Bioremediation of contaminated mixtures of desert mining soil and sawdust with fuel oil by aerated in-vessel composting in the Atacama Region (Chile)

Since early 1900s, with the beginning of mining operations and especially in the last decade, small, although repetitive spills of fuel oil had occurred frequently in the Chilean mining desert industry during reparation and maintenance of machinery, as well as casual accidents. Normally, soils and sawdust had been used as cheap readily available sorbent materials of spills of fuel oil, consisting of complex mixtures of aliphatic and aromatic hydrocarbons. Chilean legislation considers these fuel oil contaminated mixtures of soil and sawdust as hazardous wastes, and thus they must be contained. It remains unknown whether it would be feasible to clean-up Chilean desert soils with high salinity and metal content, historically polluted with different commercial fuel oil, and contained during years. Thus, this study evaluated the feasibility of aerated in-vessel composting at a laboratory scale as a bioremediation technology to clean-up contaminated desert mining soils (fuel concentration>50,000 mg kg(-1)) and sawdust (fuel concentration>225,000 mg kg(-1)) in the Atacama Region. The composting reactors were operated using five soil to sawdust ratios (S:SD, 1:0, 3:1, 1:1, 1:3, 0:1, on a dry weight basis) under mesophilic temperatures (30-40 degrees C), constant moisture content (MC, 50%) and continuous aeration (16 l min(-1)) during 56 days. Fuel oil concentration and physico-chemical changes in the composting reactors were monitored following standard procedures. The highest (59%) and the lowest (35%) contaminant removals were observed in the contaminated sawdust and contaminated soil reactors after 56 days of treatment, respectively. The S:SD ratio, time of treatment and interaction between both factors had a significant effect (p<0.050) on the contaminant removal. The results of this research indicate that bioremediation of an aged contaminated mixture of desert mining soil and sawdust with fuel oil is feasible. This study recommends a S:SD ratio 1:3 and a correct nutrient balance in order to achieve a maximum overall hydrocarbon removal of fuel oil in the weathered and aged contaminated wastes.     

Geotechnical properties of some organoclays

The engineering characteristics of clay are dependant on its mineral and chemical structure. When the clay soils interacted with water, their volume and shear strength and compressibility properties change gradually. Large amount of decrease in terms of the shear strength of clay soils due to swelling is observed. In order to solve these problems, the stabilization of clay soils using chemical additives is a prevalent subject of research. In view of this, previous research studies have employed surface active surfactants to modify the fundamental properties of soft clays. In this study, surfactant–clay complexes (organoclays) were developed using a raw clay modification with four surfactants and their geotechnical properties were determined in laboratory conditions. Two of the surfactants are cationic (cetyl trimethyl ammonium chloride, denoted as CTAC and quaternised ethoxylated fatty amine, denoted as QEFA) and the others are anionic (linear alkylbenzene sulphonic acid, denoted as LABSA and sodium lauryl ether sulfate, denoted as SLES). The experimental results indicated that the geotechnical properties of organoclays show significant change when compared to those of natural clay. The specific gravities, unconfined compression strengths and maximum dry densities of all organoclays were decreased. Optimum moisture content and swelling pressure values were decreased in cationic surfactant modified clays. However, the optimum moisture content and swelling pressure values of anionic surfactant clays are increased. A direct shear test was performed to determine the shear strength of organoclays. The test results also showed that the internal friction angles of organoclays were increased. Additionally, the change in the hydraulic conductivity was found to be insignificant.     

Influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays

Adsorption of three surfactants of different nature, Triton X-100 (TX100) (non-ionic), sodium dodecylsulphate (SDS) (anionic) and octadecyltrimethylammonium bromide (ODTMA) (cationic) by four layered (montmorillonite, illite, muscovite and kaolinite) and two non-layered (sepiolite and palygorskite) clay minerals was studied. The objective was to improve the understanding of surfactant behaviour in soils for the possible use of these compounds in remediation technologies of contaminated soils by toxic organic compounds. Adsorption isotherms were obtained using surfactant concentrations higher and lower than the critical micelle concentration (cmc). These isotherms showed different adsorption stages of the surfactants by the clay minerals, and were classified in different subgroups of the L-, S- or H-types. An increase in the adsorption of SDS and ODTMA by all clay minerals is observed up to the cmc of the surfactant in the equilibrium solution is reached. However, there was further TX100 adsorption when the equilibrium concentration was well above the cmc. Adsorption constants from Langmuir and Freundlich equations (TX100 and ODTMA) or Freundlich equation (SDS) were used to compare adsorption of different surfactants by clay minerals studied. These constants indicated the surfactant adsorption by clay minerals followed this order ODTMA>TX100>SDS. The adsorption of TX100 and ODTMA was higher by montmorillonite and illite, and the adsorption of SDS was found to be higher by kaolinite and sepiolite. Results obtained show the influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays, and they indicate the interest to consider the soil mineralogical composition when one surfactant have to be selected in order to establish more efficient strategies for the remediation of soils and water contaminated by toxic organic pollutants.     

