There has been growing concern about PFAS impacting the environment in areas where firefighting foams were used, certain manufacturing facilities, landfill leachate and other impacted sites. However, most current technologies used to remove PFAS from groundwater, industrial wastewater and leachate have significant drawbacks.
- Activated carbon, the most commonly applied technology, offers low capital cost, but high operating costs because the used media, which needs to be regularly replaced, must be transported to an accredited disposal facility where it is treated by high-temperature incineration to destroy the problematic PFAS molecules.
- Ion exchange resins are also becoming a mainstream technology for PFAS removal in water. However, most of the time they involve a single-use resin, which must then also be incinerated. If a regenerable resin is employed, the PFAS-impacted regenerant stream needs to be transported and disposed of at high cost – again, in an accredited waste management facility.
- Membrane technologies, such as reverse osmosis, can remove PFAS from water, but they also require disposal of their PFAS-contaminated reject stream. This could be a significant volume, depending on the volume of water to treat and the initial water quality, such as its total dissolved solids concentration. For remote area, this could simply not be applicable.
Cost savings over conventional methods
One of the keys to our successful use of electro-oxidation technology has been using unique long-lasting boron-doped diamond (BDD) electrodes. While these electrodes increase the capital cost of the equipment, the electrodes are expected to have a lifespan of up to 25 years, so that the initial cost is spread over a long operational life. Furthermore, the capital cost can be mitigated by leasing the equipment. These special electrodes also allow for generation of lower concentrations of by-products compared to other electro-oxidation electrode materials.
Our team has been encouraged to find that by optimizing the electro-oxidation process, we were able to provide a cost-competitive solution compared to activated carbon technology over the long term. The only operating cost of electro-oxidation is electricity to charge the electrodes and operate the process pump.
In brief, this boron-doped diamond electro-oxidation system for PFAS treatment:
- destroys PFAS molecules so there is no transfer of PFAS to other media, thereby eliminating costs for media purchase, transport, disposal or regeneration;
- uses no chemicals, produces no sludge, and the absence of filter media eliminates costly disposal;
- offers easy scalability with more arrays of boron-doped diamond plates or reactors and application of more electricity to treat a larger water flow; and
- delivers low operating costs by needing only electricity and no human intervention. Initial capital costs can be mitigated by leasing equipment.