Methods for accelerating the biodegradation of toxic organic chemicals.

Abstract

A method for treating soil in situ or ex situ to reduce the concentration of contaminating or polluting organic chemical compounds in the soil, comprising the steps of: a) determining a contaminated / polluted area in which the soil is to be treated; b) adding fertilizer in the form of thermally composted manure, or other similar compost having a nutrient content equivalent to that of thermally composted manure and in which the nutrients are correspondingly strongly bound to the compost, to a layer of soil in the area to be treated, the fertilizer being added in an amount of at least 10% (percentage by weight) of the soil in the layer to be treated, and repeated annually if necessary; c) adding iron, preferably Fe, in an amount of 1 to 4 kg per tonne of compost applied, unless the soil to be treated previously contains at least 2 kg of iron per tonne of soil, Fe. 2+ or Fe 3+ , more preferably in an amount of 1.5 to 2.5 kg of Fe per ton of compost. 2+ , most preferably 1.5 to 2.2 kg of Fe 2+ d) adjusting the soil pH to an acidic pH (pH<7), preferably to a pH of 3 to 6, more preferably to 4.5 to 6.0, or 2 to 4; and e) keeping the soil moist by adding water as needed for a predetermined period of time, preferably 12 months.

Description

[Technical field]

[0001] Summary of the Invention The present invention is a general method for the in situ or ex situ accelerated biodegradation / bioremediation (also called biostimulation) of any kind of organic molecules that are considered contaminants or pollutants in soil. The method utilizes existing scientific knowledge on accelerated biodegradation / bioremediation obtained from laboratory studies. The most important part of the method is to incorporate 10% or more nutrient-rich organic matter (preferably fertilizer such as hot composted manure) into the topsoil together with iron and a pH adjuster to make the soil acidic or, if necessary, basic.

[0002] The soil being treated must be kept moist throughout the process and is preferably covered with organic material that retains water, provides aeration, and attracts earthworms.

[0003] Biodegradation is fast, effective, cheap and sustainable, and the new method further improves soil quality and is compatible with organic agriculture.

[0004] Detailed Description The present invention relates to a method for rapid, effective, affordable and sustainable remediation of DDT and other toxic organic molecule contamination in soils either directly in situ on agricultural land or ex situ, i.e. elsewhere, and the method can also be used with muds, i.e. sludges and liquids.

[0005] A new method, also called bioremediation or biostimulation, for the accelerated in situ or other in situ biodegradation of undesirable or toxic organic compounds (contaminants or pollutants) is presented. The method utilizes a combination of a number of key elements discovered by biodegradation research in the past decades. Organic molecules are often present in toxic concentrations everywhere as contaminants. The contaminated / polluted areas of the world are so vast that it seems impossible to clean up the land. An important example is the global contamination with DDT and other organic pesticides, which were sprayed in hundreds of millions of tons on millions of hectares of farmland, nurseries, gardens, etc. and still persist in high concentrations 50 years after being banned.

[0006] Biodegradation is fast, effective, cheap and sustainable Biodegradation is fast, effective, cheap and sustainable, and is compatible with organic agriculture. New methods presented will further improve soil quality. The half-life of toxic molecules will be reduced from decades (20-30 years for DDT) to less than one year.

[0007] Key Elements Factors found to be important for biodegradation are a high content of nutrient-rich substrate (greater than 10% (by weight)), water, oxygen, iron, earthworms, and low pH. All of these factors must be carefully controlled.

[0008] The process is as follows: 1) Measure the concentration of contaminants / pollutants at the appropriate depth and compare it with the relevant threshold value. 2) Estimate the area that can be treated from the availability of fertilizers such as hot composted manure and the legal limits for their use. 3) Decide the thickness of the top layer you want to treat (i.e. 8-12 cm). 4) Mix the fertilizer into the designated area after adding 2 kg of iron and adjusting the pH, preferably to pH 4.5-5.5, or 2.0-4.0, or 7.0-9.0 if necessary. 5) Cover the area to be treated with a layer of organic matter 1-20 cm thick, preferably 3-6 cm thick, that keeps the soil moist and contains organic matter that attracts earthworms. 6) Then water the treated spot for 12 months. 7) Measure the contamination again and repeat with the same or deeper soil layer if necessary.

