Dehalococcoides
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Polychlorinated biphenyl (PCB) organohalide-respiring communities from the efflux channel of a former Delor manufacturer in Eastern Slovakia were assessed using metagenomic, statistical and cultivation-adapted approaches. Multivariate analysis of environmental factors together with terminal restriction fragment length polymorphisms of the bacterial communities in the primary sediments revealed both temporal and spatial heterogeneity in the distribution of microbial populations, which reflects the dynamic pattern of contamination and altered conditions for biodegradation activity along the channel. Anaerobic microcosms were developed from eight sediments sampled along the channel, where high concentrations of PCBs - from 6.6 to 136mg/kg dry weight, were measured. PCB dehalorespiring activity, congruent with changes in the microbial composition in all microcosms, was detected. After 10 months of cultivation, the divergently evolved consortia achieved up to 35.9 percent reduction of the total PCB concentration. Phylogenetic-analysis of the active Chloroflexi-related organohalide-respiring bacteria by partial sequencing of 16S rRNA genes in cDNA from microcosms with the highest PCB dechlorination activity revealed diverse and unique complexity of the populations. The predominant organohalide respirers were either affiliated with Dehalococcoides sp. and Dehalococcoides-like group (DLG) organisms or were composed of currently unknown distant clades of DLG bacteria. The present study should encourage researchers to explore the full potential of the indigenous PCB dechlorinating populations to develop effective bioremediation approaches that can perform the complete mineralization of PCBs in polluted environments.
- MeSH
- anaerobní bakterie klasifikace izolace a purifikace metabolismus MeSH
- bakteriální RNA genetika MeSH
- biodegradace MeSH
- chemické látky znečišťující vodu analýza MeSH
- Chloroflexi izolace a purifikace metabolismus MeSH
- DNA bakterií genetika MeSH
- fylogeneze MeSH
- geologické sedimenty chemie mikrobiologie MeSH
- halogenace MeSH
- klonování DNA MeSH
- koncentrace vodíkových iontů MeSH
- mikrobiální společenstva * MeSH
- monitorování životního prostředí MeSH
- multivariační analýza MeSH
- polychlorované bifenyly analýza MeSH
- RNA ribozomální 16S genetika MeSH
- sekvenční analýza DNA MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Slovenská republika MeSH
Biomolecular and hydrochemical tools were used to evaluate natural attenuation of chlorinated ethenes in a Quaternary alluvial aquifer located close to a historical source of large-scale tetrachloroethylene (PCE) contamination. Distinct stratification of redox zones was observed, despite the aquifer's small thickness (2.8 m). The uppermost zone of the target aquifer was characterised by oxygen- and nitrate-reducing conditions, with mixed iron- to sulphate-reducing conditions dominant in the lower zone, along with indications of methanogenesis. Natural attenuation of PCE was strongly influenced by redox heterogeneity, while higher levels of PCE degradation coincided with iron- to sulphate reducing conditions. Next generation sequencing of the middle and/or lower zones identified anaerobic bacteria (Firmicutes, Chloroflexi, Actinobacteria and Bacteroidetes) associated with reductive dechlorination. The relative abundance of dechlorinators (Dehalococcoides mccartyi, Dehalobacter sp.) identified by real-time PCR in soil from the lower levels supports the hypothesis that there is a significant potential for reductive dechlorination of PCE. Local conditions were insufficiently reducing for rapid complete dechlorination of PCE to harmless ethene. For reliable assessment of natural attenuation, or when designing monitoring or remedial systems, vertical stratification of key biological and hydrochemical markers should be analysed as standard, even in shallow aquifers.
