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Derek R Lovley - One of the best experts on this subject based on the ideXlab platform.
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Enrichment of specific protozoan populations durIng In Situ Bioremediation of uranium-contamInated groundwater
The ISME Journal, 2013Co-Authors: Dawn E Holmes, Kenneth H Williams, Michael J Wilkins, Philip E. Long, Ludovic Giloteaux, Kelly C Wrighton, Courtney A Thompson, Thomas J Roper, Derek R LovleyAbstract:The importance of bacteria In the anaerobic Bioremediation of groundwater polluted with organic and/or metal contamInants is well recognized and In some Instances so well understood that modelIng of the In Situ metabolic activity of the relevant subsurface microorganisms In response to changes In subsurface geochemistry is feasible. However, a potentially significant factor InfluencIng bacterial growth and activity In the subsurface that has not been adequately addressed is protozoan predation of the microorganisms responsible for Bioremediation. In field experiments at a uranium-contamInated aquifer located In Rifle, CO, USA, acetate amendments Initially promoted the growth of metal-reducIng Geobacter species, followed by the growth of sulfate reducers, as observed previously. Analysis of 18S rRNA gene sequences revealed a broad diversity of sequences closely related to known bacteriovorous protozoa In the groundwater before the addition of acetate. The bloom of Geobacter species was accompanied by a specific enrichment of sequences most closely related to the ameboid flagellate, Breviata anathema , which at their peak accounted for over 80% of the sequences recovered. The abundance of Geobacter species declIned followIng the rapid emergence of B. anathema . The subsequent growth of sulfate-reducIng Peptococcaceae was accompanied by another specific enrichment of protozoa, but with sequences most similar to diplomonadid flagellates from the family Hexamitidae , which accounted for up to 100% of the sequences recovered durIng this phase of the Bioremediation. These results suggest a prey–predator response with specific protozoa respondIng to Increased availability of preferred prey bacteria. Thus, quantifyIng the Influence of protozoan predation on the growth, activity and composition of the subsurface bacterial community is essential for predictive modelIng of In Situ uranium Bioremediation strategies.
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genome scale dynamic modelIng of the competition between rhodoferax and geobacter In anoxic subsurface environments
The ISME Journal, 2011Co-Authors: Kai Zhuang, Paula J. Mouser, Radhakrishnan Mahadevan, Mounir Izallalen, Hanno Richter, Carla Risso, Derek R LovleyAbstract:The advent of rapid complete genome sequencIng, and the potential to capture this Information In genome-scale metabolic models, provide the possibility of comprehensively modelIng microbial community Interactions. For example, Rhodoferax and Geobacter species are acetate-oxidizIng Fe(III)-reducers that compete In anoxic subsurface environments and this competition may have an Influence on the In Situ Bioremediation of uranium-contamInated groundwater. Therefore, genome-scale models of Geobacter sulfurreducens and Rhodoferax ferrireducens were used to evaluate how Geobacter and Rhodoferax species might compete under diverse conditions found In a uranium-contamInated aquifer In Rifle, CO. The model predicted that at the low rates of acetate flux expected under natural conditions at the site, Rhodoferax will outcompete Geobacter as long as sufficient ammonium is available. The model also predicted that when high concentrations of acetate are added durIng In Situ Bioremediation, Geobacter species would predomInate, consistent with field-scale observations. This can be attributed to the higher expected growth yields of Rhodoferax and the ability of Geobacter to fix nitrogen. The modelIng predicted relative proportions of Geobacter and Rhodoferax In geochemically distInct zones of the Rifle site that were comparable to those that were previously documented with molecular techniques. The model also predicted that under nitrogen fixation, higher carbon and electron fluxes would be diverted toward respiration rather than biomass formation In Geobacter, providIng a potential explanation for enhanced In Situ U(VI) reduction In low-ammonium zones. These results show that genome-scale modelIng can be a useful tool for predictIng microbial Interactions In subsurface environments and shows promise for designIng Bioremediation strategies.
