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    • 专利摘要:
    Procedure to treat contaminated on-site soils that includes: - addition of zero-valent iron nanoparticles to a contaminated soil, in which the addition of the nanoparticles occurs sequentially in at least two stages, - Subsequent treatment of bioremediation by mixing said contaminated soil and treated with iron nanoparticles, with a compost that has been previously subjected to preincubation. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2676911A1
    申请号:ES201730092
    申请日:2017-01-25
    公开日:2018-07-26
    发明作者:Miguel María SÁNCHEZ ARZALLUZ；Amaia MENDOZA LARRAÑAGA；Maider ORUETA AZCARGORTA；Iñigo Abdón VIRTO QUECEDO；Isabel Sonsoles DE SOTO GARCÍA；José Luis VILAS VILELA；Alazne GALDAMES IGLESIAS；Eladio LLORENTE RAMOS；Eva LIZARRAGA ESLAVA
    申请人:Iragaz Watin S A；Iragaz Watin SA；
    IPC主号:
    专利说明:

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    DESCRIPTION
    Procedure to treat contaminated soils on-site
    Field of the Invention
    The present invention is encompassed in the technology of soil decontamination procedures, in particular of soils with mixed contamination.
    State of the art
    In many places in Europe, industrial activity has caused pollution of large volumes of groundwater and large areas of soil. Specifically, the European Environment Agency (EEA) estimated in 1999 between 300,000 and 1,500,000 the number of contaminated areas or areas in Western Europe. That is why it is a serious environmental problem that the society of the new millennium must face.
    Soil is one of the most sensitive and vulnerable sources of pollution; The existence of three phases in the soil (solid, liquid and gaseous), as well as the great diversity of materials that can constitute it, make it a very complex environmental compartment. In fact, within the environmental impact that industrial activity generates in our environment, the contamination of soils and associated groundwater can pose a serious risk to people's health and to the functioning of ecosystems, in addition to make it impossible to implement certain actions in the affected soils, with the consequent loss of their economic value.
    There are currently several techniques in the market for the recovery of contaminated soils. However, the option used mostly today is the excavation and disposal in landfill, as it is a quick option in time and economic, although environmentally unsustainable and inefficient. It also implies the displacement of pollution from one area to another, without addressing its treatment. The new remediation technologies must therefore offer an economically and technically viable alternative to the traditional excavation and disposal in landfill, the development of new decontamination technologies that energize the soil market being necessary.
    There are on the one hand decontamination techniques such as:
    - Bioremediation through compost (composting): Within the technologies developed for the remediation of contaminated soils, those based on biological mechanisms have always been the least intrusive, least expensive and environmentally correct. Bioremediation involves the addition of specific compounds or exogenous microbial populations to the contaminated soil to create the necessary conditions for the degradation of the contaminants. Bioremediation in these cases would have two objectives, on the one hand (1) isolate microorganisms capable of degrading or metabolizing a specific contaminant and (2) provide the conditions for this to be carried out in the most effective way, eliminating the contaminant. The application of compost as a bioremediating agent allows the contribution of nutrients and organic matter to stimulate microbial growth in contaminated soils with low natural fertility. Thus, reductions of up to 53% in total hydrocarbons have been achieved at pilot scale in 9 weeks;
    - Nanoremediation: Zero-valent iron nanoparticles (nZVI) have demonstrated their high capacity to react with -degrade, adsorb, or transform-a wide range of contaminants in soils and groundwater, such as chlorinated solvents, heavy metals, pesticides, etc. The main advantage over macro or micrometric iron is related to the high specific surface area of the nanoparticles, providing great reactivity and reducing the need for a quantity of reagent for the treatment of contamination. Up to now, its use has been related more to groundwater, so its contribution to soil decontamination is incipient and promising. The manipulation of matter on a nanometric scale is generating a growing interest and development worldwide due to its innumerable possibilities of application in very diverse sectors. Its smaller particle size and increase in specific surface area leads to an increase in reactivity and therefore decontaminating power.
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    The high environmental compatibility of zero-valent iron (nZVI) nanoparticles and their great reactivity can lead to a reduction in the duration of treatment time. These nanoparticles have demonstrated high efficacy as a decontaminating agent against different families of compounds of high toxicity and against a wide variety of families of pollutants, including: organohalogenated hydrocarbons, chlorinated pesticides such as lindane, organophosphates, nitroamines, compounds nitroaromatics, PCBs (polychlorinated biphenyls), organic dyes, inorganic anions such as nitrate and perchlorate, heavy metals such as chromium (VI), cobalt, copper, lead, metalloids such as arsenic and selenium, radionuclides such as uranium, etc. Iron nanoparticles (nZVI) produce oxidation-reduction (redox) reactions, so that in contact with the medium they oxidize quickly and donate their electrons to pollutants, reducing them and transforming them chemically into harmless by-products that are more stable, less mobile and / or less toxic.
    The potential offered by iron on a nanometric scale has led to the fact that during the last 15 years, zero-valent nano-iron has focused attention on multiple investigations as a tool for the treatment of contaminated water and soil. However, given the considerable amount of contributions in relation to the effectiveness of nZVI in aqueous media in the degradation of different families of pollutants in water decontamination, there is a great shortage of studies of the potential decontaminator of nZVI in soils that, recently , has attracted attention given the importance of soil health for the preservation of ecosystems, natural resources and human health (C. Fajardo, M. Diaz-Gil, G. Costa, J. Alonso, AM Guerrero, M Nande, MC Lobo, M. Martin, Residual impact of aged nZVI on heavy metal polluted soils, Sci Total Environ. 535 (2015) 79-84).
    Zero-valent iron (nZVI) nanoparticles can be used as a “slurry” (or a suspension), which makes it possible to inject by in-situ (field) operations.
    Pollutants when reduced by iron nanoparticles become more stable, less mobile and / or less toxic. Among the advantages associated with the use of nZVI for soil decontamination, there is the prospect of a notable reduction in the ratio of kilograms of product per volume of soil to be treated, thanks to the large area provided by nanomaterials with respect to macroscopic materials . Granular zerovalent iron has been used for years successfully, especially in permeable reactive barriers (PRBs) for the treatment of chlorinated hydrocarbons (ethanes and ethenes), metals and metalloids (arsenic, chromium and uranium), nitroaromatics and perchlorate treatment with results limited (PG Tratnyek, RL Johnson, Nanotechnologies for environmental cleanup, Nano Today 1 (2006) 44-48)).
    The treatment of metals by nZVI occurs through immobilization, a strategy that prevents transport through the layers of soil, rivers and groundwater. So far, studies on the immobilization of metals by nZVI soils have been carried out under "in vitro" conditions. Some of the most important trials have demonstrated the immobilization of Pb and Zn in soils treated with nZVI through leachate analysis (M. Gil-Diaz, LTOrtiz, G. Costa et al., Immobilization and Leaching of Pb and Zn in an Acidic Soil Treated with Zerovalent Iron Nanoparticles (nZVI): Physicochemical and Toxicological Analysis of Leachates, Water Air Soil Pollut (2014) 225-1990), as well as promising results to reduce the mobility of arsenic, antimony and some other metals and metalloids in contaminated soils. Experimental tests have shown an increase in the fixation of heavy metals in the soil, obtaining decreases in heavy metals such as lead (70%), antimony (90%) and arsenic (64%) in leachate.
