Over the past two decades, the use of nanoscale zero-valent iron (nZVI) has emerged as a standard method of contaminated groundwater remediation. The effectiveness of this method depends on key intrinsic hydrogeological parameters, which can affect both reactivity of the nanoparticles and their migration in the aquifer. In the case of low hydraulic permeability, the migration of nanoparticles is limited, which negatively influences remediation. An application of nZVI reinforced with a DC electric field led to a significant increase in the efficiency of remediation, as demonstrated by long-term monitoring at a former industrial site in Horice (Czech Republic). For the method testing, a 12 × 9 m polygon was defined around well IS4, where the original contamination was predominantly composed of DCE (7300 μg/l), and with a total concentration of chlorinated ethenes of 8880 μg/l. During the first stage of the activities, 49 kg of nZVI was injected and monitored for two years. Subsequently, the electrodes were installed, and for three years, the synergistic action of nZVI within an applied DC field was monitored. Based on 32 monitoring campaigns performed over the six years, the combined method was compared with an application of the only nZVI in technical, environmental and economic terms. Technically, the method requires annual reinstallation of anodes as a result of their oxidative disintegration. Environmentally, the method provides significantly improved chlorinated ethane reduction, remediation of low permeable zones, and extended efficiency. Economically, the method is five times cheaper when compared to the nZVI used alone.
- MeSH
- chemické látky znečišťující vodu analýza chemie MeSH
- ethyleny analýza chemie MeSH
- halogenace MeSH
- kovové nanočástice chemie MeSH
- podzemní voda MeSH
- regenerace a remediace životního prostředí * MeSH
- železo MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Česká 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