Effect of soil type and moisture content on ground heat pump performance: Effet du type et de l''humidité du sol sur la performance des pompes à chaleur à capteurs enterrés

Three different soils (sand, silty loam and silty clay) with five different degrees of saturation (0, 12.5, 25, 50 and 100%) were used in computer simulations. The performance of a ground heat pump system was found to depend strongly on the moisture content and the soil type (mineralogical composition). Alteration of soil moisture content from complete dryness to 12.5% of saturation strongly influences the ground heat pump performance, and any decrease of soil moisture in this range has a devastating effect on the coefficient of performance (COP). Therefore, it is beneficial to keep the soil moisture value as high as possible above dry soil conditions. Soil moisture content above the quarter saturation state leads to a much better heat pump performance. It was found, however, that the effect of moisture content variation above 50% of saturation on ground heat pump performance is relatively insignificant.     

Chitosan beads as barriers to the transport of azo dye in soil column

The development of chitosan-based materials as useful adsorbent polymeric matrices is an expanding field in the area of adsorption science. Although chitosan has been successfully used for the removal of dyes from aqueous solutions, no consideration is given to the removal of dyes from contaminated soils. Therefore this study focuses on the potential use of chitosan as an in situ remediation technology. The chitosan beads were used as barriers to the transport of a reactive dye (Reactive Black 5, RB5) in soil column experiments. Batch sorption experiments, kinetic and equilibrium, were performed to estimate the sorption behavior of both chitosan and soil. The chitosan beads were prepared in accordance with published literature and a synthetic soil was prepared by mixing quantities of sand, silt and clay. The synthetic soil was classified according to British Standards. Calcium chloride was used as tracer to define transport rates and other physical experimental parameters. Dye transport reaction parameters were determined by fitting dye breakthrough curves (BTCs) to the HYDRUS-1D version 4.xx software. Fourier Transform-Infra Red (FT-IR) spectroscopy was used to reveal the sorption mechanism. The study showed that chitosan exhibited a high sorption capacity (S_max = 238 mg/g) and pseudo-first sorption rate (k₁ = 1.02 h^?1) coupled with low swelling and increased retardation for the azo dye tested. Thus it has potential as a Permeable Reactive Barrier (PRB) for containment and remediation of contaminated sites.     

The effect of EDDS addition on the phytoextraction efficiency from Pb contaminated soil by Sedum alfredii Hance

Present study reports the results of three pot experiments, conducted to investigate the chelate-assisted phytoextraction of Pb contaminated soils. The optimum phytoextraction was observed when 2.5 mM ethylene diamine disuccinic acid (EDDS) was added in single dosage for 14 days to low Pb soil (treated with 400 mg kg⁻¹ soil). On the contrary, for high Pb soil (treated with 1200 mg kg⁻¹ soil), 5 mM EDDS concentration in single dosage for 10 days produced better results. Post-harvest effects of EDDS on the concentrations of available Pb and dissolved organic carbon (DOC) were significantly higher as compared with check (CK i.e. without EDDS addition), and consequently decreased with the passage of time. Our results suggested that chelate-assisted phytoextraction was more suitable for slightly contaminated soils.     

Linear elastic constitutive relation for multiphase porous media using microstructure superposition: Freeze-thaw soils

The constitutive relation derived in our previous work based on the microstructure superposition technique is implemented here for three-phase microstructure configuration to study the mechanical behavior of freeze-thaw soils. Three scenarios were considered for the frozen soils: frozen soil consisting of only two solids, soil skeleton and ice; frozen soil with soil skeleton, ice, and void; and frozen soil consisting soil skeleton, ice and pores saturated with fluid. The frozen soil studied is Alaska frozen soil mainly consisting of clay and silt particles at temperature about −10 °C. The effective elastic constants were calculated for the media under each scenario using two sets of elastic constants of soil skeleton (clay mineral). The modeled results were compared with Hashin-Shtrikman's upper bound solution and the experimentally measured data. In addition to be able to model the mechanical behavior of freeze-thaw soils, the derived constitutive relation, as indicated in the results of this study, could also be used as a tool in determining the microstructure of freeze-thaw soils by measuring the elastic constants of soil skeleton, the elastic properties and unfrozen water content of the media.     