    Uncertainty about the long-term destiny, transformation and ecotoxicity of nZVI in environmental systems is revealed as an important point. It is necessary to predict the fate and physical, chemical and biological consequences of using nZVI when used in contaminated sites. The nanoparticles increase fear for their ability to penetrate the food chain (bioaccumulation) and also for the possibility of facilitating the spread of other non-target contaminants present in the soil.
    Thus, the aforementioned composting technique has been successfully applied to soils contaminated with petroleum-derived hydrocarbons, solvents, chlorophenols, pesticides, herbicides and polycyclic aromatic hydrocarbons, but it is not effective for heavy metals, highly chlorinated substances, such as PCB, or for materials that are difficult to degrade biologically. However, it can be improved by joint application with nanoremediation, being
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    This is a novel aspect in the application of soil remediation technologies with mixed contamination (simultaneous presence of several organic and inorganic contaminants).
    The most commonly used technique to repair a soil contaminated by PAHs (polycyclic aromatic hydrocarbons) is bacterial bioremediation, followed by fungal and phytoremediation. Although there are numerous research papers related to this topic, in most cases they are preliminary laboratory tests and / or tests using contaminated soil in the laboratory.
    Mixed decontamination techniques are known, but by ground injection and bioremediation by bacteria (not on-site and with compost). For example, CN104801540A discloses a method of remediation of contaminated soils that involves coating the surface of zero-valent nano-iron particles with a layer of organic polymer, injecting the coated particles in the soil and injecting a bacterial solution into the soil; WO9849106A1 (1998) refers to a water treatment device comprising zero-valent iron and a culture of at least one hydrogenotrophic bacterium. US2004007524A1 discloses a supported catalyst for in situ remediation of soil and / or surface water contaminated with halogenated hydrocarbons, which comprises an adsorbent impregnated with zero iron.
    The difference between in-situ and on-site is that in-situ is injected into the ground without excavation. On-site technique means that an excavation and soil extraction is performed, but the treatment is carried out at the site itself. Although apparently in-situ it seems advantageous, however it presents difficulties in distributing the reagent in the subsoil properly. On-site treatment has the advantage that it facilitates the distribution of the reagent to be used since it is done mechanically.
    A technique that can provide better results and take advantage of the synergy of the previous two (nanoremediation and bioremediation) is a mixed on-site nanoparticle-bioremediation technique, by compost and with the addition of nZVI nanoparticles in at least two successive stages separated by a time interval. The synergistic effect of the use of nZVI and bioremediation by compost is a new strategy to restore contaminated soils by the application on site of two combined advanced technologies that can contribute to implement recovery alternatives that reduce the volume of waste generated in the Decontamination processes and therefore reduce the impact on the environment.
    The on-site mixed technique using nanoparticles-compost bioremediation comprising the addition of zero-valent iron nanoparticles to a contaminated soil sequentially (i.e. at least two additions of nanoparticles separated by a time interval), and later Bioremediation stage by mixing the soil with pre-incubated compost, helps reduce the concentration of hydrocarbons by up to 50% in 6 weeks. This indicates that the addition of nZVI nanoparticles can increase the efficiency of bioremediation, through mechanisms such as reducing the bioavailability of heavy metals.
    The decontamination of soils with mixed contamination is quite complex since, for example, some compounds may inhibit the biodegradation of hydrocarbons by interacting with the enzymes of soil microorganisms. On the other hand, PAHs that are recalcitrant molecules (not degradable, because they have halogenated, sulphonated, nitro etc groups) and more recalcitrant the more benzene rings they have, can persist in the soil for a long time. In addition, the generation of new compounds during the bioremediation process can also increase the toxicity of the mixtures during the process. The association of PAHs with other pollutants such as aliphatic hydrocarbons and heavy metals can prolong the residence time of PAHs in the environment. The presence of heavy metals inhibits the metabolic activity of the microorganisms responsible for the bioremediation of PAHs. The main factors that affect the biodegradation of PAHs are: temperature, pH, oxygen, nutrient availability, moisture and the bioavailability of molecules.
    The combination of nanoremediation-bioremediation methods developed in the present invention opens up the possibility of proposing as a viable alternative a chemical / biological oxidation-reduction sequence for the degradation of a wide range of contaminants.
    The combination of chemical technologies (iron nanoparticles) and biological (bioremediation) aims to optimize the profitability of soil remediation from three points of view mainly:
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    It can save the process, reduce the decontamination time and ensure the sustainability of the process. This requires a chemical intervention sized in such a way that there is a rapid reduction in the concentration of target pollutants and thus, a more effective bioremediation and a reduction in the time of the overall treatment. Similarly, the monitoring of the chemical activity process ensures sustainability, since it reduces the use of chemicals that can sometimes be aggressive to the soil and affect their normal functions.
    The combination of treatments that constitutes the present invention has the following advantages:
    - More versatile solutions for the remediation of soils with mixed contamination (that is, different types of contamination).
    - Reduction in terms of sanitation time, which subsequently translates into more economically attractive alternatives where time is a critical point or even a requirement (for example, urban development, recovery of abandoned industrial land, etc.).
    - More sustainable interventions (based on a balance between biological and chemical approaches), and therefore preserve soil functions and avoid harmful side effects.
    Description of the invention
    The present invention relates to an on-site method for treating contaminated soils characterized in that it comprises:
    - the addition of zero-iron nanoparticles worth a contaminated soil, so that the addition of the nanoparticles occurs sequentially in at least two stages,
    - and subsequent bioremediation treatment by mixing said contaminated soil and treated with the iron nanoparticles, with a pre-incubated compost.
    The expression "sequentially in at least two stages" means that zero-iron iron nanoparticles are added at least twice with a time interval between the at least two additions.
    The term "subsequent treatment" means chronologically after the addition of the zero-iron iron nanoparticles.
    In this report the expression "zero-valent iron nanoparticles", "iron nanoparticles", "nZVI nanoparticles", and "nZVI nano iron" have the same meaning.
    The term "suspension" and "slurry" are used herein with the same meaning.
    In this report the term "biopila" has its usual meaning in the art, that is, a controlled biological process, where organic pollutants are biodegraded and mineralized. Also the biopile is called the location where the process takes place, so that a biopile is also a lot or pile of contaminated soil in which it is stimulating and producing the degradation of pollutants through biodegradation.
    The stage of adding zero-valent iron nanoparticles is also called "nanoremediation"; while the stage of mixing soil contaminated with the pre-incubated compost is also called “bioremediation”. By virtue of this two-stage designation, the procedure can also be referred to as: mixed nanoremediation technique - bioremediation by compost.
    Prior to the stage of adding zero-valent iron nanoparticles, it is necessary to extract the soil to be treated by excavation and screen it by means of screening equipment arranged on the site, to remove thick elements that are not susceptible to decontamination such as stones , rocks, slags and other thick elements present.
    The screened soil is stacked on the site, in a bounded area.
    In addition, proceed before the first addition of iron nanoparticles to:
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    - waterproof the base on which to work with geotextile and HDPE laminate (high density polyethylene) or polyurethane paint (depending on the state of the surface of the site, with or without concrete screed, etc.), to prevent infiltration of leachates into the subsoil,
    - install drains for leachates from biopiles and rainwater, as well as a collection system for leachate in raft or tank,
    - have an aeration and turning system by mechanical means (backhoe with mixer) or by forced aeration,
    - install a system to cover the biopile to protect it from precipitation, using tarps or fixed covers
    Before starting the treatment it is necessary to perform a soil and compost characterization to establish the treatment design and calculate the amount of water, slurry, surfactant and compost to be added.
