WO2012113376A1 - Method for in-situ microbial upgrading for long-term immobilization of inorganic pollutants in polluted waters - Google Patents

Abstract

The invention describes a method for the in-situ microbial upgrading for long-term immobilization of inorganic pollutants in polluted waters by arranging in sequence and controlling activated natural mineral formation processes by an in-situ treatment and in-situ upgrading of the polluted waters and the surrounding ground water conductor regions and zones and also the residues of extraction via metered introduction of a buoyant reactive material consisting of a buoyant solid support material in the form of a glass foam main body having a silicate coating made of hydrogen-releasing and/or sulphate-reduction-promoting substances and at least one additive, as loose material and/or by controlled flushing in as solids-water mixture for influencing the material conversion rates of autochthonous sulphate-reducing microorganisms, and for formation of pyrites and iron oxides. Using the invention, an effective and inexpensive method with low requirements in terms of apparatus is developed for in-situ microbial upgrading, which method, via arranging in sequence and controlling activated natural mineral formation processes, controls immobilization of the pollutants, guarantees in-situ cleaning which is effective in the long term and in the long term substantially decreases and prevents adverse effects on natural hydrochemical and geochemical ratios and interferences to ground waters, surface waters and the environment and also already mobilized inorganic pollutants at the source of pollution itself.

Description

 Process for microbial in-situ remediation for the sustainable immobilization of inorganic pollutants in polluted waters

The invention relates to a method for microbial in-situ remediation for the sustainable immobilization of inorganic contaminants in polluted waters by stringing and control of activated natural mineral formation processes by in-situ treatment and in-situ remediation of polluted waters and the surrounding aquifers areas and zones and the recovery residues by metered introduction of a buoyant reactive material, consisting of a buoyant solid support material in the form of a foam glass base with a silicate coating of hydrogen-releasing and / or sulfate reduction-promoting substances and at least one additive, as bulk material before flooding and / or controlled flushing as solid Water mixture during flooding to influence the metabolism of autochthonous sulfate-reducing microorganisms and to form pyrites and iron oxides.

In the extraction of mineral resources, in particular by leaching mining with acids, sour, oxidizing waters are generated in orders of magnitude due to the acid input and the natural Pyrite weathering. Mainly in landfills of extraction residues after cessation of production and dewatering are in accordance with the geological conditions inorganic pollutants, primarily metals, heavy metals and natural radionuclides, mobilized by acidification or acidification of the rock and dissolved in the water. These contaminated waters collect in the extraction residues, in the remaining mining buildings, in the surrounding mountains and in the leached aquifer. With these disturbances of the natural hydro- and geochemical milieu, aquifers and groundwater are put into poor chemical states, which are usually not improved by the natural self-purification processes or only over very long periods of time. Furthermore, such contaminated sites often lead to contamination of connected, non-mineralized aquifers and surface waters as well as remaining or to be rehabilitated underground facilities and

CONFIRMATION COPY Mining landscapes, so that without technical measures resulting in long-term damage to the environment and public goods.

In the treatment of areal water contamination is often a rehabilitation of the source of damage for geological, technical or cost reasons not possible.

 According to the state of the art, contaminated waters are collected and cleaned on-site with conventional water treatment plants (pump-and-treat). The purified water is either discharged into the receiving water or into the aquifer or returned to the Schadherd, optionally additionally the addition of clean water, so-called washes.

For the implementation of pump-and-treat- experienced complex technical equipment, such as extraction wells, feed pumps, piping systems and downstream extensive technical facilities for water treatment (ex site plant) required. At the same time, the operation of a water treatment by the constant consumption of energy and chemicals is associated with high operating costs and relatively labor-intensive. Furthermore fall as a result of water treatment constantly residues, which must be deposited usually with a high cost and the provision of an area.

When pump-and-treat is used, an initially intense, but short, phase of high-concentration first flush occurs, followed by a long period of low-concentration effluents, thus providing a useful life for successful purification of the contaminated waters of facilities and facilities required by decades. Especially in the period of low-concentration material discharges, conventional pump-and-treat processes are ineffective and unsuitable for a promising remediation of contaminated waters. With this process, the hydromechanical changes in geochemical conditions are only very slowly approaching their original in-situ ratios. During the indefinite duration of the process, in addition to unsatisfactory cleaning performance, further releases of pollutants and accumulations in the waters occur.

