Canada, that was a portion of a combined sewer network of the Quebec Urban Community (QUC), Canada. This site, called the Western Network, covers 65% of the entire QUC territory, represents about 15% of the total infrastructure of the QUC, and has been chosen by QUC as the first RTC area to be implemented in a phased CSO abatement plan to be completed by 2002. The Western Network has 3.5 million gal. of potential inline storage capacity within two existing tunnels. Of 22 regulated inflows to the interceptors, nine of them are controlled in real time. Four different RTC alternatives for the Western Network were evaluated in a simulation study with the use of MED-SOM simulator-optimizer software on 32 rainfall events of the summer of 1998. One of the alternatives simulated was the conventional and simple static weir-orifice mode. The three others were dynamic models, i.e., the Type 1 with set points located at the regulators, Local Reactive control Type 2 with set points located downstream of the regulators, and Optimal Global Predictive RTC aided by a radar-based CALAMAR system, which was the most advanced.
The overall outcome of evaluations of the RTC alternatives at both sites, in France and in Canada, is the same or at least very similar. The supervisory Predictive Control with CALAMAR, used at Seine-Sant-Denis is superior to the Local Reactive Control and the Optimal Global Predictive RTC, CALAMAR has been selected for implementation in Quebec. The RTC approach has the potential of saving the municipality millions of dollars by maximizing use of storage capacity in the existing sewerage system.