    The initial characterization includes physical-chemical parameters such as water retention capacity, moisture, soil texture, pH, electrical conductivity, concentration of C, N, P, K, concentration of hydrocarbons, PAH, heavy metals and other contaminants, as well. such as soil ecotoxicity (if required).
    According to specific embodiments of the procedure, the stages thereof or treatment stages are:
    1. - Design and implementation of a treatment protocol
    2. - Site conditioning
    2.- Extraction and sieving of the soil to be treated
    4. - Physical and chemical characterization of the soil
    5. - Selection and characterization of the compost
    6. - Treatment with nanoparticles
    7. - Pre-incubation
    8. - Bioremediation
    9. - Final evaluation and soil reuse
    In general, the addition of zero-iron nanoparticles valid to the contaminated soil can be carried out in solid form or in suspension form, preferably it is carried out in the form of a suspension or slurry. According to the present invention, the addition of zero-valent iron nanoparticles is carried out sequentially in at least two stages with a time interval between them of at least 3 days. The 3-day period between sequential additions is due to the nanoparticles reactivity lasting a maximum of 72 hours.
    The addition in the form of slurry can be done by irrigation and mechanical mixing (by concrete mixer or backhoe). The treatment of heavy metals by nano-iron occurs via immobilization, without physical destruction, also through the nano-iron the degradation of contaminating organic compounds occurs by reduction reactions.
    It is important to carry out a homogenization process during the addition of the zero-valent iron nanoparticles by means of a mechanical stirrer and then let it rest without any intermediate manipulation, to avoid excessive aeration of the soil and with it a possible oxidation of the nZVI nanoparticles (the nanoparticles nZVI in contact with air oxidize and lose their reactive properties).
    Preferably, during the process of adding nanoparticles as slurry, water will be added to facilitate the mixing and homogenization of the nanoparticles with the soil, and to ensure anaerobic conditions that favor their performance. The mixed quantities of soil / slurry / water will be predetermined and previously established by protocol, so that the nanoparticles are applied according to certain percentages, favoring anaerobic conditions but guaranteeing a soil moisture below 100% of the field capacity (limit maximum
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    established for bioremediation). Field capacity is the point reached by a soil after being saturated soil and once the water has moved by gravity to the subsoil, until it reaches a point where the drainage is so small that the water content of the soil it stabilizes. 100% of the field capacity is a limiting factor in bioremediation, therefore this factor must be taken into account when calculating the amount of water to be added with the nanoparticles so that it is not excessive
    An important advantage over the state of the art and for the treatment to be more effective is that the nanoparticles are added sequentially, and at least in two stages. According to the invention, between 0.1% and 5% by weight of slurry on wet soil mass, of zero-iron iron nanoparticles, preferably 1% by weight of slurry of zero-iron iron nanoparticles, are first mixed with the soil. with respect to the wet mass of the soil, and 3 days later they mix with the soil between 0.1% and 5% by weight of slurry on wet mass of soil, of zero-valent iron nanoparticles, preferably another 1% in Slurry weight of zero-iron iron nanoparticles in relation to the wet mass of the soil. Treatment with nanoparticles in sequential additions, that is, successive and separated by a time interval, has the advantage that it significantly reduces the concentration of PAHs. This fact indicates that nanoparticles may have preferential interactions with other soil components, being consumed before interactions with contaminants occur, so that, by successive additions, the treatment is more effective.
    On the other hand, the retention of the particles in the soil is very interesting because the iron nanoparticles (0) are able to react with the metals adsorbing them in their crust, and consequently, the heavy metals, together with the nanoparticles, remain retained in the soil matrix, immobilizing them and preventing them from being incorporated into other media.
    Analytical results of leaching at the end of the nanoparticles' time on a contaminated soil reflect an increase in the fixation of heavy metals in the soil when applying nZVI, which can result in decreases in the concentration of heavy metals such as lead (up to 68%), antimony (up to 90%) and arsenic (up to 64%) in the leachate.
    Therefore, in the mixed technique on-site and according to the present invention, zero-iron nanoparticles will be applied to soil contaminated prior to the treatment of bioremediation by compost.
    After finishing the treatment with nanoparticles, the bioremediation stage will begin. This stage begins with the pre-incubation of the compost. This compost will then be mixed with the contaminated soil, previously treated with nZVI nanoparticles.
    The pre-incubation of the compost is carried out by the controlled addition to a compost of a small portion of the selected contaminated soil. The pre-incubated or enriched compost consists of a compost designed tailored to the site to be treated, which will serve as a starter culture for the subsequent degradation of organic compounds in the bioremediation process.
    All necessary compost for the bioremediation treatment should be pre-incubated. In order to calculate the amounts of compost and soil destined for pre-incubation, it will be necessary to previously calculate the moisture value and the water retention capacity of the soil and compost, since the mixture (made based on dry mass) must have an amount of water preferably in the range of 70% -100% of the field capacity.
    Pre-incubation will be carried out at a temperature ranging from 20-35 ° C, mixing between 75% and 85% of dry compost mass, for example 80% of dry compost mass, with between 15% and 25% of dry mass of contaminated soil, for example with 20% dry mass of contaminated soil. Preferably, it will be carried out at a temperature ranging between 20-35 ° C, mixing 80% of dry compost mass with 20% of dry mass of contaminated soil. Compost is a compost from organic waste. It can be an example of FORM (Selective fraction of municipal organic waste) or compost of sewage sludge, always meeting established criteria for selection and characterization of compost (pH between 7-8, electrical conductivity between 4-5 mS / cm , K between 10,900-15,000 mg / kg, P between 300-9,000 mg / kg, N between 1.5-2.5%, C / N between 8-15, and absence of contaminants). If the compost meets the established requirements, the necessary amount of compost must be calculated based on the established mixtures and the amount of soil to be remedied.
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    Pre-incubation will be carried out in the form of biopiles, on the waterproofed floor and with a protective coating to prevent the entry of rain. During pre-incubation, weekly aeration and weekly moisture analysis should be performed by heating samples at 1052C for 24 hours.
    After the necessary pre-incubation time, which can be between 12 days and 20 days, preferably 2 weeks, both mixtures (contaminated soil treated with nZVI, and pre-incubated compost) will be joined to form a biopile.
    For the first bioremediation phase, it is necessary to characterize a series of parameters, the evolution of which will be controlled throughout the process, which include:
    - The water retention capacity and moisture content of the pre-incubated mixture.
    - The texture.
    - The conditions of pH and presence of soluble salts (electrical conductivity).
    - The concentrations of C, N, P and K in the soil and the pre-incubated mixture.
    - The concentration of hydrocarbons, heavy metals, and other target pollutants.
    - Soil ecotoxicity (earthworm mortality test Eisenia foetida and emergency test and seed growth of Lactuca sativa), if required.
    Thus, with the results obtained after pre-incubation, the masses and conditions of the mixture will be calculated for the realization of the biopiles in which the bioremediation will be carried out, as well as the needs of amendments and physical corrections (humidity) that will be carried out carried out in the treatment, from the data obtained, the estimate of the amount of soil to be remedied and the necessary compost, as well as its characteristics. This will obtain the final volume of the biopiles and their configuration will be designed.