[0009] Compost to be used The organic substrate used in the process must be one that slowly releases its nutrients. Hot composted manure containing chicken, cow or horse straw or wood chip bedding is used, but any compost with a high content of nutrients (N, P, K and trace nutrients) can be used. "Spot treatment" of the most contaminated areas is used, as well as "planning" of the contaminated land by gradually working deeper into the soil, to reduce the concentration of contaminants to acceptable levels.

[0010] Applicability of the method The presented method degrades any organic molecule and is particularly useful for degrading natural or synthetic toxic organic compounds, namely polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, organophosphate and carbamate pesticides, organic herbicides, and dioxin-contaminated contaminants of herbicides and wood preservatives. Small organic toxic molecules such as dioxins can also be treated. The broad applicability of the method to remove even unknown organic materials from soil makes it unique.

[0011] Chemical substances that can be biodegraded are, in principle, any simple or complex compound. Of particular interest, however, are pesticides, for example one or more of the substances DDT, DDD, DDE and / or DDTr, as well as compounds from the petrochemical industry, such as gasoline, petroleum and other polycyclic and aromatic substances.

[0012] Adding Phytoremediation and Bioaugmentation The effectiveness and applicability of the presented method can be further enhanced by combining it with other methods such as phytoremediation (using plants) and bioaugmentation (adding specific bacteria, fungi, etc.).

[0013] Suitable for organic farming The presented method is compatible with organic agriculture and improves soil quality.

[0014] General Applicability The presented method can be used to accelerate the biodegradation of organic molecules in general in solids such as soil, clay, sand, in mud (i.e., sludge), or in water.

[0015] The method can also be used when the material to be treated is not a solid material, but a sludge or a contaminated liquid, which is mixed with manure / compost / fertilizer / bacterial nutrients, with the addition of iron and adjustment of pH. The contaminated material is added to the fresh manure before or during the thermal composting of the manure, and the reduction of the concentration of contaminating or polluting organic chemical compounds in the contaminated sludge or liquid is carried out in the solid phase. The resulting compost can then be used as a normal compost or for further biodegradation. The contaminated sludge or liquid can also be added to a biogas plant, a willow clarifier or a similar system. Thus, a biogas plant can be used to remove contaminants or pollutants from the contaminated liquid. For example, the method can be used in a phytoclarifier, i.e. a willow clarifier, where biodegradation in the sludge occurs by adding iron to the accumulated sludge and adjusting the pH. In this situation, the sludge itself acts as compost.

[0016] Currently, millions of agricultural fields and land parcels are contaminated or polluted with organic chemicals that have long half-lives and therefore persist in the soil, sometimes for decades.

[0017] There are currently 250,000 contaminated agricultural sites in Europe and 295,000 in the United States. Wherever you look, you will find contaminated land that puts people at risk if you use it.

[0018] One of the most troublesome pesticides, which was used in excessive quantities almost worldwide until its toxicity was discovered and the compound banned, is DDT. DDT was selected for its extraordinary chemical stability. No energy can be obtained from the decomposition of this compound. DDT contamination, coupled with its strong anti-estrogenic effects that affect almost the entire animal kingdom, makes it a tremendous challenge, and there are thousands of research papers on the biodegradation of DDT in the laboratory and in situ.

[0019] The extensive research on DDT includes knowledge about how to degrade not only DDT but organic molecules in general, as well as the most toxic and most stable ones. The invention presented here is based primarily on laboratory studies of the biodegradation of DDT, but has general applicability.

[0020] DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane, formerly known as dichlorodiphenyltrichloroethane) is one of the most effective synthetic insecticides. DDT became available around 1940 and was used extensively as an agricultural insecticide. DDT is practically insoluble in water, but has good solubility in most organic solvents and oils and fats.

[0021] Commercially available DDT is a mixture of several related compounds (DDTr), including significant amounts (15%) of dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD). DDD and DDE isomers are as toxic and durable as DDT. Research has demonstrated that if a method works for DDT, it also works for all related molecules and is therefore generally applicable.

