Cutting the cost of wastewater treatment

2012-10-29 - An award-winning ABB medium voltage drive has reduced the energy consumption of the aeration blowers at a US wastewater treatment plant by more than 1 million kilowatt-hours a year - a reduction of more than 30 percent that saves the city utility $75,000 annually.
By ABB Communications

The aeration basins (left) and aeration blower system (right) at the City of Beloit Water Pollution Control Facility, Wisconsin

The ACS 2000 medium voltage variable speed drive was installed in July 2011 and has achieved some remarkable results within its first year of operation at the City of Beloit Water Pollution Control Facility (WPCF) in Wisconsin, United States.

The facility treats an average of 5.5 million gallons (20.8 million liters) of wastewater a day from the city’s 37,000 inhabitants, as well as industrial waste from local businesses and biological waste from food processing plants.

Like many wastewater treatment plants, Beloit uses a conventional activated sludge process for treating the wastewater. At the heart of this process are the aeration basins in which microorganisms break down the organic matter in the wastewater. These bacteria require oxygen to survive, which is provided by huge aeration blowers that blow air through diffusers at the bottom of the basin.

ACS 2000
Winner of the 2010 Frost & Sullivan European Medium Voltage Drives
New Product Innovation Award

Aeration blowers typically account for 50 percent or more of the electricity consumed by a wastewater treatment plant, and Beloit is no exception. Prior to the installation of the ACS 2000, the aeration blower system at Beloit WPCF was controlled by an inlet throttling valve – a common solution for blower control that operates at fixed speed and does not offer the same operating and cost benefits as variable speed drives.

For Beloit WPCF these benefits are wide-ranging and include soft start capability, ease of installation, direct-to line (transformerless) connection to the power supply network, minimal harmonic distortion, non-requirement of medium voltage power factor correction, compact and lightweight footprint, short payback time and low total cost of ownership.

These benefits are enhanced by an ABB DriveMonitor™ intelligent diagnostic system that performs remote and real-time monitoring and diagnostics of the drive via a wall-mounted PC connected to the telephone line.

Once the ACS 2000, was installed the power consumption of the aeration blower system dropped by more than 30 percent and total plant energy consumption by 15 percent, which is more than 1 million kilowatt-hours a year. At an average composite rate of $0.62/kWh, the annual savings for the City of Beloit amount to $75,000.

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The ACS 2000