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resistance of solid phase u vi to microbial reduction durIng In Situ Bioremediation of uranium contamInated groundwater
Applied and Environmental Microbiology, 2004Co-Authors: Irene Ortizbernad, Robert T Anderson, Helen A Vrionis, Derek R LovleyAbstract:Speciation of solid-phase uranium In uranium-contamInated subsurface sediments undergoIng uranium Bioremediation demonstrated that although microbial reduction of soluble U(VI) readily immobilized uranium as U(IV), a substantial portion of the U(VI) In the aquifer was strongly associated with the sediments and was not microbially reducible. These results have important implications for In Situ uranium Bioremediation strategies.
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anaerobes to the rescue
Science, 2001Co-Authors: Derek R LovleyAbstract:Polluted groundwater systems are very difficult to clean up. In his Perspective, [Lovley][1] charts recent advances towards In Situ Bioremediation of such systems usIng anaerobic organisms. Such organisms, which naturally exist In soils, may assist In cleanIng up hydrocarbons, chlorInated pollutants, and metals. The author concludes that anaerobic strategies are promisIng but that substantial research remaIns to be done before any of them can be adopted for routIne application. [1]: http://www.sciencemag.org/cgi/content/full/293/5534/1444
Juan L Ramos - One of the best experts on this subject based on the ideXlab platform.
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field trial on removal of petroleum hydrocarbon pollutants usIng a microbial consortium for Bioremediation and rhizoremediation
Environmental Microbiology Reports, 2015Co-Authors: Paloma Pizarrotobias, Jose Luis Niqui, Amalia Roca, Jennifer Solano, Matilde Fernandez, Felipe Bastida, C Garcia, Juan L RamosAbstract:Petroleum waste sludges are toxic and dangerous that is why environmental protection agencies have declared their treatment top priority. Physicochemical treatments are expensive and environmentally unfriendly, while alternative biological treatments are less costly but, In general, work at a slower pace. An In Situ Bioremediation and rhizoremediation field scale trial was performed In an area contamInated with oil refInery sludge under semiarid climate. The Bioremediation and rhizoremediation treatments Included the use of an artificial consortium made up of plant growth-promotIng rhizobacteria and polycyclic aromatic hydrocarbon-degradIng bacteria,and the combIned use of the mentioned consortium along with pasture plants respectively. Rhizoremediation revealed that the development of vegetation favoured the evolution of Indigenous microbiota with potential to remove petroleum wastes. This was Inferred as the declIne of total petroleum hydrocarbons 7 months after the biological treatment.
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Bioremediation of 2 4 6 trInitrotoluene under field conditions
Environmental Science & Technology, 2007Co-Authors: Pieter Van Dillewijn, Antonio Caballero, Mar M Gonzalezperez, Jose M Oliva, Juan L RamosAbstract:In Situ Bioremediation of the nitroaromatic explosive 2,4,6-trInitrotoluene (TNT) provides a cost-effective alternative for cleanIng up contamInated sites. Here we compare the effectiveness of several Bioremediation techniques: natural attenuation, bioaugmentation with TNT-degradIng Pseudomonas putida JLR11, phytoremediation with maize (Zea mays L.) and broad beans (Vicia faba L.), and rhizoremediation with maize and broad beans Inoculated with P. putida JLR11. Experiments In spiked hydroponic medium demonstrated that Inoculation with bacteria did not affect TNT levels. On the other hand, axenic plants were able to remove 32% to 38% of the TNT from the medium. However, when plants were Inoculated with bacteria, TNT disappeared to an even greater extent (80% to 88%), a result that advocates a role for P. putida JLR11 In rhizoremediation. In field experiments neither natural attenuation nor bioaugmentation with P. putida JLR11 affected TNT levels to a significant degree. However, the extractable TNT conten...
Xihui Zhang - One of the best experts on this subject based on the ideXlab platform.
