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Biogas producer fined for weekslong wastewater discharge
['Jared Strong', 'More From Author', '- April']
Date: 2022-04-08 00:00:00
A northern Iowa facility built to extract methane from industrial wastewater and organic waste leaked an estimated 72,000 gallons of wastewater into the ground, according to the Iowa Department of Natural Resources.
The wastewater entered underground tile lines and flowed into a river tributary over the course of about seven weeks while the facility’s owner repeatedly denied it was the source of the leak, the DNR said.
NLC Energy, based in Wisconsin, has agreed to pay a $10,000 fine for the waterway contamination, a recent administrative order said.
Its facility near Riceville has a large earthen pit that can hold 7 million gallons of sewage that is leftover from the extraction process of its digester. Someone reported in December 2020 that a tile outlet that drains into a tributary of the Wapsipinicon River was discharging a milky water with a septic smell.
A DNR environmental specialist who investigated the contamination noted a “strong, pungent odor” and found a large amount of white algae in the stream that was still noticeable about a quarter mile downstream. The administrative order did not estimate when the leak might have begun.
The biogas facility had been operated under the name Big Ox Energy for years. Big Ox was a subsidiary of NLC, which owned it alongside another company that operated the Big Ox facilities in at least three states. The facilities capture methane from municipal and industrial wastewater to be used as fuel.
A Big Ox biogas facility in Dakota City, Nebraska, was the subject of numerous lawsuits and environmental and workforce violations that culminated last year with a $1.1 million settlement with the U.S. Environmental Protection Agency.
“The Big Ox facility’s operations presented a significant risk to their workers and nearby property owners,” Edward Chu, a regional EPA administrator, said in September 2021.
The EPA found the facility released hazardous amounts of waste and biogas — which can also contain toxic hydrogen sulfide — at least 16 times between 2017 and 2019. The waste repeatedly overflowed from the facility and in one instance released 80,000 gallons of wastewater.
Amid the turmoil in Nebraska, the Riceville facility ceased its methane generation in February 2018 for unspecified reasons, according to the DNR order. However, it continued to accept waste.
Such facilities often have contracts with cities and companies who pay them to take the waste. The leftover material from the methane-extraction process is often applied as fertilizer to farm fields.
But in late 2018, tests of the waste in the large Riceville pit revealed that it had concentrations of selenium that were too high to be land applied. Selenium is a metalloid that is an essential mineral for human bodies but can be toxic in certain concentrations.
By July 2019, the pit was too full, the DNR determined.
In 2020, NLC Energy took over the operation of the Big Ox facilities, according to the DNR order.
To dispose of the waste, the company removed the semisolid material from the pit and put it in several large filter bags that have allowed the liquid to seep out. That will cause the material to solidify to an extent that it can go to a landfill.
The company placed the bags in a newly constructed shallow earthen basin that it lined with plastic.
“The first day I was out there, I had the inclination that it was coming from there but I didn’t have any laboratory data yet,” said Brian Jergenson, a senior environmental specialist for the DNR who investigated the stream contamination in December 2020. “I didn’t see any other source of where this could be coming from. Of course, they didn’t believe that,” he said of NLC.
Jergenson suspected the shallow basin with the bags was leaking wastewater into the ground. What followed was a weekslong exchange in which Jergenson gathered evidence that pointed to the basin that wasn’t conclusive enough for the company. The contaminated stream water had elevated levels of selenium, according to DNR reports.
Jergenson put dye in the basin water to see if the dye would be expelled from the tile outlet along with the milky water, but an icy layer on top prevented him from thoroughly mixing the dye in the water. The dye did not discharge from the tile outlet.
“If continued investigation presents evidence or determines that NLC Energy-Riceville is the source, we will cease such discharges as quickly as possible,” Mike Major, a vice president at NLC Energy, wrote to the DNR on Jan. 8, 2021, after he reviewed a DNR investigative report of the situation.
Jergenson estimated that at least a gallon of contaminated water was flowing into the stream every minute.
Ten days later, the company relented and agreed to dig to examine the tile lines that drain groundwater from the area. That happened Jan. 27, 2021, and two of the lines had a milky white sludge and a foul smell, the DNR order said. A third line had sufficient water to sample, and it showed elevated levels of ammonia and selenium.
The company plugged the tile lines to prevent further contamination from reaching the stream, and by April, tests showed that ammonia and selenium concentrations were within an acceptable range.
The company has until July to remove the material in the filter bags from the site.
“NLC Energy – Riceville, LLC is pleased to have worked out a solution with the Iowa Department of Natural Resources and is now focused on getting the plant reopened and back in operation,” said James Pray, an attorney for NLC.
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