Experimental investigation of the correlation between mass transfer and capillary potentials

The results of a determination of the mass transfer potential and capillary potential as functions of moisture content are presented, together with empirical formulas relating these potentials for sand and clay soils.     

Mobile system for extracting spilled hazardous materials from excavated soils

A technique was evaluated for the scrubbing or cleansing of excavated soils contaminated by spilled or released hazardous substances. Laboratory tests were conducted with three separate pollutants (phenol, arsenic trioxide, and polychlorinated biphenyls [PCB's]) and two soils of significantly different character (sand/gravel/silt/clay and organic loam).The tests show that scrubbing of excavated soil on site is an efficient approach for freeing soils of certain contaminants but that the effectiveness depends on the washing fluid (water + additives) and on the soil composition and particle-size distribution. Based on the test results, a full-scale, field-use, prototype system was designed, engineered, fabricated, assembled, and briefly tested under conditions where large (?2.5 cm) objects were removed by a bar screen. The unit is now ready for field demonstrations.The system includes two major soil scrubbing components: a water-knife stripping and soaking unit of novel design for disintegrating the soil fabric (matrix) and solubilizing the contaminant from the larger particles (?2 mm) and an existing, but re-engineered, four-stage countercurrent extractor for freeing the contaminants from smaller particles (<2 mm). The processing rate of the system is 2.3 to 3.8 m₃/hr (4 to 5 yd₃/hr), though the water-knife unit (used alone) can process 11.5 to 13.5 m₃/hr (15 to 18 yd₃/hr). The complete system requires auxiliary equipment, such as the EPA-ORD physical/chemical treatment trailer, to process the wastewater for recycling; under some circumstances, provision must be made to confine and treat released gases and mists. Treatment residues consist of skimmings from froth flotation, fine particles discharged with the used washing fluids, and spent carbon. The principal limiting constraint on the treatability of soils is clay content (high weight-percent), since breaking down and efficiently treating consolidated clays is impractical or not economically attractive. Most inorganic compounds. almost all water soluble or readily oxidizable organic chemicals, and some partially miscible-in-water organics can be treated with water or water plus an additive.During limited laboratory extraction tests, phenol was very efficiently removed from both organic and inorganic soils, whereas PCB and arsenic clung more tenaciously to the soils and were released less readily into the washing fluids. The extent to which the system has practical, cost-effective utility in a particular situation cannot be determined until preliminary, bench-scale lab work has been performed and acceptable limits of residual concentrations in the washed soil are adopted. Laboratory tests show that soil scrubbing has the capability of vastly speeding up the release of chemicals from soils, a process that occurs very slowly under natural leaching conditions.Note that this system requires excavation of the soil, which can subsequently be replaced or transported to a low-grade landfill. In situ washing of contaminated soil, a process in which the contaminated area is isolated for example, by grouting, and then water-flushed with removal of the wash water at a well-point is an alternative. The overall efficiency of the soil washing system is greater than that currently being achieved by in situ methods.Based on the laboratory program, a series of steps (water-knife size reduction; soaking; countercurrent extraction; hydrocyclone separation; and waste fluid treatment for reuse) was selected as the most suitable process sequence for the prototype system. The system was constructed for the U.S. (EPA) and is now being subjected to field evaluation. However, soils rich in humus, organic detritus, and vegetative matter can present special problems in the extraction of certain hazardous substances, which may not partition between the solid and fluid phases to a practical and necessary extent.     

Effects of dissolved organic matter from the rhizosphere of the hyperaccumulator Sedum alfredii on sorption of zinc and cadmium by different soils

Pot experiments were conducted to investigate the changes of the dissolved organic matter (DOM) in the rhizosphere of hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of Sedum alfredii and its effects on Zn and Cd sorption by soils. After planted with HE, soil pH in the rhizosphere reduced by 0.5-0.6 units which is consistent with the increase of DOM. The hydrophilic fractions (51%) in DOM from the rhizosphere of HE (HE-DOM) was much greater than NHE-DOM (35%). In the presence of HE-DOM, Zn and Cd sorption capacity decreased markedly in the following order: calcareous clay loam > neutral clay loam > acidic silty clay. The sorption isotherms could be well described by the Freundlich equation (R² > 0.95), and the partition coefficient (K) in the presence of HE-DOM was decreased by 30.7-68.8% for Zn and 20.3-59.2% for Cd, as compared to NHE-DOM. An increase in HE-DOM concentration significantly reduced the sorption and increased the desorption of Zn and Cd by three soils. DOM derived from the rhizosphere of the hyperaccumulating ecotype of S. alfredii could significantly reduce metal sorption and increase its mobility through the formation of soluble DOM-metal complexes.     