To minimize operating costs and process duration of the pump-and-treat process will be intensive on the development of in-situ remediation procedures worked. Combinations of the pump-and-treat processes with passive-acting barriers in the outflow of the source of damage or funnel-and-gate systems belonging to the passive technologies are known. When using the funnel-and-gate systems on the one hand, funnel walls are installed to focus the water flow, and on the other hand, permeable walls (gates) are installed transversely to the flow in the wastewater stream to treat the water flowing through, z. B. pollutants immobilized in absorber walls or degraded in reaction walls. The effectiveness of the passive barriers used depends mainly on the costs of the reactive material and the introduction of the barriers and the time in which the pollutants are actively eliminated from the waters. If the separation of the pollutants by precipitation, the precipitates put the pores of the reactive material, whereby the material is water impermeable and thus ineffective for the task to be performed. If the separation of the pollutants by adsorption is carried out, the free available surface, ie the particle size distribution of the material used is of crucial importance. In this case, the precipitation of water-insoluble carbonates or sulfates in the reactive material usually represents a limitation that puts the realization of the process in question. On the one hand, if the reactive material is too high in fineness, flow-through properties are no longer guaranteed after a short time or, on the other hand, if the pore volume is too small, the absorption capacity of the reactive material for pollutants is unacceptably low. However, it has also been found that only certain substances or groups of substances can be treated by the walls, which can be a considerable disadvantage, especially with complex contaminations. Likewise disadvantageous are the extensive structural measures required in the construction of reactive walls or funnel-and-gate systems, which are all the more costly, the deeper the groundwater aquifer to be cleaned is and the more extensive and areally the source of the damage.

Also known are active remedial measures z. B. via injection lances or infiltration wells by means of oxygen or the pumping of nutrient solutions try to stimulate the degradation of pollutants in situ or further force. The weak point of these measures lies however in the efficiency of the Mixing of contaminated water with the pumped substances. It takes a very long time until the slow and laminar flowing groundwater with the supplied materials mixed and especially in heterogeneous aquifers with preferred flow paths is often only insufficient mixing.

The applicability of established reactive-zone technologies in flooded mining pits is not given. Commonly used reactive materials can not serve as growth carriers for on-site microorganisms and precipitated mineral phases, either because they are not particulate, can not be transported in the flooded mines with the water stream, or because of their nature to mobilize pollutants, e.g. B. by release of pollutant-complexing molecules, can lead. In addition, common reactive materials do not react gradually and permanently. They do not guarantee secure immobilization while changing the environmental conditions. Conventional reactive materials are also used to enter substances that are foreign to groundwater, which complicates licensing on a large scale.

The object of the invention is to develop an effective and cost-effective and low-device method for microbial in-situ remediation for the sustainable immobilization of inorganic pollutants, primarily of metals, heavy metals, and natural radionuclides, in contaminated waters, by stringing and control of Activated natural mineral formation processes controls an immobilization of pollutants and guarantees a long-term effective in-situ purification as well

- Negative influences on the natural hydro- and geochemical conditions and thus further disturbances of the groundwaters, surface waters and the environment with pollutants are considerably reduced and prevented in the long term as well as actively developed for precast mining conditions

already mobilized inorganic pollutants immobilized in the focus itself a further release of inorganic pollutants from the rock matrix and a long-term discharge of mobile pollutants are prevented in the water - remain as reaction products in the water only substances that already occur naturally and are not harmful substances

 long-term, cost-intensive measures and expenditures, including conventional water treatment, disposal and landfill, limited in time or avoided

 - legal requirements, regulatory requirements and water regulations with regard to the reduction of concentrations of metals, heavy metals and natural radionuclides are safely met and guaranteed and the waters can be discharged with regulatory approval in receiving waters or can drain naturally.

