How Domtar odor could change with new anaerobic digester

When you think of ingredients for a city's downtown, shops and restaurants may come to mind. What about a paper mill?That's what makes Kingsport's paper mill unique, at least for Domtar Corp., the company that currently runs it. The more than 100-year-old site neighbors the city's downtown area and lives upstream from other residential housing and parks.When the mill was built in 1916, Kingsport had a population of around 5,700. Today, that number is 55,000 according to the U.S. Census Bureau. That growth also means the challenges of converting the facility to its first total recycling production process was on display for more people, more frequently.Most notably: a potent, sulfuric odor coming from its wastewater.In 2023 the mill officially made the $350 million switch from manufacturing sheet paper to recycling cardboard paper materials. After complaints from residents and city officials, it's investing an additional $75 million — about a fifth of the cost to convert the facility — to build a system that should address that odor.The system? An anaerobic digester.ANAEROBIC DIGESTER VS CURRENT SYSTEMDomtar's Kingsport mill currently uses a 25-acre lagoon for wastewater treatment.Wastewater is also known as effluent. With the mill's current system, the effluent runs through a clarifier to separate sludge and other contaminants from it. The water that remains travels to the lagoon and gets treated with oxygen.Domtar worked with environmental consultants to determine how it would treat the wastewater after the mill's conversion.The mill adjusted how it aerated the lagoon based on that prior research, said Charlie Floyd, vice president of strategic capital projects for Domtar. It also added equipment that could inject liquid oxygen to the effluent, which would help the bacteria break down more effectively and efficiently and keep odors from forming.An anaerobic digester will house bacteria that consumes the parts of the wastewater generating odor. Those elements will turn into gas. That gas will get captured, cleaned and burned."The odor will be collected and spun off of the effluent system and incinerated in the boiler so that it won't create a smell," said Floyd.Domtar will control the nutrients, pH and temperature within the digester as the effluent cycles through it."The real advantage of anaerobic over aerobic, from an overall standpoint, is that anaerobic will be less sensitive to climate, cold time versus warm, because it's contained," said Phillip Scheuerman, professor at ETSU's Department of Environmental and Occupational Health and Safety Sciences.Scheuerman emphasized that treating wastewater is "quite an art" and choosing a system is "so dependent upon the waste and what you're already treating." Constructed wetlands, which he said are similar to lagoon systems, were most optimal with his work in Florida."[Lagoons] can be very stable for industrial [waste] and it's lower cost," said Scheuerman. "But [it requires a] greater [amount of] land. And when it becomes a problem, it's more likely to be a harder to control problem."Domtar didn't install an anaerobic digester when they converted the mill because of what they learned in their initial research, Floyd said. With a 25-acre lake already installed, Domtar wasn't in a position where it needed to make space for a wastewater system."It was our understanding that people were using [anaerobic digesters] because it didn't take up nearly as much space as an aeration system where you've got a 25-acre lake," said Floyd."Because we had the aeration system here already, and we worked with consulting engineers to modify it, then we felt like it would be the system that we needed to use for our conversion."Domtar isn't the only containerboard facility that's emitted an odor strong enough to prompt complaints from residents.New Indy Containerboard in South Carolina prompted more than that after it shut off its steam stripper, a piece of pollution control equipment, that worked with its lagoon system. According to reporting from The State, some residents experienced regular headaches and nosebleeds while the stench was present.The stench and complaints from residents, which crossed state border lines, prompted a multi-agency response from state and federal regulatory agencies.The Tennessee Department of Environment and Conservation most recently investigated odor complaints about Domtar in September and found the company in compliance with its air permits.CONVERSION CHALLENGESDomtar currently brings in 1,000 to 1,500 tons of cardboard daily, breaks them down and pulps them."We basically blend up the material that's in the cardboard bale," Floyd said.After it is pulped, the material is filtered until it's free of contaminants. What's left is fiber.But recycling containerboard doesn't just involve its paper elements. It also involves the wiring and plastic that gives cardboard its structure. Using recycled materials is different from making material from scratch."You don't really have any control over what you get and how you got to deal with it," said Floyd.Wastewater can be a mixed bag, especially if it's from municipal waste, which collects from all over a city. Most of the time, industrial waste is more consistent, said Scheuerman, since those industries have a better