    For the calculation of the values of mass, volume and humidity of the biopiles, the following will be taken into account:
    1. Moisture data and water retention capacity of the initial compost and contaminated soil may undergo rapid variations. The calculation of these parameters should be done as close as possible in time to the beginning of the treatment.
    2. The density of the fine fraction of the soil (once the coarse elements have been removed) must be estimated from the soil texture, and from the compost from its own calculation and from the compost producer data.
    3. It will be necessary to calculate the total mass of soil extracted and screened, to establish the necessary quantities of reagents (nanoparticles-compost), amendments and water. The final volume of the biopiles will be calculated from the masses and densities of soil and compost.
    These data will have to be verified during the beginning and execution of the biopiles.
    The mixture of contaminated soil with the pre-incubated compost occurs in a proportion that varies between 55% to 65% in dry mass of soil and between 35% and 45% in dry mass of pre-incubated compost. Preferably, they are mixed in a proportion of 60% dry mass of contaminated soil and treated with zero-valent iron nanoparticles, with 40% dry mass of pre-incubated compost.
    The surfactant mentioned above is necessary in case of having a very hydrophobic contamination, in which case it is applied at the time of bioremediation and in a proportion up to a maximum of 10% by weight of surfactant with respect to the water added.
    During the bioremediation treatment, weekly aeration of the biopiles and weekly moisture analysis should be performed by heating samples at 105 ° C for 24 hours.
    The temperature during the bioremediation treatment should be maintained in a range that ranges between 20-35 ° C and not lower than 10 ° C. In the case of not being able to control the temperature of the test, it is recommended to perform this type of tests during the spring-summer months.
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    As a control measure during bioremediation, the humidity and temperature of the biopile will be analyzed twice a week. The following control parameters will also be analyzed with a monthly frequency:
    - pH: basic monitoring parameter, the usual range is 7-8. It should be taken into account that in acidic soils the bioavailability of metals is greater than in basic soils;
    - electrical conductivity: basic monitoring parameter, the usual range is 4-5 mS / cm.
    - High salinity can cause toxicity phenomena and stop microbial activity.
    - concentration of nutrients C, N, P and K: basic monitoring parameter, the optimal ratio for remediation is established in a C: N: P ratio of 100: 10: 1.
    - microbial respiration: indicator of biological activity in the biopile and therefore of the existence of degradation activity of the contamination. It is obtained through volumetry PEC / EN / A-091, based on ISO 16072: 2002.
    During the first days of treatment, more frequent (biweekly) controls of these parameters may be performed, since during this period bioremediation presents the most active phases.
    From the second month, the controls can be monthly.
    The control of the concentration of pollutants to be degraded (TPH C10-C40 - TPH: total petroleum hydrocarbons-, fraction of aliphatic and aromatic hydrocarbons, PAHs ...) can be carried out every 2 months.
    Finally, the ecotoxicity, if required (Eisenia foetida OECD 207 earthworm mortality test and emergency and Lactuca sativa OECD 208 seed growth test) will be analyzed at the beginning and end of the treatment. The ecotoxicity tests are carried out in order to verify that the average lethal or effective concentration (CL (E) 50) of the soil samples is within the values established by Royal Decree 9/2005, as well as to evaluate the evolution of toxicity throughout decontamination treatments. A contaminated soil is defined when the average lethal or effective concentration CL (E) 50 for soil organisms is less than 10g of contaminated soil / Kg.
    The following table 1 shows the optimal frequencies of parameter control: Table 1
     Control parameter  Month Frequency
     0 1 2 3 4 5 6 End
     Temperature  X X X X X X X X X 2 / week
     Humidity  X X X X X X X X X 2 / week
     C, N, P, K  X X X X X X X X X Monthly
     pH and CE  X X X X X X X X X Monthly
     Pollutant concentration  X X X X X Bimonthly
     Microbial breathing  X X X X X X X X X Monthly
     Ecotoxicity  X X Two controls (start-end
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    The samples taken should be composite samples. The number of samples or subsamples are estimated from the variability of the parameters observed in previous tests.
    Sample fractions of about the same size should be taken at different points and at different heights or depths of the whole stack. The location and number of extractions must take into account the way in which the stack is built, its shape and the possibility of internal segregation. Sampling should be carried out with the help of a manual catcher, a shovel or a sampler for solids at the deepest point of each hole.
    Below are the appropriate values for some essential parameters of pre-incubation and the bioremediation phase with compost:
    PARAMETER OPTIMAL INTERval FOR PRE-INCUBATION AND
    BIORREMEDIATION
    Humidity Between 70 and 100% of field capacity.
    Temperature Between 20 - 35 ° C and not lower than 10 ° C.
    Nutrient content Recommended ratio C: N: P 100: 10: 1
    The expected duration of the procedure is approximately as shown in the following table 2: Table 2
     Month 1 Month 2 Month 3 Month 4 Month 5 Month 6 Month
     Stage I: Preparatory phase: Previous analysis, design of the remediation project, preparation and adaptation of facilities  X X
     Stage II: Addition of nanoparticles    X
     Stage III: Pre-incubation      X
     Stage IV: Bioremediation stage: biopiles      X X X X X
     Stage V: Final evaluation, reports and possible corrections              X
    The total duration of the treatment will depend on the level of initial contamination of the soil to be remedied, as well as the place and time of the year in which the treatment will be carried out, that is, on the degrees accumulated during the bioremediation process. Thus, in environmental conditions it is preferable to perform bioremediation in spring-summer, when it is easier to control the optimum temperature and humidity conditions in the biopiles. In winter autumn, low temperatures and increased humidity in the biopiles cause the slowdown of biological activity.
    The on-site technique of the present invention does not prevent excavation. But if transport outside the plot is avoided, avoiding the risks inherent in the transport of contaminated materials, and the reuse of the soil on the site is allowed.
    Brief description of the figures
    Figures 1-I and 1-II show the result of the evolution of aliphatic hydrocarbons for the two soils of the test of Example 2, where 1-I corresponds to biopile I and 1-II corresponds to biopile II. In the figures the legends are: a: aliphatic fraction> C10-C12 b: aliphatic fraction> C10-C40
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    c: aliphatic fraction> C12-C16 d: aliphatic fraction> C16-C21 e: aliphatic fraction> C16-C35 f: aliphatic fraction> C21-C35 g: aliphatic fraction> C35-C40
    Examples
    Example 1 - Decontamination of a soil at pilot plant scale by means of the bioremediation technique with compost and by two mixed techniques
    It was prepared to carry out the experimental tests of the project, of the site called “PERI 05 Lutxana-Burtzena”, located in the municipality of Barakaldo. It is an area located next to the Cadagua river near its confluence with the Nervion river, with direct tidal influence, and which has been occupied in the past by potentially polluting industrial activities (ship scrapping, metal recovery, fertilizer production, etc...).
    Parallel small scale analog tests were conducted in parallel on the same contaminated soil:
    1) only bioremediation with compost
    2) mixed nanoremediation technique - bioremediation with compost sequentially with a single addition of zero-valent iron nanoparticles
    3) mixed nanoremediation technique - bioremediation with compost, but with the mixture of the nanoparticles simultaneously with the mixture of contaminated soil and pre-incubated compost
    In mixed media, only 1 addition of nanoparticles was applied.
    An initial sampling and analysis of the contaminants contained in the soil of the potentially contaminated site was carried out.
