In this edition of Peroxygen Talk, a newly available product from FMC, Klozur^® CR, is introduced. “CR” stands for combined remedy: chemical oxidation plus bioremediation. Klozur CR is a single, formulated product consisting of high pH - activated Klozur Persulfate and PermeOx^® Plus engineered calcium peroxide, uniting the strengths of both products to treat contaminant source zones and down-gradient plumes.

Background

Chemical oxidation with Klozur activated persulfate for the treatment of organic contaminants in soil and ground water has been successfully applied in the field over the past several years. In general, persulfate chemical oxidation is a very effective technology for many recalcitrant compounds. However, contaminants may reside in low permeability zones or in down-gradient portions of plumes, where soil heterogeneity may make it difficult for any in situ technology to effectively and economically remediate these problematic areas. In addition, slow re-partitioning of contaminant from soils or bedrock and non-aqueous phases may induce groundwater concentration re-bounding after the oxidant has been expended. As a result, multiple application of the oxidant or soil blending may be required to improve contact with the contaminant. Alternatively, aerobic bioremediation, enhanced through the slow release of oxygen via PermeOx Plus, is effective for the treatment of BTEX, TPH, and other aerobically biodegradable contaminant. However, bioremediation of source zones and hot spots may be difficult. The high contaminant concentrations in these areas may be toxic to microbial populations. Moreover, treatment times are often lengthy due to the slow kinetics of mass transfer, making bioremediation unattractive for time sensitive remediation applications.

Recently, combining remediation technologies in a treatment-train approach has been gaining momentum, as no currently available technology can be considered a “silver bullet”. Such combination of technological approaches for challenging sites can take advantage of the strengths of each technology, thereby increasing the probability of success in meeting clean-up target goals. One example is the combination of chemical oxidation and bioremediation. Chemical oxidation is ideal for targeting hot spot and source zones, where the ratio of contaminant to soil oxidant demand is high, driving contaminant destruction kinetics so that these zones can be treated in several weeks to months. In addition Klozur CR can increase levels of natural organic matter by the partial oxidization of soil components and solubilization due to temporary elevation of the soil and ground water pH in excess of 10. It has been hypothesized^1,2 that this increase in natural organic matter is beneficial to the nascent microbial population, increasing microbial density which can impact the rate of contaminant destruction. At sites with high groundwater flow rates, the groundwater will transport both the dissolved organic matter and oxygen into the down-gradient plume, supporting contaminant reduction beyond the initial target zone.

Klozur CR combines the speed and power of high-pH activated persulfate with the long-term efficiency of enhanced aerobic bioremediation. Initially designed for emplacement at the bottom of excavations to address residual contamination, Klozur CR has undergone beta field testing over the past year in a number of applications, including treatment of BTEX and fuel oils contaminated soils and groundwater³ and for the destruction of pentachlorophenols and PAHs including naphthalene at a wood treating facility².

Klozur CR Modes of Action

Klozur CR attacks contaminants by promoting three modes of action: chemical oxidation, aerobic bioremediation, and anaerobic bioremediation.

1. Self-activating persulfate chemical oxidation

As with high pH - activated Klozur Persulfate, Klozur CR will provide up to three months of chemical oxidation via persulfate chemistry.

S₂O₈^-2 + activator ? SO₄·^- , OH·^- + SO₄^-2

Klozur CR is self-activating, utilizing the alkalinity generated by the calcium peroxide to achieve a pH in the range of 11. In addition, calcium peroxide will slowly generate hydrogen peroxide (see the following section), allowing for peroxide activation of persulfate as well. High pH / peroxide activated persulfate can be used to treat BTEX, MTBE, polyaromatic hydrocarbons, petroleum hydrocarbons and chlorinated solvents, including PCE, TCE, DCE, TCA, DCA, and vinyl chloride. As Klozur CR is self-activating, no additional activators or chemicals need to be added to the product for use in the field.

2. Enhanced aerobic bioremediation

Following the initial chemical oxidation phase, Klozur CR will continue to release oxygen for up to one year as a result of the slow hydration of the engineered calcium peroxide.

CaO₂ + 2 H₂O ? Ca(OH)₂ + H₂O₂

2 H₂O₂ ? O₂ + 2 H₂O

The resulting oxygen will provide electron acceptors for the bioremediation of BTEX, PAHs and petroleum hydrocarbons. Subsequent diffusion and transport of oxygen down-gradient will support contaminant reductions in plume zones, and will support biological polishing of low concentration contamination in the groundwater. Benefits of adding a slow-release oxygen source have long been demonstrated by the application of PermeOx Plus at numerous sites.

3. Anaerobic bioremediation

The reaction of persulfate with organic compounds will generate sulfate ions. As discussed in the February 2007 Peroxygen Talk, sulfate reducing bacteria can utilize sulfate as an electron acceptor under anaerobic conditions to degrade BTEX, PAHs and petroleum hydrocarbons. As an example for benzene:

C₆H₆ + 3.754 SO₄^-2 + 3H₂O à 2.25H⁺ + 6HCO₃- + 3.75HS^-

It is anticipated that sulfate-induced bioremediation may take place subsequent to the consumption of dissolved oxygen, and may support contaminant destruction in down-gradient contaminant plumes and polishing of low level contaminant residual.

Klozur CR Properties

As with PermeOx Plus, Klozur CR is a sparingly soluble composition. As a result, the product will be applied in slurry form via emplacement (examples: bottom of tank pits and excavations and barrier walls), ex situ and in situ soil mixing or by direct push injection. No additional activation chemicals are required for this product. Only water is required to wet out contaminated soils and bring the oxidant in contact with the compounds of concern. 1 wt% slurries will have a pH of approximately 11, which will activate the persulfate. The typical active oxygen content of the Klozur CR is 11.3%.

Currently, the product is available in 45 lb pails (32 per pallet) or 1800 lb super sacks. It is shipped as a 5.1 oxidizer, and will have a shelf life in excess of one year under proper storage conditions. FMC always recommends a review of the MSDS prior to use of the product.

Conclusions

Klozur CR is a treatment approach for contaminants of concern that combines the speed and power of chemical oxidation with the long-term performance of aerobic bioremediation. It can target both source zones and down-gradient plumes, capable of reducing high concentrations of contaminants and providing long-term polishing of low concentration residuals. It is easy to use, requiring no additional activation chemicals. Klozur CR can be utilized as a combined remedy for the treatment of BTEX, MTBE, PAHs and petroleum hydrocarbons, or as a high-pH activated persulfate system for the destruction of chlorinated solvents and pesticides. As a result, the product can be readily applied to plumes with mixed petroleum and chlorinated solvents contamination.

1. M. Marley, et al. “A Case Study On Enhanced Reductive Dechlorination Resulting from a Chemical Oxidation Pilot Test”. DNAPL-1 Conference, Sept 2006, Pittsburgh, PA.

2. J. Studer, et al. “An Innovative Couple Chem-Bio Treatability Study Leading to Large Scale Pilot Test at a Wood Treating Facility”. Rem Tec 2007.

3. J. Studer, et al. “Design Considerations for Application of Klozur CR to Promote Sequential Chemical Oxidation and Oxidative Bioremediation”. AEHS West Coast Soils Conference, March 2008, San Deigo, CA.