Behavior of a chlorinated ethene plume following source‐area treatment with Fenton's reagent

Abstract

Monitoring data collected over a 6‐year period show that a plume of chlorinated ethene–contaminated ground water has contracted significantly following treatment of the contaminant source area using in situ oxidation. Prior to treatment (1998), concentrations of perchloroethene (PCE) exceeded 4500 μg/L in a contaminant source area associated with a municipal landfill in Kings Bay, Georgia. The plume emanating from this source area was characterized by vinyl chloride (VC) concentrations exceeding 800 μg/L. In situ oxidation using Fenton's reagent lowered PCE concentrations in the source area below 100 μg/L, and PCE concentrations have not rebounded above this level since treatment. In the 6 years following treatment, VC concentrations in the plume have decreased significantly. These concentration declines can be attributed to the movement of Fenton's reagent–treated water downgradient through the system, the cessation of a previously installed pump‐and‐treat system, and the significant natural attenuation capacity of this anoxic aquifer. While in situ oxidation briefly decreased the abundance and activity of microorganisms in the source area, this activity rebounded in <6 months. Nevertheless, the shift from sulfate‐reducing to Fe(III)‐reducing conditions induced by Fenton's treatment may have decreased the efficiency of reductive dechlorination in the injection zone. The results of this study indicate that source‐area removal actions, particularly when applied to ground water systems that have significant natural attenuation capacity, can be effective in decreasing the areal extent and contaminant concentrations of chlorinated ethene plumes.

Coupling chemical oxidation and biostimulation: Effects on the natural attenuation capacity and resilience of the native microbial community in alkylbenzene-polluted soil

“…However, recent studies indicate that, although chemical oxidation temporarily reduces microbial activity, bacterial populations have the ability to regenerate [11,15,16]. In addition chemical oxidation has also been suggested to improve further biodegradation by depleting toxic compounds for native microbial communities [17], improving the bioavailability of parent compounds [18,19] or providing oxygen to improve the aerobic conditions [20].…”

Efforts to improve coupled in situ chemical oxidation with bioremediation: a review of optimization strategies

“…However, recent work indicates that, although chemical oxidation can temporarily reduce microbial activity, bacterial populations do regenerate contaminant degradation ability both in the field (Jones et al 2009;Koch et al 2007;Ladaa et al 2008;Luhrs et al 2006;Macbeth et al 2005;Studer et al 2009) and in laboratory experiments (Aunola et al 2006;Hood et al 2006;Kao and Wu 2000;Kulik et al 2006;Ndjou'ou et al 2006). In many cases, it has been concluded that ISCO pretreatment appears to improve overall remediation by (1) decreasing the concentration of pollutants to levels less toxic for the soil biota (Chapelle et al 2005), (2) improving bioavailability of the parent compound (Kulik et al 2006;Miller et al 1996), (3) producing bioavailable and biodegradable oxidized daughter compounds (Lee and Hosomi 2001;Marley et al 2003;Miller et al 1996;Nam et al 2001), or (4) providing oxygen for aerobic biological transformation of contaminants (Kulik et al 2006). It has recently been suggested that, as ISCO treatment is not able to access and oxidize all residual contaminants, biological polishing is required to fully remediate a site ).…”

Chloroethene dechlorination in acidic groundwater: Implications for combining fenton's treatment with natural attenuation

“…Inherent in this approach is the risk that source-area alterations will negatively impact downgradient natural attenuation processes. In this regard, source area treatment using Fenton's-based in situ chemical oxidation (ISCO) is a recurrent concern (Christ et al, 2005), because field implementation of Fenton's ISCO typically involves acidification of the treatment area to a pH of 2-4 (Chapelle & Bradley, 1998;Chapelle et al, 2005;Watts et al, 1990). Low pH enhances the generation of hydroxyl radicals and, thus, the efficiency of Fenton's-based contaminant degradation (Gates & Siegrist, 1995;Yin & Allen, 1999).…”

“…However, low pH may also inhibit a number of potentially important chlorinated solvent natural attenuation mechanisms (Christ et al, 2005;Cirpka et al, 1999;Kastner et al, 2000;Sahl & Munakata-Marr, 2006;Wiedemeier et al, 1996;Zhuang & Pavlostathis, 1995). Although Fenton's-based source area treatment without acidification of the downgradient plume has been described (Chapelle et al, 2005), the potential for downgradient migration of acidic groundwater and the presumptive negative impacts of low pH on chloroethene degradation remain significant deterrents to the widespread use of this technology (Christ et al, 2005).…”