Flex Your Power Case Study: Central Contra Costa Sanitary District

Central Contra Costa Sanitary District (CCCSD) is an independent special district that collects, treats, disposes and reclaims wastewater for more than 420,000 residents of Contra Costa County. The base electrical demand for the treatment plant is 3,300 kW and can reach 6,000 kW during wet weather. CCCSD has a long history of implementing energy efficiency/conservation projects, such as the installation of a cogeneration system to produce 3,000 kW (90 percent) of the treatment plant's power requirements and the utilization of waste heat produced from cogeneration and sludge incinerators to drive a 2,500 horsepower aeration blower. This use of waste heat reduces the electrical demand by approximately 40 percent. In response to Gov. Davis' request to reduce energy usage by 10 to 20 percent and to mitigate the impact of energy cost increases, CCCSD embarked on a new energy program in 2001. The program included the installation of a modified air inlet to the cogeneration gas combustion turbine, which increased net power production by 200 kilowatts (kW). CCCSD also installed motion sensors, added more variable frequency drives (VFDs) and maximized use of alternative energy sources such as landfill gas.

The goal of this program was to reduce energy usage by 10 to 20 percent.

Although CCCSD had to replace an existing laboratory with a larger, new lab that requires an additional 100 to 200 kW, CCCSD was able to reduce imported electrical power by 58 percent in 2001 compared with 2000. CCCSD's 2001 programs successfully saved the wastewater treatment district an estimated 3 million kWh and $1 million annually. The estimated annual energy and financial savings were as follows:
• Cogeneration enhancement: 325,000 kWh and $36,000
• Motion sensors: 55,000 kWh and $6,000 with a 2-year payback
• Optimized operations: 2.6M kWh and $289,000
• Maximized use of landfill gas: $700,000 in avoided natural gas costs