Recipient Organization
UNIV OF IDAHO
875 PERIMETER DRIVE
MOSCOW,ID 83844-9803
Performing Department
(N/A)
Non Technical Summary
Cattle drinking water polluted by per- and poly-fluoroalkyl substances (PFAS) has led to contaminated milk that, if consumed by humans, will cause severe health issues. The long-term goal of this project is to establish a green, nonthermal plasma-based technology for on-farm water treatment that will be compact, easy to operate, and efficient in removing toxic PFAS in cattle drinking water in order to prevent milk contamination. This advanced technique is built on a novel, continuous-flow, liquid-phase plasma discharge (CFLPPD) reactor that is hypothesized to effectively and efficiently decompose PFAS while preserving water quality attributes. Specific objectives of this proposal are to 1) study the technical feasibility and mechanism of effective remediation of typical PFAS substances (PFOA and PFOS) by the improved continuous flow liquid-phase plasma discharge (CFLPPD) process designed for on-farm use; 2) identify significant factors that influence the PFAS degradation efficiency and water quality, and the best operational mode by the CFLPPD process. Successful completion of this seed project will lay the technical groundwork for revolutionizing the on-farm water treatment system to tackle PFAS contamination at reduced cost and reduced energy usage. This work addresses the Program Area Priorities of NIFA Foundational and Applied Science Program A1521, i.e., "Enable engineering systems for forestry and natural resources; plant and animal production".
Animal Health Component
100%
Research Effort Categories
Basic
30%
Applied
70%
Developmental
(N/A)
Goals / Objectives
The long-term goal of this proposal is to maintain US dairies in business by producing milk without per- and poly-fluoroalkyl substances (PFAS) contamination. Cattle drinking water polluted by PFAS has led to contaminated milk that, if consumed by humans, will cause severe health issues. To that purpose, this proposal will initiate a novel and efficient technology based on liquid-phase plasma discharge to decompose PFAS in water so cows will have a safe drinking water source and will not produce milk with hazardous PFAS levels. The specific objectives of this project are to 1) study the technical feasibility and mechanism of effective remediation of typical PFAS substances (PFOA and PFOS) by the improved continuous flow liquid-phase plasma discharge (CFLPPD) process designed for on-farm use;2) identify significant factors that influence the PFAS degradation efficiency and water quality, and the best operational mode andPFAS removal effciency from waterby the CFLPPD process.
Project Methods
Methods for Specific Objective 1: Study the technical feasibility and mechanism of effective remediation of typical PFAS substances (PFOA and PFOS) by the improved AC CFLPPD process designed for on-farm operationTo improve the treatment efficiency and shorten the treatment time for bulk treatment for on-farm application scenarios, a second-generation CFLPPD reactor was designed. This modified reactor configuration was to further improve the distribution of plasma discharge and the mass transfer of reactants to achieve better reaction efficiency. Instead of using one section for both ground and high voltage electrodes, two ground electrodes were used in the modified reactor design, in which the high voltage electrode was sandwiched between two ground electrodes and each pair of electrodes was separated by a dielectric plate. As such, two concentrated plasma channels (one up and one down) will form for simultaneous discharge at two orifices as the liquid passes. By adjusting input power, this design doubles the treatment effect, such that if the liquid receives incomplete treatment when flowing through the lower opening, it is treated again as it passes the upper opening. The sandwiched high-voltage electrode between two ground electrodes guarantees an enclosed electrical circuit, which also increases the safety of operation. Like the first-generation design, the second-generation CFLPPD unit consists of a polycarbonate frame holding stainless-steel electrodes connected to a high-voltage transformer with AC power supply to provide high voltage discharge to the liquid.Experiments with the operating parameters defined in the preliminary study will be performed to diagnose the double-channel plasma generation and verify the mechanism for PFOA and PFOS degradation by the 2nd-Gen CFLPPD. Important plasma properties during electric discharge in PFAS solutions will be characterized at the plasma discharge breakdown moment in continuously flowing solution. Firstly, time resolved records of voltage and current will be measured using an oscilloscope (Tektronix TBS1052B) operating up to 50 MHz with a high voltage probe (Tektronix P6015A, attenuation 1:1000) and AC Current Probe probe (Tektronix P6021) to produce current-voltage (A-V) characteristics of the discharge to interpret the driving current and voltage waveforms under the specified experimental conditions. Experiments will be repeated for 10 times and the mean values will be used for analysis. Another technique for specific plasma monitoring and quantification is to use optical emission spectroscopy (OES, Ocean- QEPro Spectrometer, Ocean Optics Inc.) to record the spectrum of plasma emission at nano-second scale and analyze the concentrations of reactive species (•OH, •N2O, O•, N•, O3) generated with plasma discharge by OES with software (OceanView, Ocean Optics Inc.).The removal rate and efficiency for PFOA and PFOS (both starting at 10 ppm) as well as their degradation pathways by CFLPPD will be analyzed to confirm the mechanism of PFAS remediation. Finally, four different operational modes, i.e., circulation, one-pass, two-pass, one-pass with two 2nd-Gen reactors connected in series, of the CFLPPD process will be compared for the PFOA/PFOS degradation to determine the feasibility for on-farm water treatment with a throughput of five liters per hour while achieving a safe water quality. As such, the plasma discharge type and formation of the reactive species in PFAS solutions will be verified. The PFAS degradation pathway and treatment time needed with different operational modes for the 2nd-Gen CFLPPD process will be determined after completion of this section.Methods for Specific Objective 2: Identify significant factors that influence the PFAS decomposition efficiency and water quality and the best operational mode for CFLPPDThe same CFLPPD reactor and measuring equipment for Specific Objective 1 will be used. Our preliminary trials have suggested that six key CFLPPD design and operation parameters could potentially influence PFAS treatment efficiency. These process parameters and the way by which they are applied to the system include 1) water flow rate, controlled by a valveless metering pump (FMI Q2V, Fluid Metering, Inc, Long Island, NY); 2) gas flow rate, controlled by a mass flow controller (SmartTrak100 C100L, Sierra Instruments, Inc, Monterey, CA); 3) input power, measured with a Watt meter and controlled by an Auto Variac high voltage transformer; 4) the thickness of quartz dielectric plate, δ; 5) the orifice diameter of the dielectric plate, ?; and 6) the influent PFAS concentration. The diameter of 12.7 mm (D) of the reactor body will be unchanged. Each treatment scenario will be performed using these six process parameters in various combinations to evaluate CFLPPD performance according to the Plackett-Burman (PB) experimental design in Table 1. Using the experimental design with the high (+1) and low (-1) values (Table 1) chosen based on preliminary trials, a total of 12 runs of experiments will be conducted in triplicate for PFOA and PFOS under the working operational modes (defined in Section 3.1.2) found in Specific Objective 1, respectively, to determine if each of these variables has significant main effects on the CFLPPD process, which is defined as having at least 70% confidence level from the PB design tests, for PFAS removal efficiency, degradation rate, and energy efficiency for PFAS removal, as well as for levels of physicochemical quality parameters.Sampling, chemical and physicochemical analysis for each operational condition will be the same as in Section 3.1.3. The PFAS degradation rate will be determined by dividing concentration reduction % by treatment time, and the energy efficiency for PFAS removal (PFAS removed/kWh) will be obtained by dividing the amount of PFAS (in mg) removed by the power consumed.The significant operating and design parameters of the CFLPPD process and the best operational mode for PFAS removal efficiency and preservation of drinking water quality will be determined.