Sewage treatment plant upgrade fizzes along

Like most sewage lagoons, Pea Ridge’s treatment plant isn’t much to look at. But that doesn’t mean there’s not a lot going on - especially recently.

Two months ago, crews finished installing an upgrade that cost $1,050,000.

Water/wastewater Department manager Ken Hayes explained that the most significant upgrade isn’t visible other than the bubbles that fizz to the surface of the four lagoons. Large compressors push air through hoses into diffusers. The air flow both aerates the water and causes it to circulate - much like a room fan stirs the air.

When the plant was built, it used a system of pipes attached to the bottom of the four 13-footdeep lagoons. The pipes were hard to clean, and just didn’t aerate the water sufficiently to ensure activity of the bacteria that digests the waste.

In the mid 1990s, that system was replaced with large floating aerators. But those, too, didn’t work well because they only aerated the top 2 feet of the lagoons. That caused ammonia (a form of nitrogen) to be discharged from the plant. Ammonia kills fish and other aquatic life. It got to the point, Hayes said, that something had to be done.

So engineers once again went to work on the issue.

The result of their work: Submersible aeration heads that create a plume of very fine bubbles that add oxygen to the water, and jets of large bubbles that create circulation. Workers using a pontoon boat can easily raise the aerators for maintenance - which was not possible with the original system because it was fastened to the bottom.

“We’re seeing good results,” Hayes said Thursday. He noted that when the aerators began operation two months ago, the water needed oxygen so badly that no bubbles rose to the surface. “We didn’t think they were working,” he noted, “but they were.”

Once the water absorbed enough oxygen, the bubbles made it to the surface.

The city paid for the project with a bond issue, by refinancing bonds that had interest of 5 percent or 6 percent to much lower rates, and by a slight rate increase, Hayes said.