A messy problem
Wastewater plants, Michigan governments assess best way to process biosolids
Most people don’t like to think about what happens to human waste once it’s flushed away but for Bryan Clor and others working on the receiving end at wastewater treatment plants (WWTP) it’s a hot-button issue.
“I want to teach people about what incineration does so they can truly understand the issue,” said the Warren Division Head of Wastewater Treatment, who is hoping to replace the city’s aging incinerator with a new system designed to remove harmful chemicals from wastewater sludge. “I am a firm proponent of burning because of where scrubber technology is at. Thermal oxidation is being pushed as a way forward.”
Despite his research and firm convictions Warren’s WWT operator finds himself stuck in a sludgy quagmire — while local governments, environmentalists and state and federal officials assess the best way to safely process biosolids.
Biosolids are the solid, organic matter recovered through treatment of sludge at wastewater facilities.
For years the practice of using biosolids as fertilizer was heralded as a way to recycle them.
But the process has since been banned in Europe and last year was outlawed in Maine, after high levels of polyfluoroalkyl substances known as PFAS were discovered in crops, groundwater, soil and cattle on several farms using biosolid fertilizer. Maine was the first state in the U.S. to ban the use of industrial and municipal sewage sludge as fertilizer, but since then Vermont is reportedly considering a similar ban and Massachusetts has stopped issuing permits for land application. However, some environmentalists say a ban on land applications will not solve the PFAS problem.
“Maine found PFAS as an issue through milk, and realized that an important source of PFAS contamination leading to milk contamination/agriculture was from the land application of sludge and septage,” said David Madore, Maine Department of Environmental Protection Deputy Commissioner. “Once that link was recognized, Maine began to investigate soil and water in earnest in areas that were licensed to accept sludge application to understand more about the extent of contamination.”
That statewide investigation led to Maine’s adoption of Public Law 2021, Chapter 641 which effectively bans land application of biosolids.
At this time, Michigan and Maine are the only two states that test sludge and soil for PFAS; Michigan allows higher levels of PFAS in sludge that is to be spread on farms than did Maine before its ban of the practice.
Currently, the United States Environmental Protection Agency (EPA) is conducting a b io solids risk assessment for two PFAS compounds: per flu oro oct anoic acid (PFOA) and per flu orooc tan esulfonic acid (PFOS). A refined risk assessment for PFOA and PFOS will include assessment of environmental pathways including groundwater migration,
crop uptake, and accumulation in farm animals that could lead to dietary exposures for a farm family that applies biosolids.
There will also be an ecological assessment of impacts to aquatic and terrestrial organisms.
The full report is due to be completed in winter 2024 at which time the EPA will use risk management to determine how to best regulate PFOA and PFOS, as necessary.
Recycling sludge
As long as humans inhabit the Earth there will be sludge that has to go somewhere.
Fifty-years ago, cities across America were flushing raw sewage directly into the nation’s waterways.
Today, ongoing improvements to underground infrastructures and wastewater treatment under strict federal and state standards have improved conditions in the waterways and enabled WWTPS to: dispose of biosolids in landfills, heat it and sell it as fertilizer, or land apply it, which is most often used.
There are two types of biosolids: Class A, which meet exceptional standards for their level of pathogen reduction and stringent metal limits; and Class B, biosolids that are treated to a point where they are safe to use as a fertilizer or soil amendment, according to the Michigan Water Environment Association (MEA). While Great Lakes Water Authority makes Class A biosolid pellets that are marketed as fertilizer in Michigan, around 50% of the WWTPS treat sewage sludge to a level considered for land application purposes.
The Michigan Department of Environmental Quality (MDEQ), the primary regulatory agency for WWTP and the land application of biosolids, determines what sites can participate in the land application process.
“The use of biosolids can significantly reduce environmental impacts from previous waste disposal (landfill and incineration) as well as the impacts from fertilizer production,” said Xiaowei Zhang, senior EQA at the Warren District Office for EGLE’S Water Resource Division. “Biosolids contain important nutrients for plant growth and soil fertility such as nitrogen, phosphorus and organic matter as well as essential micronutrients such as copper, iron, molybdenum and zinc. This combination of nutrients, micronutrients, and organic matter not only provides fertilization but improves the overall health of the soil. The use of biosolids allows for a reduction in the use of commercially produced fertilizers and saves the cost of fertilizer.”
