Choosing the Right PFAS Treatment Tech: A Review of Currently Available Technology for Landfill Leachate Management
Landfill operators face an increasingly challenging decision when it comes time to deal with PFAS. With mounting state and federal regulations, oversight, and compliance, all eyes are on landfill sites to eliminate PFAS forever – before it pervades our drinking water even further and leads to serious long-term health complications to those exposed.
Removal and disposal may seem enticing for landfill operators, especially when combined with concentration technologies that concentrate PFAS and reduce the need for negative environmental impact of options such as incineration, deep well injection, or subsequent disposal. However, forward thinking organizations are evaluating PFAS destruction technologies which, when implemented properly, can help to eliminate the need for any PFAS disposal and destroy PFAS on-site which can be highly cost-feasible and serve as an attractive option for landfill sites and the increasing regulatory oversight and compliance from the EPA and on a state-by-state basis.
Below is an outline of currently available removal and disposal options:
Removal & Disposal
Removal: Granular Activated Carbon (GAC)
GAC’s absorption properties make it a viable removal choice for long-chain PFAS; however the PFAS and spent media then need to be disposed of. GAC has been an often used solution for PFAS removal, yet many organizations are questioning the efficacy of GAC for the future, especially considering emerging destruction technologies. PFAS is absorbed into the carbon in a specialized vessel. Once the GAC can no longer adsorb PFAS, the media is removed with landfilling or incineration often following. See more below about various disposal options currently available.
Removal: Foam Fractionation
Foam fractionation is a separation technology that can concentrate PFAS up to 1000x. However, aerosols from the process may be of concern. The result of the process is super concentrated PFAS foam —sometimes, only a few gallons — making conventional disposal options (such as incineration, deep well injection and solidification) as well as newer destruction technologies more feasible. Traditional disposal methods could cause PFAS could potentially re-enter the environment and cause further cycles of harm.
While technologies such as Aclarity’s can treat raw landfill leachate, many ask the question: why concentrate first?
Once a viable option for PFAS disposal now has many questioning the process. At temperatures of >1,800°F, incineration may not destroy all of the PFAS and therefore may release some into the atmosphere and environment. This has led several states and the Department of Defense (DoD) to ban incineration and there will likely be a federal PFAS incineration ban from the EPA soon.
Disposal: Deep Well Injection
Requiring a vast amount of engineering, planning and permitting, deep well injection is the process of storing these waste liquids deep underground. It entails digging beneath drinking water aquifers (at a depth of 1,500 to more than 3,000 feet) in order to enclose the liquid waste between several layers of impermeable rock. It can't be used everywhere because it needs appropriate geology.
After PFAS are removed from landfill leachate, they can be encapsulated, often with concrete, and it back into a landfill. This process is called solidification and is generally described as encapsulation of the waste into a monolithic solid with structural integrity. However, this has some calling foul. Is it merely “kicking the ball down the road”?
Supercritical Water Oxidation (SCWO)
The SCWO process involves heating water above 705°F and getting pressure above 221.1 bar, resulting in a “supercritical” state of water that can accelerate chemical oxidation. Preliminary data indicates nearly 99% effectiveness in destroying some PFAS, but the question is how much energy is needed to make this happen and the complexity of the process (and infrastructure required) leaves some questioning its long term viability for ease of use and maintenance in the field. One well noted issue is tank integrity due to chlorides and other constituents corroding the tank and piping.
A recent study found that SCWO requires seven times greater energy than traditional electrochemical oxidation (see Table 1). Furthermore, the primary input to make SCWO viable is oxygen, which carries high costs as worldwide demand accelerates. Additionally, studies are needed to determine if energy inputs and other costs can be reduced. SCWO may have difficulty treating high salinity wastes, making landfill leachate difficult to treat.