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the use of 2d non uniform electric field to enhance In Situ Bioremediation of 2 4 dichlorophenol contamInated soil
Journal of Hazardous Materials, 2007Co-Authors: Xiangyu Fan, Hui Wang, Qishi Luo, Xihui ZhangAbstract:Abstract In Situ Bioremediation is a safe and cost-effective technology for the cleanup of organic-contamInated soil, but its remediation rate is usually very slow, which results primarily from limited mass transfer of pollutants to the degradIng bacteria In soil media. This study Investigated the feasibility of adoptIng 2D non-uniform electric field to enhance In Situ Bioremediation process by promotIng the mass transfer of organics to degradIng bacteria under In Situ conditions. For this purpose, a 2D non-uniform electrokInetic system was designed and tested at bench-scale with a sandy loam as the model soil and 2,4-dichlorophenol (2,4-DCP) as the model organic pollutant at two common operation modes (bidirectional and rotational). Periodically, the electric field reverses its direction at bidirectional mode and revolves a given angle at rotational mode. The results demonstrated that the non-uniform electric field could effectively stimulate the desorption and the movement of 2,4-DCP In the soil. The 2,4-DCP was mobilized through soil media towards the anode at a rate of about 1.0 cm d−1 V−1. The results also showed that In Situ biodegradation of 2,4-DCP In the soil was greatly enhanced by the applied 2D electric field upon operational mode. At the bidirectional mode, an average 2,4-DCP removal of 73.4% was achieved In 15 days, and the In Situ biodegradation of 2,4-DCP was Increased by about three times as compared with that uncoupled with electric field, whereas, 34.8% of 2,4-DCP was removed on average In the same time period at the rotational mode. In terms of maIntaInIng remediation uniformity In soil, the rotational operation remarkably excelled the bidirectional operation. In the hexagonal treatment area, the 2,4-DCP removal efficiency adversely Increase with the distance to the central electrode at the bidirectional mode, while the rotational mode generated almost uniform removal In soil bed.
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the use of non uniform electrokInetics to enhance In Situ Bioremediation of phenol contamInated soil
Journal of Hazardous Materials, 2005Co-Authors: Xihui Zhang, Hui Wang, Yi QianAbstract:In Situ Bioremediation is an attractive and often cost-effective technology for the cleanup of organics-contamInated sites, but it often requires extended treatment time under field conditions. This study explored the feasibility of usIng non-uniform electrokInetic transport processes to enhance In Situ Bioremediation. A bench-scale non-uniform electrokInetic system with periodic polarity-reversal was developed for this purpose, and tested by usIng a sandy loam spiked with phenol as a model organic pollutant. The results demonstrated that non-uniform electrokInetic processes could accelerate the movement and In Situ biodegradation of phenol In the soil. Bidirectional operation enhanced the phenol biodegradation more effectively than unidirectional operation. At the same time, a smaller polarity-reversIng Interval Induced a higher and more uniform removal of phenol from the soil. The results also showed that reversIng the polarity of electric field applied could maIntaIn the soil pH and moisture, but it Increased the consumption of electricity.
David Andrew Barry - One of the best experts on this subject based on the ideXlab platform.
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Use of silicate mInerals for pH control durIng reductive dechlorInation of chloroethenes In batch cultures of different microbial consortia
Applied and Environmental Microbiology, 2014Co-Authors: Elsa Lacroix, Alessandro Brovelli, David Andrew BarryAbstract:In chloroethene-contamInated sites undergoIng In Situ Bioremediation, groundwater acidification is a frequent problem In the source zone, and bufferIng strategies have to be implemented to maIntaIn the pH In the neutral range. An alternative to conventional soluble buffers is silicate mIneral particles as a long-term source of alkalInity. In previous studies, the bufferIng potentials of these mInerals have been evaluated based on abiotic dissolution tests and geochemical modelIng. In the present study, the bufferIng potentials of four silicate mInerals (andradite, diopside, fayalite, and forsterite) were tested In batch cultures amended with tetrachloroethene (PCE) and Inoculated with different organohalide-respirIng consortia. Another objective of this study was to determIne the Influence of pH on the different steps of PCE dechlorInation. The consortia showed significant differences In sensitivities toward acidic pH for the different dechlorInation steps. Molecular analysis Indicated that Dehalococcoides spp. that were present In all consortia were the most pH-sensitive organohalide-respirIng guild members compared to Sulfurospirillum spp. and Dehalobacter spp. In batch cultures with silicate mIneral particles as pH-bufferIng agents, all four mInerals tested were able to maIntaIn the pH In the appropriate range for reductive dechlorInation of chloroethenes. However, complete dechlorInation to ethene was observed only with forsterite, diopside, and fayalite. Dissolution of andradite Increased the redox potential and did not allow dechlorInation. With forsterite, diopside, and fayalite, dechlorInation to ethene was observed but at much lower rates for the last two dechlorInation steps than with the positive control. This Indicated an Inhibition effect of silicate mInerals and/or their dissolution products on reductive dechlorInation of cis-dichloroethene and vInyl chloride. Hence, despite the proven pH-bufferIng potential of silicate mInerals, compatibility with the bacterial community Involved In In Situ Bioremediation has to be carefully evaluated prior to their use for pH control at a specific site.
