The Cool-Ox® Bio-Spunge™ Reactor
Although it is expected that the bulk of the contaminant remediation will be accomplished by direct chemical oxidation, a vital role subsequent to the oxidation phase will be bio-degradation. DTI has discovered that once the oxidation reactions of the remedial work have begun taking place, the oxidation by-products create an environment ideal for the proliferation of intrinsic microbial degraders. To enhance this bio-process, DTI has developed formulations that promote accelerated biodegradation while still maintaining the vitality of the oxidation reaction. The establishment of these intrinsic microbial communities is referred to as the Cool-Ox® Bio-Spunge™ Reactor.
DTI has determined through experience gained by field applications, that a broad range of organic chemical contaminants are readily oxidized using the patented Cool-Ox® technology. Although the technology has the capability of converting the contaminants completely to carbon dioxide, this total mineralization process would prove to be prohibitively expensive because of the amount of oxidizer required. However, it has been observed at nearly every site treated, that significant contaminant reductions have been achieved with concentrations of Cool-Ox® reagents that are significantly lower than the stoichiometric ratios one would predict necessary. A study of the oxidation mechanism provided the answer to this question.
DTI has determined that a myriad of organic compounds are readily oxidized (hydroxylated) by the addition of a hydroxyl group to the molecule or the substitution (replacement) of a halogen atom by a hydroxyl group onto the molecule. This chemical reaction has been illustrated in organic chemistry textbooks and has been successfully applied, under field conditions, by DTI and DTI principles on numerous occasions. Once this conversion is complete, the resultant compounds are quite biodegradable thus setting the stage for the indigenous microbes to complete the remedial work.
In-Situ Remediation Of Groundwater
The keys to the development and successful application of the Cool-Ox® Bio-Spunge™ Reactor for the in-situ remediation of groundwater contaminants are:
The extended life of the peroxygen compounds,
The conversion of the contaminants to biodegradeable co-metabolites,
The buffering systems conversion to nutrients subsequent to the oxidation phase,
The absence of heat produced from chemical reactions,
The verification that the oxidation process actually enhances aerobic microbial activity (for more information on this phenomenon, please Contact Us.
With the development of the Cool-Ox® process, DTI became aware that at nearly all sites treated with the Cool-Ox® reagents, the proliferation of indigenous aerobic microbes increased by as much as six orders of magnitude. Upon visual inspection of samples collected from numerous sites, it was obvious that the appearance of the soil had changed from a clean material to that resembling the type of natural sponges found in marine environments. DTI also noted that contaminant concentrations found in groundwater down gradient from the injection zones, had significantly decreased; in most cases by orders of magnitude. Once this discovery was made, DTI developed Cool-Ox® reagent formulations to improve both the efficiency of the oxidation reactions and optimize indigenous microbial proliferation.
The scanning electron microscopic photographs (contributed by Dr. H. Eric Nuttall – University of New Mexico, Albuquerque) below depict clean sand particles (left) and the same soil after treatment (right). Note, the Extra-Cellular Polymeric Substances (ECPS), giving the appearance of the matrix seen in live sponges, hold the microbes in place while allowing the groundwater to flow through. This forms the matrix of the Cool-Ox® Bio-Spunge™ Reactor. This configuration increases the surface area, thus increasing the probability of contact between contaminants and microbial degraders
When the bio-fortified Cool-Ox® reagents are properly placed in the groundwater plume including the soil/groundwater interface, the indigenous microbes produce the ECPS biofilm depicted. If the injection points are properly placed and the reagent contains the formulation necessary to encourage the proliferation of microbes as well as the production of the biofilm, a filtration system (such as that depicted in the drawing below) is produced that allows the microbes to filter the groundwater as it passes through the formation. No other technology is presently available that ties chemical oxidation to subsequent bioremediation in the efficient manner as the Cool-Ox® process.
Photos courtesy of Dr. Eric Nuttall, University of New Mexico
The Cool-Ox® Bio-Spunge™ Reactor
(Groundwater Defined Flow (Streamline) Application)
This drawing illustrates the Cool-Ox® Bio-Spunge™ Reactor installation at a site where the soil consists of a permeable matrix and where the groundwater flow is defined. This installation technique calls for the placement of the Cool-Ox® reagents in a configuration perpendicular to the direction of the groundwater flow. Contaminants located in the installation zone are rapidly oxidized while the microbial population indigenous to the treatment zone are stimulated by the nutrient fortified Cool-Ox® reagents and begin accelerated proliferation. This technique is especially economical because contaminated plumes can be mitigated by treating only a fraction of the area and volume of the overall mass of groundwater. For example, DTI successfully used Cool-Ox® to remediate a BTEX contaminated groundwater plume over limestone bedrock overlain by hard clay. The groundwater area impacted was approximately three-hundred (300) feet long by sixty (60) feet wide (18,000 square feet). The scope of work consisted of placing six (6), twenty (20) feet wide by sixty (60) feet long injection zones (6,000 square feet) equally spaced and perpendicular to the length of the plume. The vertical injection interval extended from the bed rock surface, five (5) feet upwards into the clay. DTI successfully decontaminated the groundwater plume in approximately sixty (60) days with approximately only thirty percent (30%) of the entire area injected.
The Cool-Ox® Bio-Spunge™ Reactor
Static (Static Groundwater (Matrix) Application)
Although the defined flow application technique works very well in remediation of moving groundwater, it is less effective at sites where the groundwater is static, present in low permeable soils, or is doming or moving in different directions over a broad area. To meet the static groundwater treatment challenge, DTI has developed the matrix or checkerboard injection technique. In the matrix technique, the area of the contaminant plume is subdivided into a series of squares resembling the configuration of a checkerboard. The Cool-Ox® Bio-Spunge™ Reactor is then injected into the alternating squares (for example, only the black squares of the checkerboard). This injection technique immediately reduces the treatment area by one-half thereby, instantly offering significant cost savings.
As depicted in the above figure, the injection point spacing that would normally be required to deliver sufficient Cool-Ox® reagents to oxidize the contaminants in the low permeability soil/groundwater matrix is maintained only in the treated squares. This approach assures that contaminant reductions will be accomplished in these areas and that the nutrient fortified Cool-Ox® reagents will stimulate the accelerated proliferation of indigenous microbial degraders. This technique establishes a matrix of so called “clean zones” within the contaminant plume. As the groundwater slowly moves about within the plume area the Cool-Ox® Bio-Spunge™ Reactors ultimately facilitate the mitigation of the groundwater. Periodic analysis of the groundwater will reveal if and when supplemental Cool-Ox® reagent injections are required.