Recycling of solvent used in a solvent extraction of petroleum hydrocarbons contaminated soil

The application of water washing technology for recycling an organic composite solvent consisting of hexane and pentane (4:1; TU-A solvent) was investigated for extracting total petroleum hydrocarbons (TPH) from contaminated soil. The effects of water volume, water temperature, washing time and initial concentration of solvent were evaluated using orthogonal experiments followed by single factor experiments. Our results showed that the water volume was a statistically significant factor influencing greatly the water washing efficiency. Although less important, the other three factors have all increased the efficacy of water washing treatment. Based on a treatment of 20 g of contaminated soil with a TPH concentration of 140 mg g(-1), optimal conditions were found to be at 40°C, 100 mL water, 5 min washing time and 660 mg g(-1) solvent. Semi-continuous water extraction method showed that the concentration of the composite solvent TU-A was reduced below 15 mg g(-1) d.w. soil with a recovery extraction efficiency >97%. This finding suggests that water washing is a promising technology for recycling solvent used in TPH extraction from contaminated soils.     

Theoretical Study of Benzene Interaction on Kaolinite

Clay minerals represent a growing research area in the development of new materials. Clay and clay-based materials have been widely investigated in efforts to design adsorbents. Furthermore, adsorption has been applied in order to remove organics and as an important strategy to remediate soils and groundwater contaminated with petroleum hydrocarbons. Among clays, kaolinite, Al₂Si₂O₅(OH)₄, is a layered aluminosilicate of 1:1 clay minerals family. Therefore, we have performed semi-empirical AM1 and ab initio RHF/3-21G* calculations in order to investigate the benzene interaction on kaolinite surface. The cluster model method was employed. Benzene structure was fully optimized. Molecular orbitals and electrostatic potential was also analyzed. The ab initio and semi-empirical results shows the benzene molecule largely tilted in relation to the hydroxyl layer. The π orbital of benzene has changed slightly indicating the interaction through the hydroxyl and benzene π orbital.     

Effect of processing parameters and clay volume fraction on the mechanical properties of epoxy-clay nanocomposites

The influence of processing parameters and particle volume fraction was experimentally studied for epoxy clay nanocomposites. Nanocomposites were prepared using onium ion surface modified montmorillonite (MMT) layered clay and epoxy resin (DEGBF). Two different techniques were used for dispersing the clay particles in the epoxy matrix, viz. high-speed shear dispersion and ultrasonic disruption. The volume fraction of clay particles was systematically varied from 0.5 to 6%, and mechanical properties, viz. flexural modulus and fracture toughness, were studied as a function of clay volume fraction and the processing technique. The flexural modulus was observed to increase monotonously with increase in volume fraction of clay particles, while, the fracture toughness showed an initial increase on addition of clay particles, but a subsequent decrease at higher clay volume fractions. In general, nanocomposites processed by shear mixing exhibited better mechanical properties as compared to those processed by ultrasonication. Investigation by X-ray diffraction (XRD) revealed exfoliated clay structure in most of the nanocomposites that were fabricated. Morphologies of the fracture surfaces of nanocomposites were studied using a scanning electron microscopy (SEM). Presence of river markings at low clay volume fractions provided evidence of extrinsic toughening taking place in an otherwise brittle epoxy.     

Growth responses of three ornamental plants to Cd and Cd-Pb stress and their metal accumulation characteristics

