Air flow meters recognized for energy efficiency at CA wastewater treatment plant

Dublin San Ramon Services District has earned an energy-efficiency rebate for its air flow meters in its WWTP aeration basins.

May 7, 2013 -- Dublin San Ramon Services District has earned an $18,869 energy-efficiency rebate from Pacific Gas and Electric Company (PG&E) for installing lightning-fast, highly accurate air flow meters in the aeration basins at its wastewater treatment plant. The eight new meters should reduce annual electricity costs by at least $36,000 and save enough energy to power 10 average homes for a year. Test results indicate savings could be as much as $50,000, depending on operating conditions.

Aeration (adding air) is energy intensive, consuming a third of all the power DSRSD uses to treat wastewater. Four-hundred-horsepower electric blowers run around the clock supplying oxygen to beneficial bacteria that break down organic material in wastewater. An interconnected system of meters and valves constantly monitors the dissolved oxygen level in the water and adjusts the flow of air to maintain ideal conditions for the bacteria to work. The new meters control air flow much more quickly and precisely than the old equipment, thereby minimizing unnecessary blower adjustments that waste energy.

"The old meters took up to two minutes to react when conditions changed. With that lag time, the system would constantly hunt and adjust, looking for the right air flow setting. With the new meters, response time is less than a second. The adjustments are exact and air flow stays very steady, which is the most efficient way to run the blowers," said Steve Delight, the DSRSD senior civil engineer who managed the project.

DSRSD installed the same type of meter, which is manufactured by Kurz Instruments of Monterey, Calif., on its digester gas (methane) pipelines in 2009. Impressed with the meter's accuracy and fast response time, DSRSD contracted with Alliance Power of Centennial, Colo., to test the meter's efficiency in one of the District's aeration basins. The initial test demonstrated energy savings of 17.2 percent. Based on the savings potential of the improved air flow monitoring, DSRSD applied for PG&E’s Calculated Incentive program and qualified to receive an $18,869 rebate, more than half the cost of eight meters. Including installation and testing, the entire project cost $90,000. The payback period is two years. Alliance Power is using data from the DSRSD installation to demonstrate the energy efficiency of the meters to other wastewater treatment utilities.

Since 1991, DSRSD has received $116,439 in PG&E rebates for energy efficiency projects that have saved more than 2.7 million kilowatt-hours of electricity (estimated annual savings in the year the projects were installed), enough to power 128 average homes for a year.

Founded in 1953, Dublin San Ramon Services District serves 157,000 people, providing potable and recycled water service to Dublin and the Dougherty Valley area of San Ramon, wastewater collection and treatment to Dublin and south San Ramon, and wastewater treatment to Pleasanton (by contract). More information about the District can be obtained at

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