St. Joseph’s Water Protection plant added a biosolids dryer to its facility two weeks ago, and the hope is to use it to make money from the ammonia removal process.
Assistant Director of Public Works and Transportation Andy Clements said the dryer cost somewhere between $4 million and $5 million, but it will bring revenue for the city.
He said that sludge removed from wastewater traditionally was used as fertilizer, but the dryer will create small pellets of phosphorous and nitrogen that will be more efficient to sell.
“What we used to do for the last 30 to 40 years was to land apply that on fields for farmers,” Clements said. “With the biosolids dryer, we can eliminate that part of the process and create a fertilizer that we can sell to formulators and actually make a little bit of money.”
The dryer is the final part of $50 million process to remove ammonia from the city’s waste water. The project is mandated by the Missouri Department of Natural Resources and the Environmental Protection Agency.
Clements said a single batch of pellets were made before a faulty part on the machine stopped production.
“There’s a drying belt that carries the biosolids through the process and that was damaged ... of course that’s a contractor and supplier issue and they’re covering the cost of that,” Clements said.
Water Protection Operations Manager Chad Hiserote explained the drying process:
At the plant, wastewater goes into a clarifier, a basin that allows water to be skimmed from the top while sludge settles to the bottom. The water continues on to aeration basins and the solid sludge is pumped into a facility where it is squeezed by belts into a “cake” to remove moisture.
Hiserote said that once the equipment is operational, that “cake” will be cooked and pelleted.
“It’s heated up to over 300 degrees and it forms pellets and it’s conveyed over to the hoppers where we store it,” Hiserote said.
Hiserote also said that, eventually, the plant hopes to use methane gas that escapes from the waste in the clarifiers to fuel the dryer in order to cut down on natural gas costs.
Clements said that the city will have to receive a permit once every five years to operate the dryer. The permit process requires an air test of the exhaust let off by the machine to make sure that greenhouse gasses and noxious chemicals aren’t being released.
The City Council approved a $55,000 work order Monday to allow HDR Engineering Inc., which designed the dryer, to assist in the permit process, and for a subcontractor to perform the air test.
According to Clements, the MDNR limits St. Jospeh to 10 milligrams of ammonia per liter of wastewater released to the river, and the city is currently operating at 1 milligram per liter.
Clements said that the facility is preparing to make changes in order to lower phosphorus and nitrogen levels in the water next.
“At this point we’re kind of tuned to do one third of the plant’s job,” Clements said. “Over the next six to nine months we’ll be fine-tuning those processes to see what we can do in terms of ratcheting down our phosphorus discharges as well as our total nitrogen.”
The biosolids dryer is expected to be fully operational next week.