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Background Nanoscale zero-valent iron (nZVI) is commonly used for remediation of groundwater contaminated by chlorinated ethenes (CEs); however, its long-term reactivity and subsurface transport are limited. A novel nZVI–AC material, consisting of colloidal activated carbon (AC) with embedded nZVI clusters, was developed with the aim of overcoming the limitations of nZVI alone. Results Application of a limited amount of nZVI–AC to an oxic, nitrate-rich, highly permeable quaternary aquifer triggered time-limited transformation of CEs, with noticeable involvement of reductive dechlorination. Reductive dechlorination of CEs was dominantly abiotic, as an increase in the concentration of vinyl chloride (VC) and ethene did not coincide with an increase in the abundance of reductive biomarkers for complete dechlorination of CEs (Dehalococcoides, Dehalogenimonas, VC reductase genes vcrA and bvcA). Application of nZVI–AC under unfavourable hydrochemical conditions resulted in no dramatic change in the microbial community, the reducing effect resulting in temporal proliferation of nitrate and iron reducers only. At a later stage, generation of reduced iron induced an increase in iron-oxidizing bacteria. High concentrations and a continuous mass influx of competing electron acceptors (nitrate and dissolved oxygen) created unfavourable conditions for sulphate-reducers and organohalide-respiring bacteria, though it allowed the survival of aerobic microorganisms of the genera Pseudomonas, Polaromonas and Rhodoferax, known for their ability to assimilate VC or cis-1,2-dichloroethene. A potential for aerobic oxidative degradation of CE metabolites was also indicated by detection of the ethenotroph functional gene etnE. Conclusions This pilot study, based on the application of nZVI–AC, failed to provide a sustainable effect on CE contamination; however, it provided valuable insights into induced hydrogeochemical and microbial processes that could help in designing full-scale applications.
Marie Czinnerova; Nhung H. A. Nguyen; Jan Nemecek; Katrin Mackenzie; Christopher Boothman; Jonathan Lloyd; Tamas Laszlo; Roman Spanek; Miroslav Cernik; Alena Sevcu. In situ pilot application of nZVI embedded in activated carbon for remediation of chlorinated ethene-contaminated groundwater: effect on microbial communities. Environmental Sciences Europe 2020, 32, 1 -15.
AMA StyleMarie Czinnerova, Nhung H. A. Nguyen, Jan Nemecek, Katrin Mackenzie, Christopher Boothman, Jonathan Lloyd, Tamas Laszlo, Roman Spanek, Miroslav Cernik, Alena Sevcu. In situ pilot application of nZVI embedded in activated carbon for remediation of chlorinated ethene-contaminated groundwater: effect on microbial communities. Environmental Sciences Europe. 2020; 32 (1):1-15.
Chicago/Turabian StyleMarie Czinnerova; Nhung H. A. Nguyen; Jan Nemecek; Katrin Mackenzie; Christopher Boothman; Jonathan Lloyd; Tamas Laszlo; Roman Spanek; Miroslav Cernik; Alena Sevcu. 2020. "In situ pilot application of nZVI embedded in activated carbon for remediation of chlorinated ethene-contaminated groundwater: effect on microbial communities." Environmental Sciences Europe 32, no. 1: 1-15.
A stall of cis-1,2-DCE and vinyl chloride (VC) is frequently observed during bioremediation of groundwater chloroethenes via reductive dechlorination. These chloroethenes may be oxidised by aerobic methanotrophs or ethenotrophs co-metabolically and/or metabolically. We assessed the potential for such oxidation at 12 sites (49 groundwater samples) using hydrochemical and molecular biological tools. Both ethenotroph (etnC and etnE) and methanotroph (mmoX and pmoA) functional genes were identified in 90% of samples, while reductive dehalogenase functional genes (vcrA and bvcA) were identified in 82%. All functional genes were simultaneously detected in 78% of samples, in actively biostimulated sites in 88% of samples. Correlation analysis revealed that cis-1,2-DCE concentration was positively correlated with vcrA, etnC and etnE, while VC concentration was correlated with etnC, etnE, vcrA and bvcA. However, feature selection based on random forest classification indicated a significant relationship for the vcrA in relation to cis-1,2-DCE, and vcrA, bvcA and etnE for VC and no prove of relationship between cis-1,2-DCE or VC and the methanotroph functional genes. Analysis of hydrochemical parameters indicated that aerobic oxidation of chloroethenes by ethenotrophs may take place under a range of redox conditions of aquifers and coincide with high ethene and VC concentrations.
Jan Němeček; Kristýna Marková; Roman Špánek; Vojtěch Antoš; Petr Kozubek; Ondřej Lhotský; Miroslav Černík. Hydrochemical Conditions for Aerobic/Anaerobic Biodegradation of Chlorinated Ethenes—A Multi-Site Assessment. Water 2020, 12, 322 .
AMA StyleJan Němeček, Kristýna Marková, Roman Špánek, Vojtěch Antoš, Petr Kozubek, Ondřej Lhotský, Miroslav Černík. Hydrochemical Conditions for Aerobic/Anaerobic Biodegradation of Chlorinated Ethenes—A Multi-Site Assessment. Water. 2020; 12 (2):322.
