"Forever Chemicals" in Retained Sludge

"Forever Chemicals" in Retained Sludge

June 6, 2023

Wastewater treatment is a complex cycle consisting of many processes and technologies. Treatment processes involve the removal of various contaminants to ensure effluent water is safe for continued use and downstream ecosystems. One important contaminant removed and retained in activated sludge are poly and per-fluorinated substances (PFAS). Read on to learn more about the dangers of PFAS and considerations for environmentally friendly disposal, including an EnviroZyme® product designed to assist with sludge reduction.

Due to the strength of the substances, PFAS are highly resistant and nearly impossible to dispose of – earning the name “forever chemicals."

What Are PFAS?

A man-made group of chemicals, PFAS were first developed in the 1930s and were quickly integrated into commercial and industrial products by the 1940s and 1950s. At the time, they were regarded as exceptional substances due to their carbon-fluorine bond, making them heat resistant and extremely strong. Soon after their creation, the chemicals were manufactured into inks, varnishes, construction materials, firefighting foams, cleaning solutions, lubricants, and much more.

Common examples of PFAS include perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Recently, a survey reported the existence of over 4,500 varying chemical iterations of PFAS. Due to the strength of the substances, PFAS are highly resistant and nearly impossible to dispose of – earning the name “forever chemicals.”

They have been detected throughout the environment and do not biodegrade easily, leading to excessive accumulation in water and soil.

Human Health Concern

The Agency for Toxic Substances and Disease Registry, a subsidiary of the CDC, claims that prolonged exposure to PFAS can raise cholesterol levels, decrease vaccine response in children, increase cancer risk, and pose a collection of challenges for pregnant women and infants. Humans are most likely to be exposed through accidental contact with contaminated soil, ingesting contaminated water, using consumer products treated with PFAS, and eating food grown or raised near locations that produced or processed PFAS.

Repurposing and Disposing of Sludge with Retained PFAS

Industrial categories that tend to discharge PFAS often discharge to municipal wastewater treatment plants, which are usually not designed to effectively remove PFAS. This is why PFAS ultimately end up in retained sludge. While activated sludge – also known as a biosolid – absorbs harmful contents and effectively removes them from effluent water, the sludge itself is left highly contaminated with PFAS as an unfortunate byproduct of wastewater treatment. Proper activated sludge management and disposal processes are imperative for healthy wastewater treatment plant outcomes, as excessive exposure to PFAS poses health risks.

Following collection from a settling tank, contaminated sludge is most often hauled away. However, there are limited options for safe, cost-effective disposal, and many wastewater treatment plants face regulatory challenges concerning the disposal of sludge. Various countries have imposed stringent regulations on sludge management, and the growing concern surrounding PFAS adds another layer of complexity. Disposing of PFAS-contaminated sludge may require special treatment or designated disposal facilities or landfills certified for biological waste, which can be expensive and limited in availability.

Another method of sludge disposal is repurposing the biosolid into a useful product, like fertilizer. Despite their toxicity, biosolids containing PFAS have been widely added into fertilizers for decades. It was not until the last 20 years that the USFDA ruled that biosolids were not to be applied on farms growing organic fruits, vegetables, or dairy products. However, countless commercial fertilizers sold by major consumer-facing home improvement stores contain repurposed biosolids, meaning the general public is coming in direct contact with these harmful “forever chemicals,” and PFAS are being added to the soil content near their homes.

Mitigating the Impact of PFAS

Wastewater treatment plants can explore advanced treatment techniques to improve the removal efficiency of PFAS during primary and secondary treatment stages. Technologies such as activated carbon adsorption, reverse osmosis, and advanced oxidation processes show promise in reducing the concentration of PFAS. Innovative sludge treatment methods, such as thermal treatment or wet air oxidation, can be employed to break down PFAS and minimize their persistence.

"EnviroZyme® Sludge and Lagoon Pucks can help alleviate the immediate fiscal burden of disposal by reducing the volume of activated sludge."

Integrating the aforementioned sludge reduction systems into regular operating procedures is not an easy task. For wastewater treatment plants to accommodate required equipment and technology, a large amount of funds would need to be allocated towards improving plant processes. Rather than completely altering plant infrastructure, EnviroZyme® Sludge and Lagoon Pucks can help alleviate the immediate fiscal burden of disposal by reducing the volume of activated sludge. These pucks reduce sludge and accelerate waste digestion, and can be added to lagoons and holding ponds, allowing for the extended release of concentrated bacterial strains.

PFAS are also on the radar of the EPA, which has created a multi-year PFAS Strategic Roadmap to research, restrict, and remediate PFAS. This includes restriction of PFAS in discharges from industrial sources through a new Effluent Limitations Guidelines program and leveraging NPDES permits to reduce PFAS discharges. The document in its entirety can be read here.

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