In early October, the Pecan Creek Water Reclamation Plant smelled like the solids that fall out of wastewater as it’s treated during the city’s multistage treatment process.
“It smells like money,” said Rusty Willard, the city’s water reclamation superintendent. “Actually, it usually doesn’t smell this bad. We’re under a little bit of construction right now. That’s the reason for it. Usually, it’s not bad at all.”
Willard was joined by Denton’s Water Utilities Director Stephen Gay and Chief of Staff Ryan Adams on a Tuesday morning in October for a tour of the Pecan Creek facility. We were discussing the city’s biosolids program — which turns leftover wastewater sludge into Dyno Dirt — and the so-called “forever chemicals” known as PFAS, which have been found in biosolids, drinking water and wastewater, not only in Denton but in cities around the country.
The Environmental Protection Agency released the first batch of PFAS testing data in August and found that hundreds of tap water systems around the country are contaminated with PFAS, an abbreviation for perfluoroalkyl and polyfluoroalkyl substances. The agency will continue to roll out test results over the next three years.
Dr. Kapil Sharma, who specializes in environmental toxicology and industrial chemical exposure at UT Southwestern Medical Center at Dallas, told KERA earlier this year that PFAS have been used in many consumer products for decades.
“PFAS is actually a broad name for a group of almost 300 different chemicals,” Sharma said. “They all refer to something called polyfluorinated, which means that these are, if you go back to your basic chemistry, carbon chains that are attached to multiple fluoride groups. And that bond between the carbon and the fluoride group is very, very strong and very, very hard to break.”
In December, the EPA plans to finalize a National Primary Drinking Water Regulation for six PFAS chemicals, including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS).
The EPA is currently conducting a biosolids risk assessment for PFOA and PFOS in biosolids.
Both PFOA and PFOS have been discovered in Denton’s water system at lower levels — and at higher levels closer to the Pecan Creek facility — since 2020, according to the city’s 2022 PFAS sample information report.
In the report, city staff said they use the EPA’s Method 537, which can analyze 29 different PFAS chemicals, to test the city’s water and found that the results were well below Texas Commission on Environmental Quality limits for groundwater consumption by humans and “soil limits for residential use including growing vegetables for human consumption.”
Under the EPA’s proposed new regulation, the maximum contaminant level for PFOA and PFOS is 4 nanograms per liter or parts per trillion, and the agency proposes to implement it as a national standard in 2024 to “prevent thousands of deaths and reduce tens of thousands of serious PFAS-attributable illnesses,” according to a March 14 news release from the EPA.
Those regulations will affect drinking water systems serving an estimated 70 million to 90 million people.
Denton is one of those systems, in part because it can’t reach the EPA’s recommended maximum contaminant level, Gay said.
“Right now, truthfully, we don’t have the instrumentation that can detect those levels,” Gay said. “We can get down to maybe 7 [parts per trillion], so it’s really difficult.”
Miracle chemical
DuPont chemist Roy J. Plunkett is credited with first discovering the first forever chemical in 1938. DuPont patented the PFAS chemical as Teflon in 1945, and 3M chemical company became its main manufacturer. By 1948, DuPont was producing about 2 million pounds of Teflon, and the chemical grew into a billion-dollar business in 2004, according to an EcoWatch report from 2016.
In 1947, PFOA — also known as C8 — entered the manufacturing picture due to its nonstick and stain-resistant properties. Several years later, DuPont started using it in the production of Teflon, EcoWatch reported.
According to Denton’s 2022 PFAS sample information report, forever chemicals, such as PFOA and PFOS, have been used in stain- and water-repellent carpets, upholstery and clothing, as well as nonstick cookware, shampoo, dental floss and cosmetics. They’ve also been used in food packaging like pizza boxes and microwave popcorn bags and in firefighter gear and firefighting foam.
It’s also in our drinking water, wastewater and biosolids.
The Centers for Disease Control and Prevention used data from the National Health and Nutrition Examination Survey (NHANES) and found PFAS in 97% of Americans’ blood, according to the National Institute of Environmental Health Sciences (NIEHS).
“Another NHANES report suggested blood levels of PFOS and PFOA in people have been reduced since those chemicals were removed from consumer products in the early 2000s,” the NIEHS reported. “However, new PFAS chemicals have been created and exposure to them is difficult to assess.”
PFAS chemicals don’t break down quickly. Instead, they build up over time through exposure. The CDC warns that exposure to some PFAS chemicals can lead to cancer, increased cholesterol levels and immune system effects. It also leads to birth defects, as documented in The Devil We Know, a 2018 investigative documentary on PFOA.
Industries are currently allowed to flush PFAS-containing waste into wastewater drains that flow to treatment plants — at least until the EPA finalizes its rules.
During the sewage treatment process, it’s reported that the chemicals are not removed but instead settle in biosolids, the solid materials that are separated out from liquids in the treatment process.
PFOS was phased out of production in the U.S. in 2002, followed by PFOA in 2015, but thousands of PFAS chemicals are still found in many consumer, commercial and industrial products, according to the EPA.
“This makes it challenging to study and assess the potential human health and environmental risks,” the EPA wrote in a report, “PFAS Explained.”
Sewage sludge
At the Pecan Creek facility, Willard, Gay and Adams lead a tour past the pools of wastewater that’s being treated and the compost mounds of Dyno Dirt, which will be sold for public use when it’s ready. The city describes Dyno Dirt as a “nutrient-rich compost” that is “ideal for lawns, flower and vegetable gardens, and trees and shrubs.”