- MeSH
- biodegradace MeSH
- chemické látky znečišťující vodu analýza MeSH
- Chloroflexi MeSH
- ethyleny analýza MeSH
- halogenace MeSH
- monitorování životního prostředí * MeSH
- podzemní voda chemie MeSH
- tetrachlorethylen chemie MeSH
- vysoce účinné nukleotidové sekvenování MeSH
- železo analýza MeSH
- Publikační typ
- časopisecké články MeSH
A low-permeability locality with heterogeneous geology contaminated primarily by tetrachloroethene (PCE) present partially in the free phase in the unsaturated zone was treated on a pilot scale via direct push pneumatic fracturing combined with the hydraulic delivery of a remediation suspension consisting of milled iron, sulphidated nanosized zerovalent iron and sand in guar gum solution. Afterwards, a whey solution was injected into the fractures as a carbon source for bacteria. The unsaturated and saturated zones were treated. Long-term monitoring of the groundwater revealed that the abiotic reduction of PCE and trichloroethene was the dominant remediation processes for several months after the injections. A complex microbial consortium was developed that was capable of effective, long-term chlorinated ethenes (ClE) dechlorination. The consortium consisted mainly of Dehalococcoides but also of other anaerobic bacterial strains capable of partial dechlorination of ClE, including the sulphate-reducing bacteria; Geobacter and Desulfitobacterium. The average chlorine number in the groundwater decreased from 3.65 to 1.38 within 2.5 years after the injections, while the average ClE concentration increased from 13.5 to 31.5 mgL-1 because of the substantial acceleration of the ClE mass-transfer to the groundwater caused by the treatment. The remediation processes remained fully active for 2.5 years.
Nanoscale zero-valent iron (nZVI) is recognized as a powerful tool for the remediation of groundwater contaminated by chlorinated ethenes (CEs). This long-term field study explored nZVI-driven degradation of CEs supported by electrokinetic (EK) treatment, which positively affects nZVI longevity and migration, and its impact on indigenous bacteria. In particular, the impact of combined nZVI-EK treatment on organohalide-respiring bacteria, ethenotrophs and methanotrophs (all capable of CE degradation) was assessed using molecular genetic markers detecting Dehalococcoides spp., Desulfitobacterium spp., the reductive dehalogenase genes vcrA and bvcA and ethenotroph and methanotroph functional genes. The remediation treatment resulted in a rapid decrease of the major pollutant cis-1,2-dichloroethene (cDCE) by 75% in the affected area, followed by an increase in CE degradation products methane, ethane and ethene. The newly established geochemical conditions in the treated aquifer not only promoted growth of organohalide-respiring bacteria but also allowed for the concurrent presence of vinyl chloride- and cDCE-oxidizing methanotrophs and (especially) ethenotrophs, which proliferated preferentially in the vicinity of an anode where low levels of oxygen were produced. The nZVI treatment resulted in a temporary negative impact on indigenous bacteria in the application well close to the cathode; but even there, the microbiome was restored within 15 days. The nZVI-EK treatment proved highly effective in reducing CE contamination and creating a suitable environment for subsequent biodegradation by changing groundwater conditions, promoting transport of nutrients and improving CE availability to soil and groundwater bacteria.
- MeSH
- biodegradace MeSH
- chemické látky znečišťující vodu * MeSH
- ethyleny MeSH
- podzemní voda * MeSH
- železo MeSH
- Publikační typ
- časopisecké články MeSH
ISCO using activated sodium persulphate is a widely used technology for treating chlorinated solvent source zones. In sensitive areas, however, high groundwater sulphate concentrations following treatment may be a drawback. In situ biogeochemical transformation, a technology that degrades contaminants via reduced iron minerals formed by microbial activity, offers a potential solution for such sites, the bioreduction of sulphate and production of iron sulphides that abiotically degrade chlorinated ethenes acting as a secondary technology following ISCO. This study assesses this approach in the field using hydrochemical and molecular tools, solid phase analysis and geochemical modelling. Following a neutralisation and bioaugmentation, favourable conditions for iron- and sulphate-reducers were created, resulting in a remarkable increase in their relative abundance. The abundance of dechlorinating bacteria (Dehalococcoides mccartyi, Dehalobacter sp. and Desulfitobacterium spp.) remained low throughout this process. The activity of iron- and sulphate-reducers was further stimulated through application of magnetite plus starch and microiron plus starch, resulting in an increase in ferrous iron concentration (from
- MeSH
- chemické látky znečišťující vodu analýza metabolismus MeSH
- chlor metabolismus MeSH
- Chloroflexi metabolismus MeSH
- čištění vody metody MeSH
- Desulfitobacterium metabolismus MeSH
- ethyleny metabolismus MeSH
- halogenace MeSH
- oxidace-redukce MeSH
- Peptococcaceae metabolismus MeSH
- podzemní voda analýza chemie mikrobiologie MeSH
- regenerace a remediace životního prostředí metody MeSH
- rozpouštědla metabolismus MeSH
- sírany metabolismus MeSH
- sloučeniny sodíku MeSH
- tetrachlorethylen analýza metabolismus MeSH
- trichlorethylen analýza metabolismus MeSH
- železo metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Česká republika MeSH
