How to stop PFAS from sneaking out the back door of a landfill

Today’s landfills play a big role in keeping humanity and nature safe. Landfills lock away many harmful materials, including heavy metals such as mercury and lead, volatile organic compounds, and decomposing food waste.

Landfills are also a great repository for products containing per- and polyfluoroalkyl substances (PFAS). These are manufactured chemicals used in firefighting foam, breathable outerwear, fast-food packaging, non-stick cookware and other products (see here to learn more). Increasing concern about the health and environmental impacts of PFAS means that there is a need for keeping these potentially harmful materials isolated.

In this post, we’ll look at how landfills do this, how a little-known “back door” may be allowing PFAS in landfills to escape, and how Onvector is working on ways to close that back door.

Landfills are amazing technology – but there’s a weakness

Today’s landfills use high levels of technology to keep you safe from your trash. There is a whole discipline within the engineering profession – solid waste engineering – devoted to landfill design, construction, and operation.

Municipal-waste landfills are designed to accept household and some industrial waste and keep it there. That includes capturing gases and liquids coming from landfills that might otherwise escape into the surrounding environment. These are:

Landfill gas (LFG): As the anaerobic environment of the landfill goes to work on the trash, gases such as methane are produced. Methane is a particularly potent greenhouse gas – and also a good fuel for generating heat and power. Today, some landfills simply flare off their LFG, but many now use it to produce electricity that they can sell as “renewable” energy.

Leachate: Rain that falls on the working parts of the landfill tends to flow down through it, potentially picking up troublesome materials such as PFAS on its way. This “leachate” cannot be legally released without treatment, as we’ll see. (To learn more about the ways to manage PFAS in liquids including leachate, see our previous blog post.)

To deal with LFG and leachate, modern landfills are as carefully designed as any bridge or building.

It all starts with a hole in the ground that might cover the area of many football fields. This area is then sealed to prevent contaminating groundwater, first with a layer of clay and then a layer of impervious plastic on top of the clay.

As each section or “cell” of the landfill is filled with trash, two pipeline systems are built into it. One collects the gas, and the other leachate.

Solving the problem of PFAS in leachate

One of the biggest challenges facing landfill operators today is what to do about their leachate after it is collected. Traditionally, many landfills would pipeline or truck it to a nearby Publicly Owned Treatment Works (POTWs). It would be included with the rest of the municipality’s sewage flow for treatment and then, usually, the plant’s effluent would be released to surface water.

However, POTWs are designed to treat household sewage and other domestic effluent – their systems are not intended for industrial compounds, and are not effective for removing PFAS.

Because of rising public concern about the need to protect the environment, many POTWs are becoming concerned about what’s in their effluent. They’re well aware that they may be sanctioned through regulations intended to protect surface water and the fish, animals and people who depend on it.

As a result, increasing numbers of POTWs are saying “no” to leachate, leaving the landfills with few or any options for safely disposing of the leachate they produce each day.

Some landfills put two problems together to come up with a solution – they burn their LFG to create heat that they use to evaporate away the water in their leachate. There are several problems with this approach:

  • This reduces the volume of leachate, but doesn’t eliminate it
  • There’s growing concern that PFAS may be escaping up the evaporator unit’s exhaust stack, to be distributed widely
  • Many landfills find that they’re losing a potential revenue stream – generating “green” natural gas that can be sold for an attractive price

So the problem remains, how to stop PFAS from escaping from the landfill via the leachate stream?

A two-step solution to dealing with leachate

As you may have read in a previous blog post, dealing with wastewater (such as leachate) containing PFAS is a two-step process.

The first step takes the highly dilute leachate and isolates the impurities in it. This means that the remaining water is easier to treat – or perhaps if it meets regulatory standards, be released into the natural environment. The second stage involves the challenging task of breaking PFAS molecules into their constituent atoms or benign molecules.

One of the most promising ways to do this is called plasma vortex. This technology destroys PFAS molecules by harnessing the fourth state of matter, plasma. Within the plasma vortex reactor, a voltage gradient is applied between two electrodes. This creates an electric field that strips electrons from the inflowing gas molecules, creating charged ions and releasing a plasma discharge. The ions are highly chemically reactive, and can break down PFAS molecules. This produces harmless by-products like fluoride, sulfate, carbon dioxide and water.

Our company, Onvector, uses plasma vortex technology. We’ve shown it to be reliable, energy efficient and cost effective.

Next step: reach out to us for an exploratory conversation

If you have a PFAS problem you want to solve, please reach out and we’ll have a conversation to see if there’s a fit between what you need and what we can offer. We’re also interested in skilled professionals who might want to join our team.