The City of Pacific’s lagoon wastewater treatment plant is working well, city officials and engineers say, with the exception of ammonia levels not always meeting new state safety limits.
Pacific’s four-cell wastewater lagoon at 2400 S. Denton Road was the subject of discussion at a Thursday, Aug. 20 meeting of the city’s Operations Committee, which includes Mayor Debbie Kelley and half the city’s aldermen.
Effective July 1, Missouri Department of Natural Resources (DNR) permit limits now require ammonia amounts of 7.3 milligrams per liter from April to September and 9.5 milligrams per liter from October to March. The city has entered into negotiations with the DNR for an abatement order of consent to develop a timeline of milestones so they can, eventually, come into compliance with the new limit.
Ammonia buildups in lagoons are caused by urea, cleaning products and the breakdown of proteins in wastewater. DNR environmental program specialist Christopher Maher, who spoke at the meeting, said ammonia can be toxic to mussels and other invertebrates when discharged into rivers. Lagoons often have more difficulty than mechanical treatment facilities meeting ammonia limits, he added.
In an Aug. 14 data report, Pacific’s public works commissioner Robert Brueggemann compiled ammonia levels dating back to 2018. The data shows the lagoon’s ammonia levels only falling below the monthly allowable limit some 45 percent of the time, usually during the summer.
Brueggemann told the committee in his report that he is working with Archer-Elgin Engineering of Rolla to study what treatment improvements are necessary.
Archer-Elgin wastewater engineer Jeff Meadows spoke with the committee at the meeting about the state of their wastewater treatment facility and said the ammonia increase in colder weather is commonplace.
“What happens when it gets cold is the nitrifying bacteria slow down dramatically. They’re not as active. They’re not reducing that ammonia as much in the wintertime as they are in the summertime,” Meadows said.
Meadows stressed that, aside from ammonia levels, Pacific’s lagoon is in good shape and is producing quality effluent.
“We work with a lot of small-to-medium-sized communities in the State of Missouri and the condition of your plant, the operability and so forth, is fantastic,” he said.
He added that new DNR phosphorus limits will likely be rolled out in 2033, which the city would also have to be compliant with. Meadows said his team explored and recommended using a moving bed bioreactor lagoon modification that would build upon the lagoon’s eight-year-old Triplepoint Environmental water treatment system and include provisions for a future phosphorous limit.
The committee heard another proposed solution for its ammonia problems. Bo Higgins of Heartland Environmental Distributors pitched his business’s sludge-reducing Bacillus microbes as a way to lower ammonia levels.
Higgins’s Fulton-based company grows the microbes for agricultural, wastewater treatment and hydrocarbon purposes and ships them across the country and internationally.
“All microbes have to have a carbon source, a nitrogen source and a phosphorous source, and that ratio is 100:10:5,” Higgins said. The Bacillus release enzymes that can break down ammonia-producing organic matter, like the sludge in the lagoon, with nitrogen and phosphorus found within. These nitrifiers, which can convert ammonia into nitrites and later nitrates, normally reproduce every 20 minutes. However, in cold temperatures they take 20 hours to reproduce, limiting their effectiveness.
Higgins proposed raising colony forming unit counts “through the roof,” pumping vast quantities of the microbes into the lagoon to turn the organic sludge into water and carbon dioxide. This would, in theory, lower ammonia levels as well.
Meadows said the DNR has not yet approved Heartland Environmental Distributors’ microbial solution for reducing ammonia levels, and that Archer-Elgin would evaluate it based on demonstration projects and write additional engineering reports as to whether it works or not.
Brueggeman noted how officials from Cabool worked with Higgins in 2019 and said they couldn’t say enough good things about his work.
Higgins gave other examples of his microbe solution working across the country. He said it would take 13,000 gallons of water per day to manage 11 trailers constantly pumping microbes into the lagoon. The operation would cost a total of $1.2 million for around three months of continuous work. Brueggemann said the city could use American Rescue Plan Act funds to pay for the work.
It would cost an additional $23,000 per month, Higgins said, to run the trailers during the winter for an additional few months to manage sludge levels. He said his company has a guarantee where if the microbes do not effectively manage sludge levels, the city doesn’t have to pay anything.
“It looked promising, it’s a good presentation, and like you said, I hope it’s the magic bullet,” Alderman Scott Lesh said.
The committee recommended having Meadows present Archer-Elgin’s studies at a future Board of Aldermen meeting.
Lesh also asked Meadows whether some of the findings of an independent study, by Cochran Engineering for Beltline Energy, LLC, would have any impact on lagoon improvements. Beltline had proposed building a data center complex on land outside of Pacific, potentially using wastewater effluent from the lagoon to cool it. The city recently enacted a yearlong stay of acceptance for data center applications.
City administrator Lee Litterell said the lagoon discussion was planned before Beltline withdrew from a zoning application for the data center project with the city earlier in August.
Cochran’s report was based on a single sample of lagoon effluent discharge from March 2026. It suggests that the lagoon should be replaced or substantially upgraded with a mechanical treatment process and that the lagoon by itself could not reduce ammonia levels below the new DNR standards. Meadows did not think this to be the case and said DNR has experience with lagoon enhancement technology that would be sufficient in lowering ammonia levels.
“Ten years ago, that may have been the philosophy. I think today, seeing some of these enhancements, we’re seeing proven performance out of those, so I don't think that’s an issue,” he said.
He said his calculations are that lagoon modifications could bring ammonia limits not just to the new DNR limits, but below them.
“What we found in our analysis is the two lagoon enhancements are significantly cheaper than to replace it with a mechanical plant, actually about half the cost,” Meadows said.
Brueggemann reiterated that the lagoon works great in all facets, with ammonia levels being the only exception.