[0022] Due to its lipophilic nature, DDTr tends to accumulate in the fatty tissues of ingesting organisms along the food chain. DDTr has been reported to be a potent endocrine disruptor in both birds and mammals. DDTr poisoning can cause eggshell thinning in birds and impaired fertility in both males and females in humans, as it interferes with all animal and human tissues sensitive to sex hormones, further causing cancer and many neurological disorders.

[0023] Many experiments have been tried to remove DDT from soil by mechanical treatment. One effective method is to incinerate the soil, another is to use ozone (O 3 The treatment of entire fields of soil with ozone or other chemicals in mechanical systems (reaction chambers) is very expensive and impractical for the average farmer wanting to rid his field of DDT.

[0024] However, biodegradation is considered to be the most effective. Biodegradation is the process by which organic substances are broken down by enzymes produced by living organisms. This process works for all organic molecules, simple and complex, and fortunately also for toxic organochlorine molecules such as DDT.

[0025] The most promising recent experiments have found that the half-lives of DDT, DDE and DDE are reduced in soil from 20-30 years to a few weeks. If this rate of degradation could be replicated in a general procedure that could be applied to clean up DDT contamination of agricultural land such as old vegetable fields and apple orchards, this would be of great importance to the world, and this is where our research began.

[0026] It was soon discovered that many microorganisms apparently possess a remarkable naturally occurring microbial catabolic diversity that degrades or transforms hydrocarbons (e.g., petroleum), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHSs).

[0027] Known microorganisms that have been found to be capable of degrading DDT include: Bacteria: Escherichia coli Enterobacter aerogenes Enterobacter cloacae Klebsiella pneumoniae Pseudomonas aeruginosa Pseudomonas putida Bacillus spp. Hydrogenomonas fungi: Saccharomyces cerevisiae Phanerochaete chrysosporium Trichoderma viridae Includes:

[0028] Many of these organisms are commonly found in soil and in horse, cow and chicken manure. DDTr is metabolized via cometabolic pathways under favorable conditions by a large number of facultative and obligate microorganisms.

[0029] Studies have clearly demonstrated that normal soils contain a wide variety of microorganisms, both bacteria and fungi, that are capable of degrading complex organic molecules even if they are not available as nutrients, such as DDTr. The rate of biodegradation depends on both the concentration of microorganisms and substrate, and on the biodiversity of the soil, i.e., the large number of different microorganisms in the soil.

[0030] In laboratory experiments where bacteria were added to soil containing DDT, it was found that after only 25 days a significant amount of DDT (30-50%) was broken down by certain bacteria, but more importantly, a combination of different bacteria dramatically accelerated the process, resulting in a half-life of only 13 days (where 83% of the DDT was broken down).The logical consequence of this discovery is that instead of culturing a single specific bacterium (as is done in bioaugmentation), one should find a growth medium in which many different bacteria are already present in large quantities and add it to the soil.

[0031] In other experiments, a fungal environmentally friendly enzyme, laccase, was found to be effective in breaking down DDT with a half-life of about 100 days. Unfortunately, this is not a realistic method in agriculture, as the enzyme itself is very expensive and needs to be used in large quantities. Thus, the discovery of this interesting chemical process did not translate into a successful commercial solution.

[0032] A discovery of potentially huge practical importance was made in 2010, when it was found that iron-containing fertilizer dramatically accelerates the biodegradation of complex organic molecules such as DDT. It was found that the substrate must be rich in iron, with optimal biodegradation occurring at 1.9 kg of iron (metal powder, Fe) per tonne of fertilizer added. 2+ or Fe 3+ , Fe 2+is the preferred form).

[0033] Another study showed that soil should not be so wet that it stops the diffusion of oxygen into the soil (9).

[0034] A similar pattern was observed in the remediation of DDT-contaminated soil with laccase under different flooding conditions: the higher the concentration of oxygen in the soil, the lower the residues of DDT components and DDTr in the soil. DDT residues in non-flooded soils were reduced by 16.7% compared to flooded soils at the end of the incubation period, and DDT residues in soils treated with laccase were lower in the pH range of 2.5-4.5. Here we refer to one example where a low pH is important for the degradation process of many degradative enzymes.

