Ozone-based in situ chemical oxidation (ISCO) is a technique that utilizes subsurface injection of ozone to modify specific chemical compounds, reducing their toxicity. Ozone can be employed independently or in conjunction with other peroxides to establish an advanced oxidation process (AOP). An AOP refers to any process that generates the hydroxyl radical. When used alone, ozone selectively reacts with targeted chemicals. In contrast, the hydroxyl radical lacks specificity and can attack virtually all organic molecules.
Advantages & Disadvantages Using Ozone
Ozone-based ISCO offers several benefits. It allows for the injection of higher ozone concentrations, and ozone exhibits greater stability in the gas phase compared to the liquid phase. Moreover, it enables enhanced diffusive transport and the attainment of higher velocities. However, there are also drawbacks to consider. These include the potential for inadequate distribution of ozone within the subsurface and the limited distance from the injection point over which effective results can be obtained.
Advantages of Ozone ISCO
Utilizing ozone-based in situ chemical oxidation offers numerous advantages. Injecting air below the water table through this method results in the volatilization of specific organic compounds, provides oxygen for aerobic bacteria, and facilitates the mixing of groundwater. Ozone, being a potent oxidizer, directly converts various chemicals into less toxic substances, thereby enhancing the efficacy of air sparging. For detailed and comprehensive information on ozone and its properties, please find the following comprehensive resource.
Air Sparging with Ozone
In numerous instances of ISCO implementation, ozone is injected as a subsurface gas along with air. When ozone is combined with air sparging, it needs to diffuse from the injection site in order to reach the contaminants or be carried upward due to buoyancy. Designing a sparging system necessitates a thorough comprehension of soil characteristics and the distribution of contaminants. It is advisable to entrust the design to engineering specialists. Implementing ISCO-based advanced oxidation processes adds further complexity, as the lifetime of the hydroxyl radical, once formed, is measured in microseconds.
Consequently, the hydroxyl radical formed cannot travel significant distances. In the case of ozone peroxide, a sequential injection process is followed where peroxide is injected first, and then ozone is sparged into the ground. This sequential injection allows the hydroxyl radical to form as the ozone diffuses away from the injection point. The concentration of peroxide chosen plays a crucial role in maximizing the effectiveness and range of a specific injection well. In many cases, the pump and treat approach may be a more suitable option for implementing advanced oxidation.