According to the invention, the object is achieved by a method for microbial in-situ remediation for the sustainable immobilization of inorganic pollutants, primarily metals, heavy metals and natural radionuclides, in contaminated waters and to suppress ongoing pollutant mobilizations by stringing and controlling activated natural mineral formation processes in a reactive zone for an in-situ treatment and in-situ remediation of polluted waters and the surrounding aquifers areas and zones and the extraction residues a temporally and / or spatially metered introduction of a buoyant reactive material consisting of a buoyant solid support material in the form of a _. Foam glass base body with a silicate coating of hydrogen-releasing and / or sulfatred uktionsfördernden substances, as a bulk material and / or controlled by flushing introduced as a solid-water mixture, solved. The controlled flushing of the buoyant reactive material for in-situ treatment and in-situ remediation of the polluted waters takes place via naturally existing hydraulic connections and / or technically produced accesses and outlets with technical equipment and facilities.

The buoyant solid support material in the form of a foam glass base body with a silicate coating of hydrogen-releasing and / or sulfate reduction-promoting substances and at least one homogeneously incorporated into the silicate coating additive influences the substance conversions autochthonous sulfate-reducing microorganisms by reduction occurring and / or supplied sulfate and contributes to the formation of pyrite and iron oxides by gradual surface oxidation of buoyant reactive material by occurring oxygen by inflowing groundwater and / or gradual supply of oxygen through technical equipment and facilities in the Schadherd.

The buoyant solid support material in the form of a foam glass base body of glass flour and blowing agent, with a silicate coating of hydrogen-releasing and / or sulfate reduction-promoting substances and at least one homogeneously incorporated in the silicate coating additive, during the contact of the buoyant reactive material with polluted waters with hydrogen Rates from 0.0005 mol / kg ^* d to 0.05 mol / kg * d free and stimulates the autotrophic microbial sulfate reduction with reduction rates from 0.75 mg / l * d to 70 mg / rd. The metered introduced and / or controlled flushed buoyant reactive material is for the in-situ treatment and in-situ remediation of polluted waters in the form of a foam glass body with a particle size of 1 mm to 50 mm and a density of 0.2 g / cm ³ to 1 g / cm ³ and the silicate coating of hydrogen-releasing and / or sulfate reduction-promoting substances of water glass with a mass fraction of 20 weight percent to 50 weight percent and homogeneously embedded in the water glass powdered iron-carbon alloy with a particle size of 10 pm to 500 μηι at a mass fraction of 5 percent by weight to 40 percent by weight and at least one additive having a mass fraction of 5 percent by weight to 10 percent by weight based on the buoyant solid foam glass base body introduced. To improve convection and throughput, water can be purposely removed and / or supplied at suitable points from the polluted waters.

The in-situ treatment and in-situ remediation of contaminated waters and surrounding aquifers and zones and recovery residues is accomplished by sequencing and controlling activated natural mineralization processes or inducing sequences of mineral formation reactions consisting of sulfide precipitation, Pyritization and gradual surface oxidation of iron sulfides, introduced by the buoyant reactive material with a silicate coating of hydrogen-releasing and / or sulfate reduction-promoting substances.

The autotrophic microbial catalyzed sulfate reduction is effected by the stimulation of the metabolic rates of autochthonous sulfate-reducing microorganisms with reduction of occurring, site-specific and / or added sulfate by the silicate coating of hydrogen-releasing and / or sulfate reduction-promoting substances. The natural self-cleaning processes are stimulated and supported.

 The pyritization and gradual surface oxidation of the sulfides formed is carried out by on-site occurring oxygen and / or by gradual supply of oxygen through technical equipment and facilities, after the sulfide formation has taken place at a defined rate over a defined period of time.

