Advanced Oxidation

The application of Oxidation methods allows for the chemical conversion of hazardous contaminants to non-hazardous or less toxic compounds that are more stable, less mobile, and/or inert.

Process Overview:

Chemical oxidants most commonly employed to date include peroxide, ozone, and permanganate. These oxidants have been able to cause the rapid and complete chemical destruction of many toxic organic chemicals.  The chemical oxidation process also commonly provides for partial degradation of contaminants as an aid to subsequent bioremediation. In general, the chemical oxidation process has demonstrated the capability of achieving high treatment efficiencies (e.g., > 90 percent) for unsaturated aliphatic (e.g., trichloroethylene [TCE]) and aromatic compounds (e.g., benzene), with very fast reaction rates (90 percent destruction in minutes). As is the case with technology application, the key to successful implementation and achieving performance goals lies in the matching of oxidant and in situ delivery system to the contaminants of concern (COCs).

• Ozone and/or Concentrated Oxygen Injection:

Technology Description: Ozone and/or concentrated Oxygen gas can oxidize contaminants directly or through the formation of hydroxyl radicals.  Due to the high reactivity and instability of ozone’s and/or pure both are produced onsite using specialized generation equipment.    The delivery system(s) generally require closely spaced injection points (e.g., air sparging wells).  The resultant oxygen supply is commonly greater than the total oxygen demand.  This fact allows for stimulation of In situ decomposition by indigenous chemotroph bacteria (biostimulation), for faster and more efficient site cleanup.  Variations on the basic concept of concentrated oxygen injection form the basis of the bioventing and/or biosparging methodologies.  Bioventing is primarily applied to the unsaturated (vadose) zone.   In contrast to soil vapor vacuum extraction, bioventing uses low air flow rates to provide only enough oxygen to sustain microbial activity.   Injection of oxygen into the saturated zone constitutes – biosparging.  Both methods provide in situ remediation technology that stimulates the natural biodegradation of aerobically degradable compounds in soil.

• Peroxide

Technology Description: Oxidation using liquid hydrogen peroxide (H2O2) in the presence of native or supplemental ferrous iron (Fe+2) produces Fenton’s Reagent which yields free hydroxyl radicals (OH-). These strong, nonspecific oxidants can rapidly degrade a variety of organic compounds. Fenton’s Reagent oxidation is most effective under very acidic pH (e.g., pH 2 to 4) and becomes ineffective under moderate to strongly alkaline conditions.

• ORC (Oxygen Release Compound) Application

Technology Description: Regenesis Bioremediation Products, Inc. has developed 2 slow release compounds for the in-situ treatment of contaminated groundwater that contain petroleum hydrocarbons from compounds such as gasoline and fuel oil, chlorinated solvents such as PCE, TCE and TCA, and heavy metals such as lead, hexavalent chromium and arsenic. The products are applied into the ground using a high pressure injection pump. The ORC chemically reacts with the groundwater to release oxygen for the treatment of the petroleum products through an aerobic degradation process. The HRC releases lactic acid when it contacts groundwater. Resulting fermentation produces hydrogen that provides a mechanism for an accelerated breakdown of the chlorinated compounds. Both processes are accomplished with a minimum disruption of site activities. The equipment used for the installation is typically a direct push rig that injects the appropriate product into the saturated zone using a high-pressure positive displacement pump. For brownfields sites a reinjectable point can be constructed to permit multiple applications without business disruption.

Applicability:
The rate and extent of degradation of a target COC are dictated by the properties of the chemical itself and its susceptibility to oxidative degradation as well as the matrix conditions, most notably, pH, temperature, the concentration of oxidant, and the concentration of other oxidant-consuming naturally occurring substances.   Oxidant consuming substances include: natural organic matter, reduced minerals as well as carbonate and other free radical scavengers. Given the relatively indiscriminate and rapid rate of reaction of the oxidants with reduced substances, the method of delivery and distribution throughout a subsurface region is of paramount importance. Oxidant delivery systems often employ vertical or horizontal injection wells and sparge points with forced advection to rapidly move the oxidant into the subsurface.

Case Study

Project Name: Former Gasoline Retail/Service Station
Client: Government Agency

Impact Characterization: - Mixed fuels, primarily gasoline, resulting from activities associated with the operation of a former retail gasoline storage/sales facility.  Contaminate impact was documented to both the subsurface soil and groundwater regimes.  Contamination was documented beneath the site proper as well as in the subsurface of an adjacent neighborhood due to prolonged groundwater transport.

In-Situ Technical Overview: The subject project is one of several sites being addressed by a 1999 EPA Brownfield.  The area of remediation extends to multiple commercial and residential properties including County owned properties.  Precision was contracted in 2004 to provide expert technical evaluation of a remedial corrective action plan (CAP) designed by others under the Brownfield Grant.  Evaluation efforts focused on the effectiveness and applicability of the remedial action proposed by others.  To accomplish the evaluation objectives, Precision implemented the recommended remedial CAP at the subject site via a small-scale pilot test. 

The Team of PES and Aquifer Drilling and Testing, Inc. (ADT) initiated the bench-scale testing procedures by installing a network of pilot remedial test points including:  piezometers, groundwater extraction and monitoring wells to various depths within the overburden at the site.

The installed pilot test points were used to test applicability of the proposed remedial method under site-specific conditions.  The proposed high vacuum – total fluid extraction (multi phase recovery) was pilot tested using a vacuum truck.  PES technical staff collected data from surrounding monitoring points to assess effectiveness of the remedial method.