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Utilization of silicate mInerals for pH control durIng In Situ Bioremediation of chlorInated solvent
2011Co-Authors: Elsa Lacroix, Alessandro Brovelli, David Andrew BarryAbstract:Chloroethenes such as tetrachloroethene (PCE) and trichloroethene (TCE) are among the most prevalent contamInants In groundwater due to their extensive use In Industrial processes. In Situ Bioremediation (ISB) is an attractive technology for removal of these compounds. It relies on an anaerobic process In which specialized bacteria obtaIn energy for growth usIng chloroethenes as an electron acceptor via organohalide respiration. EngIneered Bioremediation is achieved by stimulatIng these microorganisms through the addition of electron donor In the subsurface. This technology has been widely used for Bioremediation of chloroethene plumes and recent studies have Indicated promisIng results for Bioremediation of chlorInated solvent source zones. However, application of source zone ISB is still a significant technical challenge. One of the maIn issues is the groundwater acidification due to organohalide respiration and fermentation processes, which can Inhibit the activity of dehalogenatIng micro-organisms. The maIn objective of this work was to develop an efficient pH control strategy for chloroethene ISB by usIng the acid neutralizIng potential of silicate mInerals. To do so, modelIng and experimental approaches were combIned. A geochemical model, implemented withIn PHREEQC, was developed to select appropriate buffer candidates and to help determIne maIn parameters InfluencIng mIneral bufferIng capacity. The model Included chloroethene microbial degradation kInetics, mIneral dissolution kInetics and chemical speciation. Second, anaerobic microcosm experiments were performed to determIne the Influence of pH on dehalogenation. These microcosms were Inoculated with enriched consortia of dehalogenatIng bacteria and fed with PCE and hydrogen. Another set of microcosm experiments was carried out to compare the bufferIng capacity of ten silicate mInerals and to Investigate Interactions between mInerals and dehalogenatIng bacteria, e.g., the potential Inhibitory effect of mInerals on the dehalogenatIng activity. These microcosms were amended with 5 mmol l-1 of PCE and 4 g l-1 of mIneral with graIn sizes between 50 and 100 μm. The cultivation medium was modified such that the silicate mIneral powder was the sole pH buffer present. Chloroethenes, pH and dissolved cation measurements were conducted to determIne the system efficiency. Abiotic dissolution experiments were also performed to determIne mIneral dissolution rates In the absence of bacteria. The model confirmed that the efficiency of the system is dependent maInly on mIneral dissolution kInetic constants, equilibrium constants and reactive surface area. The geochemical model and literature parameter data were used to pre-select mInerals with a bufferIng capacity sufficient to counterbalance acidity produced by dehalogenatIng bacteria at a rate of 4 mmol l-1.d-1of chloride. Of the 31 silicate mInerals for which there were published kInetic data, 10 were identified as suitable candidates. The Inhibitory pH for the dehalogenatIng consortia was found to vary between 5 and 6. The last steps of the dechlorInation from DCE to ethene were more sensitive to pH than the first steps from PCE to DCE, as has been noted In other dechlorInation studies. Results of microcosm experiments with silicate mInerals demonstrated that, under the selected conditions, the pH control behavior and the impact on bacterial activity exhibited strong variations dependIng on the mIneral. Of the ten mInerals tested experimentally, three (olivIne, fayalite and diopside) maIntaIned the pH In the appropriate range, i.e., between 5.5 and 6.5 and led to complete transformation of PCE. For the other mInerals tested, either the acid neutralization capacity was Insufficient due to slow dissolution kInetics (glaucophane and staurolite) or dechlorInation activity was Inhibited by (unmeasured) compounds released durIng mIneral dissolution. Both modelIng and experimental results demonstrated the feasibility of usIng selected silicate mInerals as a bufferIng agent durIng ISB. However, the experimental results also revealed a mIneral-Induced potential Inhibitory effect that should be Investigated prior to application at a contamInated site.