    There was also the “Detailed investigation of soil quality” carried out at said site by Ondoan S. Coop in 2002, which indicated the presence of both organic and inorganic contaminants. At different points in the enclave, contamination by parameters such as heavy metals (Cr, Ni, Zn, Cd, Pb, As, Hg, Cu), aromatic polycyclic compounds HAPs (benzo (a) pyrene, fluorantene, phenanthrene, naphthalene) was detected , PCBs (polychlorinated biphenyls), total hydrocarbons in the range C10-C40, BTEX (volatile organic compounds whose origin is related to the presence of gasoline) and phenols among others.
    After a detailed analysis of the site study, soil samples were extracted at various points strategically chosen within the bounded terrain. A total of eleven calicatas were made by excavation, extracting samples of the different layers of each one, proceeding to the characterization of its polluting load.
    For each sample we analyzed: heavy metals, total oil hydrocarbons (C10-C40), and polycyclic aromatic hydrocarbons.
    It was found that the sample with the highest concentration of total hydrocarbons was the soil of calicata 9 with a concentration of 23,000 mg / kg. Therefore, and exceeding the value of 500 ppm (Basque Law 4/2015) it was considered an altered soil.
    The polluted soil chosen also showed high levels of heavy metals such as lead and arsenic, and a very high concentration of PAHs and Total Hydrocarbons, considerably exceeding the industrial VIE B reference limit values (Basque Law 4/2015) in many of them .
    Table 3. Concentration of hydrocarbons, heavy metals and AHAPs (mg / kg) of the soil selected for the tests (tasting soil 9).
     Chemical Parameter  Soil Chemical parameter Soil Chemical parameter Soil
     Ace  30 Acenafteno 180 Indeno (1,2,3-, d) Pyrene 320
     CD  2 Fluorene 280 Dibenzo (a, h) anthracene 110
     Cu  70 Phenanthrene 1800 Benzo (g, h, i) perylene 230
     Cr  6.2 Anthracene 390 C10-C12 hydrocarbons 120
     Hg  4.9 Fluorantene 2000 C12-C16 3100 Hydrocarbons
     Neither  12 Pyrene 1200 Hydrocarbons C16-C20 2400
     Pb  630 Benzo (a) anthracene 900 Hydrocarbons C20-C24 2700
     Zn  900 Chrysane 900 Hydrocarbons C24-C28 13000
     Total hydrocarbons  23000 Benzo (b) fluorantene + Benzo (j) fluorantene 1000 Hydrocarbons C28-C32 1100
     Naphthalene  4000 Benzo (k) fluorantene 320 C32-C36 500 hydrocarbons
     Acenaphylene  1.4 Benzo (a) pyrene 600
    The mixed treatment of nanoparticles-bioremediation through compost is planned for a soil with the presence of hydrocarbons and PAHs, alone, or together with other compounds such as heavy metals (lead, arsenic, antimony, mercury, Cr VI), organochlorine compounds, pesticides and other compounds on which zero-valent Fe nanoparticles are effective. For this reason, this sample was selected for the performance of the tests, so the complete soil characterization was carried out. The soil selected from calicata 9 was a soil with high sand content (more than 70%) and low clay content (less than 10%), which gives it a frank sandy texture.
    10 Table 4. Texture of the soil sample (soil 9) selected for the test.
     USDA texture  Sandy Sandy
     Sand (%)  74.45
     Slime (%)  20.41
     Clay (%)  5.14
    In the next stage or phase the contaminated soil was removed to be remedied by backhoe, previously delimiting the surface and depth to be extracted. In this process it was necessary to calculate the total mass of soil extracted, to establish the necessary quantities of reagents (nanoparticles-15 compost), amendments and water.
    This can be done by weighing or by estimating from the volume and density of the soil screened (less precise).
    It is usual that the contamination is in the fine fraction of the soil, therefore, once the contaminated soil was extracted and screened, the soil was characterized in terms of texture to determine clay, silt and sand content, according to the USDA classification. We also obtained data on density, humidity, field capacity, wilting point (situation in which a soil is
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    when a plant can no longer extract water from it) and chemical properties such as pH, electrical conductivity and nutrient content.
    The following table 5 shows the pH, electrical conductivity, nutrient content, humidity, field capacity and wilting point of the selected soil.
    Table 5:
     Sample  pH (CE) K P N C / N Humidity Capacity Pto.
     1: 2.5) Wilt field
     (mS / cm) (mg / kg s) (mg / kg s)%% g / g g / g
     9 floor  8.74 1,920 197.35 6.22 0.38 10.97 32.69 0.25 0.11
    To eliminate the risk of the site derived from the contamination of the soil chosen, it was necessary to reduce the concentrations of TPH C12-C28, arsenic and some PAHs (Benzo-b-fluorantene, Benzo-a-anthracene, Benzo-a-pyrene , Benzo-k-fluorantene, indene-1,2,3-cd-pyrene, naphthalene and Dibenz-a, h- anthracene).
    Commercial iron nanoparticles called NANOFER 25S (from NANOIRON) were used, previously analyzing their ability to degrade aromatic polycyclic hydrocarbons (PAHs) in in vitro assays. Mobility and adsorption capacity of metals by NANOFER 25S nanoparticles were studied in larger-scale tests.
    The composition of the Nanofer 25S product according to commercial information was 77% water, 14-18% zero-iron iron nanoparticles, 2-6% iron oxides, 0-1% carbon and 3% surfactant ( PAA and coating based stabilizer). The average size of the nanoparticles was 10-100 nm and an average surface area of 20-25 m2 / g.
    Therefore, the pre-incubation of the soils was first carried out for the three parallel tests, and in the meantime in the case of sequential mixed technique, 1% of nZVI was applied to the contaminated soil before mixing the pre-incubated compost with the soil.
    Pre-incubation was done by mixing 80% dry compost dough with 20% dry mass of contaminated soil. During the pre-incubation, the temperature and humidity data were taken twice a week and aeration tasks were carried out twice a week, in order to ensure that the pre-incubation conditions were adequate. Thus it was necessary to add water with surfactant (Tween 20 to 10% or similar in weight) twice during pre-incubation to guarantee humidity values within the optimum range. 25 liters of water with 1% by weight of tween 20 surfactant were added at the beginning of pre-incubation and 9 liters of water with 0.6% by weight of tween 20 surfactant on the eighth day of pre-incubation. Humidity levels were maintained between 70% of the field capacity (59.5% humidity) and 100% of the field capacity (85% humidity) during the pre-incubation of the compost.
    The compost used was a compost from municipal organic waste called “Garbiker compost”, which was previously characterized, analyzing its water retention capacity, concentrations of N, P, K and F, its pH and its electrical conductivity (EC).
    The data of the Garbiker compost used, before pre-incubation are shown in table 6:
     Sample  pH (CE) K P N C / N Humidity Capacity Pto.
     1: 5) wilt field
     (mS / cm) (mg / kg s) (mg / kg s)%% g / g g / g
     Garbiker compost  7.9 5.4 13546 391.2 2.43 8.07 35.83 0.9 0.8
    The pre-incubated Garbiker compost data is shown in Table 7: Table 7:
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     Sample  pH (CE) K P N C / N Humidity Capacity Pto.