Up to now, there was no document on ornamental plants that had been applied to phytoremediation, which can remedy contaminated environment and beautify it at the same time. Thus, the growth responses and possible phytoremediation ability of three ornamental plants selected from the previous preliminary experiments were further examined under single Cd or combined Cd-Pb stress. The results showed that these tested plants had higher tolerance to Cd and Pb contamination and could effectively accumulate the metals, especially for Calendula officinalis and Althaea rosea. For C. officinalis, it grew normally in soils containing 100 mg kg(-1) Cd without suffering phytotoxicity, and the Cd concentration in the roots was up to 1084 mg kg(-1) while the Cd concentration in the shoots was 284 mg kg(-1). For A. rosea, the Cd accumulation in the shoots was higher than that in the roots when the Cd concentration in soils was <100 mg kg(-1), and reached 100 mg kg(-1) as the criteria of a Cd hyperaccumulator when the Cd concentration in soils was 100 mg kg(-1). Their accumulation and tolerance to Cd and Pb were further demonstrated through the hydroponic-culture method. And A. rosea had a great potential as a possible Cd hyperaccumulator under favorable or induced conditions. Furthermore, the interactive effects of Cd and Pb in the three ornamentals were complicated, not only additive, antagonistic or synergistic, but also related to many factors including concentration combinations of heavy metals, plant species and various parts of plants. Thus, it can be forecasted that this work will provide a new way for phytoremediation of contaminated soils.     

Stabilization of cadmium contaminated soils using synthesized zeolite

This research investigates the effect of synthesized zeolite on stabilizing Cd-contaminated soil, using 0.01 M CaCl₂ leaching solution in batch and column experiments. The zeolite was synthesized from fly ash obtained from a Coal-Fired Power Plant, by adding 2 N NaOH and subjecting to 90°C for 24 h. The experiment used two groups of soil samples: (1) addition of Cd to four series of background soils: Pinchen, Jente, Erlin and Chengchung; (2) actual contaminated soils from Chungsing and Tsasta sites. The result of the batch experiment indicates that the addition of zeolite reduces Cd leaching from all types of contaminated soils. The more zeolite added, the lower Cd concentrations were detected in the leaching solution. The stabilized Cd in soils in the presence of zeolite is also demonstrated in the column experiments; the leachate contains insignificant Cd, and Cd depth analysis of the soil columns shows little Cd migration. For example, for Pinchen and Jente soils, after 12 and 49 pore volumes of leaching solution, the remaining Cd levels in the soils were 12% and 35%, respectively, of the original Cd values with no zeolite added, as compared to 96% and 99% in the presence of 16% zeolite. The higher cation exchange capacity of the zeolite/soil mixtures and higher pH are responsible for stabilizing Cd in soils. The effect is most useful in application to the acidic sandy soils to prevent contaminated heavy metals from leaching.     

Evaluation of quicklime mixing for the remediation of petroleum contaminated soils

Quicklime mixing is an established solidification/stabilization technique to improve mechanical properties and immobilise contaminants in soils. This study examined the effects of quicklime mixing on the concentrations and leachability of petroleum hydrocarbon compounds, in two natural soils and on a number of artificial sand/kaolinite mixtures. Several independent variables, such as clay content, moisture content and quicklime content were considered in the study. After mixing the soils with the quicklime, pH, temperature, moisture content, Atterberg limits and concentrations of petroleum hydrocarbon compounds were determined on soil and leachate samples extracted from the treated soils. Significant decreases in concentrations of petroleum hydrocarbon compounds were measured in soils and leachates upon quicklime mixing, which may be explained by a number of mechanisms such as volatilization, degradation and encapsulation of the hydrocarbon compounds promoted by the quicklime mixing. The increase in temperature due to the exothermic hydration reaction of quicklime when in contact with porewater helps to volatilize the light compounds but may not be entirely responsible for their concentration decreases and for the decrease of heavy aliphatics and aromatics concentrations.     

Design thermal values for unfired clay bricks

This paper reports on a laboratory and theoretical method for determining the design values for thermal conductivity and thermal resistance of unfired clay masonry bricks from both experimental and theoretical design point of view. The paper describes the methodology of obtaining these values using the measured lower and upper lambda limits. In order to determine the basic design thermal value and the design thermal resistance, a Laser-comp FOX 200 thermal conductivity meter equipped with WinTherm32an software package was employed for the laboratory data collection and analysis. Lime or Portland cement (PC)-activated Ground Granulated Blastfurnace Slag (GGBS) binder was used to stabilise Lower Oxford Clay (LOC) for unfired masonry brick specimen production. The major influence of the design values on the thermal conductivity and thermal resistance are illustrated in this study, using two different types of unfired clay bricks (LG and PG) at 2% moisture content prior to test. This paper covers conductivity test for each unfired clay bricks within the temperature range 2.5–17.5 °C. The measured thermal properties of the unfired clay bricks were compared to the design thermal properties of fired bricks. The results were used to predict the design thermal values of unfired clay masonry bricks at varied density and moisture contents prior to testing. A comparison of the measured thermal values for the unfired bricks to the design thermal values of fired clay bricks can also be seen. The results demonstrate that the unfired clay bricks were able to comply with the design thermal requirements for clay masonry units, suggesting that the unfired clay bricks can be used for low-medium cost housing and energy efficient masonry structures.     