Table 1: Energy Consumption for PFAS Destruction Tech
|Technology||Energy Consumption (kW·h/m3)||Reference|
|Traditional Electrochemical Oxidation||256||Schaefer et al. (2018)|
|Plasma||294||Singh et al. (2019)|
|Supercritical Water Oxidation||1,506||McDonough et al. (2022)|
As a result of the high energy inputs, startups and universities are beginning to look into an alternative to oxygen for SCWO – the use of air to lower economic barriers to entry for this technology. Recent studies have conducted baseline costs with and without oxygen as an input (Zhang et al., 2018, 2020, 2022), demonstrating the potential to make SCWO more cost-feasible in the coming years.
Aclarity Electrochemical Oxidation (EOx)
A newer version of EOx from Aclarity has succeeded where past EOx have failed. In 2022 the company demonstrated considerable destruction across a wide spectrum of PFAS contamination with the added advantages of low energy costs (50 w-hr/gal), additional destruction of other contaminants such as ammonia, and ability to treat high salinity wastes.
In addition to relatively low energy inputs, the process is safe and simple. It does not require extreme high pressure, high temperatures or harsh caustic amendments. As a result, landfill operators do not need to be highly involved in the operational process. This is also an important economic consideration, as the opportunity cost of overseeing more complicated PFAS destruction methods onsite could lead to further complexities for landfill operators. Aclarity offers a service model with a 24/7 staffed destruction installation that is essentially plug and play. It can hook right into existing leachate tanks with no interruption of site operations or site personnel required after initial installation.
On-site destruction also eliminates the need to preconcentrate which still requires some form of disposal, sometimes off-site requiring trucking: Why concentrate first if technologies such as Aclarity's can destroy PFAS on-site?
This may be the most practical and workable way to completely eradicate PFAS. Though it can be combined with other technologies to treat drinking water, groundwater and a host of other applications, this technology excels in treating landfill leachate and can process and destroy PFAS in landfill leachate with zero pretreatment. Organizations can use Aclarity's technology to eliminate PFAS on-site with little upkeep and no byproduct disposal needed.
Recently, the U.S. Air Force designed and tested a plasma reactor to destroy PFAS. The reactor first concentrates PFAS using argon gas and then “the plasma reduces the PFAS molecule chain down into smaller compounds and elements, through several cycles. No additional chemicals or additives are needed.” Plasma has low energy inputs based on a recent peer-reviewed study.
The EPA is also researching this technology, and initial results showed roughly a 70% reduction in high concentrations of PFAS. Further enhancements and studies are ongoing to determine if plasma can hit 99% effectiveness and as it is currently on the bench scale, it will be some time before it can be validated and proven in the field though there are several start up companies working on PFAS destruction using plasma. Concerns with plasma are many; however the most often cited is the availability/cost of argon gas and the need for highly specialized reactors.
Hydrothermal Alkaline Treatment (HALT)
This is a newer process that relies on extremely hot, compressed water along with an added chemical reagent to break the strong carbon-fluorine bonds that hold PFAS together. The process requires high levels of energy to heat more than 350°C in order for the process to occur. While it has shown promise of PFAS destruction, the process also requires a caustic amendment to be effective. There are opportunities to recapture some of the energy used with additional processes.
Landfill operators evaluating technology should always ask what consumables a process requires and what volume it will require to get a better understanding of the costs and labor that may be associated.
As PFAS destruction technologies continue to advance, a pressing distinction is how effective they will be in handling both short- and long-chain PFAS. In addition, the safety and overall efficacy are of top concern for landfill operators. Workplace safety is a paramount concern for landfill operators, with sweeping ramifications should issues arise onsite. When evaluating new technologies, technological readiness factor is extremely important. Aclarity had an independent leading company validate at a Technology Readiness Level of 9 (max) while others in the emerging PFAS destruction field had TRL of 6 or lower.
At the moment, removal and disposal of PFAS could sound alluring, especially when combined with concentration methods that concentrate PFAS and lessen the need for options like incineration, deep well injection, or further disposal that have detrimental environmental effects. However, forward-thinking companies are assessing PFAS destruction technologies that eliminate the need for any PFAS disposal and destroy PFAS on-site, which can be very cost-feasible and serve as a desirable alternative for landfill sites as the increasing regulatory oversight and compliance designations from the EPA loom.