     1: 5) Wilt field
     (mS / cm) (mg / kg s) (mg / kg s)%% g / g g / g
     Garbiker compost  7.76 4.66 10868 373.6 1.54 12.25 63.33 0.85 0.63
    After two weeks, the mixture of contaminated soil and pre-incubated compost was carried out. In the case of the simultaneous mixed technique after two weeks of pre-incubation, 1% of nZVI and the pre-incubated compost were applied simultaneously on the ground. The contaminated soil mixture (with the 10 nanoparticles in the case of mixed media) and the pre-incubated compost was performed in a proportion of 60% dry soil and 40% dry pre-incubated compost.
    The duration of the entire procedure was 2 + 6 weeks, where the first two weeks refer to the two weeks of pre-incubation.
    The chronology of the trials was as shown in table 8 below:
    15 Table 8
     essays  Weeks
     one  2 3 4 5 6 7 8
     Bioremediation Test
     Phase I: pre-incubation  X X
     Phase II: bioremediation stage      X X X X X X
     Simultaneous mixed technique trial
     Phase I: pre-incubation  X X
     Application of nanoparticles      X
     Phase II: bioremediation stage      X X X X X X
     Mixed technique sequential test
     Phase I: pre-incubation  X X
     Application of nanoparticles  X
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     Phase II: bioremediation stage      X X X X X X
    The following results were extracted from the parametric control:
    The humidity must remain between 70 and 100% of the field capacity). The field capacity of the bioremediation test (test without application of nanoparticles) is 45% and in the two mixed technique tests (the sequential or with a mixture of compost and soil combined with the addition of the nanoparticles) bioremediation - nanoparticles, the field capacity has a value of 51%. Humidity values were maintained in the correct ranges for practically the entire test, with periods of values slightly above the range.
    Nutrient content The recommended C: N: P ratio for this type of assay is 100: 10: 1 (Chemlala et al., 2012; De la Torre-Sanchez et al., 2006; Kriipsalu et al., 2007). At the beginning of this stage, the C: N: P ratio was calculated and N was added to present the relationship. Initially, it was estimated that the C: N: P ratio in the bioremediation test was 12.64: 0.93: 0.02, in the sequential test this ratio was 14.64: 1.13: 0.02 and finally in the simultaneous trial it was 13.43: 1.02: 0.02.
    Decontamination:
    The concentration of contaminants (hydrocarbons and PAHs) was analyzed at the beginning and at the end of the test.
    The following table 5 shows the percentages of evolution of PAHs with respect to the initial concentration in the three trials: the sequential addition test of nanoparticles compared with tests carried out of bioremediation only and nanoparticles - bioremediation, but according to the simultaneous technique, that is, addition of nZVI and mix with the compost pre-incubated simultaneously. Negative values indicate concentration reduction:
    Table 9
     Sequential Test Simultaneous Test Bioremediation Test
     Acenafteno  -23.21 -18.1 - 11.0
     Anthracene  -27.89 * -18.3 -8.3
     Benzo anthracene  -55.62 * -46.4 * -32.3 *
     Benzo Pyrenees  -72.19 * -69.3 * -62.4 *
     Benzo (b) fluorantene  -65.37 * -58.1 * -42.5 *
     Benzo (k) fluorantene  -46.14 * -41.5 -29.6
     Chrysane  -58.79 * -53.6 * -46.1 *
     Dibenzo (a, h) anthracene  -66.76 * -67.3 * -64.1 *
     Fluorantene  -43.81 * -31.3 -13.4
     Fuoreno  -25.30 -17.1 -8.9
     Indeno (1,2,3, cd) pyrene  -74.45 * -67.0 * -62.8 *
     Naphthalene  -11.35 -0.8 -7.5
     Pyrene  -39.5 * -25.7 -6.2
    It is found that some aromatic compounds such as benzo (a) pyrene, indene (1,2,3, cd) pyrene and dibenzo (a, h) anthracene, show decreases around 70%.
    In addition, an average reduction in the concentration of C10-C40 total hydrocarbons of 27.1% for the simultaneous test, 25.4% for the sequential test and 3.6% in the bioremediation test is observed. In turn, mixed techniques cause a greater decrease in aliphatic (-40% vs. -10%) and aromatic (-30% vs. -7%) hydrocarbons than the individual bioremediation technique. In view of the results, it is observed that the addition of nanoparticles causes a greater decrease in aliphatic and aromatic hydrocarbons.
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    The levels of decontamination obtained with the sequential mixed technique are higher than those obtained with the simultaneous mixed technique, which indicates that the addition of nanoparticles in this type of tests improves the technique when they are added to the ground before.
    Example 2 - decontamination of two different soils on a pre-industrial scale using the sequential mixed technique
    Sequential mixed technique was evaluated on a pre-industrial scale in biopile tests to validate said soil decontamination strategy in uncontrolled environmental conditions and with two types of soils, of different origin and contamination: Soil I (from an Industrial Soil contaminated) and Soil II, (artificially contaminated). The application of nZVI for in situ immobilization of As and Cr in both soils was studied, as well as the results of global decontamination at the end of treatment.
    The chronology of the example is shown in the following table 10:
    Table 10
     STAGES  AGO SEP OCT NOV DIC JAN FEB
     Stage I: Previous analysis and trial design  X X
     Stage II: Soil contamination and nanoparticle addition    X
     Stage III: Pre-incubation      X
     Stage IV: Biopiles      X X X
     Stage V: Final evaluation, reports and possible corrections            X X
    Chemical reagents. standards and materials Floors and compost
    In this case a Soil I was used, same soil as in Example 1 and selected due to its high concentration of hydrocarbons and Soil II, a natural soil with no known contamination. Both soils were initially screened by a 1x1cm metal mesh of mesh size, consequently obtaining the following quantities of soil available for biopiles: Soil I = 212.8 kg (weight); Soil II = 688.1 kg (weight).
    Soil II was artificially contaminated, following a pre-established design and calculations, adapted to the objectives of the tests. The controlled contamination process was carried out by adding diesel, potassium dichromate and sodium arsenate to Soil II. To calculate the target concentrations, the dry weight (487.6 kg of dry soil) of the sieved soil was considered. These concentrations were established on the basis of VIE B reference values of Regional Law 4/2015 for the prevention and correction of soil contamination, seeking to exceed these values.
    Soil I and Soil II after being artificially contaminated were analyzed in triplicate to obtain an accurate characterization. The two soils had high concentrations of total hydrocarbons; Soil I also had very high concentrations of PAHs and Pb. Soil II had a high content of As, total Cr and TPH. The results of these analyzes are shown in Table 11.
    Table 11
    Initial average concentration of hydrocarbons, heavy metals and other contaminants (mg / kg) of the soils used in the study. The underlined values indicate values above the limits of the industrial VIE B (Basque Law 4/2015).
