scholarly journals Full-scale application of ELS® microemulsion Technology for the Treatment of an Aquifer Contaminated with perchloroethylene and trichloroethylene via Ehnanced Reductive Dechlorination

2020 ◽  
Author(s):  
Alberto Leombruni ◽  
Federica Morlacchi ◽  
Linda Collina ◽  
Daniel Leigh ◽  
Mike Mueller
Keyword(s):  
Electron Donor ◽  
Source Area ◽  
Organic Substrate ◽  
Low Flow ◽  
Innovative Technology ◽  
Effective Electron ◽  
Chlorinated Organics ◽  
Pump And Treat ◽  
Reducing Conditions

Mixed plumes of chlorinated organics and oxidized metals are a common contaminant at many sites. The oxidized metals can be mediated by the establishment of moderately reducing conditions. The chlorinated organics have been demonstrated to be degradable by specific dechlorinating microrganisms in anaerobic environment such as Dehalococcoides sp. Enhanced biological dechlorination requires the presence of an effective electron donor to provide molecular hydrogen (H2) to completely degrade chlorinated ethenes. Distribution of the electron donor results in the biologically mediated establishment of highly reducing conditions in the treatment zone. This process also results in the reduction and precipitation of the oxidized metals via sulphate-reducing conditions. Peroxychem LLC has developed an innovative electron donor, ELS® Microemulsion Reagent (ELS) for in situ treatment of chlorinated organics and metals. This substrate has been successfully applied at numerous sites to address a variety of contaminants. ELS® is an organic electron donor composed of an easily fermentable organic substrate based on lecithin, and designed to enhance in situ anaerobic bioremediation aquifers contaminated by organochlorine compounds and heavy metals such as hexavalent chromium Cr[VI]. The product is easy to mix, dilute and inject into the subsurface. Once in the groundwater, indigenous microorganisms utilize ELS to rapidly generate highly reducing conditions, favoring biotic dechlorination reactions and the reduction of oxidized metals such as Cr[VI]. This innovative technology was successfully applied to a former manufacturing site in the center of Italy, where groundwater was historically contaminated with Tetrachloroethylene (PCE > 5.5 milligrams per Liter; mg/L), Trichloroethylene (TCE > 2 mg/L), 1,2-Dichloroethene (1,2-DCE > 1 mg/L) and, to a lesser extent, Vinyl Chloride (VC) and 1,2-Dichloropropane (DP). A pump-and-treat system (P&T) installed in the source was active as a source containment measure and to speed up the overall groundwater remediation. However, there was concern that the pumping could affect the ELS treatment effectiveness because of the increased groundwater flow velocity and the potential for removal of the injected bioremediation substrate. To mitigate this potential some wells were switched off the flow rates of others was adjusted to ensure compatibility with the planned product injection. In particular, an upstream low-flow-rate pump and treat system was maintained over the ELS® treatment period, primarily to delay the fast-downstream diffusion of the amendments in the aquifer, thus enhancing the source treatment. Following the calibration of the P&T system, approximately 4,900 kg of ELS® concentration was injected under high pressure at 51 locations into the source area. In about 12 months from injection of ELS® Microemulsion into the groundwater in the main source area, concentrations of PCE, TCE and the recognized catabolites, such as DCE and VC, rapidly reduced, compared to the pre-treatment concentrations, until they reached the statutory national limits (CSC D.lgs 152/06) in the main monitoring piezometers of the area, also highlighting the establishment of clear and enhanced biotic reducing conditions. No rebound effects have been observed in the next three years of monitoring.

scholarly journals Phosphate Induced Arsenic Mobilization as a Potentially Effective In-Situ Remediation Technique—Preliminary Column Tests

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2364
Author(s):  
Martin V. Maier ◽  
Yvonne Wolter ◽  
Daniel Zentler ◽  
Christian Scholz ◽  
Charlotte N. Stirn ◽  
...  
Keyword(s):  
Microbial Activity ◽  
Ph Value ◽  
Surface Complexation ◽  
Contaminated Sites ◽  
Contaminated Site ◽  
Anoxic Conditions ◽  
Arsenic Mobility ◽  
Pump And Treat ◽  
Reducing Conditions