Chicago/Turabian StyleJan Němeček; Kristýna Marková; Roman Špánek; Vojtěch Antoš; Petr Kozubek; Ondřej Lhotský; Miroslav Černík. 2020. "Hydrochemical Conditions for Aerobic/Anaerobic Biodegradation of Chlorinated Ethenes—A Multi-Site Assessment." Water 12, no. 2: 322.
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 ‘polishing 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
Jan Němeček; Magda Nechanická; Roman Špánek; František Eichler; Josef Zeman; Miroslav Černík. Engineered in situ biogeochemical transformation as a secondary treatment following ISCO – A field test. Chemosphere 2019, 237, 124460 .
AMA StyleJan Němeček, Magda Nechanická, Roman Špánek, František Eichler, Josef Zeman, Miroslav Černík. Engineered in situ biogeochemical transformation as a secondary treatment following ISCO – A field test. Chemosphere. 2019; 237 ():124460.
Chicago/Turabian StyleJan Němeček; Magda Nechanická; Roman Špánek; František Eichler; Josef Zeman; Miroslav Černík. 2019. "Engineered in situ biogeochemical transformation as a secondary treatment following ISCO – A field test." Chemosphere 237, no. : 124460.
In situ bioremediation (ISB) using reductive dechlorination is a widely accepted but relatively slow approach compared to other technologies for the treatment of groundwater contaminated by chlorinated ethenes (CVOCs). Due to the known positive kinetic effect on microbial metabolism, thermal enhancement may be a viable means of accelerating ISB. We tested thermally enhanced ISB in aquifers situated in sandy saprolite and underlying fractured granite. The system comprised pumping, heating and subsequent injection of contaminated groundwater aiming at an aquifer temperature of 20-30°C. A fermentable substrate (whey) was injected in separate batches. The test was monitored using hydrochemical and molecular tools (qPCR and NGS). The addition of the substrate and increase in temperature resulted in a rapid increase in the abundance of reductive dechlorinators (e.g., Dehalococcoides mccartyi, Dehalobacter sp. and functional genes vcrA and bvcA) and a strong increase in CVOC degradation. On day 34, the CVOC concentrations decreased by 87% to 96% in groundwater from the wells most affected by the heating and substrate. On day 103, the CVOC concentrations were below the LOQ resulting in degradation half-lives of 5 to 6days. Neither an increase in biomarkers nor a distinct decrease in the CVOC concentrations was observed in a deep well affected by the heating but not by the substrate. NGS analysis detected Chloroflexi dechlorinating genera (Dehalogenimonas and GIF9 and MSBL5 clades) and other genera capable of anaerobic metabolic degradation of CVOCs. Of these, bacteria of the genera Acetobacterium, Desulfomonile, Geobacter, Sulfurospirillum, Methanosarcina and Methanobacterium were stimulated by the substrate and heating. In contrast, groundwater from the deep well (affected by heating only) hosted representatives of aerobic metabolic and aerobic cometabolic CVOC degraders. The test results document that heating of the treated aquifer significantly accelerated the treatment process but only in the case of an abundant substrate.
Jan Němeček; Jana Steinová; Roman Špánek; Tomáš Pluhař; Petr Pokorný; Petra Najmanová; Vladislav Knytl; Miroslav Černík. Thermally enhanced in situ bioremediation of groundwater contaminated with chlorinated solvents – A field test. Science of The Total Environment 2018, 622-623, 743 -755.
AMA StyleJan Němeček, Jana Steinová, Roman Špánek, Tomáš Pluhař, Petr Pokorný, Petra Najmanová, Vladislav Knytl, Miroslav Černík. Thermally enhanced in situ bioremediation of groundwater contaminated with chlorinated solvents – A field test. Science of The Total Environment. 2018; 622-623 ():743-755.
Chicago/Turabian StyleJan Němeček; Jana Steinová; Roman Špánek; Tomáš Pluhař; Petr Pokorný; Petra Najmanová; Vladislav Knytl; Miroslav Černík. 2018. "Thermally enhanced in situ bioremediation of groundwater contaminated with chlorinated solvents – A field test." Science of The Total Environment 622-623, no. : 743-755.
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.
Jan Němeček; Iva Dolinová; Jiřina Macháčková; Roman Špánek; Alena Ševců; Tomáš Lederer; Miroslav Černík. Stratification of chlorinated ethenes natural attenuation in an alluvial aquifer assessed by hydrochemical and biomolecular tools. Chemosphere 2017, 184, 1157 -1167.
AMA StyleJan Němeček, Iva Dolinová, Jiřina Macháčková, Roman Špánek, Alena Ševců, Tomáš Lederer, Miroslav Černík. Stratification of chlorinated ethenes natural attenuation in an alluvial aquifer assessed by hydrochemical and biomolecular tools. Chemosphere. 2017; 184 ():1157-1167.
