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PER-PETUAL System™ (Patent Pending)


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The PER-PETUAL System (TM) is a system for the remediation of ground water by enhancing the ground water with hydrogen peroxide and using chemical oxidation the formation of hydroxyl radicals and naturally occurring bacteria (bioremediation) to remove contaminants from the ground water. The system injects a continuous flow of peroxide solution directly into the groundwater. (varied according to site)

Background
Hydrogen Peroxide is easily converted to hydroxyl free radicals (OH*) which breakdown a variety of organic compounds. The oxidation of organic compounds reduces the carbon chain into smaller and smaller pieces, ultimately to carbon dioxide, water and simple compounds. Chemical oxidation using hydrogen peroxide essentially “steals” electrons from another molecule. This process is called oxidation. All organic compounds can be oxidized.

During chemical oxidation remediation, an oxidant (hydrogen peroxide) is injected at varying concentrations into the aquifer. Because there is typically no oxidant in the deep soil pores and low permeability soil layers, there is a strong driving force (concentration gradient) for the oxidant to diffuse into these locations where contaminants are sequestered and chemically oxidize the contamination. Dissolved oxidant concentrations that “flood” the high permeable soil layer may be 1,000 times the dissolved contaminant concentrations that reside in the low permeable layers. Therefore, the rate of diffusion of the oxidant “inward” into the low permeable layers can be up to 1,000 times the rate of diffusion of the contaminant “outward”. Since the oxidant gets “used up” performing the oxidation, this tendency to diffuse will continue, rather than decrease over time the way the diffusion of contamination outward does.

Some soils, especially iron rich soils can convert hydrogen peroxide molecules to hydroxyl radicals better than others. The object of injecting hydrogen peroxide into the ground water is to facilitate the chemical oxidation of the contaminant and to increase the dissolved oxygen concentration. One of the by products of left over oxidation is molecular oxygen. This left over oxygen from the hydrogen peroxide can increase dissolved oxygen concentrations in the range of more than 100 ppm or greater. As stated earlier, oxygen is needed for bacteria to convert contamination into carbon dioxide. At most sites of contamination, oxygen is significantly limited reducing the rate at which bacteria can convert contamination into carbon dioxide.

The secondary purpose of the PER-PETUAL System is to provide an ample amount of oxygen for the bacteria to survive and thrive. Like we humans, bacteria do not like oxygen deficient environments nor do they like oxygen rich environments. The system should be operated to maintain an oxygen concentration of between 15% and 25%. As discussed previously soil gas should be collected and analyzed to determine the oxygen concentration in the area of oxygen injection. Should the oxygen concentration fall below 15% in the vadose zone, just above the area of the hydrogen peroxide injection, the rate of hydrogen peroxide injection should be increased slightly to achieve the desired concentration of between 15% and 25%. Conversely, should the oxygen concentration exceed 25% in the vadose zone, just above the area of the hydrogen peroxide injection, the rate of hydrogen peroxide injection should be decreased slightly to achieve the desired concentration range. Dissolved oxygen concentrations in grond water should also be collected.

A baseline should be established prior to system start up and the injection of hydrogen peroxide. It is recommended that samples be collected and the system monitored once per week for the first month. After the first month, the system can be sampled and monitored once per month for the next two months and then quarterly thereafter. An increase in carbon dioxide in the area of groundwater impact can be anticipated within the first month. This increase in carbon dioxide is a result of increased contaminant degradation because of both chemical oxidation and the increase in the bacterial population. Additional sample parameters can also be collected (e.g. plate counts and bacterial species analysis) however; the results of the carbon dioxide analysis are telltale signs of bacterial activity and can be relied upon as good indicators of contaminant degradation and a bacteria population.

It is recommended that ground water temperature and pressure at each peroxide delivery point and monitoring well be monitored to determine if unwanted temperatures and pressures are being developed at the site. Should these unwanted temperatures and pressures become evident, adjusts to the system can be completed as necessary.

As the system operates overtime the hydrogen peroxide flow rate will require adjusting from time to time. The level of hydrogen peroxide supplied can be anticipated to diminish over time as contamination is reduced resulting in less chemical oxidation and a smaller bacterial population. The monitoring of soil gas can be used to evaluate system performance.

To learn more about the system, download the Per-Petual System™ Installation and Operations and Maintenance Manual.

American Remediation
8666 E. Traverse Highway - Traverse City, Michigan 49684
Phone:(231) 933-7035 - Fax: (231) 933-7135 - Cell: (231) 218-7955
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