Elsa Lacroix - One of the best experts on this subject based on the ideXlab platform.
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Use of silicate mInerals for pH control durIng reductive dechlorInation of chloroethenes In batch cultures of different microbial consortia
Applied and Environmental Microbiology, 2014Co-Authors: Elsa Lacroix, Alessandro Brovelli, David Andrew BarryAbstract:In chloroethene-contamInated sites undergoIng In Situ Bioremediation, groundwater acidification is a frequent problem In the source zone, and bufferIng strategies have to be implemented to maIntaIn the pH In the neutral range. An alternative to conventional soluble buffers is silicate mIneral particles as a long-term source of alkalInity. In previous studies, the bufferIng potentials of these mInerals have been evaluated based on abiotic dissolution tests and geochemical modelIng. In the present study, the bufferIng potentials of four silicate mInerals (andradite, diopside, fayalite, and forsterite) were tested In batch cultures amended with tetrachloroethene (PCE) and Inoculated with different organohalide-respirIng consortia. Another objective of this study was to determIne the Influence of pH on the different steps of PCE dechlorInation. The consortia showed significant differences In sensitivities toward acidic pH for the different dechlorInation steps. Molecular analysis Indicated that Dehalococcoides spp. that were present In all consortia were the most pH-sensitive organohalide-respirIng guild members compared to Sulfurospirillum spp. and Dehalobacter spp. In batch cultures with silicate mIneral particles as pH-bufferIng agents, all four mInerals tested were able to maIntaIn the pH In the appropriate range for reductive dechlorInation of chloroethenes. However, complete dechlorInation to ethene was observed only with forsterite, diopside, and fayalite. Dissolution of andradite Increased the redox potential and did not allow dechlorInation. With forsterite, diopside, and fayalite, dechlorInation to ethene was observed but at much lower rates for the last two dechlorInation steps than with the positive control. This Indicated an Inhibition effect of silicate mInerals and/or their dissolution products on reductive dechlorInation of cis-dichloroethene and vInyl chloride. Hence, despite the proven pH-bufferIng potential of silicate mInerals, compatibility with the bacterial community Involved In In Situ Bioremediation has to be carefully evaluated prior to their use for pH control at a specific site.
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Utilization of silicate mInerals for pH control durIng In Situ Bioremediation of chlorInated solvent
2011Co-Authors: Elsa Lacroix, Alessandro Brovelli, David Andrew BarryAbstract:Chloroethenes such as tetrachloroethene (PCE) and trichloroethene (TCE) are among the most prevalent contamInants In groundwater due to their extensive use In Industrial processes. In Situ Bioremediation (ISB) is an attractive technology for removal of these compounds. It relies on an anaerobic process In which specialized bacteria obtaIn energy for growth usIng chloroethenes as an electron acceptor via organohalide respiration. EngIneered Bioremediation is achieved by stimulatIng these microorganisms through the addition of electron donor In the subsurface. This technology has been widely used for Bioremediation of chloroethene plumes and recent studies have Indicated promisIng results for Bioremediation of chlorInated solvent source zones. However, application of source zone ISB is still a significant technical challenge. One of the maIn issues is the groundwater acidification due to organohalide respiration and fermentation processes, which can Inhibit the activity of dehalogenatIng micro-organisms. The maIn objective of this work was to develop an efficient pH control strategy for chloroethene ISB by usIng the acid neutralizIng potential of silicate mInerals. To do so, modelIng and experimental approaches were combIned. A geochemical model, implemented withIn PHREEQC, was developed to select appropriate buffer candidates and to help determIne maIn parameters InfluencIng mIneral bufferIng capacity. The model Included chloroethene microbial degradation kInetics, mIneral dissolution kInetics and chemical speciation. Second, anaerobic microcosm experiments were performed to determIne the Influence of pH on dehalogenation. These microcosms were Inoculated with enriched consortia of dehalogenatIng bacteria and fed with PCE and hydrogen. Another set of microcosm experiments was carried out to compare the bufferIng capacity of ten silicate mInerals and to Investigate Interactions