Chicago/Turabian StyleJan Němeček; Iva Dolinová; Jiřina Macháčková; Roman Špánek; Alena Ševců; Tomáš Lederer; Miroslav Černík. 2017. "Stratification of chlorinated ethenes natural attenuation in an alluvial aquifer assessed by hydrochemical and biomolecular tools." Chemosphere 184, no. : 1157-1167.
Tomas Cajthaml; Jan Němeček; Petr Piokorný; Ondřej Lhotský; Vladislav Knytl; Petra Najmanová; Jana Steinová; Miroslav Černík; Alena Filipová; Jan Filip. Combination of nanoscale-zero-valent iron and organic substrate stimulation for efficient remediation of co-mingled plume contaminated with Cr(VI) and chlorinated solvents. New Biotechnology 2016, 33, S6 .
AMA StyleTomas Cajthaml, Jan Němeček, Petr Piokorný, Ondřej Lhotský, Vladislav Knytl, Petra Najmanová, Jana Steinová, Miroslav Černík, Alena Filipová, Jan Filip. Combination of nanoscale-zero-valent iron and organic substrate stimulation for efficient remediation of co-mingled plume contaminated with Cr(VI) and chlorinated solvents. New Biotechnology. 2016; 33 ():S6.
Chicago/Turabian StyleTomas Cajthaml; Jan Němeček; Petr Piokorný; Ondřej Lhotský; Vladislav Knytl; Petra Najmanová; Jana Steinová; Miroslav Černík; Alena Filipová; Jan Filip. 2016. "Combination of nanoscale-zero-valent iron and organic substrate stimulation for efficient remediation of co-mingled plume contaminated with Cr(VI) and chlorinated solvents." New Biotechnology 33, no. : S6.
The paper describes a pilot remediation test combining two Cr(VI) geofixation methods - chemical reduction by nanoscale zero-valent iron (nZVI) and subsequent biotic reduction supported by whey. Combination of the methods exploited the advantages of both - a rapid decrease in Cr(VI) concentrations by nZVI, which prevented further spreading of the contamination and facilitated subsequent use of the cheaper biological method. Successive application of whey as an organic substrate to promote biotic reduction of Cr(VI) after application of nZVI resulted in a further and long-term decrease in the Cr(VI) contents in the groundwater. The effect of biotic reduction was observed even in a monitoring well located at a distance of 22 m from the substrate injection wells after 10 months. The results indicated a reciprocal effect of both the phases - nZVI oxidized to Fe(III) during the abiotic phase was microbially reduced back to Fe(II) and acted as a reducing agent for Cr(VI) even when the microbial density was already low due to the consumed substrate. Community analysis with pyrosequencing of the 16S rRNA genes further confirmed partial recycling of nZVI in the form of Fe(II), where the results showed that the Cr(VI) reducing process was mediated mainly by iron-reducing and sulfate-reducing bacteria.
Jan Němeček; Petr Pokorný; Lenka Lacinová; Miroslav Cernik; Zuzana Masopustová; Ondřej Lhotský; Alena Filipová; Tomáš Cajthaml. Combined abiotic and biotic in-situ reduction of hexavalent chromium in groundwater using nZVI and whey: A remedial pilot test. Journal of Hazardous Materials 2015, 300, 670 -679.
AMA StyleJan Němeček, Petr Pokorný, Lenka Lacinová, Miroslav Cernik, Zuzana Masopustová, Ondřej Lhotský, Alena Filipová, Tomáš Cajthaml. Combined abiotic and biotic in-situ reduction of hexavalent chromium in groundwater using nZVI and whey: A remedial pilot test. Journal of Hazardous Materials. 2015; 300 ():670-679.
Chicago/Turabian StyleJan Němeček; Petr Pokorný; Lenka Lacinová; Miroslav Cernik; Zuzana Masopustová; Ondřej Lhotský; Alena Filipová; Tomáš Cajthaml. 2015. "Combined abiotic and biotic in-situ reduction of hexavalent chromium in groundwater using nZVI and whey: A remedial pilot test." Journal of Hazardous Materials 300, no. : 670-679.
Tomáš Cajthaml; Jan Němeček; Petr Pokorny; Lenka Lacinová; Miroslav Černík; Zuzana Masopustová; Ondřej Lhotský. Reduction of hexavalent chromium using combination of nanoscale zero-valent iron and biological treatment in situ. New Biotechnology 2014, 31, S64 .
AMA StyleTomáš Cajthaml, Jan Němeček, Petr Pokorny, Lenka Lacinová, Miroslav Černík, Zuzana Masopustová, Ondřej Lhotský. Reduction of hexavalent chromium using combination of nanoscale zero-valent iron and biological treatment in situ. New Biotechnology. 2014; 31 ():S64.
Chicago/Turabian StyleTomáš Cajthaml; Jan Němeček; Petr Pokorny; Lenka Lacinová; Miroslav Černík; Zuzana Masopustová; Ondřej Lhotský. 2014. "Reduction of hexavalent chromium using combination of nanoscale zero-valent iron and biological treatment in situ." New Biotechnology 31, no. : S64.