Soil Washing is a promising alternative treatment method for contaminated site remediation. An industry contaminated site - the OMEX site was selected for the study, and several extraction additives (chelating agent and surfactant) were used to investigate the application of soil washing for the removal of heavy metals and hydrocarbons. The interactions and transport of the contaminants were studied by bench-scale experiments for both heavy metals and hydrocarbons. Soil characterization was performed before the experiments.The soil characterization indicated that the OMEX soil contained large amounts of Pb, Zn (heavy metal) and total petroleum hydrocarbons (TPH). The contaminant concentrations were 986 mg/kg of Pb, 284 mg/kg of Zn, and 29000 mg/kg of TPH. The contaminated soil was also high in moisture content, organic content and total organic carbon (TOC). From soil analyses on different particle size fractions, most contaminants were concentrated in the fine soil fraction, below 150gm, which constituted about 35% by weight of the contaminated soil.Heavy metal removal by chelating agents was conducted first. The results showed that 3% EDTA solution offered the highest removal efficiency for both Pb and Zn. About 90% of Pb and 65% of Zn were removed by using 3% EDTA solution for 29 hours. The extraction kinetics proved to be slow, reaching equilibrium in a relatively long time (more than 10 hours). In soil washing the solution pH had some effect on the removal of both Pb and Zn with marginally better removals observed at a lower pH. The experimental study indicated that the ratio of washing solution volume to soil weight (LIS) had little effect on the percentage removal of both Pb and Zn.In hydrocarbons removal tests, experiments verified that surfactant solutions can be effective in removing organics from coarse soil fraction, while some amount of surfactants were ++ / adsorbed by fine soil particles. Anionic surfactants such as SIDS exhibited less sorption capacity than nonionic surfactants due to the electrostatic repulsion of the former. 4% SDS solution had the highest TPH removal efficiency for OMEX soil, but the 2% SIDS solution was used as it produced only marginally lower results than the 4%. The percentage removal of TPH was about 78% by using 2% SIDS solution. The TPH removal by SDS solution was observed to be a slow and non-equilibrium process. Higher solution temperature can improve removal efficiency of TPH from OMEX soil. Combined washing with a chelating agent and a surfactant was effective in removing both heavy metals and hydrocarbons. Removals of 78% Pb, 82% Zn and 81% TPH were obtained from OMEX soil in the combination test. However, the TPH concentration in fine soil was still very high after washing and would need further treatment.

Among current technologies used for the treatment of polycyclic aromatic hydrocarbons (PAHs) -contaminated media, adsorption has been reported to offer relatively high PAH removal efficiency while being rapid and cost-effective. Therefore, the main goal of this research was to assess and optimize the adsorption process for the removal of PAHs from contaminated water and soil using recoverable magnetic activated carbon-based composites. In the first phase, 6 different composites, 3 magnetic powder activated carbon (MPAC) composites and 3 magnetic granular activated carbon (MGAC) composites, were synthesized, and then, characterized using XRD, FE-SEM, EDS, and FTIR methods. The adsorption experiments revealed that all the recoverable MPACs and MGACs were capable of removing the PAHs from water, with removal percentages ranging from 87.2 to 99.3%. The PAH-loaded MPAC and MGAC with the highest PAH removal efficiency were also subjected to a series of desorption studies. The results indicated that the PAHs desorption was in the range 38.1-60.1% for low molecular weight (LMW) PAHs and 23.4 to 57.2% for the high molecular weight (HMW) PAHs. In the second phase, the adsorption kinetics and isotherms studies were performed on MPAC synthesized by a precipitation (MPAC-Prec.) method, which showed the highest PAH removal efficiency among the prepared magnetic activated carbons (MACs). The PAHs adsorption by MPAC-Prec. was rapid, reaching equilibrium in 6 h with the removal efficiency ranging from 95.6 to 100.0% under the conditions of this study. Among the studied kinetics