[0035] A way to introduce more oxygen into the soil is to use surfactants. This method works well in the laboratory but is considered economically impractical for typical farm implementation. The effectiveness of surfactants in laboratory experiments highlights the need for good airflow for the biodegradation process and explains many of the positive findings of accelerated biodegradation associated with the presence and high concentrations of earthworms, which are known to effectively drain and aerate soils.

[0036] Most of the research, motivated by commercial interests, has been in search of a "wonder bacterium" that could be sold to farmers and sprayed on the soil to remove DDT. No such wonder bacterium has yet been found, nor has any magical surfactant-like wonder chemical been identified that would provide more oxygen to the soil in situ.

[0037] Major laboratory experiments using biodegradation have demonstrated that a combination of naturally occurring organisms, under optimal conditions, may be used to degrade DDT and similar stable molecules extremely rapidly. While a few weeks in situ may be highly optimistic, half-lives of around 3 weeks are frequently seen in the laboratory, with half-lives reduced to 11 days.

[0038] What appears to be effective in agricultural soils is a combination of large microbial communities, both bacteria and fungi, that appear to work together in complex ways in processing the organic matter in the soil and breaking down organic molecules, including large stable, "nasty" film-seeking, lipophilic organic molecules such as DDT, DDE and DDD.

[0039] Studies have also shown that the rate of biodegradation of organic molecules such as DDT and its derivatives is highly dependent on earthworms, and perhaps even proportional to the number of earthworms in the soil, so anything that increases the number of worms, such as dead leaves and other organic matter that worms love, such as compost or manure, will significantly accelerate the rate of decomposition.

[0040] Many practical experiments are in progress and already suggest the need to support worms, bacteria and fungi, for which a good organic substrate would be hot-composted manure added in significant quantities to agricultural land. Naturally, the addition of leaves or similar organic matter to the top layer, which the worms prefer to feed on, is also recommended, as this will contribute to the worm content of the soil.

[0041] Interestingly, the composting method patented in 1997 was based on mixing large amounts of manure into the soil. This method worked and seemed to work. The downside was that the protocol was very complicated and somewhat illogical, making the procedure both time-consuming and labor-intensive. Due to the needlessly complicated and lengthy repetition of steps, this method was rarely used and is still little known or used today. However, this project was definitely a big step in the right direction and strongly suggested that there is a simple and good solution to the problem of contamination with organic chemicals such as DDT. If only we could find it.

[0042] Other studies have shown that molecules like DDT can be broken down within a few days if the biodegradation process occurs at around 60°C, but this temperature is obviously not practical for agricultural soils. Similar results have been seen in studies with a very low pH, around 2-3. Again, this pH is incompatible with worms, which often die at a pH below 4.5, and therefore such a low pH is not practical for living soils.

[0043] Another series of biodegradation studies was conducted using chicken manure, and similarly, high concentrations of water were found to accelerate the biodegradation process. The team also found that gradually increasing the amount of chicken manure added resulted in gradually increasing concentrations of decomposition products. The conclusion, again, was that the more manure and water added, the better the biodegradation. The experiments were carried out in clay soil.

[0044] From many experiments it has been found that the type of soil is important. Some of the experiments mentioned above were carried out in tropical soils which differ from the soils in Nordic countries, but there is no reason to think that the processes tested would work differently in Nordic soils.

[0045] For this reason, research over the past 20 years has identified the necessary factors that must be taken into account if one wishes to accelerate biodegradation (bioremediation, biostimulation) and remove organic molecules, especially those that are difficult to degrade such as DDTr, from soil.

[0046] There is now enough knowledge to reduce the half-life of chemicals like DDTr from 20-30 years to a few months, even when they are poorly bound in soil. There are still uncontrollable local factors that can slow the process down and take years, such as localized waterlogging, high pH from chalk, and a lack of earthworms. However, the process generally accelerates the biodegradation process, reducing the half-life of molecules like DDTr from 20-30 years to a few months.

[0047] We conclude that DDTr, many other organic pesticides, and other toxic or non-toxic organic chemicals could be removed from the land using accelerated biodegradation.

[0048] The progress of the presented method can be appreciated by comparing it with the list of currently most commonly used methods (Table 1).

[0049] [Table 1]

[0050] Many experiments have been carried out in the past two decades to accelerate the biodegradation processes of complex organic molecules such as the extremely stable DDT, as well as its toxic derivatives DDE and DDD, as mentioned above.

