PFAS stay in wastewater treatment, may enter crops

Beneficial reuse of treated wastewater is an increasingly common practice in which treated wastewater is used for irrigation and other non-potable purposes. Credit: Heather Preisendanz, Penn State. All Rights Reserved.

PFAS (per-and-polyfluoroalkyl substances) are known to affect ecological and human health negatively.

PFAS are a group of more than 4,700 fully synthetic compounds widely used in industrial and manufacturing processes and many consumer products. They persist through wastewater treatment at levels that may impact the long-term feasibility of “beneficial reuse of treated wastewater.” This is all according to a study conducted by researchers at Penn State and recently published in the Journal of Environmental Quality.

They are often called “forever chemicals,” and are used for making fluoropolymer coatings and products that resist heat, oil, stains, grease and water. They have been found in various products, from clothing and furniture to food packaging and non-stick cooking surfaces.

“PFAS are so pervasive and persistent that they have been found in the environment all over the world,” said Heather Preisendanz, associate professor of agricultural and biological engineering at Penn State. “Unfortunately, these compounds have been shown to impact ecological and human health. This is particularly because they can bioaccumulate up the food chain. It can affect development in children and increase the risk of cancer. They can also contribute to elevated cholesterol levels, interfere with women’s fertility and weaken immune systems.”

PFAS enters wastewater treatment plants

Because of their wide variety of uses, PFAS enter wastewater treatment plants from household and industrial sources, said Preisendanz.

The beneficial reuse of treated wastewater is an increasingly common practice. Treated wastewater is used for irrigation and other non-potable purposes. This practice allows the soil to act as an additional filter for PFAS. It reduces the immediate impact of the direct discharge of PFAS to surface water. However, the risks and potential tradeoffs of using treated wastewater for irrigation practices are poorly understood.

“PFAS are taken up by crops and enter the food chain when the crops are consumed. When treated wastewater is used for irrigation activities in agricultural fields, understanding these tradeoffs is of critical importance,” she said.

Preisendanz and her colleagues analysed PFAS concentrations in water that passed through a water reclamation facility. They collected bi-monthly water samples from fall 2019 through winter 2021 before and after treatment. The treated water from the wastewater treatment plant is used to irrigate nearby crops. The team also collected tissues from those crop plants to assess the presence of PFAS.

Different types can make it into groundwater and crops

The team identified ten types of PFAS across the site. There was an average total measured concentrations of 88 ng/L in the wastewater effluent and concentrations as high as 155 ng/L (nanograms per litre) in the downstream monitoring wells. The conclusions suggest that the occurrence of PFAS across the site is nearly ubiquitous and that levels increase with the direction of groundwater flow.

“The United States Environmental Protection Agency recently released updated health advisories for two of the most important PFAS such that ‘any detectable level is considered a risk to human health,'” said Preisendanz. “This presents potential challenges for beneficial reuse of wastewater.”

The team found several PFAS compounds in crop tissue samples collected at both irrigated and non-irrigated portions of the site.

“This suggests that PFAS may enter the food chain when these crops are fed to livestock,” Preisendanz said. He added that future research is needed to determine potential risks to livestock health and the potential implications of PFAS presence in meat and dairy products. “Our study results have important implications to ensure that beneficial wastewater reuse activities achieve desired goals to reuse water and nutrients. It will also ensure PFAS levels are safe from a human health perspective.”

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