News

City saves a buck by mixing muck

The South County Spotlight
Wed, 02/16/2011
By Tyler Graf

St. Helens hopes for eventual savings with new solar wastewater mixers

The purchase of nine new solar-powered wastewater mixers in St. Helens, to be used in the primary and secondary wastewater lagoons at the Wastewater Treatment Plant, is the realization of a decade-long energy-saving plan for the city’s facility.

The first seven of the mixers were bought last fall for use in the secondary lagoon, which receives waste from Boise Inc.'s paper mill facility, while two more will be purchased this week to be used in the primary lagoon.

The moving paddles of the mixers, purchased from North Dakota-based firm SolarBee, aerate the lagoon and help to reduce odors and decrease the levels of organic waste. Without mixing and aerating the water, the lagoon’s natural process of breaking down waste, which relies on tiny microorganism eating away at the organic matter, would not occur.

Now, with the help of a 70 percent rebate for the equipment coming from the Bonneville Power Administration (BPA), that work can be done in a manner that could save Boise and the city as much as 50 percent annually on its energy costs, said project leaders.

Aaron Kunders, superintendent of the city’s wastewater treatment facility, said buying solar-powered mixers was an idea first floated at the wastewater treatment facility a decade ago. The city couldn’t move on the project until the upfront costs decreased, however.

“At the time, there was too much money going toward fixing the aerators,” Kunders said. There are 23 aerators at the primary lagoon and another seven at the secondary lagoon. “With the financial incentives we now have, though, it would be crazy not to [buy the mixers].”

Energy consultants at Cascade Energy Engineering expect the cost of the aerators will be paid back in approximately two-and-a-half years through energy savings.

The city spent $104,570 on the first seven mixers. That cost is expected to drop to $31,371 with the 70 percent rebate, Kunders said. 

The project was not put out to bid.

The city did not go through a bidding process because the joint city/Boise technical advisory team determined that, with the 70 percent rebate, SolarBee’s prices were the lowest in the market. And because the city is staying with the same model it previously purchased, it can cut down on the spare parts inventory, Kunders said.

The city and Boise purchased and installed the seven original aerators last September. Since they were installed, energy use at the lagoon has dropped by 40 percent, according to officials.

City officials believe the additional two mixers could cut down energy costs in the primary lagoon by 50 percent.

That percentage is likely to fluctuate when the project completes, said Tim Lammers, energy services supervisor at Columbia River PUD. The PUD worked with the city and Boise on the energy-efficient project.

Lammer’s job was to convince officials at the BPA, that the project would provide energy savings.

“When [the mixers] were put in place, everyone was unsure about how it would work,” Lammers said. “On a project of this size, we want to be sure we are buying energy savings.”

With the first of the mixers in place, the energy savings have been slightly less than anticipated, Lammers said. Nonetheless, he added that he expects the new mixers to save 342,804 kilowatt hours, a cost savings of $76,876.