New Meters Earn Energy Efficiency Rebate for Wastewater Treatment Plant

From the Dublin San Ramon Serivices District

The 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.