: The U.S. Environmental Protection Agency (EPA) Engineering Issue Papers are a series of technology transfer documents that summarize the latest available information on specific technical issues, including fate and transport, specific contaminants, selected treatment and site remediation technologies, and related other issues. This Engineering Issue Paper is intended to provide remedial project managers (RPMs), on-scene coordinators (OSCs), contractors, and other state, industry, or private remediation managers with information to assist in the evaluation and possible selection of appropriate in-situ chemical oxidation (ISCO) remedial alternatives. This Engineering Issue Paper provides an up-to-date overview of ISCO remediation technology and fundamentals, and is developed based on peer-reviewed literature, EPA reports, web sources, current research, conference proceedings, and other pertinent information.

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In-Situ Chemical Oxidation

A continuous-flow column study was conducted to investigate the long-term effects of persulfate oxidation on the abundance and activity of the indigenous microbial community and phenanthrene-degrading bacteria in contaminated soil from a former manufactured gas plant (MGP) site. Approximately six pore volumes of a 20 g/L persulfate solution were introduced into the column, followed by simulated groundwater for 500 days. Soil samples were collected from the surface of the soil bed and along the column length immediately before and after persulfate injection and up to 500 days following injection. Exposure to persulfate led to a 2- to 3-log reduction in total bacterial 16S rRNA genes, severe inhibition of 14C-acetate mineralization (as a measure of general microbial activity), and a decrease in community diversity. However, relatively rapid recovery of both bacterial gene abundance and activity was observed within 30 days after persulfate exposure. Mineralization of 14C-phenanthrene was also inhibited but d...

/pdf/recovery-of-phenanthrene-degrading-bacteria-after-simulated-1ht6mgl97l.pdf

Recovery of phenanthrene-degrading bacteria after simulated in situ persulfate oxidation in contaminated soil.

Contamination of the subsurface by persistent organic contaminants remains a significant problem, even after decades of research on remediation. First, approaches focused on excavation, pump and treat via activated carbon, bioremediation, and natural attenuation. In the 1990s the first reports on in situ chemical oxidation (ISCO) were published, which is a technique involving the introduction of chemical oxidants into the subsurface in order to transform contaminants into less harmful substances. Hydrogen peroxide was the first chemical oxidant investigated and used in full scale. Shortly after ozone and permanganate came into use. In the past few years persulphate has provided yet another option. In this chapter, the chemical reactions of the most common chemical oxidants used in ISCO are reviewed and the applicability of the two most relevant modified Fenton's reagent and activated sodium persulphate are demonstrated using the Kaergaard Plantation megasite in Denmark as case study. This site represents one of the most difficult remediation challenges in Scandinavia and, therefore, regulatory agencies have been evaluating remediation techniques for source area remediation.

In situ Chemical Oxidation: The Mechanisms and Applications of Chemical Oxidants for Remediation Purposes

Contamination by chloroethenes represents serious risks to both the environment and human life due to their toxic and sometimes carcinogenic effects. Coupling in situ chemical oxidation (ISCO) and in situ bioremediation (ISB) approaches to clean the sites contaminated by chloroethenes is increasingly being considered as a biphasic technology. Successful implementation of ISB after ISCO, however, requires an understanding of ISCO effects on indigenous microbial population responsible for biodegradation. This review focuses on interactions between three main ISCO approaches and microbial populations in chloroethenes contaminated subsurface. Chloroethenes toxicity and fate in the subsurface have also been discussed. The review further summarizes ISCO and microbial strategies for chloroethenes remediation. Indigenous microbial degrading capacity, especially the anaerobic step, may be damaged by aggressive conditions that are required for successful ISCO treatment. Therefore, the impact of oxidation agents on soil geochemistry and bioprocesses have been investigated. The review also provides up-to date summary in coupled ISCO and ISB for chloroethenes remediation. Finally, future research needs are proposed to optimize the application of this biphasic technology for the chloroethenes contaminated sites remediation.

Coupling in situ chemical oxidation with bioremediation of chloroethenes: a review

https://cdr.lib.unc.edu/downloads/vm40xs09d

Effects of in situ bioremediation strategies on the biodegradation and bioavailability of polycyclic aromatic hydrocarbons in weathered manufactured gas plant soil

In situ chemical oxidation has the potential for degrading large quantities of organic contaminants and can be more effective and timely than traditional ex situ treatment methods. However, there is a need to better characterize the potential effects of this treatment on natural processes. This study focuses on potential inhibition to anaerobic dechlorination of trichloroethene (TCE) in soils from a large manufacturing facility as a result of in situ oxidation using potassium permanganate (KMn04)Previous microcosm studies established that natural attenuation occurs on-site and that it is enhanced by the addition of ethanol to the system. A potential remediation scheme for the site involves the use of potassium permanganate to reduce levels of TCE in heavily contaminated areas, then to inject ethanol into the system to "neutralize" excess oxidant and enhance microbial degradation. However, it is currently unknown whether the exposure of indigenous microbial populations to potassium permanganate may adversely affect biological reductive dechlorination by these microorganisms. Consequently, additional microcosm studies were conducted to evaluate this remediation scheme and assess the effect of potassium permanganate addition on biological reductive dechlorination of TCE. Samples of subsurface soil and groundwater were collected from a TCE-impacted area of the site. A portion of the soil was pretreated with nutrients and ethanol to stimulate microbial activity, while the remainder of the soil was left unamended. Soil/groundwater microcosms were prepared in sealed vials using the nutrient-amended and unamended soils, and the effects of potassium permanganate addition were evaluated using two permanganate concentrations (0.8 and 2.4 percent) and two contact times (1 and 3 weeks). TCE was then re-added to each microcosm and TCE and dichloroethene (DCE) concentrations were monitored to determine the degree to which microbial dechlorination occurred following chemical oxidation. Evidence of microbial degradation was generally detected within four weeks after TCE addition. Increases in DCE concentrations were consistent with decreases in TCE. The concentration of TCE in the nutrient-amended samples exposed to 2.4% KMnO4 for one week degraded somewhat more slowly than the samples exposed to the 0.8% KMnO4. The rates of degradation did not correlate with the length of KMn04 exposure for the nutrient-amended microcosms. Microbial degradation of TCE in the unamended microcosms was generally similar to that observed in the nutrient-amended microcosms. One treatment condition (unamended, one week exposure, 2.4% KMnO4) was exposed to elevated levels of ethanol and showed little evidence of degradation. It is suspected that the high levels of ethanol were toxic to the microorganisms. The results of the study indicate that exposure of indigenous soil and groundwater microbial populations to KMnO4 at concentrations of 0.8 to 2.4% do not impair the ability of the microbial populations to dechlorinate TCE. Consequently, the combination of chemical oxidation followed by enhanced biological reductive dechlorination appears to be a viable remedial strategy for highly-impacted subsurface areas of the site.

https://ntrs.nasa.gov/api/citations/20010067175/downloads/20010067175.pdf

Martin A. Rowland

Papers

Effects of Potassium Permanganate Oxidation on Subsurface Microbial Activity