The stimulated microbial sulfate reduction causes the conversion of the sulfate present in the Schadherd and / or fed into sulfide, which forms with harmful or inherent cations sulfidic minerals, preferably iron sulfides, wherein the microbial sulfate reduction proceeds with consumption of hydrogen ions. In this case, dissolved inorganic pollutants are immobilized by precipitation or co-precipitation (eg zinc, arsenic), sorption or surface reduction (eg uranium). The stimulated autochthonous sulfate-reducing microorganisms also cause a direct microbial uranium reduction. In addition, the sulfides formed as redox buffer, z. B. by reduction of dissolved oxygen used. The contact with oxidizing agents is controlled so that iron-II-hydroxides are formed, in the crystallization of which the inorganic pollutants, primarily metals and heavy metals, are trapped. The formation of new crystalline iron (hydr) oxides on the coatings prevents oxidative redissolution of reductively bound inorganic pollutants and serves as a sorbent for inorganic pollutants. This allows the sustainable immobilization of inorganic pollutants even after completion of the introduction of the buoyant reactive material to stimulate the metabolism of autochthonous sulfate-reducing microorganisms. The described method for microbial in-situ remediation by the juxtaposition and control of activated natural ineralbildungsprozessen the stimulated microbial sulfate reduction in a reactive zone for sustainable immobilization of inorganic pollutants applicable.

The metered introduction of a buoyant reactive material as bulk material and / or controlled flushing as a solid-water mixture in the Schadherd for microbial in-situ remediation for the sustainable immobilization of inorganic pollutants in contact with polluted waters run the following essential reactions / ₂ SiO ₂ + x H ⁺ -> Si (OH) _x pH buffering in the range

 > 4.5 by dissolving basic mineral components

Fe ⁰ + 2 H ₂ 0 - Fe ²⁺ + H ₂ + 2 OH ^' Release of elemental

 Hydrogen and reduction of the redox potential to <500 mV

SO4 ^{2 "} + H ⁺ + H ₂ - HS ^" + 4 H ₂ O Sulfate reduction, microbiologically catalyzed (microbial colonization of the reactive material)

Me ²⁺ + HS ^" ^ MeSj + H ⁺ metal sulfide precipitation

2 FeS + 0.5H ₂ O + 0.75 O ₂ -> FeS ₂ + FeOOH pyrite formation

FeS ₂ + 3 H ₂ 0 + 6 Fe ³⁺ -> 7 Fe ²⁺ + S ₂ O ₃ ^{2 "} + 6 H ⁺ Surface oxidation of pyrite

Fe ²⁺ + 2H ₂ O Fe (OH) ₂ + 2H ⁺ surface precipitation of Fe (OH) ₂ and subsequent pollutant reactions uranium reduction, precipitation of pollutant sulfides, arsenic precipitation in iron sulfide and pollutant adsorption on Fe (OH) ₂ and FeOOH. Key processes include the release of hydrogen through the reaction of elemental iron with contaminated waters and buffer reactions, which in the long term creates a shift in the hydro- and geochemical milieu towards neutral, intermediate conditions. The improvement of the hydro and geochemical environmental conditions are in turn a prerequisite for a significant course of the heterotrophic sulfate reduction processes. With the described method, a hydro- and geochemical milieu improvement, a pollutant fixation, the degradation of sulphate and a suppression of continuous pollutant mobilization is achieved in the source of the malady, and no foreign substances or hardly degradable substances or pollutants are introduced into the groundwater body. As reaction products remain in the aquifer and in the surrounding aquifers areas and zones and the extraction residues iron (hydr) oxides and sulfides, the mineral carrier material (silicates), metal (hydr) oxides and sulfides. These substances occur naturally in orebodies and aquifers.

embodiment

The exemplary embodiment describes a pilot experiment of the method according to the treatment of acid, strongly oxidizing flooding water of an underground pit. After completion of the leaching mining on uranium, the pit has been flooded in a controlled manner for several years. The hydrochemical environment of the flooding water is so far sour and oxidizing. A natural decrease of the pollutant concentrations in the flooding water takes place only very slowly by dilution and leaching. The flooding water is currently completely captured and cleaned in a conventional water treatment plant, costly and labor-intensive. According to available prognoses, the pollutant concentrations in the flooding water sink only very slowly, so that considerable expenses over many years for the water treatment are expected and estimated.

