Optimization of Wastewater Lift Stations for the Reduction of Energy Usage and Greenhouse Gas Emissions

The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) demonstrates a clear relationship between increasing greenhouse gas (GHG) concentrations and higher global temperatures (IPCC, 2007). One key component of sustainable water and wastewater infrastructure is the mitigation of indirect GHG emissions resulting from off-site energy providers, thereby providing a program that is adaptive to the demands that climate change poses with each coming decade. One of the major sources of GHG emissions from wastewater utilities is energy use caused by lift stations operation, especially in flat topographic regions where hundreds of such lift stations are required. Many of the collection system lift stations still operate with local or basic controls that have no hydraulic relationship with other collection system lift stations, and are operated with instrumentation and control systems that were developed many years ago. Upgrading existing systems to operate as sustainable infrastructure is a relatively new but rapidly growing concept.A new control system featuring new generation SCADA configurations allows data communication directly from the lift station to the wastewater central control room. This configuration eliminates slow, conventional limited two-way communication via aging radio, telephone and hardwired copper networks that require data to pass through data concentrators located miles away from the central control room.The research team conceptualized a revised operational control method for the lift station system utilizing hydraulic modeling results generated from specific site conditions through optimizing the pumping units and reducing simultaneous running cycles. This method of operation was hypothesized to reduce operating pressures in a common forcemain, reduce the energy demands of the pumping units by 15 to 25-percent, and stabilize the influent flow entering the wastewater treatment facility (WWTF), which could ultimately result in lower energy costs that are associated with the aeration requirements for the biological processes used.Pilot testing was conducted in order to validate the above operating hypothesis. The first demonstration test was conducted in an area that is known not to have infiltration and inflow (I&I) problems. To ensure repeatability, a second pilot study was performed in an area, which had documented I&I problems. Innovyze InfoWorks CS software was utilized for hydraulic modeling and Siemens SINAUT system was installed as the SCADA system for the pilot testing.The final product of this study will be a guidebook for utilities that detail how wastewater lift stations can be optimized using advanced hydraulic modeling and new generation SCADA systems. Key objectives of this study were to:• Reduce greenhouse gas emissions from not only the wastewater collection system by operating the system more efficiently, but also at the WWTF by providing a more uniform influent flow the facility.• Reduce forcemain operating pressures, total dynamic head, and thereby reduce power consumption.• Reduce overall wastewater collection and WWTF operating costs by designing system capacity based on optimized system operations.• Schedule motor and pump operating cycles to increase equipment service life and consequently to reduce service calls that are associated with overtaxed pumping systems.• Reduced capital costs by designing system capacity based on optimized system operations (i.e. reduced pumping capacity, forcemain capacity, peaking flow treatment works capacity), as well as for system peaking capacity through the ability to control insystem storage capacity by integrating real-time system data with controlling operating models (e.g., flow rates, rates of change, storage elevations, etc.).This project was funded under the WERF-USEPA cooperative agreement Innovation and Research for Water Infrastructure for the 21st Century (Project No. INFR3R11). MWH is leading this research project with collaboration from JEA, a water, wastewater and electric utility located in northeast in Florida.