    Chemical parameters Soil Soil Chemical parameters Soil I Soil II
    I II
     Ace  47.3 244 Naphthalene 159 1.5
     CD  4.5 <0.40 Phenanthrene 701 2.7
     Cr  31.4 52.7 Pyrene 731 2.0
     Cr (VI)  0.35 1.11 Sum of 16 HAP 6737 12.1
     Cu  315 23.3 TPH Fraction> C10 - C40 16533 11033
     Pb  1162 35.8> C10 - C40 Aliphatic Fraction 962 8197
     Hg  15.7 <0.20> C10 - C12 Aliphatic Fraction 42 709
     Mo  10.6 0.5> C12 - C16 Aliphatic Fraction 73.1 2840
     Neither  53.4 32.1> C16 - C21 Aliphatic Fraction 129 3160
     Zn  2710 101> C16 - C35 Aliphatic Fraction 710 4640
     Acenafteno  124 0.5> C21 - C35 Aliphatic Fraction 581 1480
     Acenaphylene  0.5 0.1> C35 - C40 Aliphatic Fraction 138 4.5
     Anthracene  225 0.4> C 6 - C 8 Aliphatic Fraction <5.0 <5.0
     Benz anthracene  754 0.4> C 8 - C10 Aliphatic Fraction <5.0 73.4
     Benzo Pyrenees  556 0.4> C10 - C12 Aromatic Fraction 142 126
     Benzo (b) fluorantene  772 0.7> C10 - C40 Aromatic Fraction 15567 2840
     Benzo (g.h.i) perylene  211 0.3> C12 - C16 Aromatic Fraction 545 874
     Benzo (k) fluorantene  291 0.2> C16 - C21 Aromatic Fraction 3937 1137
     Chrysane  676 0.4> C21 - C35 Aromatic Fraction 9967 697
     Dibenz (a.h) anthracene  83.1 0.1> C35 - C40 Aromatic Fraction 994 5.8
     Fluorantene  1043 0.7> C 7 - C 8 Aromatic fraction 0.3 0.2
     Fluorene  130 1.3> C 8 - C10 Aromatic fraction <0.80 11.2
     Indeno (1.2.3.cd) pyrene  283 0.3 C 6 - C 7 Aromatic fraction 0.2 <0.120
    Due to its high availability, the compost of MSW (urban solid waste) from the Garbiker Bizkaiko Konpostegia plant (Bizkaia, Spain) was obtained. This compost is obtained from the municipal organic fraction, selectively collected. It has a relatively high salt content and a C / N 5 ratio lower than that recommended for bioremediation.
    The chemical characteristics of both soils (concentrations in organic C, total N, P and K available) and the compost, as well as their physical characteristics (water retention capacity and apparent density) were determined following standard procedures for soils (MR Carter, Soil sampling and methods 10 of analysis. CRC Press LLC, Boca Raton, FL, USA.). and are shown in Table 12.
    Table 12
    PH, electrical conductivity, nutrient content, moisture, water content at field capacity and wilting point of soils and compost
    PH sample
    Floor I 8.74
    EC (1: 5) mS / cm
    1,920
    K mg / Kg P mg / Kg N%
    197.3 6.22 0.38
    C %
    4.18
    C / N
    11.0
    humidity
    %
    15.5
    Field capacity g / g
    0.25
    Pto.
    wilting
    g / g
    0.11
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    Four. Five
     Floor II  7.5 0.113 46.8 4.65 0.17 1.29 7.62 22.1 0.33 0.17
     MSW Compost  8.2 4.23 14904 318 2.5 20.3 8.12 22.1 0.91 0.63
    Soil I had a basic pH, a high concentration of soluble salts (typical of a swampy soil) and a C / N ratio suitable for bioremediation (the C / N ratio recommended for bioremediation is 10). Soil II also had a basic pH, but a low concentration of soluble salts and a C / N ratio lower than recommended was observed (Table 12).
    Soil texture, as a known factor that determines the soil's hydraulic properties, was also measured for Soil I and Soil II. Soil I had a high sand content (74.5%) and a low clay content (5.14%), resulting in a texture of silty sand, according to the USDA soil texture classification. On the other hand, the artificially contaminated soil (Soil II) had a high silt content (58%), resulting in a texture of silty sediment.
    A sampling procedure was designed and applied to ensure a better uniformity in soil composition, based on the UNE-EN 932-1 standard. Thus, for the analysis, three samples were collected from each soil, consisting of 15 random points. Each sample of about 8 kg of mixture (about 0.5 kg per point), was thoroughly mixed and divided into 4 quarters to take the necessary amount for chemical analysis.
    NANOFER 25S commercial nanoparticles were selected, manufactured and supplied by NANOIRON (Rajhrad, Czech Republic). The product is supplied as an aqueous dispersion, with a composition by weight: 77% water, 14-18% iron nanoparticles from Valencia zero, 2-6% iron oxides, 0-1% carbon and 3 % surfactant (stabilizer based on PAA and coating).
    Site Conditioning
    Soil remediation tests were carried out at Iragaz facilities in Azkoitia (Spain). Before carrying out the test, a concrete safety cube was prepared to isolate the test from any eventuality. The floor of the basin was waterproofed with a HDPE sheet, to prevent infiltration of leachate into the subsoil and through the wall of the cuvette. Tents were also installed to protect the biopiles from precipitation.
    Pre-incubation, training and control of biopiles
    The trials were established in a sequence with three steps.
    First, the two soils were conditioned as described above, and mixed with zero-valent iron nanoparticles. The nanoparticles used were previously characterized, showing a high degree of dispersion and low sphericity, and a high content of crystalline iron and magnetite was observed in the X-ray diffractograms. The mixture of Soil I and Soil II with nanoparticles was performed by adding 1% by weight of slurry on the weight of the wet soil. The mixture was allowed to react for 72 h, and another suspension of 1% by weight nanoparticles was subsequently added. During the addition process, water was added to facilitate the mixing of the nanoparticles and to ensure anaerobic conditions that favor their performance.
    The process was controlled in each addition of nanoparticles. To check the effectiveness of the treatment by nZVI, the concentration and leaching of the metals in the initial soils (without addition) was analyzed and three days after adding each portion of nZVI. This is intended to evaluate the evolution of metals both in concentration parameters in the soil and in leaching. The samples were taken in accordance with Standard UNE-EN 932-1 and the samples extracted were leached according to UNE-EN 12457-4 and analyzed to determine the total concentration of As, Cr and Fe in the leachate at each stage of the process.
    Second, the compost was pre-incubated with subsamples of the two soils. This was done on the basis of previous experiments to allow a better development of populations of microorganisms native to both soils and capable of degrading hydrocarbons. The presence of this type of microorganisms is common in these soils. Preincubation involves inoculating a small sample of soil into the compost and adjusting the temperature, water content and nutrients to optimal conditions for
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    its development The availability of carbon from compost implies that these microorganisms can grow under non-limiting conditions. The development of these populations allows better degradation of soil hydrocarbons when the final biopiles are formed. The mixing ratio of the compost and the soil for incubation was 80-20 on a dry mass basis, for the total amount of compost used in the biopiles. The mixing was done mechanically to ensure a homogeneous distribution of soil in the compost. Water was added to ensure the minimum availability of water at 70% of the retention capacity in the field of the mixture. The total available C, N, K and P content was monitored and remained at non-limiting intervals for microbial growth. Pre-incubation was carried out for two weeks. During the 2 weeks that the pre-incubation lasted, the temperature value was taken to ensure adequate conditions (20-35 ° C), the humidity of the samples was analyzed three times and aeration tasks were performed once a week.
    Finally, with the use of the pre-incubated compost, biopiles were established for bioremediation for a final soil compost ratio of 52.9% -47.1% (dry mass base) for Soil I and 54.3% - 45, 7% for Soil II. Both soils had previously been mixed with nanoparticles as described above. Water was added to ensure a water content between 70% and 100% of the field capacity of each mixture. The content of organic C, total N and available P was monitored and found to remain in a ratio of 100: 10: 1 throughout the bioremediation procedure.
    Biopiles were established in outdoor cells to better simulate natural conditions. They were protected from rain under tents and covered with HDPE sheets to avoid excess moisture that could hamper microbial activity, and the experiment was carried out for 66 days.