models, pseudo-second order fitted the experimental data very well, implying that all the MPAC adsorption sites had an equal affinity for PAHs. The results of the kinetic studies also indicated that the greater molecular weight PAHs had a slower adsorption rate due to the slower transfer of their molecules to the MPAC adsorption sites. With an R2 in the range 0.73-0.96, the Langmuir model described the isotherms adsorption of LMW and HMW PAHs better than the other isotherms models. Furthermore, according to the Langmuir model, the maximum adsorption capacity of MPAC-Prec. was determined to be between 8.7 and 11.4 µg/mg for the LMW PAHs, and 8.4 and 20.2 µg/mg for the HMW PAHs. In the third phase, a series of soil washing tests using MGAC synthesized by co-precipitation (MGAC-CoP) method, were carried out to explore the effect of MAC on the PAHs removal from soil. The employed MGAC was the second most efficient MAC in the PAHs adsorption experiments (first phase of research), and it showed greater recovery from soil washing mixture compared to the MPAC-Prec. in the preliminary tests. The MGAC-CoP composite had a surface area and total pore volume of 837.9 m2/g and 0.5 cm3/g, respectively, which were approximately 10% lower than the bare GAC, according to BET test results. Soil washing parameters were optimized for the treatment of a real contaminated soil, which were MGAC-CoP dose of 2% (w/w), washing time of 24 h, liquid to soil ratio of 15:1, stirring speed of 100 rpm, pH of 8.3, and temperature of 25 ˚C. Under these optimized conditions, an average PAHs removal of 47.4% was obtained. Among the LMW and HMW PAHs, anthracene (ANT), and fluoranthene (FLUO) showed the highest affinity to MGAC during the treatment process, with 57.7% and 67.1% removal from soil, respectively. The thermodynamic studies revealed that the adsorption of the LMW and HMW PAHs onto MGAC in soil washing was non-spontaneous and endothermic as the values of Gibbs free energy (∆G˚>0) and Enthalpy change (∆H˚>0) were positive. In the fourth phase, the efficiency of MGAC-CoP in surfactant-enhanced soil washing for the PAH removal and the recovery of the surfactant solution was studied. The effective parameters of soil washing with the surfactant (Tween 80) were assessed using a real contaminated soil sample, and the results showed that 5% Tween 80, a liquid to soil ratio of 10:1, and a 72-hour washing time at 20°C were optimum operating conditions. Under these conditions, the average PAHs removal efficiency was 67.6%, which was higher than the 47.4% obtained for the same soil with no surfactant addition in phase 3. The possibility of recycling and reusing the Tween 80 solution was investigated by adding MGAC-CoP to the soil and surfactant solution mixture during the soil washing process. For this purpose, 5% Tween 80 and 2% (w/w) MGAC were used in 7 successive washing cycles, with no regeneration process for the MGAC composite. The results revealed that the combination of surfactant and MGAC was capable of removing 68.6, 70.7, 70.3, 61.6, 55.5, 50.2, and 39.4% of the PAHs from soil in the 7 washing cycles, respectively. Furthermore, the recycled Tween 80 and non-regenerated MGAC did not produce any waste or effluent after 6 times reuse in the treatment process, while successfully recovered and reused. This implies that soil washing with Tween 80 and MGAC is a very affordable, efficient, and practical method for remediation of PAH-contaminated soils.

The purpose of this research was to determine if two commonly used soil-washing extracting agents, namely EDTA and nitric acid, could be recycled and reused in subsequent soil-washing processes. This research focuses on the removal of lead from three real-world soils collected from military installations and the evaluation of a chelating polymer termed Type-M Forager® Sponge to recycle the soil-washing effluent. The results of this experiment indicate that the EDTA soil-washing effluent was as effective at removing lead from soil after two recycle processes as it was during the initial simulated soil-washing process. The nitric acid extracting agent solution, however, was neutralized during the first soil-washing simulation for each of the soils tested. Therefore, the Type-M Forager® Sponge was evaluated and proved to be effective as a waste minimization process for the acid soil-washing effluents.

