Grantee Research Project Results
Final Report: Plasma’s Role in Potable Reuse for PFAS Remediation
EPA Contract Number: 68HERC21C0019Title: Plasma’s Role in Potable Reuse for PFAS Remediation
Investigators: Mujovic, Selman
Small Business: Purafide, LLC
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2021 through August 31, 2021
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2021) RFA Text | Recipients Lists
Research Category: SBIR - Land Revitalization , Small Business Innovation Research (SBIR)
Description:
Government taskforces, municipal water utilities, and manufacturers must adapt to contaminants of emerging concern. The most prevalent, persistent, and problematic of these pertinent pollutants are per- and polyfluoroalkyl substances (PFAS). PFAS are difficult to breakdown, linked to many adverse health effects, and found in nearly all Americans’ blood and in more than 200 million Americans’ tap water. Resource managers need reliable and resilient technologies that convert waste streams to value streams while satisfying regulations.
Current state of practice for PFAS management is primarily physical removal. These techniques produce hazardous waste that must be properly disposed, which can be costly and introduces long-term liabilities. For instance, filtration produces spent media and membranes yield reject water. On the other hand, incineration is the only approved destruction method, but it is associated with dangers and very high average costs. Furthermore, water qualities with high concentrations of background constituents significantly hinder the efficacies of filtration and other destruction technologies, such as electrochemical oxidation. The sustainability and versatility of these existing techniques can be enhanced by complementing them with plasma.
Without consumables, plasmas can destroy PFAS in waters that are difficult to remediate. Plasma, or ionized gas, interacting with water results in a cascade of collisions, hence reactions, that mineralize contaminants into harmless byproducts including carbon dioxide and water. Plasma is fairly resilient and can function despite interferences present in complex water qualities. Consequently, plasmas can support sustainable, simultaneous, and synergistic treatment of PFAS and enable economically viable resource recovery, which is critical for water reuse. However, previous plasma-based purifiers could not scale. At atmospheric pressure, plasmas are filamentary and cannot treat large volumes of water due to the very small discharge contact area (think lightning incapable of penetrating water). Thus, simple designs that improve the contact area are needed to make plasma cost effective.
Purafide can provide customers with a pioneering platform technology that is effective, efficient, customizable, versatile, and scalable. Purafide’s proposed Plasma Water Reactor (PWR) uses close-packed water streams to amplify plasma ignition and propagation. The water lattice is designed such the plasma self-propagates along the water surfaces, thus treating more water without increasing power. Indeed, this geometric approach minimizes energy consumption and maximizes the plasma-water interface, enabling scale to relevant industrial flow rates for the first time ever. The PWR can be easily modified to tailor treatment and provide customized water quality using variable power and geometries. The PWR is the first of its kind to use multi-fluid manipulation that further improves the plasma-water interface, which should promote even greater efficiency and treatment synergy. Collectively, these innovations further the PWR as a pioneering platform water treatment technology. Combined with the ability to treat some of the harshest waters, these innovations unlock many commercial applications, which need to be investigated in order of prioritized need. Particularly, previous plasma-based purifiers have not been studied in water reuse schemes. Addressing water qualities found in water reuse applications would tremendously contribute to the security of our water resources.
The purpose of this research was to demonstrate plasma-based PFAS destruction in complex water reuse-related matrices with the PWR—a platform product that uses a novel geometric approach to scale. Using variable pulsed power to tailor treatment, the PWR was assessed in groundwater (GW) and reverse osmosis concentrate (ROC)—rejected membrane water with a high contaminant load that is ocean discharged. Provided by Orange County Water District (OCWD), the GW is local drinking water supply and the ROC is from OCWD’s GW Replenishment System. The success criterion was a 1+ log-reduction (90%+ removal) or the California response level (RL) for perfluorooctanoic acid (PFOA, 10 ppt) and perfluorooctane sulfonate (PFOS, 40 ppt)—the two most studied PFAS. The bonus success criteria were 1+ log- reduction of other PFAS, the CA notification level (NL) for PFOA (5.1 ppt) and PFOS (6.5 ppt), and a total PFAS concentration of 70 ppt, which is based on the EPA’s health advisory for PFOA and PFOS combined.
The goal was to optimize water treatment in each water reuse matrix to demonstrate effectiveness, efficiency, and versatility. Kept constant throughout the experiments, the PWR design was chosen based on initial computational analysis and ease of manufacturing; much more work is needed to determine the optimal configuration. Nonetheless, the power supply variables, specifically the voltage and frequency, were spanned for each stream as the PWR system operated in batch mode. Three parameter combinations were chosen based on the qualitative and quantitative features of the plasma discharge (brightness, power, distribution, etc.); the two settings that corresponded to lower power focused on energy efficiency whereas the higher power focused on effectiveness. PFAS concentrations were determined using EPA Method 537.1 by a certified analytical laboratory.
