PULSEOX TECHNOLOGY OVERVIEW
Applied’s PulseOx in situ chemical oxidation technology (patents pending) is designed to deliver ozone (O3), hydrogen peroxide (H2O2), oxygen (O2), and air into a contaminated water bearing zone via one or more nested injection points. The chemical oxidation process can be used to achieve the rapid degradation of dissolved contaminants.
The Ozone and Hydrogen Peroxide Chemical Oxidation Process
The reactants (ozone and hydrogen peroxide) are injected directly into the groundwater along with oxygen and air via nested, stainless steel injection points in controlled ratios at one or more locations across the treatment zone.
The hydrogen peroxide and ozone react in the groundwater to form hydroxyl radicals (•OH-), which are among the most powerful oxidizers available. A proprietary reagent injection methodology maximizes the distribution of reagents, formation of hydroxyl radicals, and occurrence of chemical reactions which take place in the treatment zone. This proprietary technique also aids in the extraction or flushing of absorbed contaminants off of the saturated soil surrounding the injection well.
Individually, ozone and hydrogen peroxide will react with organic contaminants due to their relatively high oxidation potentials (2.07 volts and 1.77 volts, respectively). Since hydroxyl radicals have a higher oxidation potential (2.80 volts) than either ozone or hydrogen peroxide individually, and due to the rapid chemical reactions involved, it is beneficial to introduce ozone followed by hydrogen peroxide in saturated soils.
The formation of hydroxyl radicals through the introduction of ozone and hydrogen peroxide is performed by the following reaction:
2O3 + H2O2 → 2OH + 3O2
Hydrogen peroxide and ozone will also individually react with iron in the subsurface soils to form hydroxyl radicals. The hydroxyl radical is a strong oxidizer that reacts with organic contaminants, breaking them down to carbon dioxide and water. For example, consider the breakdown of MTBE in the following diagram:
The diagram shows how MTBE is broken down into carbon dioxide, water, and oxygen. Each reaction occurs very rapidly.
Enhanced Biodegradation
The injection of ozone and hydrogen peroxide significantly increases dissolved oxygen concentrations in groundwater (typically up to 15 to 25 mg/l). While the high concentrations of ozone and hydrogen peroxide near the injection points (chemical oxidation zone) preclude microorganism growth, the elevated dissolved oxygen concentrations typically extend well beyond the chemical oxidation zone. These elevated down-gradient dissolved oxygen concentrations will promote and enhance the natural degradation of remaining dissolved contaminants that are aerobically biodegradable. This aerobic biodegradation of contaminants will continue well after oxidant injection has concluded.
Identifying Suitable Site Locations
The effectiveness of virtually every in-situ groundwater treatment technology is dependent, in part, on the permeability of the saturated soils that contain the contaminants. The more permeable the soils the more effective the technology is likely to be. Advanced drilling techniques, such as the use of hydraulic or pneumatic fracturing may be suitable at some locations, but will involve additional costs and potential risks.
In-situ solutions will not be appropriate in every case. Care must be exercised to determine whether a particular site is appropriate for one technology or another. As part of any potential in-situ project, Applied first works with site engineers and geologists to determine whether a site is suitable for in-situ solutions generally, and advanced oxidation in particular.
We understand that there is no value in applying good technology to the wrong site. We work with our customers to determine the viability of an in-situ solution, which can be supported by a well-defined bench and/or pilot test.
|