Once the pilot test study was completed PES presented the results in a comprehensive site investigation report.  Pilot test results indicated the need to augment the proposed corrective action plan.  PES therefore recommended the Department seek a remedial alternative for the site.  In conjunction with feedback from the Department, PES proceeded to implement aerobic bioremediation via concentrated oxygen injection.  The methodology consists of the injection of oxygen below the water table to stimulate and enhance aerobic biodegradation of petroleum hydrocarbons.

To implement the remedy, PES technical staff fabricated and installed 43, pre-pack, ¾-inch diameter, injection well points in a 15ft by 15ft grid pattern at the site.  Injection well points were installed utilizing direct push methods ten-feet into the adversely impacted water-bearing zone.  The oxygen delivery system was then connected to a remedial trailer utilizing individual ½-inch diameter HDPE piping.  To complete the integrated system PES utilized remedial equipment that had previously been purchased by the Department, which resulted in a significant cost savings for the client.

Precision is currently performing periodic monitoring and maintenance of the system to gauge site advancement towards closure. Monitoring efforts consist of routine assessment and remedial point sampling for various physical and chemical parameters within the groundwater as well as system operation, maintenance and optimization.  Data is collected and reviewed by PES and disseminated to the Department in groundwater monitoring/remedial progress reports.

Vapor Intrusion Assessment and Engineered Controls:  In response to the existence of both commercial and residential structures within the footprint of the documented contaminant plume, PES was asked to perform a vapor intrusion study of several buildings.  The study involved a building assessment and collection of sub slab, indoor and outdoor air samples using six-liter, stainless steel, summa canisters.  All aspects of the comprehensive study were performed in accordance with recently published New York State Department of Health (NYSDOH) Guidelines.  The results of the vapor intrusion assessment indicated the need to install structure-specific soil vapor extraction system(s) to reduce subsurface/sub slab contaminant levels as well as provide a mechanism to reduce/prevent adverse impacts to indoor air quality.

During the response action, the PES/ADT Team installed nine, four-inch diameter, vapor extraction wells and several additional groundwater monitoring wells at the former Gillette and Millington properties.  Limited special access required utilization of ADTs limited access hollow stem auger rig.  Standard hollow stem auger methods – coupled with continuous split spoon sampling were used during the installation of each soil vapor extraction well.  PES geologic staff oversaw all drilling activities to ensure the wells were installed in accordance with the design principles of the SVE system.

Following install of the extraction wells, PES construction staff installed a network of trenches to allow for pipe installation to connect the remedial system to the extraction wells. PES procured an equipment shed to house the remedial equipment, provided for the installation of primary and secondary electrical services and installed the completed system in July 2007.

Site Progression Specifics: - PES and ADT performed the work, including soil boring and well installations, sampling and technical review, vapor intrusion study work, remedial system installation, operation and maintenance utilizing properly trained and skilled PES/ADT personnel and equipment.

PES began work at this spill site in 2004 with the review of the ROD as produced by others.  The initial remedial system (oxygen injection) was installed in the Fall of 2004.  Vapor intrusion work was completed in Winter 2007 and the soil vapor extraction system was designed, installed and completed in the Spring/Summer of 2007.  PES continues to perform ongoing site monitoring and remedial system operation, maintenance and evaluation for the Department.

Work completed at this spill site has been done on a time and materials basis with budgets established for large portions of the work.  The work has been performed within the time and budget framework for the site to the satisfaction of the client.

Case Study

INTERIM REMEDIAL SOIL EXCAVATION and FEROX INSITU TREATMENT

Case Study No.: 6
Project Name: Manufacturing Facility
Client: Government Agency
Location: Down State - New York

Impact Characterization: Release of unknown quantities of chlorinated solvents, including Freon 113, resulting in an adverse impact to the subsurface soil and groundwater regimes. Sensitive receptors to the release include a regulated wetland area.

Technical Overview: PES initiated its site involvement with a technical evaluation of (existing) subsurface investigation and groundwater monitoring files.  A limited subsurface investigation was conducted to pre-characterize soil associated with a documented Freon 113 impacted area. The remedial approach was tailored to provide substantial financial relief for the project by pre-planning and live-loading contaminated soils as well as to accelerate contaminant mitigation.

The presence of Freon 113, necessitated additional pre-remedial action planning that included the creation of a Site Management Plan, Erosion Control Plan, CIH certified Health and Safety Plan, and Soil Transportation Plan. 

Following diversion of the drainage utility by PES the remedial soil excavation phase of the project commenced utilizing cut and fill excavation methodology.  Excavation direction was performed utilizing regular field screening via a properly calibrated photo-ionization detector (PID) and headspace methods during the excavation process.   A total of approximately 100 tons of impacted material was excavated, transported to, and disposed of at Seneca Meadows. 

Documentation of the end result of the excavation on the environmental quality of the site’s soil was provided through the collection of soil samples for laboratory analysis.  Resulting data was used to confirm compliance with the project objectives.

Ferox Application:

PES in conjunction with ARS Technologies implemented Ferox Technology at the subject site.  The injection process was implemented to facilitate the insitu reduction of documented halogenated compounds.   The Ferox technology process consisted of multi-phase injection (using a gas carrier) and emplacement of specific quantities of highly reactive zero-valent iron (ZVI) powder directly into identified subsurface contaminant zones. 

The Ferox Technology provided direct treatment of the target organics.  In addition, the process creates favorable insitu treatments areas down gradient of the primary target area.    To maximize the dispersion of the ZVI powder, ARS utilized a gas based atomization approach.  Pneumatic fracturing methods were utilized (where required) to enhance existing fractures and planes of weakness surrounding each injection well.  The enhancement of the fracture network provides increased reagent distribution.