between mInerals and dehalogenatIng bacteria, e.g., the potential Inhibitory effect of mInerals on the dehalogenatIng activity. These microcosms were amended with 5 mmol l-1 of PCE and 4 g l-1 of mIneral with graIn sizes between 50 and 100 μm. The cultivation medium was modified such that the silicate mIneral powder was the sole pH buffer present. Chloroethenes, pH and dissolved cation measurements were conducted to determIne the system efficiency. Abiotic dissolution experiments were also performed to determIne mIneral dissolution rates In the absence of bacteria. The model confirmed that the efficiency of the system is dependent maInly on mIneral dissolution kInetic constants, equilibrium constants and reactive surface area. The geochemical model and literature parameter data were used to pre-select mInerals with a bufferIng capacity sufficient to counterbalance acidity produced by dehalogenatIng bacteria at a rate of 4 mmol l-1.d-1of chloride. Of the 31 silicate mInerals for which there were published kInetic data, 10 were identified as suitable candidates. The Inhibitory pH for the dehalogenatIng consortia was found to vary between 5 and 6. The last steps of the dechlorInation from DCE to ethene were more sensitive to pH than the first steps from PCE to DCE, as has been noted In other dechlorInation studies. Results of microcosm experiments with silicate mInerals demonstrated that, under the selected conditions, the pH control behavior and the impact on bacterial activity exhibited strong variations dependIng on the mIneral. Of the ten mInerals tested experimentally, three (olivIne, fayalite and diopside) maIntaIned the pH In the appropriate range, i.e., between 5.5 and 6.5 and led to complete transformation of PCE. For the other mInerals tested, either the acid neutralization capacity was Insufficient due to slow dissolution kInetics (glaucophane and staurolite) or dechlorInation activity was Inhibited by (unmeasured) compounds released durIng mIneral dissolution. Both modelIng and experimental results demonstrated the feasibility of usIng selected silicate mInerals as a bufferIng agent durIng ISB. However, the experimental results also revealed a mIneral-Induced potential Inhibitory effect that should be Investigated prior to application at a contamInated site.
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bufferIng agent for ph control durIng In Situ Bioremediation of chlorInated solvent source zones
SGM Annual congress 2010, 2010Co-Authors: Elsa Lacroix, D A Barry, Christof HolligerAbstract:Chloroethenes such as tetrachloroethene (PCE) and trichloroethene (TCE) are among the most prevalent contamInants In groundwater. Because of their low aqueous solubility, PCE and TCE are often present as dense non aqueous phase liquid (DNAPL) that can act as a long term source of groundwater contamInation. In Situ enhanced Bioremediation is an attractive technology for removal of PCE and TCE. It relies on a process called dehalorespiration In which dehalogenatIng bacteria reduce PCE to ethene, which is a harmless compound for the environment. Enhanced Bioremediation is achieved by stimulatIng the activity of these specialized bacteria through the addition of an electron donor. This method has been widely used for remediation of chlorInated ethene plumes for more than thirty years and recent studies have Indicated that it is a promisIng technology for Bioremediation of source zone. However, application of source zone Bioremediation is still a significant technical challenge. One of the maIn issues is groundwater acidification due to dechlorInation and fermentation processes thereby InhibitIng activity of dehalogenatIng micro-organisms. Objective of this project is to develop an efficient bufferIng strategy for source zone remediation. Utilisation of silicate mIneral as bufferIng agent has been Investigated through geochemical modelIng and batch experiment. A methodology to select appropriate silicate mInerals for pH control based on their kInetics properties and field characteristics has also been developed. A geochemical model, done with the chemical speciation code Phreeqc, IncludIng transport phenomena has been implemented to assess the Influence of silicate dissolution on acidity. PrelimInary results have demonstrated that certaIn mInerals belongIng to alumInosilicate (nephelIne) and magnesium iron silicate (olivIne) present kInetics fast enough to neutralize acidity typically produced durIng Bioremediation of DNAPL source zone. Experimental studies IncludIng mIneral dissolution and reductive dechlorInation by bacterial culture are currently performed to validate the results of this model.
