ROYAL CITY - An upgrade at the Royal City Wastewater Treatment Plant that will improve water quality and cut the city's cost of running the plant is nearing completion.

The study that led to the $250,000 upgrade was made in November of 2012. Construction began in November of 2013.

Construction of the improvements is nearing completion, with the final (third) dissolved oxygen blower to be brought on-line this week.

"The new system has already led to improved quality of our effluent," Public Works Director John Lasen said. "We are confident that tracking energy consumption at the wastewater treatment plant over the next 12 months will prove how effective the improvements have been in saving energy."

The decision to upgrade came out of an energy audit performed by McKinstry Consulting. The purpose was to determine if there were any city utility operations or processes where it could reduce energy consumption.

"For the most part, the audit showed the city was a good steward of energy," Lasen said. "The only operation that showed any need for improvement was at our wastewater treatment plant."

It was determined that an upgrade to the mechanical and controls systems was needed.

The treatment plant is equipped with three blowers to provide oxygen to process microorganisms that breakdown waste. The original blowers were on a timer that turned them on and off as needed to maintain dissolved oxygen (DO) levels in the system process. This process works most efficiently when DO is maintained at consistent levels.

"We learned that the original on/off operation was an inefficient method to maintain optimum DO levels," Lasen said.

It was determined that replacing the original blower system with blowers driven by more energy efficient motors and operated with a variable frequency drive (VFD) system would reduce energy use by a minimum of 1.2 percent annually.

The findings of the audit were then used to apply for an Energy Efficiency Grant through the Washington State Department of Commerce to replace the original blowers and control systems.

The grant application was successful and, in March of 2013, the City was awarded a $250,000 grant to make improvements.