Thesis (MScEng (Process Engineering))--Stellenbosch University, 2008. / A substance called CRUD (Chalk River Unidentified Deposit) was deposited together with gold tailings to the East Paydam tailings dam. Previous research conducted on the material has shown that the crud leaches Mn and Ni at concentrations that are above their acceptable risks limits as well as Zn which leaches at concentration slightly below its acceptable limits thereby posing an environmental risk. The main objective of the research was to test the hypothesis stating that soil washing in series with bioremediation can be used to remove the heavy metals from the material from the East Paydam tailings dam. Various laboratory and pilot scale tests were conducted to investigate critical soil washing and bioremediation parameters and their respective influence on the treatment process. Laboratory work involved column tests and batch tests. These tests were crucial in determining the critical parameters for the pilot scale tests such as the selection of the suitable lixiviant from the four that were investigated. The optimal concentration of the lixiviant was also determined together with the optimum soil: liquid ratio. These parameters were employed in the pilot scale tests. Pilot scale tests involved soil washing in series with bioremediation. The bacterial growth over the bioremediation period was also determined. Precipitation of the heavy metals from leachate was investigated by varying the pH and temperature. Results showed that the soil from the East Paydam can effectively be treated by soil washing in series with bioremediation. Oxalic acid was selected for soil washing of the payable slimes at a concentration of 0.001M. However, material that contains high amount of CRUD (deeper down the slime dam) required the relatively concentrated 0.1M oxalic acid and mechanical agitation. Bioremediation was determined to increase the amount of heavy metals that was leached from the material from the East Paydam slimes dam. Precipitation of the heavy metals at a pH of 12 achieved up to 98% removal of heavy metals from leachate.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2016-10-04T21:35:58Z No. of bitstreams: 1 2010 - Andr? Fern?o Martins de Andrade.pdf: 4307696 bytes, checksum: d679370ce9902b97ed91c98436c9103a (MD5) / Made available in DSpace on 2016-10-04T21:35:58Z (GMT). No. of bitstreams: 1 2010 - Andr? Fern?o Martins de Andrade.pdf: 4307696 bytes, checksum: d679370ce9902b97ed91c98436c9103a (MD5) Previous issue date: 2010-08-31 / UNIFOA / This study begun with a field survey in a one hectare area of petroleum drill waste (rocks and mud came from perforation) in Santa Maria do Oeste, in Paran? state, Brazil. It was verified different levels of metal contamination in the area, according to the surface position and with depth, with barium and lead over the investigation standard according to legislation. The highest level contaminated material was collected and used in a laboratory and greenhouse experiment at the campus of the Universidade Federal Rural do Rio de Janeiro, initiated on December, 2007, and completed on June, 2010. The objective was to evaluate the efficiency of remediation by washing contaminated soil (in situ and ex-situ) as well as phytoremediation. The waste washing ex-situ was simulated such as the contaminant would be removed from soil using a rotating device, with soil mixed with an ethylenediaminetetraacetic acid (EDTA) solution in the proportion of 1:10. Removal of lead and calcium increased proportionally to concentration of extractor (from 100 to 1500 mmol L-1). Removal of barium increased considerably above 600 mmol L-1. Iron and manganese showed little influence by different concentration of extractor. The soil washing in-situ was simulated by addition of two solutions of EDTA, with concentration of 150 and 300 mmol L-1, and the control (water). The material was incubated in plastic columns, for three weeks, after that volumes of 100 mL of deionized water were added weekly for three weeks, and after that samples were taken daily up to a total of ten. The leached was collected and the barium and lead content were analyzed, also other metals that could interfere with the extraction. The fractions (exchangeable, iron