Valves Improve Air Flow Control for Aeration Basins

Ten new valves are allowing Regional Wastewater Treatment Facility staff to more effectively operate the site’s five aeration basins, a critical step in the wastewater treatment process.

The aeration basins (208 feet long, 30 feet wide, and 15 feet deep) are part of secondary wastewater treatment. They provide oxygen for the millions of beneficial microscopic organisms that break down dissolved organic material in the water after it has passed through primary treatment. The oxygen is delivered to the basins via three high-horsepower blowers, though typically only one or two blowers are used simultaneously, with the third for backup.

“The blowers are one of the biggest energy loads at the plant,” says Principal Electrical Engineer Maurice Atendido.

Wastewater Treatment Plant Operations Superintendent Virgil Sevilla checks the aeration basins at the facility.

Previously, the air flow to the blowers was controlled by pneumatic valves operated under air pressure. The new Rexa brand valves are controlled by electric motors that run hydraulic motors. The new valves provide finer control of the air flow. “We’re not wasting air with the new valves,” Atendido says. “And the less air you use, the less energy we need for operation.”

Two DSRSD divisions—the Mechanical Maintenance Division and the Instrumentation, Controls & Electrical Division—worked together to replace the aging valves for this $80,000 project. The work began in FY2020 and was postponed until later in FY2021 due to coronavirus precautions with wastewater.

“We didn’t finish up the project until it was confirmed it was safe to be around the aeration basins, which were considered a high-risk area,” says Mechanical Superintendent Shawn Quinlan.

In June 2021, treatment plant staff were still making adjustments in the Supervisory Control and Data Acquisition (SCADA) computer system with the new valves. Wastewater operators monitor and control plant facilities via SCADA. At that time, they had already tracked more than 100,000 different cycles with the new valves showing the adjustments of the new valves versus the old. Previously, the valves would cause delays and could adjust air flow too much or too little. The updated valves respond immediately and allow for more minute adjustments.

“The new ones are exact literally every time,” Quinlan says. “We’re anticipating a fairly sizeable energy savings.” It will take staff about a year to see trends and determine how much energy is actually being saved, but Quinlan estimates a 10% efficiency gain in use of the blowers based on preliminary research. “We’re already seeing savings because the blowers are running less.”

Posted: July 8, 2021