Geochemical and Microbiological Characteristics during in Situ Chemical Oxidation and in Situ Bioremediation at a Diesel Contaminated Site

Abstract

While in situ chemical oxidation with persulfate has seen wide commercial application, investigations into the impacts on groundwater characteristics, microbial communities and soil structure are limited. To better understand the interactions of persulfate with the subsurface and to determine the compatibility with further bioremediation, a pilot scale treatment at a diesel-contaminated location was performed consisting of two persulfate injection events followed by a single nutrient amendment. Groundwater parameters measured throughout the 225 day experiment showed a significant decrease in pH and an increase in dissolved diesel and organic carbon within the treatment area. Molecular analysis of the microbial community size (16S rRNA gene) and alkane degradation capacity (alkB gene) by qPCR indicated a significant, yet temporary impact; while gene copy numbers initially decreased 1-2 orders of magnitude, they returned to baseline levels within 3 months of the first injection for both targets. Analysis of soil samples with sequential extraction showed irreversible oxidation of metal sulfides, thereby changing subsurface mineralogy and potentially mobilizing Fe, Cu, Pb, and Zn. Together, these results give insight into persulfate application in terms of risks and effective coupling with bioremediation.

Remediation of diesel‐contaminated soil using in situ chemical oxidation (ISCO) and the effects of common oxidants on the indigenous microbial community: a comparison study

“…In addition, it has been reported that BOD 5 /COD ratios of crude petroleum were increased by the oxidation of Fenton's reaction, resulting in the enhancement of the biodegradability of petroleum compounds . Sutton et al also reported that concentrations of dissolved TPH and dissolved organic carbon (DOC) were increased after persulfate treatment at a diesel‐contaminated site. In addition, Sutton et al has demonstrated that DOC derived from diesel oxidation by Fenton's reagent was a preferential substrate for microorganisms.…”

Microbial Community Response of an Organohalide Respiring Enrichment Culture to Permanganate Oxidation

“…Whereas ISB has been successfully implemented following ISCO for the remediation of aliphatic and aromatic hydrocarbons [ 20 – 23 ], coupling chemical oxidation with an anaerobic bioremediation step for the treatment of chlorinated solvents is more challenging. In addition to the direct oxidative stress inflicted by the oxidant, increased oxidation-reduction potential associated with chemical oxidation may be detrimental to strictly anaerobic OHRB or other non-dechlorinating community members.…”

Persulfate Oxidation Coupled with Biodegradation by Pseudomonas fluorescens Enhances Naphthenic Acid Remediation and Toxicity Reduction

“…The reduction in pH is a disadvantage when using persulfate and is likely a primary reason for studies that noted detrimental effects in microbial density following persulfate oxidation [ 41 , 45 , 89 , 90 ]. In this study, pH was monitored and controlled to avoid microbial stress due to changing pH (data not shown).…”