Biosolids can be used to provide nutrients and soil conditioning in mine reclamation programs, tree farms, and forest lands.
Vicki Westrick of St Clair County is among the farmers in the Michigan Biosolids Program.
“I think it’s a good program. We’re helping to get rid of the waste so it doesn’t go to the landfill and we’re not using it for anything that’s food,” said Westrick, who grows soybeans for commercial products and corn for ethanol.
Westrick insists he would never use anything on his land that was harmful to the environment but admitted he’s at the mercy of the lab and the state.
‘I said no to the program,” said George Van Houtte, who once rolled a giant boulder onto a manhole cover owned by the township in order to protect his field from sewage overflow after a heavy rain.
“They came to me with this speech about free fertilizer. I said nothing comes for free,” said Van Houtte, who owns a farm that has been providing fresh produce for local residents and markets in Romeo for more than 50 years. “I don’t need to have anyone coming back with contaminated vegetables.” Or tainted milk.
A dairy farmer in Maine had to shut down his operation, because the milk from his cows tested with high levels of PFAS compounds. The contamination was traced to cows feeding on plants that were grown on fields spread with biosolids.
High levels of PFAS have also been found in fertilizers containing biosolids sold by wastewater treatment plants after it has been dried and treated for biological contaminants.
The key word and ongoing debate is high levels. Now that research has shown PFAS to be harmful there is a movement to raise the bar in terms of the level at which sewage sludge can be safely considered for land application.
Among the states moving forward is Michigan, which recently adopted an interim strategy for land application of biosolids containing PFAS.
It calls for stepped up testing of biosolids at WWTP, prior to their application to fields.
“The best improvements here are to make our inputs into WWTP less toxic to begging with, so that we can apply wastewater sludge without worrying about the buildup of all the chemicals that are currently functionally unregulated in the United States,” said Christy Mcgillivray, political and legislative director for Sierra Club Michigan Chapter. “More upstream solutions, ban the sale and use of PFAS, and put the precautionary principle in place federally. Our entire chemical regulatory system is broken.”
Instead of the industry having to prove their products are safe before putting them on the market it is the public that is shouldered with the burden of showing it is being harmed by toxic chemicals.
Mcgillivray said our WWTPS are doing what they can to deal with the inevitable outcome created by products containing PFAS, but it’s the culprits at the top of the stream that need to be held accountable.
The alternatives
If the EPA tightens regulations for ground application of biosolids or if the federal or state government bans the process, wastewater treatment facilities will have to seek alternative methods for dealing with biosolids.
Clor would like to replace Warren’s incinerator, which was built in 1971 and upgraded most recently in 2016, with a new, high tech thermal oxidation and drying process for biosolids.
EGLE, however, is not keen on sewage sludge incineration.
“First, there are many unknowns with PFAS,” said Jeff Johnson, a spokesperson for EGLE. “There are hundreds of different types of PFAS, many of which we know very little about. Second, air quality compliance relies heavily on stack testing to measure the levels of PFAS coming out of an incinerator stack. It is important to have a method to stack test for PFAS emissions so we can determine how much is being emitted and whether it is below air permit limits.
Clor insists the new technology reportedly eliminates 99% of polyfluoroalkyl substances known as PFAS contained in the wastewater sludge and that Warren already conducts regular stack testing for air quality.
The BIOCONERS system Clor prefers dries sludge at a temperature of 2,100 degrees Fahrenheit and uses an energy recovery system to fuel the drying and reduce emissions.
The city’s current incinerator has a life expectancy of another five years so Clor said it is imperative plans are made for its replacement. He does not expect land application, which is the system preferred by EGLE, to be part of Warren’s plan for wastewater sludge in the future.
Warren is one of three cities in Michigan using a traditional incinerator to process sewage sludge.