bound, organic matter bound, and residual) that metals were associates in the waste, before and after washing, were also determined. It was found, in the higher EDTA concentration, a small extraction of barium, while lead had about 20% of the total in soil extracted. The phytoremediation was carry on with two species, Brachiaria decumbens cv. Basilisk, an herbaceous plant, and Cordia africana, an arboreal. The plants growing up in vases with 4 kg of substratum were irrigated with deionized water and Hoagland nutrient solution (25% of ionic power). Two treatments were used in the phytoextraction induced with EDTA, in the concentration of 6 mmol L-1 (with one single application, and 3 dosages of 2 mmol L-1), plus the control. After 150 days for Brachiaria and 270 days for Cordia, the plants were collected, and analyzed (root and shoots) for heavy metal content. EDTA was effective to induce metal absorption, except for barium and calcium, where lead concentrated in the roots and barium in leaves (with highest concentration for EDTA applied in one dose). For Cordia, barium distributed equally in the plant sections, and lead concentrated in the roots. / Este trabalho iniciou-se com levantamento de campo na ?rea de despejo do res?duo de perfura??o de po?o de prospec??o de petr?leo (cascalhos e fluidos da broca) em Santa Maria do Oeste, Estado do Paran?, que possui ?rea aproximada de um hectare. Constatou-se que a ?rea apresentava diferentes n?veis de contamina??o de metais, estando, de acordo com sua posi??o no plano e em profundidade, com n?veis de b?rio e o chumbo na faixa de investiga??o, conforme norma legal. O material com maior n?vel de contamina??o foi coletado e utilizado em experimento de laborat?rio e casa de vegeta??o no campus da Universidade Federal Rural do Rio de Janeiro, a partir do m?s de dezembro de 2007 e finalizado em junho de 2010. Objetivou-se avaliar a efici?ncia da remedia??o atrav?s da lavagem do solo contaminado (in situ e ex-situ) bem como da sua fitorremedia??o. A lavagem do res?duo ex-situ foi simulada como aquela em que o contaminante seria removido do solo em um reator rotativo, onde o solo seria misturado em batelada a solu??o de EDTA na propor??o 1:10. A remo??o de chumbo e c?lcio aumentou com o aumento da concentra??o do extrator (de 100 a 1500 mmol L-1). A remo??o do b?rio aumentou consideravelmente acima de 600 mmol L-1; ferro e mangan?s foram pouco influenciados pelas diferentes concentra??es. A lavagem do solo in situ foi feita com adi??o de duas solu??es de ?cido etilenodiamino tetra-ac?tico diss?dico (Na2EDTA), de concentra??es 150 e 300 mol L-1, al?m da testemunha (?gua), em colunas est?ticas que, ap?s um per?odo de tr?s semanas de incuba??o, receberam 100 mL de ?gua deionizada a cada semana por tr?s semanas e, depois, uma coleta por dia at? perfazer 10 coletas. Os lixiviados foram coletados e analisados os teores dos contaminantes b?rio e chumbo, al?m de outros metais interferentes com a extra??o. Determinou-se, ainda, as diversas fra??es (troc?vel, ligada a ?xidos, ligada ? mat?ria org?nica e residual) em que esses metais se encontravam no res?duo antes e ap?s a lavagem. Foi verificada, na maior concentra??o de EDTA, extra??o insignificante de b?rio, enquanto o chumbo teve extra?do cerca de 20% do seu total no solo. A fitorremedia??o deu-se por meio do uso de duas esp?cies, uma herb?cea (Brachiaria decumbens cv. Basilisk) e outra lenhosa (Cordia africana). As plantas se desenvolveram em vasos com 4 kg de substrato, recebendo fertirriga??o (solu??o de Hoagland a 25% de for?a i?nica). Foram usados dois tratamentos na fitoextra??o induzida com EDTA, na concentra??o de 6 mmol L-1 em duas formas de aplica??o (3 aplica??es de 2 mmol.L-1 e uma de 6 mmol L-1) e a testemunha. Ap?s per?odo de desenvolvimento de 150 dias para a braqui?ria e de 270 dias para a c?rdia, as plantas foram coletadas tendo suas ra?zes e a parte a?rea analisada quanto ao conte?do de metais. Na braqui?ria, o EDTA foi efetivo na indu??o da absor??o dos metais com exce??o do b?rio e do c?lcio, tendo o chumbo se concentrado nas ra?zes e o b?rio nas folhas (com maior concentra??o no tratamento de aplica??o ?nica de EDTA). Na c?rdia, o b?rio distribuiu-se igualmente entre as partes analisadas e o chumbo se concentrou nas ra?zes.