Arsenic (As) contamination of groundwater is commonly remediated by pump and treat. However, this technique is difficult to apply or maintain efficiently because the mobility of arsenic varies depending on the geochemical aquifer conditions. Arsenic interacting with the sediment can cause strong retardation, which is counteracted by ions competing for sedimentary sorption sites like silica, bicarbonate and phosphate. Phosphate competes most effectively with arsenic for sorption sites due to its chemical similarity. To accelerate an ongoing but ineffective pump and treat remediation, we examined the competitive effect of increasing phosphate doses on contaminated aquifer material of different depths and thus under distinct geochemical conditions. In the columns with phosphate addition, significant amounts of arsenic were released rapidly under oxic and anoxic conditions. In all tests, the grade of leaching was higher under anoxic conditions than under oxic conditions. As(III) was the dominant species, in particular during the first release peaks and the anoxic tests. Higher amounts of phosphate did not trigger the arsenic release further and led to a shift of arsenic species. We suggest that the competitive surface complexation is the major process of arsenic release especially when higher amounts of phosphate are used. Commonly arsenic release is described at iron reducing conditions. In contrast, we observed that a change in prevailing redox potential towards manganese reducing conditions in the oxic tests and iron reducing conditions in the anoxic column took place later and thus independently of arsenic release. The reduction of As(V) to As(III) under both redox conditions is presumed to be an effect of microbial detoxification. A loss of sulphate in all columns with phosphate indicates an increased microbial activity, which might play a significant role in the process of arsenic release. Preliminary tests with sediment material from a contaminated site showed that phosphate additions did not change the pH value significantly. Therefore, a release of other metals is not likely. Our results indicate that in-situ application of phosphate amendments to arsenic-contaminated sites could accelerate and enhance arsenic mobility to improve the efficiency of pump and treat remediation without negative side effects. The novelty of this approach is the use of only small amounts of phosphate in order to stimulate microbial activity in addition to surface complexation. Therefore, this method might become an innovative and cost-effective remediation for arsenic contaminated sites.

scholarly journals Decontamination of dense nonaqueous-phase liquids in groundwater using pump-and-treat and in situ chemical oxidation processes: a field test

RSC Advances ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 4237-4246
Author(s):  
Tian Xie ◽  
Zhi Dang ◽  
Jian Zhang ◽  
Qian Zhang ◽  
Rong-Hai Zhang ◽  
...  
Keyword(s):  
Field Test ◽  
Chemical Oxidation ◽  
Nonaqueous Phase Liquids ◽  
Dense Nonaqueous Phase Liquids ◽  
In Situ Chemical Oxidation ◽  
Oxidation Processes ◽  
Pump And Treat

The combination of pump-and-treat and in situ chemical oxidation processes can effectively accelerate the remediation of DNAPL pollutant in groundwater.

Characterization of the Metamitron Deaminating Enzyme Activity from Sugar Beet ( Beta vulgaris L.) Leaves

1979 ◽  
Vol 34 (11) ◽  
pp. 948-950 ◽  
Author(s):  
Carl Fedtke ◽  
Robert R. Schmidt
Keyword(s):  
Cytochrome C ◽  
Sugar Beet ◽  
Electron Donor ◽  
Nitrogen Atmosphere ◽  
Enzyme Preparations ◽  
Reducing Conditions ◽  
Trade Name ◽  
Membrane Bound

Abstract The enzymatic activity from sugar beet leaves which is responsible for the detoxification of the herbicide metamitron (4-amino-4,5-dihydro-3-methyl-6-phenyl-1, 2, 4-triazin-5-one, trade name Goltix®) has been characterized in vitro. The detoxification occurs by rapid deamination in vivo as well as in vitro. However, the deamination in vitro is only maximal under reducing conditions, i. e. with an electron donor and in a nitrogen atmosphere. The electron donor may be cystein, glutathione, dithionite or ascorbate. The enzymatic deamination further requires the addition of cytochrome c and a “supernatant factor”, which may be replaced by FMN, FAD or DCPIP. However, in the presence of FMN or DCPIP cytochrome c is not essential but only stimulatory. The partic­ulate as well as the soluble metamitron deaminating enzyme preparations obtained take up oxygen when supplied with cysteine and FMN. The particulate enzyme appears in the peroxysome-fraction. It is therefore suggested, that the enzymatic deamination of metamitron in sugar beet leaves is mediated by a proxisomal membrane bound electron transport system which alternatively may reduce oxygen or metamitron (deaminating).

Nitrogen loss in a nitrifying biofilm system

1999 ◽  
Vol 39 (7) ◽  
pp. 13-21 ◽  
Author(s):  
C. Helmer ◽  
S. Kunst ◽  
S. Juretschko ◽  
M.C. Schmid ◽  
K.-H. Schleifer ◽  
...  
Keyword(s):  
Nitrogen Loss ◽  
Comparative Sequence Analysis ◽  
Organic Substrate ◽  
Ammonia Oxidizing Bacteria ◽  
Autotrophic Nitrification ◽  
Batch Tests ◽  
Causative Agents ◽  
Do Concentration ◽  
Nitrogen Elimination

