A $58,434 payment to the Rice Lake Construction Group, out of Deerwood, signals the end of construction work for adding onto and modifying the city’s wastewater processing plant that sits just south of the golf course.
Excavating equipment has been operated adjacent to the facility for some weeks now to remove the sludge soil remaining from the old lagoon that had been used under the previous plant design.
The newly modified plant uses natural techniques in the form of reed grasses and a new way of processing so the processed water no longer ends up in a lagoon for slow seepage into the ground. Now the treated water is sent straight to the river east of the wastewater plant.
Rice Lake Construction was the main contractor in the approximately two-year construction project that tripled the processing capacity of the plant.
Another contractor handled about $474,434 worth of construction to install a pipe to carry the treated effluent from the plant to the river. The actual plant construction came out to $10.337 million and there was more than $261,175 figured for altering several stream banks in the area to reduce phosphorous leaching into the rivers during erosion of soil. Phosphorous buildup in streams leads to plant growth as far downstream as Lake Pepin in the Mississippi River. That last item was one of the requirements under the state permit for the wastewater project. The decommissioning of the old lagoon cost about $801,000.
Another cost was preparing the site to carry the weight of the added structures, which was about $870,000.
Brett Repulske, with the United States Department of Agriculture’s rural development program provided the figures on the cost of the project. They show that the grand total for construction is close to $12.71 million, that engineering was set at $1.74 million, legal costs at $26,203, interim financing at $593,214, and there was a contingency fund of $98,714.
The grand total for the project comes out to about $15.17 million, according to Repulske’s figures that were given to City Administrator Mark Karnowski this year.
“It’s actually gone fairly well,” Karnowski said of the project. “There were some issues with the reed beds.”
The 12 concrete structures that can hold beds of a reed grass are one of the new features at the processing plant. The reeds consume the nutrients in the sludge, reducing the solids, so there is very little sludge remaining. The city had to haul out the sludge from the plant before it was modified and spread it on farm fields. The reeds will save that cost. The reeds also reduce phosphorous in the water that drains out of the reeds beds to be sent back to the processing plant for one more go around before heading to the river.
Eight of the concrete enclosures have reeds in them now. They got off to a slow start last year, but are now thriving. What happened was that the reeds planted last fall got in so late in the year that they didn’t survive and had to be replanted this year. The City Council had contemplated billing the general contractor for the cost of replanting them but after consulting with an attorney, decided that the city should pay the cost.
“We’re still in the learning phase of the operation of the plant,” Karnowski said last week. For one thing, the operator is trying to determine how much sludge to put onto the reeds to fertilize them and the city is working with the company that supplies the reeds, Karnowski added.
The operator of the plant is Chris Klinghagen, who recently passed the state wastewater plant operator’s test to be licensed for the job. Karnowski lauded Klinghagen for being able to pass the test on the first try, Karnowski explaining that most don’t pass that exam on the first time.
With Klinghagen getting the license, the city can now divest itself of the interim operator it had been hiring, Karnowski said.
The wastewater plant now has enough capacity that the city is using about 25 percent of it at this time, Karnowski said.
Because of having all that extra capacity, the city is working with United States Distilled Products in the industrial park to see if the effluent from USDP’s operation of mixing alcohol with sugars and flavorings can be treated at the wastewater treatment facility. But that effluent would have to be pretreated to bring down its amount of sugars so the facility can handle it, Karnowski said.
The “strength” of wastewater is measured in units of biological oxygen demand, or BOD. The more BOD units in the wastewater, the more work the microbes in the facility have to perform to break it down. The higher the BOD also means the more oxygen that is needed to break it down.
If the BOD is so high that it overwhelms the ability of the microbes to break down the wastewater, then the plant would stop working, Karnowski said.
The agreement with USDP would require a phasing in of the amount of USDP effluent going to the facility. The city would expect that USDP would be monitoring the strength of its effluent going to the plant so that if USDP suspects there is a slug of high-strength liquid heading toward the facility entry point, it would notify the city immediately, Karnowski said.
The city regularly monitors the effluent in the plant to determine what it is in it, and that’s Klinghagen’s responsibility. He watches a computer to see readings in the plant and can even access that information remotely.
Klinghagen calls what the reeds do at the plant “amazing.” He said the reeds that are in the reed beds now grew very fast this year, as much as one foot per week when the temperatures were in the 90s.
Tomato plants in sludge
He also noticed something odd going on in the reed beds: Scores of tomato plants were growing up in the sludge. The tomato plants have to be removed from the reed beds so they don’t continue to grow new plants.
The seeds from consumed tomatoes pass through into the wastewater and when the seeds sit in the sludge in the reed beds, they grow into tomato plants and grow tomatoes, Klinghagen explained. He said the cherry tomato plants are the most prolific there.
But the reeds are “working amazingly,” he said. He said he understands the reeds will get to be 10-15 feet tall next year.
“Next fall when they are brown, we will either burn them up or cut them off and they will grow back in the spring,” he said.
Klinghagen said he enjoys his job there. “You learn something new every day down here,” he explained.
But he allowed that “some days are not very fun.” Those are the times that the screens get plugged in the screen room where the raw sewage passes through screens with quarter-inch holes. That means having to pressure wash the screens.
Grease is the worst thing for plugging the screens, he noted.