Summary/Accomplishments (Outputs/Outcomes):
The preliminary low-power results suggested that the unoptimized PWR was still able efficiently destroy PFOA and PFOS. The PWR achieved a low electric energy per order (EEO~10 kWh/m3) for PFOA in GW and PFOS in ROC, where EEO is defined as the amount of energy needed to remove 90% of a contaminant in a given volume of water. On the other hand, high- power proved to be very effective. In both matrices, all 16 long- and short-chain PFAS measured exhibited decreases in concentration, except for 6:2 fluorotelomer sulfonate in GW which slightly increased due to leaching from the Teflon tape used in the PWR system. Consequently, it is recommended to avoid Teflon-based products when assessing PFAS destruction. Nevertheless, at high-power, the total PFAS concentration decreased in both matrices with GW approaching 70 ppt, one of the bonus success criteria. This indicates that the PWR is successfully fully mineralizing PFAS into harmless byproducts including carbon dioxide, water, and fluoride.
For high-power, in GW, PFOA and PFOS approached the NL whereas in ROC, PFOA approached the RL and PFOS achieved sub-NL. Furthermore, in ROC, high-power yielded 1+ log- reduction of PFOS, perfluorononanoic acid, and perfluorodecanoic acid. Interestingly, regardless of power configuration, PFOA and PFOS were destroyed at similar rates in GW and PFOS was predominately destroyed in ROC. PFOS is typically harder to destroy than PFOA so more research is needed to understand why PFOS was more effectively and efficiently destroyed in ROC, especially given the presence of plentiful scavengers in the background matrix. In both matrices, the EEO for a given PFAS increased over time, suggesting that the effective destruction rate was not obeying expected first-order kinetics. More research is needed to assess the relationship between efficiency, effectiveness, and contaminant and scavenger concentrations. Future work will also involve scaling to pilot flow rates and evaluating the true lifecycle cost. For instance, savings from plasma’s synergistic capabilities, such as the elimination of hazardous waste produced by separation (e.g., ROC), must be economically quantified, field-tested, and incorporated into the cost analysis of the entire advanced treatment train.
Conclusions:
Each of the experiments performed by our multidisciplinary team were novel and promising: using variable power to tailor treatment, the PWR was evaluated for PFAS destruction in practical water reuse matrices including contaminated groundwater and reverse osmosis concentrate. Given that these matrices were vastly different in terms of water quality, these results indicate that plasma is very versatile and can be a viable destruction alternative in water treatment. This study has tremendous implications since the PWR can destroy PFAS with required and recommended limits indiscriminate of water quality, suggesting the PWR can withstand an evolving regulatory landscape and increasingly complex and challenging water qualities. Specifically, the PWR can address short-chain PFAS, which many technologies currently struggle with. This would immensely impact the water world since the PWR can destroy PFAS in relevant water qualities where other technologies are ineffective, hence alleviating significant pains for customers. Destruction technologies used for other contaminants may ultimately be replaced with the PWR since it can synergistically destroy more contaminants, implying robust versatility. Furthermore, the PWR exhibited the ability to transition between efficiency and effectiveness. This discovery has immediate commercial impact where entities can cheaply cleanup a contained contamination site or rapidly remediate an uncontained spill. Though more research is needed, these pioneering investigations provided insight into the best reuse applications for plasma and enabled plasma performance to be modeled as a function of power and water quality. Overall, this study has contributed to strengthening the security, stability, and sustainability of water.
Purafide has performed and continues to perform customer discovery by speaking with water stakeholders and operators at various organizations including golf courses, government remediation taskforces, landfills, manufacturing sites, municipal treatment plants, and commercial developments. Water treatment operators want to comply with stricter regulations, reduce the use of chemical disinfectants, upgrade aging infrastructure, and promote water reuse. Purafide’s strongest piece of evidence for product-market fit was when an interviewee said, “the other technologies we tried did not work.” Indeed, there is an urgent need to address contaminants with existing and pending regulations that current technologies are ineffective against, such as PFAS. This gives Purafide plenty of opportunity to penetrate the water treatment market.
Purafide can provide customers with a pioneering plasma-based water treatment technology that is effective, efficient, customizable, versatile, and scalable. Purafide’s platform technology can be strategically applied to various water segments. Customer discovery suggests Purafide’s value propositions are initially best suited in water reuse as a polishing technology (The final stage in treatment trains is disinfection, which is conservatively estimated as a $4.4 billion global market). Purafide’s PWR can be applied as a standalone and complementary technology throughout advanced water treatment trains, alleviating significant pains for manufacturers, government taskforces, and water utilities. Engineering firms, renowned water utilities, and state environmental agencies, such as Brown & Caldwell, Carollo Engineers, Great Lakes Water Authority, Orange County Water District, Southern Nevada Water Authority, New Jersey Department of Environmental Protection, and Michigan Department of Environment, Great Lakes, and Energy, have expressed their willingness to support research efforts. The engineering firms and utility pretreatment programs serve as channels to early adopters. Nonetheless, deploying the PWR throughout potable reuse systems would significantly accelerate the transition of plasma-based technologies into the water industry. Thus, Purafide has the potential to revolutionize how we clean water and protect our environment.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.