“We add heat,” Gay said. “Nature kind of does the rest.”
Inside a metal building, an industrial belt press machine — which resembles an old newspaper printing press — takes the biosolids through a system that removes the wastewater, much like the old press imprinting images on pages.
The compost is then left to cure in piles in the sun, allowing Mother Nature to do her work for 16 to 28 days, as Gay and Willard explained. Dyno Dirt is made from biosolids and ground-up yard trimmings.
“So we’re taking all the sludge and putting the two together to form a compost pile,” Willard said. “And we let nature take its course, basically.”
Willard grabbed a handful of biosolid as it came off the belt press and held it out as an offering. Colored like charcoal, it looked dry and reminded me of fertilizer. I wasn’t about to hold it.
Left over from the sewage treatment process, biosolids must meet stricter EPA standards and fall as either Class A (no pathogens harmful to health) or Class B (some pathogens may exist). They have been used nationwide as crop fertilizer and applied to farmland, sports fields and golf courses.
“By the time it gets here, it’s like an exoskeleton,” Willard said. “It’s not even sludge. … So everybody has that misconception that it’s sludge, but it’s really the exoskeleton of all the stuff that’s digesting the contaminants in the wastewater.”
Dyno Dirt is a Class A biosolid, as the Record-Chronicle reported in 2020.
Denton sells Dyno Dirt for $21 to $30 per cubic yard. City parks maintenance crews use Dyno Soil — a mixture of 60% Dyno Dirt and 40% sandy soil — on fields and parks as part of soil enhancement, field leveling and fertility improvement processes, Adams said in an email Aug. 30.
Linda Birnbaum, director of the NIEH, said in 2019 that there wasn’t a lot of data available on PFAS in biosolids but that the available data “suggests it’s a problem,” according to a report from The Associated Press.
“We are finding that there are elevated levels of different PFAS in biosolids,” Birnbaum said in 2019. “We clearly need more research in this area.”
In 2020, questions were raised about whether Denton’s biosolids were safe. City leaders brought in two experts who found the biosolids that the city had been treating and selling since the late 1990s were safe based on current standards.
Gay said the city has been testing its biosolids and Dyno Dirt for PFAS annually since 2021.
Mayor Pro Tem Brian Beck requested PFAS testing results, which are also available online, in May 2022 and learned that besides being detected in the water and wastewater, it was also detected in low levels on the biosolids belt press and in Dyno Dirt in September 2021.
“Folks were correct to ask about PFAS/PFOS/PFOA and microplastics, and I asked for the testing,” Beck said in an email. “However, currently, we are below thresholds on those compounds. Should that ever change, we’ll have to re-evaluate our processes.”
The Natural Resources Defense Council, an environmental advocacy group, claimed in August that PFAS chemicals can be toxic at “extremely low levels” and that “exposure has been linked to a long list of health effects, including cancer, immune suppression, and developmental harms.”
In August, Adams said in an email that the PFAS results are below state limits for residential use. He also pointed to the Sierra Club’s 2021 report “Sludge in the Garden” and said that the biosolids Denton produces are within the range for non-biosolids commercial compost.
What Texas’ limits are for residential use isn’t clear since the state doesn’t require monitoring and reporting of PFAS chemicals.
Instead, Texas counties, municipalities and other jurisdictions have established their own standards, monitoring processes or other regulations related to biosolid disposal or land application, according to a January report by the Environmental Council of States, an environmental organization in Washington, D.C.
TCEQ plans to develop drinking water standards for public water systems once the EPA publishes its final PFAS drinking water rules. The state agency is in the process of systematically collecting PFAS data for the eventual derivation of toxicity factors in accordance with the most recent TCEQ toxicity factor guidelines, according to the commission’s February PFAS report.
In “Sludge in the Garden,” the Sierra Club writes, “available evidence suggests that PFAS and related chemicals in sewage sludge could jeopardize the safety of the commercial food supply and home gardens. We recommend home gardeners do not purchase biosolids-derived fertilizers for use on fruit and vegetable beds.”
Instrument woes
As the October tour of the Pecan Creek facility came to an end, city staff mentioned that not a lot of cities were doing compost like Denton but starting to look into it since the landfills are filling up.
“We’re running out of space,” Gay said. “It’s not just the city of Denton. It’s everywhere.”
Adams pointed out it’s why the city has been pressing for reuse, recycling and diversion, particularly at the commercial levels, to extend the life expectancy of the municipal landfill.
Gay had recently attended a utility conference where new treatment methodology for PFAS was discussed — methods that are not only better at filtering out the chemicals but also destroying them.
“But then there’s the whole physics equation,” Gay said. “Once you destroy it, do you really destroy it?”
Forever chemicals have led to lawsuits filed by firefighters and the International Association of Fire Fighters against the companies that manufacture them. A bipartisan group of 12 states and the District of Columbia have also filed litigation against PFAS chemical manufacturers.
Four of those states have settled their lawsuits, including Minnesota, Delaware and New Jersey. In June, Arkansas Attorney General Tim Griffin filed a lawsuit against more than 30 chemical companies.
Part of the problem with new instrumentation to detect the EPA’s 4 parts per trillion recommendation, Gay said, is that once it hits the market, it’s going to cost more than what it would if it had been available for years.
Gay said the EPA recognizes that the cities “don’t have the instrumentation that reads that low” and would look at the 4 parts per trillion recommendation again and possibly consider a higher one that cities can read.
“We know what we can measure,” Gay said. “We can keep it below that.”