Investigating Ultrasound as a Technology to Treat Contaminants
We are studying the effects of ultrasonic waves on the degradation of water pollutants. Ultrasonic waves, when applied to water, result in cavitation bubbles shown in the picture beneath an ultrasonic probe. These microscopic bubbles grow and collapse with the ultrasound. Upon collapse, the bubbles generate extremely high temperatures (hotter than the sun!) and pressures (approximately 1000 atmospheres). As a result of these extreme conditions, the chemical bonds of water are broken generating reactive and highly oxidizing chemical species. In addition, contaminants in the water entering the cavitation bubbles undergo high temperature gas phase reactions.
The Weavers research group is exploiting these processes to selectively degrade pollutants that preferentially accumulate on air/water surfaces (i.e., on the bubbles). In addition, we are exploring the use of pulsed ultrasound to increase the efficiency of the ultrasound in environmental applications. Pollutants that Dr. Weavers and her students have targeted include PFAS compounds, free and complexed EDTA, linear alkyl benzene sulfonate surfactants, and pharmaceuticals and personal care products (PPCPs).
Another of Dr. Weavers’ current ultrasound-based research projects is focused on desorption of toxic inorganic and organic contaminants from sediments. Specifically, she and her team are interested in understanding exactly how ultrasound works to treat contaminated sediments. This will enable them to determine if ultrasound could be used to treat all types of contaminated sediment and to understand how to make the process work better and cheaper.
Testing Ultrasound to Mitigate Harmful Algal Blooms
In addition, the Weavers research group is investigating the use of low power ultrasound for the mitigation of harmful algal blooms in reservoirs. Harmful algal blooms (HABs) are a challenge that utilities across the country face and pose a significant threat in Ohio. Ultrasound is a physical reservoir management strategy that may be an important bloom prevention and mitigation strategy with over 10,000 installations worldwide. Ultrasound is a low energy technology that does not require the use of chemicals, such as algaecides, and potentially could kill cells without releasing their toxins. In this study we are evaluating the effect of a commercially available ultrasonic device on HABs.
Developing Novel Membranes for Water Treatment (click here for more details)
Membranes are used increasingly in water and wastewater applications in both industrial and municipal settings. In fact, the membrane industry is a multi-billion dollar industry and growing rapidly. A continuing issue with membranes however is their tendency to foul. Fouling can occur due to particles, dissolved constituents, or biofilm formation. Current defouling technologies include back flushing, forward scouring with water or air, and chemical cleaning. However, these methods are not fully effective, require the equipment to be taken off-line, and require the use of chemicals, which is not always feasible or desirable.
One defouling technology that requires no chemicals and offers in situ application is sonication. Ultrasound at frequencies from 20 kHz to 1 MHz and at sufficient power levels results in the formation of cavitation bubbles in solution. Depending on the ultrasonic device and application method, these cavitation bubbles may be dispersed throughout solution or localized near the irradiating device. Work in Weavers’ laboratory has shown that cavitational mechanisms are important in detaching particles from the membrane surface while turbulence associated with ultrasound plays a role in the transport of particles away from the surface following detachment. Particle removal occurred on the order of seconds restoring the flux through the membrane. Continuous sonication during membrane operation would prevent fouling and the consequent gradual decrease in water flux. Weavers and co-workers hold a patent on this process. In current work we are collaborating with colleagues in Material Science to develop a piezoceramic membrane that generates ultrasound in-situ.
Developing Design Criteria for “Emerging Technologies”
We are addressing innovation in the water industry in Ohio. In this effort we are working with collaborators in the water industry on how to increase access to modern water technologies for small and medium water utilities. The project focuses, not on developing new technology, but on the intersection between regulator that approves the technology, water utility, and design engineer—creating design standards for modern technologies with a substantial track record. In Ohio, the current process of requiring pilot studies before design and implementation creates a large barrier, particularly for small and medium water utilities, hindering the use of modern technologies even though these technologies may provide better water quality at lower cost. The first design standard, for low pressure membranes, has been created and is currently under review by Ohio Environmental Protection Agency for inclusion in their Plan Approval Process for installation of new technologies at a water plant.
Measuring PFAS in Watersheds
Public concern over PFAS is growing. Scientific understanding is growing as to how PFAS enters the environment, how it moves into water supplies, and, importantly, what strategies are effective in removing it from water supplies. Ohio is particularly susceptible to the effects of PFAS as these “forever chemicals” are more prevalent in watersheds with industrial sites, military fire training areas, and multiple wastewater treatment plants. Given the state’s manufacturing base, military installations, and large population density, we are working with Dr. Andy May to understand the atmospheric spread of PFAS.
Check out a recent article on our work in C&E News