The appearance of 2-butanone (MEK) and acetone (unwanted solvents) is a transient intermediate occasionally formed as naturally occurring TOC, or the injected organic hydrogen donor, undergoes conversion to solvents rather than organic acids. Additionally, some metal oxides can convert acetic acid into acetone, in applications where ZVI is introduced the iron oxides generated early in the program can be responsible for the acetic acid/acetone; buteric acid/2-butanone conversions.
In addition to the abiotic transformations, when an impacted aquifer is amended with carbon under low pH or nutrient limiting conditions the fermentable organic matter may be converted to a variety of ketones, including acetone or methyl ethyl ketone (MEK; 2-butanone). The processes might temporarily raise groundwater concentrations for such compounds above site-specific cleanup levels and also may trigger regulatory concerns, unless one completely understands the methods, fate and transport of ketone production. Acetone is a VOC, but it also provides a readily biodegradable food source for soil microbes that perform reductive dechlorination. In groundwater, acetone generally has a half-life that varies from 19 to 197 days. The occasional, transient production of acetone and/or MEK generally occurs when carbohydrates are converted to the undesirable ketones. When ketones appear it is an indicator that the environment’s pH and/or nutrient supply are driving the biotic conversions of the carbohydrates to the solvents rather than the organic acids. When this occurs the ORP generally will not decrease into the desired negative 100 to 300 range due to the absence of hydrogen production from the fermentation process. Acetone and MEK production is frequently seen by IET early in a remedial program. Most often the disappearance of the acetone occurs as quickly as it appeared as the pH from water hydroylisis at the ZVI surface provides hydroxides. The solvent formation is generally associated with pH levels below 6.
The appearance of solvents in lieu of acids has been noted in various laboratory studies and peer reviewed papers for over 30 years. One such pH link was described by Ennis and Maddox (1987), working with a substrate of whey permeate. They reconfirmed that at relatively low sugar concentrations, low pH favored solventogenesis, but growth and sugar utilization were poor. Conversely, at higher pH values, growth and sugar utilization were much improved with limited solvent production.
Additionally, phosphate limiting conditions effect the production of solvents rather than organic aids. In phosphate-limited batch cultures, Bahl, Andersch and Gottschalk (1982) described how solvent production occurred after exhaustion of phosphate from the medium. In conditions of excess phosphate, the fermentation produced acids rather than solvents, and thus there may be a case for removal of this anion from commercial media.
To confirm the possibility that the o-PO4+ has been sequestered by high carbonate concentrations an o-PO4+ analysis should be performed utilizing both a total o-PO4+ evaluation performed at the in-situ pH and acidified. Under the acidified condition the o-PO4+ sequestered by carbonate will be liberated where as the non-acidified sample will provide evidence for the bioavailability of the o-PO4+.
About Innovative Environmental Technologies, Inc. (IET)
Origins of the Company: Formed in 1998, Innovative Environmental Technologies, Inc. (IET) was inspired by the observed need for a remedial contractor in the environmental industry that could provide state-of-the-art remedial technologies to environmental consultants and engineers. To achieve this objective, IET would have to continuously develop, patent and license innovative and emerging technologies. Further, IET would have to position itself as a remedial contractor and technology vendor to a sophisticated and knowledgeable customer base. Unencumbered by any one product supplier relationship, IET could provide its customers coordinated remedial programs integrating a variety of remedial products.
Evolution of the Company: In the early years, IET focused on the development of efficient in-situ delivery processes that would be capable of injecting a wide variety of materials to targeted subsurface formations. These efforts resulted in the patenting of IET’s apparatus for in-situ injections as well as the design and manufacturing of its own proprietary injection tooling (US Patent 7,044,152). During these early years, IET’s focus was primarily aerobic biomineralization processes for the treatment of dissolved and sorbed phase petroleum hydrocarbons. The success of these treatment validated IET as a resource to numerous consulting engineering companies across the country. By 2001, IET was approached by several of its clients to evaluate and propose treatments for chlorinated solvents. Between 2001 and 2003, IET proposed and implemented many in-situ programs targeting chlorinated ethenes and ethanes. IET applied various oxidative and reductive technologies during these years, finally focusing on a synergistic biotic-abiotic approach for the treatment of chlorinated solvents (US Patent 7,129,388). Since 2001 IET has designed and implemented over 700 in-situ remedial projects focused on chlorinated solvents.
Establishing and maintaining the relationships with its customers while focusing on the company’s image as a technology resource to these customers required IET to evolve into a value-added contractor. To add value to it’s services, IET chose to provide free data analysis of the projects it had implemented. Together with lump-sum pricing for turn-key remediation services, IET has been able to become an invaluable resource to its customers while maintaining a connection to the individual projects’ data. It has been this “connection” that has allowed IET to evaluate the efficacies of individual remedial compounds and the implemented programs. The interpretation of the biological, abiotic, geochemical and hydrogeologic changes in conjunction with treatment efficacies has resulted in unique treatment strategies, additional patents and proprietary treatment approaches. This continuous evolution and innovation has become the hall-mark of IET and its value to our customers.