In a biological contactor that is part of the biological pretreatment of landfill leachate in Mechernich (Germany) nitrogen elimination of 60% or more was observed under low dissolved oxygen (DO) conditions. Ammonia was converted without accumulation of nitrite and with only little nitrate production. Interestingly, due to limited supply with organic substrate in the system, this observation cannot simply be explained by a combination of conventional autotrophic nitrification and heterotrophic denitrification. In situ hybridization with 16S rRNA-targeted probes revealed the presence of large microcolonies of at least three different types of ammonia-oxidizing bacteria in those biofilm regions where extremely high nitrogen losses occurred. These results were confirmed by comparative sequence analysis of biofilm-derived amoA (encoding the active-site polypeptide of ammonia-monooxygenase) clones for molecular fine-scale analysis of the ammonia-oxidizing population. In batch tests inoculated with biofilm material nitrogen loss occurred without dosage of organic substrate at a DO concentration of 1 mg/l. The simultaneous presence of ammonia and nitrite in the reactor induced the process of complete nitrogen elimination. N2 was identified to be the gaseous end product of the reaction. These results indicate that under low DO concentrations autotrophic ammonia-oxidizers might be the causative agents of the observed nitrogen loss by performing aerobic/anoxic denitrification with nitrite as electron acceptor and ammonia (or perhaps hydroxylamin) as electron donor.

scholarly journals Regional hydrology controls stream microbial biofilms: evidence from a glacial catchment

2004 ◽  
Vol 1 (1) ◽  
pp. 497-531 ◽  
Author(s):  
T. J. Battin ◽  
A. Wille ◽  
R. Psenner ◽  
A. Richter
Keyword(s):  
Landscape Heterogeneity ◽  
Low Flow ◽  
Detection Rates ◽  
Stream Communities ◽  
Stream Discharge ◽  
Carbon Production ◽  
Microbial Biofilms ◽  
Short Period ◽  
Alpine Stream

Abstract. Glaciers are highly responsive to global warming and important agents of landscape heterogeneity. While it is well established that glacial ablation and snowmelt regulate stream discharge, linkage among streams and streamwater hydrogeochemistry, the controls of these factors on stream microbial biofilms remain insufficiently understood. We investigated glacial (metakryal, hypokryal), groundwater-fed (krenal) and snow-fed (rhithral) streams – all of them representative for alpine stream networks – and present evidence that these hydrologic and hydrogeochemical factors differentially affect sediment microbial biofilms. Average microbial biomass and bacterial carbon production were low in the glacial streams, whereas bacterial cell size, biomass, and carbon production were higher in the tributaries, most notably in the krenal stream. Whole-cell in situ fluorescence hybridization revealed reduced detection rates of the Eubacteria and higher abundance of α-Proteobacteria in the glacial stream, a pattern that most probably reflects the trophic status of this ecosystem. Our data suggest low flow during the onset of snowmelt and autumn as a short period (hot moment) of favorable environmental conditions with pulsed inputs of allochthonous nitrate and dissolved organic carbon, and with disproportional high microbial growth. Krenal and rhithral streams with more constant and favorable environments serve as possible sources of microbes and organic matter to the main glacial channel during periods (e.g. snowmelt) of elevated hydrologic linkage among streams. Ice and snow dynamics have a crucial impact on microbial biofilms, and we thus need better understanding of the microbial ecology and enhanced consideration of critical hydrological episodes in future models predicting alpine stream communities.

scholarly journals Potential forMethanosarcinato contribute to uranium reduction during acetate-promoted groundwater bioremediation

2017 ◽  
Author(s):  
Dawn E Holmes ◽  
Roberto Orelana ◽  
Ludovic Giloteaux ◽  
Li-Ying Wang ◽  
Pravin Shrestha ◽  
...  
Keyword(s):  
Field Experiment ◽  
Electron Donor ◽  
Enrichment Culture ◽  
Cell Suspensions ◽  
Contaminated Groundwater ◽  
Subunit A ◽  
Sedimentary Environments

AbstractPrevious studies ofin situbioremediation of uranium-contaminated groundwater with acetate injections have focused on the role ofGeobacterspecies in U(VI) reduction because of a lack of other abundant known U(VI)-reducing microorganisms. Monitoring the levels of methyl CoM reductase subunit A (mcrA) transcripts during an acetate-injection field experiment demonstrated that acetoclastic methanogens from the genusMethanosarcinawere enriched after 40 days of acetate amendment. The increased abundance ofMethanosarcinacorresponded with an accumulation of methane in the groundwater. An enrichment culture dominated by aMethanosarcinaspecies with the sameMethanosarcina mcrAsequence that predominated in the field experiment could effectively convert acetate to methane. In order to determine whetherMethanosarcinaspecies could be participating in U(VI) reduction in the subsurface, cell suspensions ofM. barkeriwere incubated in the presence of U(VI) with acetate provided as the electron donor. U(VI) was reduced by metabolically activeM. barkericells, however, no U(VI) reduction was observed in inactive controls. These results demonstrate thatMethanosarcinaspecies could play an important role in the long-term bioremediation of uranium-contaminated aquifers after depletion of Fe(III) oxides limits the growth ofGeobacterspecies. The results also suggest thatMethanosarcinahave the potential to influence uranium geochemistry in a diversity of anaerobic sedimentary environments.

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