Pond Doctors perform sewer surgery

October 15, 2001 11:00 pm
Kim Lethlean manages the facility on site at the sewer lagoon where treatment programs are carried and data is logged. (Baker City Herald photograph by S. John Collins).
Kim Lethlean manages the facility on site at the sewer lagoon where treatment programs are carried and data is logged. (Baker City Herald photograph by S. John Collins).

By JAYSON JACOBY

Of the Baker City Herald

Smooth water is a good thing if youre sailing, but a bad thing if youre trying to get rid of sewage.

Nobody is planning any regattas on Baker Citys four sewage lagoons, of course.

But these are places where city officials dont mind making waves.

Calm water is a negative at sewer lagoons because it suppresses the transfer of oxygen, which in turn retards the activity of bacteria and other wildlife that eat sludge before it accumulates in the lagoons, said Dick Fleming, the citys public works director.

When that sludge piles up, as it has in Baker Citys lagoons since they were built more than 35 years ago, theres less storage space for raw sewage, Fleming said.

The accumulated sludge also leads to more frequent, longer-lasting algae blooms, which further reduce the lagoons efficiency, he said.

A solution to a problem

These problems have worsened the past few years at Baker Citys complex of four lagoons just north of town, Fleming said, prompting city officials to consider having the lagoons dredged for the first time.

That would cost an estimated $500,000, and might have necessitated a larger increase in sewer rates than the one the City Council approved earlier this year.

Instead, Fleming called in a doctor.

Fifteen doctors, in fact.

Theyre not physicians, but Pond Doctors, the trade name for a relatively simple electric pumping device that keeps the lagoon water stirred up.

The city installed the Pond Doctors in late July, at a cost of about $337,000, Fleming said.

There are 12 in the main lagoon, which covers 70 acres, and one in each of the three 10-acre ponds.

Each Pond Doctor is powered by a 1/8-horsepower electric motor. All are designed to run on solar power, but seven also have auxiliary power units that allow them to run on AC, too, Fleming said.

Each unit can pump about 1 million gallons of sewage per day, he said.

The Pond Doctors suck the liquid through a hose, then pump it out of a small cone-shaped nozzle set just below the water surface, Fleming said.

Although city workers havent measured the depth of the sludge layer since the Pond Doctors were installed, Fleming said it appears the units are working.

Kim Lethlean, the city employee responsible for maintaining the lagoon complex, agrees.

Lethlean said hes seen at least a 100-percent increase in the population of red shrimp tiny organisms that, like bacteria, eat sludge.

The more bug action you have the better youre going to break down the (sludge), he said.

Although the units could work even more efficiently if the nozzles were placed above the surface, like fountains, doing so, Fleming said with a certain delicacy, could create odor problems.

Were taking a more conservative approach, he said.

Lethlean said the Pond Doctors actually are reducing the unpleasant odors that emanate from the lagoons and that can, when the wind blows from the north, waft over Baker City as well.

By agitating the water, the Pond Doctors prevent distinct warm and cold layers from forming in the lagoons, Lethlean said.

When those layers turn over, it smells pretty bad, he said.

Pond Doctors should be beneficial year-round, Fleming said.

Sludge-eating bacteria always are more active during the warmer months, but the Pond Doctors should boost bacterial appetites during the winter, too, as well as help prevent the lagoons from icing over as soon, he said.

Performance guaranteed

Baker City didnt buy the Pond Doctors without securing a guarantee.

Fleming said the citys contract with the supplier calls for a 30-percent reduction in the sludge layer within one year, and 50 percent within two years.

It was nice to see what I consider a pretty good test written into the contract, he said.

If the Pond Doctors performance falls short of those standards, the city could ask the supplier to remove the units and refund the citys money, Fleming said.

But he hopes that wont be necessary.

And Lethlean thinks theres a good chance it wont be.

It wouldnt surprise me if they do better than (the numbers in the contract), he said. Im sold on (the Pond Doctors).