Contaminated soils are a large issue worldwide and much effort has been made to find efficient remediation methods. At many contaminated sites, mixtures of dif­ferent contaminants with different properties are present, which may lead to addi­tional problems, and thus additional costs, during the remediation process. This thesis presents the results from soil remedia­tion of two mixed contaminated soils, containing explosives and heavy metals and polycyclic aromatic hydrocarbons (PAH) and arsenic, respectively. The re­sults demonstrate that bioremediation may be an efficient method for moderate explosives concentration, but that too high contaminant concentrations may prevent the biodegradation, measured by both chemical and ecotoxicological analyses. If the contaminant concentration is very high, soil washing with alkaline pH (~12, NaOH) may be a good alterna­tive, which was observed to remove both explosives and heavy metals. For a PAH and arsenic contaminated soil, little degradation of organics was ob­served during the bioremediation. However, the arsenic present was re-distributed in the soil, which could poten­tially lead to increased availability and thus in­creased risk for contaminant spreading. Soil washing at alkaline pH (~12-13; Ca(OH)2) with a combination of a biodegradable non-ionic sur­factant and a biodegradable chelating agent, executed at high temperature (50°C), reached treatment goals for both arsenic and PAH after 10 min treatment. Measurement of ecotoxicity using Microtox® demonstrated that remaining surfactant in the soil may lead to increased toxicity despite lower con­taminant concentrations. Soil is a basically non-renewable resource and thus re-cycling of remediated soil ought to be commonly occurring. Yet, the re-cycling of remediated masses has so far been limited in Sweden, mainly because of the risk of spreading of pollu­tant remains. However, a recent proposition from the Swedish EPA opens for re-cycl­ing, even though the thresholds are very con­servative. Risk assessment of the re­mediated soil includes the utilization of leach­ing tests to estimate the risk of spreading of remaining pollutants. A comparison of the leaching from four reme­diated soils using three different leaching solutions reveals that leaching of both heavy metals and PAH occurs. In addition, differ­ences between different legisla­tions were observed, which could imply that the same soil could be re-cycled in one country (the Netherlands) but not another (Sweden).

Ce travail de recherche porte sur l'optimisation des procédés de lavage de sol permettant le traitement des sites contaminés par des métaux lourds. Cette étude se concentre sur le cycle complet de ce type de traitement, incluant la possibilité de réutilisation et un traitement adapté de la solution de lavage de sol utilisée. La conception et l'exploitation d'un procédé de lavage de sol sont étudiées dans le but d'optimiser leur coût et leur efficacité. Dans ce but, les paramètres et la configuration du réacteur utilisé pour ce procédé sont étudiés en détail à travers des tests à l'échelle du laboratoire, et les cinétiques sont simulées par une modélisation mathématique. Les échantillons de sol utilisés au cours de cette étude proviennent de terres agricoles présentant une forte contamination en cuivre. Parmi plusieurs agents chélateurs de la famille des aminopolycarboxylates, il a été choisi d'utiliser l'acide éthylènediamine-N, N'-disuccinique (EDDS) pour sa biodégradabilité - largement rapportée dans la littérature – et son efficacité importante d'extraction des métaux lourds, y compris du cuivre. Le travail bibliographique a permis d'identifier les deux paramètres cruciaux pour l'optimisation du procédé de lavage de sol : le rapport molaire EDDS : Cu et le rapport liquide-solide (L/S). Des tests réalisés dans un réacteur à agitation continue (RAC) en fonctionnement discontinu ont permis d'étudier l'influence de ces deux paramètres sur le rendement et la cinétique d'extraction du cuivre. L’augmentation du rapport molaire EDDS : Cu a permis une meilleure amélioration de l'efficacité du procédé, comparée à l'augmentation du rapport L/S. Par ailleurs, les tests réalisés en discontinu ont clairement mis en évidence une première étape cinétique rapide au début du traitement, suivie d'une seconde étape d'extraction plus lente jusqu'à la fin du traitement. Il a donc été formulé un modèle empirique basé sur deux termes cinétiques. Les paramètres du modèle ont été calibrés puis validés grâce à deux séries de données expérimentales différentes. Ce