Intelligent CSO Control: Results of the First Two Years of Operation in Louisville, Kentucky

The Louisville and Jefferson County Metropolitan Sewer District (LMSD) has successfully implemented and operated the first phase of its Global Optimal Predictive Real Time Control (GOP RTC) system as part of the Combined Sewer Overflow (CSO) Long Term Control Plan (LTCP). The LMSD is the first Publicly Owned Treatment Works (POTW) in the United States to commission and implement such a sophisticated level of RTC to manage its complex Morris Forman sewer network.The first phase of the GOP RTC system contained five control points and was projected to provide a system-wide average annual overflow volume reduction of 10 to 20%. The system has been operating since April 2006. The performance results of Phase I in terms of CSO reductions met and exceeded the expected performance defined in the RTC studies. Indeed, more than 1,200 MG of overflow volume was captured and treated during operation in 2006 and 2007.The second phase, currently being implemented, includes the addition of four control points. The ultimate build-out of the entire RTC program is targeted to be approximately twenty control points. The in-line control portion of the program is targeted to cost approximately 30M, whereas cost for off-line storage facilities is significantly lowered due to reduced storage volume requirement as an advantage of applying RTC. The total program using RTC proposes a cost of 90M to meet the same environmental objectives as the 1996/1997 LTCP drafts where the construction cost of the conventional solutions was originally estimated at 250M without RTC. The LMSD can obtain a significant saving of 160 M (64%) on the estimated CSO program costs through the implementation of intelligent control with RTC technology.The LMSD entered into a Federal consent decree in August 2005 regarding SSOs and CSOs. Efforts are currently underway to produce a final Sanitary Sewer Discharge Plan (SSDP) and the Long Term Control Plan. Based on the performance results of the first year of operation, GOP RTC will remain the base strategy in the LTCP and may be incorporated into the SSDP.