    Sample collection and parameter control were performed in the same way in both biopiles. During this time aeration tasks were performed twice a week and I analyzed the humidity (in the internal laboratory) and the temperature (in-situ) of the tests once a week.
    As a control measure, the pH, electrical conductivity, concentration of C, N, P and K were analyzed five times throughout the treatment, in order to maintain an optimal nutrient content (ratio C: N: P close to 100: 10: 1). Microbial respiration was analyzed five times throughout the treatment, coinciding with nutrient analysis. The concentration of pollutants (aliphatic and aromatic fractions of petroleum hydrocarbons, TPH and 16 HAPs) was analyzed at the beginning and at the end of the test and finally, the ecotoxicity (Eisenia foetida earthworm mortality test and emergency test and Seed growth in land plants Linum usitassimum sp.) was analyzed in the initial soil and at the beginning and end of the biopile test.
    Table 13. Controls performed in the tests.
     Parameter  Week Observations
     0  1 2 3 4 5 6 7 8 9 10
     Temperature  X X X X X X X X X X X Weekly control
     Humidity  X X X X X X X X X X X Weekly control
     C, N, P, K  X X X X X Five controls
     pH and CE  X X X X X Five controls
     Pollutant concentration  X X Two controls
     Microbial breathing  X X X X X Five controls
     Ecotoxicity  X X Two controls
    A triplicate analysis of the concentration of hydrocarbons and PAHs in the compost was also carried out, before mixing with the soils. He gave an average of 104.3 mg / kg of TPH (> C10 - C40 Fraction) and 2.25 mg / kg of the sum of 16 PAHs.
    Results:
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    The adsorption of Cr and As was monitored in different stages in order to determine the effectiveness of the immobilization of these metals during the time of treatment with nZVI. The results obtained from the concentration measures both in soil and in leaching of both metals in the different phases (in the first stage with the addition of 1% of nZVI in slurry format and after 72 hours with the addition of another 1% of nZVI) are summarized in the following tables 14 and 15:
    Table 14
    Cr obtained in the leachate of the different phases of the treatment in relation to the concentration of Cr determined in soil samples.
     Sample  mgCr / Kg Soil I mgCr / L leachate I% Cr leachate I Sample mgCr / Kg Soil II mgCr / L leachate II% Cr leachate II
     YES Start  34.8 0.0030 0.009 SII start. 61.9 0.1100 0.177
     YES 1% NP  34.2 0.0059 0.017 IBS 1% NP 61.2 0.1250 0.204
     YES 2% NP  33.7 0.0018 0.005 SII 2% NP 67.8 0.0375 0.055
    Table 15
    As obtained in the leachate of the different phases of the treatment in relation to the concentration of As determined in soil samples.
     Sample  mgAs / Kg Soil I mgAs / L leached I% As leachate I Sample mgAs / Kg Soil II mgAs / L leached II% As leached II
     YES Start  46.1 0.0065 0.014 SII start. 231.2 0.3850 0.166
     YES 1% NP  39.0 0.0170 0.044 IBS 1% NP 281.7 0.4800 0.170
     YES 2% NP  43.2 0.0034 0.008 SII 2% NP 274.7 0.1900 0.069
    The application of nZVI for the immobilization of As and Cr in these two soils, Soil I and Soil II (artificially contaminated), has shown a tendency to reduce the concentration of these metals in the leachate when successive applications of nZVI are made, achieving a decrease in the concentration of As in 48% for Soil I and 51% for Soil II, and a decrease in the concentration of 40% of Cr for Soil I and 66% for Soil II.
    For both Cr and As in Soil I and Soil II, there was a tendency towards reducing the concentration in leachate after adding 2% of nZVI.
    With regard to the results on hydrocarbons, the addition of compost and nanoparticles under uncontrolled environmental conditions in biopiles was able to produce a decrease in the concentration of aliphatic hydrocarbons of up to 60% in the two biopiles. Especially, there was a degradation and transformation of the longer chains. In the case of biopile II, a decrease in total TPH hydrocarbons of 53% was also obtained. A significant reduction in ecotoxicity was observed throughout the process in the soil II biopile, not reaching the LC50 (concentration of contaminated soil from which mortality is greater than 50% of individuals) even with 100% of the sample after treatment, both in worm growth tests and in
    seeds. The results of biopile I, show a decrease in the toxicity of the mixture for terrestrial plants, reducing markedly at the beginning of treatment.
    Figures 1-I and 1-II show the result of the evolution of aliphatic hydrocarbons for the two test soils where 1-I corresponds to biopile I and 1-II corresponds to biopile II.
    权利要求:
    Claims (11)
    [1]
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    1. A procedure for treating contaminated soils on-site characterized in that it comprises:
    - the addition of zero-iron nanoparticles worth a contaminated soil, in which the addition of the nanoparticles occurs sequentially in at least two stages,
    - Subsequent bioremediation treatment by mixing said contaminated soil and treated with the iron nanoparticles, with a compost that has been previously pre-incubated.
    [2]
    2. A method according to claim 1, wherein the addition of zero iron nanoparticles valid to the contaminated soil is carried out in the form of a suspension.
    [3]
    3. A method according to claim 2, wherein the addition of zero-iron nanoparticles valid to the contaminated soil is carried out in the form of a suspension, in two stages separated from each other for a time interval of three days.
    [4]
    4. A method according to claim 2 or 3, wherein the addition in the form of a suspension is carried out by irrigation and mechanical mixing.
    [5]
    5. A method according to any one of claims 1 to 4, wherein the addition of the iron nanoparticles is carried out sequentially, mixing with the soil between 0.1% and 5% by weight on wet soil mass, of slurry of nanoparticles of zero-iron and 3 days later they are mixed again between 0.1% and 5% by weight on wet mass of soil, of slurry of nanoparticles of zero-iron iron, with the soil.
    [6]
    6. A method according to any one of the preceding claims, wherein the pre-incubation of the compost comprises mixing between 75% and 85% of dry compost mass with between 15% and 25% of dry mass of contaminated soil.
    [7]
    7. A method according to any one of the preceding claims, wherein the pre-incubation of the compost lasts between 12 and 20 days.
    [8]
    8. A method according to any one of the preceding claims wherein the pre-incubation of the compost is carried out at a temperature between 20 and 35 ° C.
    [9]
    9. A method according to any one of the preceding claims, wherein the bioremediation treatment is carried out at a temperature between 20 and 35 ° C.
    [10]
    10. A method according to any one of claims an, wherein the bioremediation is carried out with a compost from organic waste.
    [11]
    11. A method according to claim 1, wherein the mixing of said soil contaminated and treated with the iron nanoparticles, with the compost previously subjected to pre-incubation occurs in a proportion ranging from 55% to 65% in dry mass of dry soil contaminated and treated with iron nanoparticles and between 35% and 45% of pre-incubated compost.
    image 1
    FIG. 1 - I
    2500
    2000
    1500
    Aliphatic fractions
    a:> C10-C12 b:> C10-C40 c:> C12-C16 d:> C16-C21 e:> C16-C35 f:> C21-C35 g:> C35-C40
    image2
    a b c d e f g
    FIG- 1- II
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    同族专利:
    公开号 | 公开日
    ES2676911B1|2019-01-25|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    CN104801540A|2015-04-15|2015-07-29|刘骁勇|Method for remedying contaminated site through combination of nanoscale zero-valent iron and reducing microorganisms|
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