modèle permet d'abord d'évaluer la validité de l'hypothèse d'un procédé reposant sur deux étapes cinétiques différentes. Cela représente aussi un nouvel outil pour prévoir l'efficacité du procédé en fonction de l'évolution du ratio molaire EDDS : Cu et du temps de traitement. Les coûts d'exploitation du procédé ont été minimisés en étudiant différentes configurations de traitement. En particulier, deux configurations en réacteur piston ont été analysées et comparées à celle en RAC. Les réacteurs pistons ont été simulés en utilisant plusieurs réacteurs en série et en variant les temps de rétention et le fractionnement de l'injection de la solution de lavage de sol. Comparés à la configuration en RAC, les résultats obtenus en réacteur piston ont montré une amélioration du rendement et de la cinétique d'extraction du cuivre, ainsi qu'une réduction de la quantité de solution de lavage utilisée. Pour finir, un procédé électrochimique a été mis en place pour le traitement et la récupération de la solution d'EDDS utilisée. Des tests en réacteur discontinu ont permis d'optimiser les paramètres de ce procédé (densité de courant, pH et conductivité de la solution de lavage de sol). La solution récupérée a ensuite été utilisée pour d'autres étapes de lavage de sol. Les résultats obtenus ont prouvé l'efficacité du traitement électrochimique pour la récupération de la solution d'EDDS, et permettent d'envisager l'application de cette technique pour réduire le coût des procédés de lavage de sol utilisant l'EDDS / The object of the present research work is the optimization of soil-washing processes applied to heavy metal contaminated soils. The work focuses on the whole cycle of these treatments, including the possible recovery and the proper disposal of the used washing solution. Both the design and the exploitation of a soil washing treatment are investigated, in order to maximize their efficacy, in terms of cost and process efficiency. At this aim process parameters and reactor configurations are studied in details through lab-scale tests, and the observed kinetics are simulated through mathematical modeling. Soil samples used for the experimental activity were collected from an agricultural field located in Southern Italy, mainly contaminated by copper. Among several Aminopolycarboxylate (APC) chelating agents, Ethylenediamine-N,N'-disuccinic acid (EDDS) was selected, for its recognized biodegradability, widely reported in literature works, and its efficiency as extracting agent towards several heavy metals, including Cu. Literature review allowed determining the two most important process parameters to be investigated for washing optimization. The two parameters were identified as EDDS : Cu molar ratio and liquid to soil ratio (L/S). In order to investigate the effect of these parameters on process kinetics and Cu extraction yield, batch washing tests in continuous-stirred tank reactor configuration (CSTR) were carried out. EDDS : Cu molar ratio increase was found to be able to enhance process efficiency more than L/S increase. Batch tests clearly displayed a first fast kinetic step at the beginning of the treatment, followed by a second slower kinetic extraction step, which lasted until the end of the treatment. According to this observation, an empirical mathematical model based on two-kinetic terms was formulated. Model parameters were firstly calibrated and then validated using two different sets of experimental data. The derived mathematical model was useful to assess the validity of the two-kinetic steps process hypothesis, and to provide a tool for process efficiency prediction depending on EDDS : Cu molar ratio and treatment time length. Exploitation costs of the process were minimized studying different treatment configurations. In details two Plug-Flow configurations were analyzed and compared to the CSTR one. The two Plug-Flow configurations were simulated using several reactors in series, varying the detention time of the reactors, and fractionating the injection of the washing solution. Achieved results displayed improvements in terms of Cu extraction yield and process kinetic for the tested Plug-Flow conditions compared to the CSTR one, and showed that the use of a Plug-Flow reactor allows to reduce the amount of required washing solution. Finally, an electrochemical process was tested for the treatment and the recovery of the spent EDDS solution. Batch tests were carried out to optimize electrochemical process parameters (e.g. current density, washing solution pH and conductivity). The recovered solution was also used for a multi-washing test. Results proved the effectiveness of the electrochemical treatment for EDDS solution recovery and its potential application as technique for EDDS-enhanced soil washing costs reduction