[0051] Because stable chemicals such as DDTr that do not bind well in soil and are often stored in this manner have long half-lives, often 10 to 30 years, finding inexpensive, safe and effective in situ methods for land cleanup is critical.

[0052] The conclusion of a recent review was that although many methods could be considered for removing chemicals such as DDT from soil, for economic and practical reasons in situ biodegradation was the only realistic option. A method that would work in the relatively cold conditions of Sweden was required.

[0053] The literature was systematically reviewed to identify the key factors that must be controlled in a method that allows for rapid and effective biodegradation of organic molecules in situ.

[0054] The most effective substrates tested in the experiments were simple hot-composted manure, most often from chicken, cow or horse. Adding 10% or more of such substrates to soil, thoroughly mixing and adjusting iron and pH, is an affordable and sustainable solution to the problem of contamination by organic molecules such as DDTr.

[0055] With better control of the in situ process, the half-lives of stable toxic molecules such as DDTr may one day rival laboratory results, where half-lives are measured in weeks.

[0056] The most interesting thing we learned from the literature is that the long list of bacterial and fungal assemblages typically found in rich, vibrant soils, when properly stimulated, can degrade almost any simple or complex organic molecule, even DDTr and other organochlorine pesticides, which are among the most stable and least bioavailable molecules known to man.

[0057] Thus, the presented method degrades organic compounds found at contaminated sites, large toxic molecules mostly derived from oil or natural gas such as polycyclic aromatic hydrocarbons (PAHs), organochlorine, organophosphate and carbamate pesticides, organic herbicides. Small molecules such as toxic dioxins can also be degraded. The broad applicability makes the method unique.

[0058] Globally, there is a strong need for methods that can completely and effectively degrade these undesirable materials in soil. Without well-functioning in situ biodegradation methods, there is no realistic and affordable way to clean up contaminated land.

[0059] To solve the problem practically, a biodegradation method is needed that is as close to normal land farming as possible and can be carried out using existing agricultural machinery without requiring large new investments.

[0060] The presented method of accelerating biodegradation is just that. It is easy and its simple steps can be used by any farmer. Also, the money invested in cleaning up agricultural land with this method will be paid back in the form of improved soil quality, as fertilizers are added that contribute to the soil's humus content.

[0061] This method improves the quality of the soil, making it immediately usable after treatment. In many cases, depending on the type of contaminant and its concentration, the land is still useful during treatment, making the presented method attractive to farmers and investors.

[0062] Description of the method of accelerating the biodegradation of toxic organic chemicals according to the present invention The method of accelerated biodegradation is non-specific: all organic molecules in the soil are degraded, i.e., toxic or non-toxic, complex or simple contaminants or pollutants. Overall, the environmental risks of the method described herein for in situ remediation of contaminated soils are assessed to be negligible.

[0063] One example of applicability is the degradation of DDT and its derivatives (DDTr).

[0064] DDT may be the single most prevalent and threatening agricultural contaminant worldwide. The presented method is useful for anyone with a farm, nursery or other land parcel that needs to be cleaned of DDT (dichlorodiphenyltrichloroethane) or another organic compound that contaminates or pollutes the land. The method is useful when there are mixtures of compounds, even when the chemical structures or combinations of compounds are unknown.

[0065] The methods of the invention can be carried out in situ, i.e., at the natural or original location where the contamination or contamination occurred, or the methods can be carried out ex situ, i.e., external, off-site, or away from the natural or original location, for example, in a selected land area or soil treatment plant.

[0066] In the context of this application, the term "soil" refers to the naturally occurring unconsolidated upper layer of land. Soils typically comprise or consist essentially of organic matter, humus, weathered rock, sand, clay and / or sludge. The soil to be treated may be an agricultural soil, a horticultural or fruit garden soil, a garden soil, a building foundation soil, a roadside soil containing contaminated asphalt tar, or a forest soil, or a soil from another location ex situ.

[0067] The following steps provide a method for in situ or ex situ biodegradation.

[0068] A. Measuring and mapping pollution The levels of soil contamination / pollution (i.e. DDTr contamination) at various reasonable levels are measured in a reasonable number of test spots, taking into account the proposed use of the land and compared with recognised thresholds for the relevant type of contamination, and the areas requiring biodegradation are then mapped.