The pilot test is carried out in a column containing 25 kg of sandstone granules (<3 mm) and 4.5 kg of pit iron hydroxide sludge and 2.4 kg of reactive material consisting of a buoyant, solid foam glass body, glass powder, preferably recycled glass, and a Blowing agent, with a silicate coating, which consists of 40% sodium silicate, 30% cast iron powder (45 pm) and 9% Portland cement (CEM I 52.5) based on the foam glass base filled. After filling with the solids, the 1.45 m long column with a total volume of 65.6 l was gassed with N ₂ and charged with 8.0 l of acidic oxidizing flooding water from the pit. The flow through the Column is carried out under saturated conditions. The untreated flooding water is characterized by the following parameters:

 - pH 2.9

 - Redox potential 770 mV

 - Iron 67.7 mg / l

 - Arsenic 31 mg / l

 - Zinc 6.7 mg / l

 - uranium 8.9 mg / l.

 For the experiment, the conditions in the flooded pit are taken into account for the residence time of the flooding water in the column. The volume flow through the column averaged 0.25 l / d. Thus, the average residence time of the flooding water in the column is about 1 month.

 The experimental column was operated for 270 days. After about 1 month of experimentation until the end of the experiment, no more pollutants were detected in the column effluent at pH values 9 to 10 and redox potentials of about 330 mV and the following values were reached:

 - iron <0.04 mg / l

 - uranium <5 g / l

 - zinc <50 igf

 - Arsenic <10 pg / l.

 The contaminants of the solids (rock granules and Eisenhydroxidschlämme) and all pollutants registered with the flood water were retained in the column. Examination of the reactive material after the end of the experiment showed its microbial colonization, the appearance of pyrite and the enrichment of uranium and zinc (pollutants with the highest concentrations in the flood water) on the material surfaces. As a predominant pollutant binding form, the binding was determined in poorly crystalline iron (hydr) oxides.

Claims

claims 1. Method for microbial in-situ remediation for the sustainable immobilization of inorganic pollutants in polluted waters by juxtaposition and control of activated natural mineralization processes characterized in that for an in-situ treatment and in-situ remediation of polluted waters and the surrounding aquifers areas and Zones and the extraction residues by a temporally and / or spatially metered introduction of a buoyant reactive material as bulk material and / or controlled flushing as a solid-water mixture on naturally existing hydraulic connections and / or technically produced access and outlets with technical equipment and facilities consisting of a buoyant solid support material in the form of a foam glass base, of glass powder and blowing agent, with a silicate coating of hydrogen-releasing and / or sulfatred uktionsfördernden S. substances and at least one additive homogeneously incorporated in the silicate coating, for influencing the conversion of autochthonous sulfate-reducing microorganisms by reduction of occurring and / or supplied sulphate and / or occurring oxygen by inflowing groundwater and / or gradual supply of oxygen via technical equipment and facilities for formation of pyrites and iron oxides by gradual surface oxidation on buoyant reactive material releasing hydrogen at rates of 0.0005 mol / kg * d to 0.05 mol / kg ^* d during contact with polluted waters and autotrophic microbial sulfate reduction at rates of Stimulate 0.75 mg / l ^* d to 70 mg / l ^* d, in which the focus is deliberately introduced. 2. The method according to claim 1, characterized in that the metered introduced and / or controlled flushed buoyant reactive material for in-situ treatment and in-situ remediation of polluted waters in the form of a foam glass body with a particle size of 1 mm to 50 mm and a density of 0.1 g / cm ³ to 1 g / cm ³ and with a silicate coating of hydrogen-releasing and / or sulfate reduction-promoting substances from water glass with a mass fraction of 20 weight percent to 50 weight percent and homogeneously embedded in the water glass powdered iron-carbon alloy with a particle size of 10 μιη to 500 μιτι at a mass fraction of 5 weight percent to 40 Weight percent based on the floating solid foam glass base body and at least one additive with a mass fraction of 5 weight percent to 10 weight percent based on the floating solid foam glass base body is introduced. 3. The method according to claims 1 and 2, characterized in that specifically taken to improve the convection and the flow at suitable locations from the polluted waters water and / or supplied.