After soil washing in the former wood preservation industry, the concentration of As (arsenic) have increased in the groundwater. The purpose of this study was to investigate different parameters that could increase the mobility of As in the groundwater. The impact the soil wash has on the soil and it is effect on mobility will also be consider. This study will also show how As, Cu and Cr changes over time, however, the focus will be on As when the soil washing have been controlled by the As concentration. Soil and groundwater samples have been collected. Through filtration Fe (iron), Al (aluminium) and TOC (Total organic carbon) together with As have been analysed to determine a possible relation. Redox potential and As specification have also been analysed. As occur probably dissolved in the groundwater or together with DOC (Dissolved organic carbon). No link between colloids and complexes with Fe and Al together with As was found through filtration. Redox potential has no impact since the water was well oxygenated and As occurred as As(V). As and Cu follow the same time trend, while different for Cr. It is clear that the concentration of As increased in the groundwater after soil washing and that soil excavating have not the same problem with increased levels. The ground structure is changed and the clay mineral with adsorption surface is removed with soil washing. This could explain the increase of As in the groundwater.

L'objectif de cette thèse a été de développer une technologie pour l'assainissement des sols / sédiments sélénifères et d’étudier la réduction microbienne des oxy-anions de sélénium dans différentes conditions de respiration et de configurations du bioréacteur.Le sol sélénifère prélevé, dans les terres agricoles cultivées de blé au Pendjab (Inde), a été caractérisé et son lavage a été optimisé en faisant varier les paramètres tels que le temps de réaction, la température, le pH et le rapport liquide / solide. Afin de maximiser l'élimination et la récupération du sélénium à partir de ce sol, l'effet des ions compétiteurs et les composés oxydants comme les agents d'extraction pour le lavage du sol, ont également été étudiés. Bien que les agents oxydants aient montré une efficacité maximale d'élimination du sélénium (39%), la présence d'agents oxydants dans le lixiviat et le sol agricole peut augmenter le coût de leur post-traitement. Les plantes aquatiques, Lemma minor et Egeria densa ont été utilisées pour étudier la phyto-remédiation du lixiviat du sol contenant des agents oxydants. Cependant, l'efficacité d'élimination du sélénium par les plantes aquatiques a été significativement affectée par les fortes concentrations de ces agents oxydants dans le lixiviat du sol.Le rinçage du sol sélénifère a révélé un motif de migration du sélénium à travers la colonne du sol. La migration de la fraction de sélénium soluble de la couche supérieure vers la couche inférieure et sa réduction et son accumulation subséquentes dans les couches inférieures de la colonne de sol, ont été observées pendant le rinçage du sol. L'efficacité d'élimination du sélénium par la méthode de rinçage du sol a diminué avec une augmentation de la hauteur de la colonne. De plus, le lixiviat contenant des oxy-anions de sélénium obtenus à partir du lavage du sol, a été traité dans un réacteur UASB en faisant varier l'alimentation organique. Des effluents contenant moins de 5 μg de sélénium L-1 ont été obtenus, ce qui est conforme aux normes de l'USEPA pour la limite de rejet de sélénium dans les eaux usées.De plus, la bio-remédiation ex situ des oxy-anions de sélénium a été étudiée dans des conditions variables. Une bactérie aérobie (Delftia lacustris) capable de transformer le sélénate et le sélénite en sélénium élémentaire, mais aussi en composés d'ester de sélénium solubles jusque-là inconnus, a été isolée et caractérisée de manière fortuite. Alternativement, la bio-réduction anaérobie du sélénate couplé au méthane en tant que donneur d'électrons, a été étudiée dans des bouteilles de sérum et un filtre percolateur en utilisant des sédiments marins comme inoculum. Enfin, l'effet de la contamination d'autres oxy-anions chalcogènes, en plus du sélénium, a été étudié. La réduction simultanée de la sélénite et de la tellurite par un consortium microbien mixte ainsi que la rétention