The influence of electrokinetic bioremediation on subsurface microbial communities at a perchloroethylene contaminated site

Abstract

There is an increased interest in finding remedies for contamination in low permeability and advection-limited aquifers. A technology applicable at these sites, electrokinetic-enhanced bioremediation (EK-BIO), combines traditional bioremediation and electrokinetic technologies by applying direct current to transport bioremediation amendments and microbes in situ. The effect of this technology on the native soil microbial community has only been previously investigated at the bench scale. This research explored the influence of EK-BIO on subsurface microbial communities at a field-scale demonstration site. The results showed that, similar to the findings in laboratory studies, alpha diversity decreased and beta diversity differed temporally, based on treatment phase. Enrichments in specific taxa were linked to the bioaugmentation culture and electron donor. Overall, findings from our study, one of the first field-scale investigations of the influence of electrokinetic bioremediation on subsurface microbial communities, are very similar to bench-scale studies on the topic, suggesting good correlation between laboratory and field experiments on EK-BIO and showing that lessons learned at the benchtop are important and relevant to field-scale implementation. Key points• Microbial community analysis of field samples validates laboratory study results • Bioaugmentation cultures and electron donors have largest effect on microbial community

Electrokinetic-Enhanced Bioremediation of Trichloroethylene-Contaminated Low-Permeability Soils: Mechanistic Insight from Spatio-Temporal Variations of Indigenous Microbial Community and Biodehalogenation Activity

“…The influence of electric field on the variation of microbial communities in soils has been investigated to some extent, ,− and the electron donors (i.e., lactate) transported by EK and the products (H + , O 2 and OH – , H 2 ) from electrode reactions were documented to be the controlling factors. , The pH variation due to electrode reactions could reduce α diversity of microbial communities and cause the spatio-temporal difference of β diversity. − The biodehalogenation activity was reflected either by the remaining TCE in soils after EK treatment or by the functional gene copies (i.e., Dhc 16S rRNA , vcrA ). ,, In all, the knowledge regarding the influence of EK on microbial communities and biodehalogenation activity is still preliminary. As a fundamental aspect for understanding EK-Bio, the spatio-temporal variations of indigenous microbial communities and biodehalogenation activity of the background soil matrix remain unknown, particularly for the treatment of widespread CEs in a low-permeability matrix.…”

“…The influence of electric field on the variation of microbial communities in soils has been investigated to some extent, 14,29−32 and the electron donors (i.e., lactate) transported by EK and the products (H + , O 2 and OH − , H 2 ) from electrode reactions were documented to be the controlling factors. 14,31 The pH variation due to electrode reactions could reduce α diversity of microbial communities and cause the spatio-temporal difference of β diversity. 29−31 The biodehalogenation activity was reflected either by the remaining TCE in soils after EK treatment or by the functional gene copies (i.e., Dhc 16S rRNA, vcrA).…”

Contaminant Back Diffusion from Low-Conductivity Matrices: Case Studies of Remedial Strategies

“…An environmental investigation of the Jacksonville NAS started in 1979 and identified potential sources of contamination, including the base’s former dry cleaner, which operated from 1962 to 1990. This location has been the subject of several environmental research studies, including one on alternative endpoints at challenging sites [ 81 ], natural attenuation of NAPL source zones [ 82 ], high-resolution soil core sampling for generating source history [ 19 , 52 ], and electrokinetic (EK)-enhanced bioremediation [ 64 , 65 ]. The works reported by Adamson et al [ 19 ], Cox et al [ 64 ], and Meinel et al [ 65 ] are the primary basis for this case study.…”

“…Subsequent work by Meinel et al [ 65 ] examined the effects of EK bioaugmentation on the microbial communities at the Jacksonville pilot study using groundwater samples from the second stage. The authors concluded that the influence of EK bioremediation on the dechlorinating microbes is similar at both the laboratory and field scales and further supports the work by Cox et al [ 64 ] regarding the ability of this technology to promote CVOC degradation.…”

“…A better understanding of the mechanisms and factors affecting this migration is needed for optimal system design. At Jacksonville, the spatial distribution of lactate was estimated to be about twice as large as the zone reached by microbial amendments [ 65 ]. This is in line with previous EK bioaugmentation studies that showed that lactate transport was driven by electromigration and microbial transport by electroosmosis [ 90 , 91 ].…”