Bioremediation of endosulfan contaminated soil and water -- optimization of operating conditions in laboratory scale reactors

A mixed bacterial culture consisted of Staphylococcus sp., Bacillus circulans-I and -II has been enriched from contaminated soil collected from the vicinity of an endosulfan processing industry. The degradation of endosulfan by mixed bacterial culture was studied in aerobic and facultative anaerobic conditions via batch experiments with an initial endosulfan concentration of 50mg/L. After 3 weeks of incubation, mixed bacterial culture was able to degrade 71.58+/-0.2% and 75.88+/-0.2% of endosulfan in aerobic and facultative anaerobic conditions, respectively. The addition of external carbon (dextrose) increased the endosulfan degradation in both the conditions. The optimal dextrose concentration and inoculum size was estimated as 1g/L and 75mg/L, respectively. The pH of the system has significant effect on endosulfan degradation. The degradation of alpha endosulfan was more compared to beta endosulfan in all the experiments. Endosulfan biodegradation in soil was evaluated by miniature and bench scale soil reactors. The soils used for the biodegradation experiments were identified as clayey soil (CL, lean clay with sand), red soil (GM, silty gravel with sand), sandy soil (SM, silty sand with gravel) and composted soil (PT, peat) as per ASTM (American society for testing and materials) standards. Endosulfan degradation efficiency in miniature soil reactors were in the order of sandy soil followed by red soil, composted soil and clayey soil in both aerobic and anaerobic conditions. In bench scale soil reactors, endosulfan degradation was observed more in the bottom layers. After 4 weeks, maximum endosulfan degradation efficiency of 95.48+/-0.17% was observed in red soil reactor where as in composted soil-I (moisture 38+/-1%) and composted soil-II (moisture 45+/-1%) it was 96.03+/-0.23% and 94.84+/-0.19%, respectively. The high moisture content in compost soil reactor-II increased the endosulfan concentration in the leachate. Known intermediate metabolites of endosulfan were absent in all the above degradation studies.     

Sorption behavior of cesium on various soils under different pH levels

In the present study we investigated the sorption behavior of Cs in four different soils (sandyloam, loam, clayloam and clay) by using batch experiment. Cs sorption characteristics of the studied soils were examined at 4 mgL(-1) Cs concentration, at various pH levels, at room temperature and with 0.01 M CaCl(2) as a background electrolyte. Among different soils the decrease of k(d) (distribution coefficient) of cesium, at all pH levels, followed the sequence sandyloam > loam > clayloam > clay, indicating that the particle size fractions and especially the clay content plays predominant role on sorption of Cs. The effect of pH on cesium sorption displays a similar pattern for all soils, depending on soil type. At acid pH levels less cesium was sorbed, due to a greater competition with other cations for available sorption sites. The maximum sorption of Cs was observed at pH 8, where the negative charge density on the surface of the absorbents was the highest. For all soils was observed significantly lower Cs sorption at pH 10.     

Evaluation of technology for wastes and soils contaminated with dioxins,furans, and related substances

The objectives of the U.S. EPA Dioxin-Engineering program are: (a) to conduct basic/ applied research on the behavior of 2,3,7,8-TCDD in contaminated soils, applying this knowledge to methods useful for the in-situ stabilization of such soils and investigating the viability of special organisms or chemical reagents for the destruction of this artifact and related toxic chemicals; and (b) to develop and evaluate, both in the laboratory and in the field, technologies for the detoxification, destruction, or control of PCDD-contaminated liquids and soils.Resource levels for the program amount to $3.3 million for 1984–1986 with an additional $7.2 million from the Superfund to accelerate this program and provide quality assurance/control support to the data gathering and certification efforts.In approximately one and one-half years, significant contributions have been made in the following areas:• Sorption/desorption characteristics of 2,3,7,8–TCDD in contaminated soils have been investigated.• In-situ stabilization techniques for soils are being evaluated.• Phanerochaete chrysosporium, a white rot fungus, has shown the ability to degrade 2,3,7,8-TCDD in laboratory experiments.• Shallow mines for contaminated soils have been evaluated and the concept appears technically and environmentally feasible.• Field testing of the EPA Mobile Incineration System in Missouri is continuing. Destruction and removal efficiencies of > 99.9999% were achieved; ash and scrubber water were delisted.• Alkali polyethelene glycolate reagents are being studied and results are encouraging.