Working out Lewiston’s wastewater woes

Nate Smith confidently grabbed a handful of brown material from a conveyor belt at Lewiston’s wastewater treatment plant and began squeezing it like Play-Doh.

The biosolids he was touching are part of what’s left after the plant processes what’s flushed down every Lewiston toilet.

As supervisor of the facility that essentially is the city’s colon and urinary tract, Smith understands how fragile the system he oversees was before a $34.1 million renovation that will be finished in August.

The project is one of six at various stages that together will cost in excess of $80 million. (See accompanying list.)

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At the sewer plant, located in North Lewiston near the Clearwater River Railroad Bridge, the city is getting help through a loan from Idaho’s state revolving fund. The money is being repaid with a one-time 40% hike in Lewiston’s sewer and water rates that started in fiscal year 2018-19.

City officials believe the investments are essential to the community’s vitality and are being completed as inexpensively as possible without sacrificing performance.

The state’s revolving fund offers a low rate, which is reducing the overall cost and allowing the work to happen more quickly, said Dustin Johnson, Lewiston’s public works director.

The improvements will add capacity, resilience and new functions to the infrastructure that delivers and cleans the city’s water and treats it after it’s been drunk, watered lawns and fought fires.

Before the 40% increase, the rates covered treatment, handling and transmission of water and wastewater, but not future replacement or upgrades, Johnson said.

“I tend to use the car or home analogy,” Johnson said. “If you’re not saving for contingencies (like roofing or painting), it’s going to get you in the long run. That’s kind of where Lewiston got painted a little bit into a corner.”

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At the wastewater treatment plant, the infusion of cash is making a huge difference. The system consists of two lift stations that funnel wastewater into the plant’s headworks. From there, the water goes into primary clarifiers, aeration basins and secondary clarifiers, before being sanitized with ultraviolet lights and released into the Clearwater River.

As the water travels through, solids are extracted and treated in a digester. They go to presses that squeeze out moisture, and what’s left is placed on trucks and hauled to Clearwater Composting. That business treats that material further and adds yard waste, which results in compost.

Every part of the plant is expected to function better when the upgrade is complete, starting with the north shore lift station, which is being replaced. The concrete on it was degrading severely. Its design only allowed staff to remove garbage such as flushable wipes, chip bags and condoms twice a year.

Employees would have to clean out bits of wipes that got hooked on valves and other parts of equipment, Smith said.

At one point, a 2-foot layer of trash accumulated, and a crane was hired to help remove it.

The plant’s south shore lift station was constructed with different technology and doesn’t have those types of issues.

A second machine has been added to wash and compact rags that are removed from the water at headworks. When there was only one machine, crews had to rake them out by hand if it broke down.

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Not far away from headworks, a third primary clarifier has been added. Also, all of the metal parts, motors, drives and components of the two existing ones installed in 1958 are being replaced. The concrete walls will remain because they are in good condition.

That eases one of Smith’s biggest concerns.

“These two were worn out to the point we were worried about … one actually collapsing, the center column was so crooked,” he said. “If it was to completely collapse, we wouldn’t be able to treat water in a few days.”

Similarly, a third aeration basin and a third secondary clarifier are being put in, and the ones that went online 1972 have been rebuilt.

The aeration basins are better equipped to remove ammonia, something that is likely to be required by regulators soon.

Previously, the plant was able to lower ammonia levels to somewhere between about 15 to 25 milligrams per liter. Now that’s expected to be in the single digits.

Downstream from the aeration basins and secondary clarifiers, ultraviolet lights that disinfect the water are being updated to run on less energy and fewer bulbs. Only 250 instead of 900 bulbs will have to be replaced every six months.

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The inadequacies of the plant before the upgrade extended to the parts that handle its solids.

At one point, the city had two presses to extract water from solids. The larger one had failed.

“We had a small one that could barely keep up,” Smith said. “We had three replacement parts for every piece on it in the building so if something went wrong we could rebuild it, because we wouldn’t have another option.”

Two new presses were part of the first phase of the project. The city is keeping the smaller one and runs it once a month to ensure it’s available as backup if the need arises.

As extensive as the work is at the plant, the overall capacity will remain at 5.7 million gallons per day. That is anticipated to meet the city’s needs well into the future. Right now the plant runs 3.4 million gallons per day.

And there are some emerging issues the work doesn’t address, such as residue from pharmaceuticals. Questions are beginning to surface about the impact of prescription drugs on water quality.

“I know that there are some cities that do testing on that kind of stuff to see the effects of it,” Smith said. “We don’t, and I don’t know any current technology that could even remove something like that.”

Williams may be contacted at ewilliam@lmtribune.com or (208) 848-2261.