[0069] Measurement sites should ideally be selected based on historical knowledge of land use, and should then be chosen precisely in suspect areas to provide a good and realistic picture of contamination / pollution.

[0070] In the case of DDT contamination: measure the concentrations of DDT, DDD and DDE (or better, total DDTr) in both the surface soil (0-30cm below) and in the deeper soil (30-100cm below). It is most likely that only the surface soil will be found to have concentrations that are too high.

[0071] B. Analyze the amount of compost / composted manure / organic substrate available for use on land The next step is to analyse the amount of fertiliser / compost / hot-composted manure that can be legally added to one hectare of farmland, using the N, P and K values ​​of the product and the legal amounts given by the local authorities.

[0072] Manure used for agricultural land cleanup should always be composted with compacted fertilizers, since if it is not compacted, the nutrients can leach out and contaminate groundwater. Thermally composted manure is recommended, as it acts over a long period of time. It releases the nutrients into the soil over a period of 2-3 years, with very little N and P bound. For this reason, thermally composted manure hardly burns the roots of plants. The nutrients are released and can be used by microorganisms.

[0073] Thermally composted manure always has approximately the same nutrient content; that is, you can find tables of values ​​for all the most common products. It may also work if you want to use a homemade compost with a mixture of different things. In this situation, you may need to analyze the compost product and find out the exact content of N, P and K. Then you need to compare it with the thermally composted manure to make sure that the product has approximately the same nutrient profile and is useful for the biodegradation process.

[0074] C. Calculate how many square meters can be purified at one time and plan the spots to be treated. To ensure that sufficient organic substrate is present for the biodegradation process, at least 10% (weight percent) of nutrient-complete organic substrate should be added and mixed into the soil. It is recommended to use 12-15% (weight). When treating soil to the bottom 10 cm, the rate is 150-160 kg / m 2 The processing speed is about 15 to 20 kg / m 2 Compost is needed.

[0075] If it is permitted to spread 100 tonnes of thermally composted horse manure per hectare over a five year period, then if the soil is dug 10cm deep during this period, then the application rate is 100,000 kg / 20 kg / m 2 =5000m 2 It can also process 2500m 2 By treating the soil twice, it is possible to purify the soil to a depth of 20 cm, or 1667 m. 2 It is possible to completely remove contamination up to 30 cm below.

[0076] It is clear from these calculations that under these circumstances two five-year periods would be required to purify an entire hectare of cultivated land to a depth of 10 cm.

[0077] It may be possible to obtain exemptions from local authorities to use more substrate or to obtain permission to spread permitted uses unevenly over the land, or manure from adjacent fields can be used on the contaminated land.

[0078] This all depends on the understanding and goodwill of local authorities.

[0079] Once you know the area of ​​land that can be treated with the amount of substrate available, you can plan exactly which areas of the land you want to treat and when. A 10-year plan is often required.

[0080] D. Plan ways to avoid poisoning people, especially children, and to avoid contamination of the local environment. Clean-up of contamination / pollution must be carried out in close dialogue with local environmental authorities. This is particularly important to prevent accidents and environmental contamination.

[0081] As the contaminated land surface erodes, it creates a potentially dangerous situation: the contaminated material is now accessible; small children can eat the soil, animals and humans can become poisoned, and there is a risk of contamination spreading to the environment.

[0082] As soil disperses, so will contaminants into sensitive environments. In this situation, it is essential to address the access to contamination and immediately treat the toxic materials in line with the suggestions made here.

[0083] During all work in contaminated areas selected for spot treatment, great care should be taken to prevent the spread of contamination. Protect the area from children and the public with fences and appropriate signs to inform the public of the hazards. Lock gates as necessary.

[0084] It is also a good idea to cover the now open contaminated soil with organic material such as straw or, even better, dead tree leaves to support the earthworms.

[0085] Naturally, contamination of the groundwater and surrounding environment with N, P and K from the manure must be carefully avoided. If contamination is suspected, testing for N and P in the groundwater downstream of the treatment area is recommended.

