Per- and polyfluoroalkyl substances (PFAS) are pollutants that have demonstrated a high level of environmental persistence and are very difficult to remediate. As the body of literature on their environmental effects has increased, so has regulatory and research scrutiny. The widespread usage of PFAS in industrial applications and consumer products, complicated by their environmental release, mobility, fate, and transport, have resulted in multiple exposure routes for humans. Furthermore, low screening levels and stringent regulatory standards that vary by state introduce considerable uncertainty and potential costs in the environmental management of PFAS. The recalcitrant nature of PFAS render their removal difficult, but existing and emerging technologies can be leveraged to destroy or sequester PFAS in a variety of environmental matrices. Additionally, new research on PFAS remediation technologies has emerged to address the efficiency, costs, and other shortcomings of existing remediation methods. Further research on the impact of field parameters such as secondary water quality effects, the presence of co-contaminants and emerging PFAS, reaction mechanisms, defluorination yields, and the decomposition products of treatment technologies is needed to fully evaluate these emerging technologies, and industry attention should focus on treatment train approaches to improve efficiency and reduce the cost of treatment.

Per- and polyfluoroalkyl substances (PFASs) are a family of highly toxic emerging contaminants that have caught the attention of both the public and private sectors due to their adverse health impacts on society. The scientific community has been laboriously working on two fronts: (1) adapting already existing and effective technologies in destroying organic contaminants for PFAS remediation and (2) developing new technologies to remediate PFAS. A common characteristic in both areas is the separation/removal of PFASs from other contaminants or media, followed by destruction. The widely adopted separation technologies can remove PFASs from being in contact with humans; however, they remain in the environment and continue to pose health risks. On the other hand, the destructive technologies discussed here can effectively destroy PFAS compounds and fully address society’s urgent need to remediate this harmful family of chemical compounds. This review reports and compare widely accepted as well as emerging PFAS destruction technologies. Some of the technologies presented in this review are still under development at the lab scale, while others have already been tested in the field.

Prior video technologies such as closed-circuit television (CCTV) cameras have been used for culvert inspection. They are limited by the range of the area scanned and by the direction in which the camera is oriented because of a limited field of view (FOV). In this research, a 360-degree camera mounted on a remote-controlled crawler was designed and modified to travel through a culvert to scan and take videos of the culvert’s interiors. With the unique mounting and coverage of the 360-degree camera, a continuous view of the inner walls of the culvert was captured, as if by a human eye, making visual inspection of hard-to-reach areas possible. The video was analyzed manually, and areas suggesting defects were studied. Snapshots of defective areas were further analyzed using computer software developed in-house, where defects were identified by differences in color and texture. Calculations made from the data collected helped to pinpoint the location of the defects within the culvert and estimate the area of the defects in order to provide culvert inspectors with quantitative information on the condition of the infrastructure.

PFASs, or per- and polyfluoroalkyl substances, comprise a diverse group of synthetic chemicals known for their widespread use, persistence, and potential environmental and health risks. The sonolytic treatment of PFASs is one of the technologies with the ability to complete destruction without harmful byproducts. This study aims to provide a theoretical explanation for the sonolytic treatment of PFAS. Combining insights from molecular dynamics simulations with experimental data, the influence of chain length and functional headgroups on the PFAS destruction mechanism was investigated. The findings revealed that the impact on functional head groups and chain length on PFAS degradation via sonolysis treatment is complex and multifaceted. The preliminary degradation step is attributed to be headgroup cleavage, while differences in degradation rates between perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) are primarily influenced by adsorption at the air–water interface of micro/nanobubbles created by ultrasound and dictated by compound hydrophobicity characteristics. Moreover, longer-chain PFAS compounds tend to degrade faster than shorter-chain counterparts due to their enhanced hydrophobic characteristics, facilitating adsorption and subsequent mineralization. The sonolytic environment significantly influences PFAS degradation, with aqueous sonolysis proving the most effective compared to dry pyrolysis or thermal combustion, highlighting the importance of considering environmental factors in remediation strategies. These insights provide valuable guidance for designing effective PFAS remediation strategies, emphasizing the need to consider molecular structure and environmental conditions. Further research and technological innovation are essential for developing sustainable approaches to mitigate PFAS pollution’s adverse impacts on human health and the environment.

In this paper, nonlinearity associated with intense ultrasound is studied by using the one-dimensional motion of nonlinear shock wave in an ideal fluid. In nonlinear acoustics, the wave speed of different segments of a waveform is different, which causes distortion in the waveform and can result in the formation of a shock (discontinuity). Acoustic pressure of high-intensity waves causes particles in the ideal fluid to vibrate forward and backward, and this disturbance is of relatively large magnitude due to high-intensities, which leads to nonlinearity in the waveform. In this research, this vibration of fluid due to the intense ultrasonic wave is modeled as a fluid pushed by one complete cycle of piston. In a piston cycle, as it moves forward, it causes fluid particles to compress, which may lead to the formation of a shock (discontinuity). Then as the piston retracts, a forward-moving rarefaction, a smooth fan zone of continuously changing pressure, density, and velocity is generated. When the piston stops at the end of the cycle, another shock is sent forward into the medium. The variation in wave speed over the entire waveform is calculated by solving a Riemann problem. This study examined the interaction of shocks with a rarefaction. The flow field resulting from these interactions shows that the shock waves are attenuated to a Mach wave, and the pressure distribution within the flow field shows the initial wave is dissipated. The developed theory is applied to waves generated by 20 KHz, 500 KHz, and 2 MHz transducers with 50, 150, 500, and 1500 W power levels to explore the effect of frequency and power on the generation and decay of shock waves. This work enhances the understanding of the interactions of high-intensity ultrasonic waves with fluids.