understanding of what will be in the waste and how to treat it.Floyd said Domtar's wastewater is still "pretty steady.""I will say, though, that our raw material, which is those cardboard bales, we don't know what's going to be in it when it's brought in out of a recycling facility that bailed it together," said Floyd."It could be full of plastic, it could be full of oil, it could be full of a lot of things…There is some variability, but that variability is probably fairly similar to what a municipal wastewater handling system would be."SHORT-TERM REMEDIESIn a 2024 letter to TDEC, Domtar outlined the adjustments it has made to the mill's wastewater treatment system since its conversion.Domtar 2024 Corrective Action Plan TDECThat includes working with environmental and wastewater consultants throughout 2023 and connecting with the National Council for Air and Stream Improvement, a research group that advises forest product industries on sustainability, for guidance on improving its wastewater treatment.Until the anaerobic digester is complete, Domtar is trying to address odor by changing how it uses liquid oxygen.The company injects oxygen sooner in the wastewater treatment process. They've moved those systems next to the primary wastewater clarifier, where the water leaves after having solids settled out of it."We're doing all that we can, in all honesty, and we've tried a number of different things," said Floyd.Treating the wastewater with different chemicals is another method the mill is trying for now. Floyd said they spend several hundreds of thousands of dollars a month on those chemicals."Some have worked, some have not, but we're constantly trying to figure out how to use those," Floyd said.Oxygen injection is where they've had the "majority of the success" in terms of treating the wastewater odor, he said.In an email to Six Rivers Media, Domtar said community complaints have dropped and employee feedback guides their efforts to address how the wastewater treatment process is generating odor.WHEN THE DIGESTER IS COMPLETEIncorporating an anaerobic digester system will take some fine-tuning. There will be a period of time where both the new and old system will be active."We'll have them both ready to be in order in case we do have a significant issue with the anaerobic until we figure out how to operate it," said Floyd.Floyd said it's too early to know when the lagoon would be phased out, and by how much, when the construction on the anaerobic digester is finished."Having a 25-acre pond to handle your wastewater is not something you have to go manage by the minute every day. Because the water goes out there, and then it settles and aerates, and then it's ready to go into the river," said Floyd. "Now that we're designing the anaerobic digester system, it's going to become another regular operating area."Floyd said trained operators will regularly monitor the effluent in the digester, testing the chemicals in it and responding accordingly.An aerobic process will still be integral to treating the wastewater, said Floyd. The new plan for wastewater: it will run through the anaerobic digester, then through an aerobic digester, then head to the river."Most metabolism, most biological degradation of wastes or just organic material is much quicker and more efficient and more complete aerobically," said Scheuerman."Anaerobic gives you the advantage that it's not sensitive to climates."Floyd knows people experience odor subjectively. He also knows the way the mill's odor dissipates down the Holston River Valley is affecting communities downstream, including the Ridgefields neighborhood."What offends one person may not offend another, but that's not an excuse because we do know that we generate some odor with our effluent here," said Floyd. "Determining and guessing when the odor will be gone enough that it won't bother somebody would be kind of tough. Different things generate odor. It's kind of hard to say. It really is."Floyd said he's still confident the anaerobic digester will significantly improve the severity of the odor."Believe me, if we continue to get complaints, we will continue to work on it, and we'll try to figure out what it's going to take," he added.Domtar wants the community's input on how successful their efforts are by submitting input at their website: https://domtarpackagingkingsport.com/."That will be one of the criteria that tells us whether or not we're successful is the community's input," said Floyd.Domtar said it will continue to monitor feedback submitted to its website throughout the installation and integration of the anaerobic digester."In the environmental field, it's the unintended consequences of good intentions," said Scheuerman."When we deal with any kind of waste, we're really not destroying most of them. We're just moving them. And sometimes moving them or changing how we treat them, creates things that we didn't anticipate."This is part of a reporting series about odor in Kingsport after the Domtar paper mill conversion — how it's affecting residents and how it's being addressed.Jorgelina Manna-Rea is an environmental reporter at Six Rivers Media through Report for America.More CoverageThis is part of a reporting series about odor in Kingsport after the Domtar paper mill conversion — how it's affecting residents and how it's being addressed.