Using Ozone Nanobubbles to Restore Groundwater from Organic Contamination
Nano+, a company specializing in nano-bubble systems for water treatment, and LDD, an expert in groundwater restoration, introduce nanobubbles as an innovative and effective solution for treating groundwater and removing organic impurities. How does this method work, and why does it have the potential to bring significant change to the world?
Groundwater pollution is a major environmental issue worldwide. In Israel alone, hundreds of millions of cubic meters of groundwater are contaminated with various organic and inorganic pollutants. These contaminants originate from numerous industrial, civilian, and security sources, as well as from energy facilities and security activities, according to reports from the Water Authority. {Need to state which ‘Water Authority}
LDD has been dedicated to groundwater restoration for over two decades, employing various technologies tailored to the specific needs of each site. One of LDD’s projects was through the Tel Aviv Municipality to restore the groundwater at the Magen site in Tel Aviv, Israel. Within less than a year from the start of the restoration, a substantial improvement in groundwater quality was already evident (see diagram number 1).
IN SITU chemical oxidation (directly in the groundwater) is a widely accepted method for treating groundwater contaminated with organic substances. Oxidizers such as persulfate, permanganate, and Fenton’s reagent are commonly used globally for this purpose, but each of these oxidizers has its limitations.
Oxidation reactions are advantageous due to their rapid operation, but they also come with notable disadvantages. For instance, the Fenton reaction depends on the water’s pH and releases a large amount of oxygen gas quickly, which can clog water passages in soil pores. Persulfate, while relatively stable, requires special activation and subsequently releases a significant amount of sulfate into the groundwater, causing secondary pollution. Permanganate is highly effective for treating chlorinated organic solvents but has a low oxidation potential, limiting its range of effectiveness. It cannot oxidize pollutants such as fuels, which require a higher oxidation potential to break their carbon-hydrogen bonds.
Ozone is widely used for water treatment due to its strong oxidizing properties. However, its effectiveness in groundwater treatment is limited by its relatively low solubility (a few parts per million) and rapid decomposition in the aqueous phase. Attempts to use chemical substances to prolong ozone activity in water have not yielded satisfactory results.
Another project undertaken by LDD involved restoring a site contaminated with the fuel component MTBE using a combination of ozone and hydrogen peroxide (see diagram number 3).
The entire water purification industry is a driver for Israeli company NANO+. This company uses its advanced systems to apply ozone in nanobubbles for various water treatment applications. Groundwater restoration is a key focus of the collaboration between NANO+ and LDD. Their partnership maximizes the benefits of using ozone for groundwater restoration, creating a significant global impact in the field of water purification.
Ozone is used to treat drug residues in drinking water facilities and to address algae toxins in surface water. It also plays a crucial role in wastewater treatment due to its strong oxidizing capabilities. In recent years, methods to enhance the stability of ozone in subsurface environments have garnered significant attention. Ozone nanobubbles, ranging in size from tens to a few hundred nanometers and numbering in the hundreds of millions per cubic centimeter of water, facilitate rapid mass exchange with water due to their enormous surface area. These nanobubbles can persist in water for extended periods—weeks to months—without escaping or merging into larger bubbles. Their small diameter results in high internal pressure, significantly increasing the gas’s solubility in water. Due to their small diameter, nanobubbles don’t rise to the water’s surface and remain submerged, moving with the water flow. Their size and negative charge allow them to navigate through micron-sized pores without getting stuck.
In a 2018 experiment [1], combining ozone nanobubbles with hydrogen peroxide (perezone) was found to reduce the concentration of TCE in water from 100 ppm to less than 1 ppm in under ten minutes. The decomposition rate of TCE using the combination was three times more effective than using ozone nanobubbles alone. In a subsequent field experiment by the same researchers, similar results were achieved even 5 meters from the injection well.
At the 2022 BATTELLE conference in the USA, RAMBOLL consulting company presented their findings on using ozone nanobubbles in combination with the oxidizer persulfate. The ozone nanobubbles eliminated the need for a persulfate activator, as ozone served this purpose. Analytical results showed that this combination significantly increased the oxidation potential of the groundwater and substantially reduced TCE concentrations at the site. RAMBOLL also reported that the same method was tested at a site contaminated with hydraulic oil, successfully reducing the hydraulic oil concentration in the groundwater by 95%.
LDD, in collaboration with NANO+, recently initiated several experiments using ozone nanobubbles for groundwater treatment. They successfully removed iron and manganese from polluted groundwater by oxidizing them with ozone and then filtering out the insoluble oxidized particles. Currently, they are beginning an experiment using ozone nanobubbles to treat fuel contaminants absorbed into the soil at a gas station that has suffered from pollution for many years.
Clearly, ozone has numerous applications in pollutant treatment due to its strong oxidizing properties. NANO+ and LDD are leveraging nanobubbles for groundwater restoration, providing an innovative and effective tool for groundwater treatment.