des nanostructures de Se et de Te biogènes dans l'EPS, ont été réalisées durant une opération de 120 jours dans un bioréacteur UASB / The aim of this Ph.D. was to develop a technology for the remediation of seleniferous soils/sediments and to explore microbial reduction of selenium oxyanions under different respiration conditions and bioreactor configurations.Seleniferous soil collected from the wheat-grown agricultural land in Punjab (India) was characterized and its soil washing was optimized by varying parameters such as reaction time, temperature, pH and liquid to solid ratio. In order to maximize selenium removal and recovery from this soil, effect of competing ions and oxidizing agents as chemical extractants for soil washing were also studied. Although oxidizing agents showed a maximum selenium removal efficiency (39%), the presence of oxidizing agents in the leachate and the agricultural soil may increase the cost of their post-treatment. Aquatic plants, Lemma minor and Egeria densa were used to study phytoremediation of the soil leachate containing oxidizing agents. However, the selenium removal efficiency by aquatic weeds was significantly affected by the high concentrations of these oxidizing agents in the soil leachate.Seleniferous soil flushing revealed the selenium migration pattern across the soil column. Migration of soluble selenium fraction from the upper to the lower layers and its subsequent reduction and accumulation in the lower layers of the soil column was observed during soil flushing. The selenium removal efficiency by the soil flushing method decreased with an increase in the column height. Furthermore, the soil leachate containing selenium oxyanions obtained from soil washing was treated in a UASB reactor by varying the organic feed. Effluent containing less than 5 μg L-1 selenium was achieved, which is in accordance with the USEPA guidelines for selenium wastewater discharge limit.Moreover, ex situ bioremediation of selenium oxyanions was studied under variable conditions. An aerobic bacterium (Delftia lacustris) capable of transforming selenate and selenite to elemental selenium, but also to hitherto unknown soluble selenium ester compounds was serendipitously isolated and characterized. Alternatively, anaerobic bioreduction of selenate coupled to methane as electron donor was investigated in serum bottles and a biotrickling filter using marine sediment as inoculum. Finally, the effect of contamination of other chalcogen oxyanions in addition to selenium was studied. Simultaneous reduction of selenite and tellurite by a mixed microbial consortium along with the retention of biogenic Se and Te nanostructures in the EPS was achieved during a 120-day UASB bioreactor operation

Soils contaminated by hydrophobic organic pollutants like polycyclic aromatic hydrocarbons (PAHs) are a common concern since they are extremely difficult to remove and their potential toxicological impacts are significant. As an alternative to traditional thermal or physical treatments, soil washing and soil flushing processes appear to be conceivable and efficient approaches, especially for higher level of pollution. However, the treatment of highly loaded soil washing/flushing solutions is another challenge to overcome. In that way, a new integrated approach is suggested: soil washing/flushing processes combined to an electrochemical advanced oxidation process (EAOP) in a combination with a recirculation loop (to save extracting agents) and/or a biological post-treatment step (to minimize energy cost).Extraction efficiency of the extracting agent like hydroxypropyl-beta-cyclodextrin (HPCD) is compared to the traditional non-ionic surfactant Tween 80 in synthetic and real soil washing solutions. A new simple fluorescent sensitive and selective quantification method is developed to monitor Tween 80 oxidation. Two EAOPs were compared: electro-Fenton (EF) and anodic oxidation (AO). Platinum (Pt) (in EF process) and boron doped diamond (BDD) (in both treatment) anodes are the respective electrodes employed to recycle effluents and to consider a biological post-treatment, respectively. Regarding the extracting agent recovery, the biodegradability evolution of effluent and the energy consumption (in kWh (kgTOC)-1) during EAOP, HPCD is more advantageous than Tween 80. However, in terms of extraction efficiency, costs of extracting agents and impact on soil respirometry, Tween 80 is much more efficient. By considering all these advantages and drawbacks, Tween 80 could still appear to be the best option