[0086] A simple way to minimise the risk of groundwater and environmental contamination is by "spot treating", treating only the most contaminated areas with large amounts of manure. If only a small proportion of the contamination is treated each year, the risk of contamination from manure is also minimised.

[0087] It is also important that there are sufficient other plants, such as trees or grasses, on the land that can use the nutrients, especially N and P, as they are released from the fertilizer, again to avoid contamination with nitrogen and phosphorus.

[0088] E. Treatment of soil with compost / thermocomposted manure Now, a sufficient amount of slow decomposing organic fertilizer / manure or compost can be added to the soil, i.e., at least 10% (by weight), to treat the contaminated area.

[0089] Many studies have shown that incorporating manure into soil accelerates the biodegradation process, but high concentrations of substrate (>10%) are required for the process to proceed successfully.

[0090] It is known that adding well-treated thermally composted manure to land will lower the pH. In agriculture, it is a common procedure to readjust the soil pH with chalk, but fungal decomposition of chemicals like DDTr and many other complex organic molecules generally occurs more rapidly in acidic soils (pH = 3.0-6.5, ideal pH is around pH = 5.5), so chalk (lime, calcium carbonate) should not be added to either the compost or the land during the biodegradation stage.

[0091] It is also known that the process depends on the availability of iron in the soil. If iron is not present in a chemical form useful to the process, it must be added to the process along with the manure. The addition of iron is preferably in the amount of 1-4 kg of Fe, Fe per tonne of manure applied, unless the soil to be treated already contains at least 2 kg of iron per tonne of soil. 2+ or Fe 3+ , and more preferably 1.5 to 2.5 kg of Fe per ton of compost. 2+ Iron, most preferably Fe in an amount of 1.5-2.2 kg 2+ It is.

[0092] Therefore, the organic substrate must be rich in iron: 1.9 kg of metal powder, Fe, Fe per ton of compost. 2+ or Fe 3+ It is preferred to use this as this has been found to be the ideal iron concentration.

[0093] Mix the iron into the compost or spread the manure / compost / substrate over the determined area to "sprinkle" the iron salts needed for the biodegradation process. Adjust the plough to a depth of 10cm and work the substrate well into the soil. Ensure the soil and compost are well mixed.

[0094] It is the combination of a nutrient-rich support for large microbial communities, both bacteria and fungi, that results in rapid and effective biodegradation of simple and complex organic molecules.

[0095] In order for bacteria, fungi, worms, etc. to act on organic contaminants in the soil, it is believed that there must be intimate contact between the soil and the substrate. Ideally, each litre of soil should contain about 100-200 grams of added substrate.

[0096] (What exactly the best local composition of the soil / substrate mixture is is not yet known from in situ experiments, but a qualified guess can be made from a theoretical standpoint. Fungi, bacteria and other microorganisms benefit from locally high concentrations of substrate, so the ideal situation is for the soil to contain a mass of substrate (manure) of about 0.1-1 dl. You will need to experiment a lot to see what works best.)

[0097] The mixing process can be messy because a normal plow digs up the soil but does not actually mix it, so it is highly recommended that you carefully supervise the mixing process and continue working the soil until you reach the ideal conditions described above.

[0098] To ensure that the soil / substrate mixture is up to the "treatment standard," the soil is cut open at random locations with a spade to reveal the structure. Photographs should be taken to document proper soil / substrate mixing. Another important consideration is not to accidentally dig too deep into the soil, since as the study above found, contaminant half-lives can be much longer when substrate concentrations are diluted in the soil. Control photographs of cut open prepared fields should also show the depth of the treated soil.

[0099] We think it would be wise to start by treating only the surface soil. We think it would be best to treat only the top 10cm of soil initially. By raising large numbers of worms, finding the right pH and optimum concentration of iron in the soil, we can start the biodegradation process in the soil well.

[0100] More rapid decomposition can be obtained by adding more fertilizer to the soil, from 10 to 100% by weight or more.

[0101] F. Cover the soil with organic matter that is good for earthworms. After mixing the soil with the substrate using a plow and other suitable tools, cover the treated soil with worm food in the form of organic material such as hay, leaves, wood chips, straw and other cellulosic materials. Enough topping material should be used to prevent water from evaporating from the top soil layer on warm or windy summer days. Using too much topping material will block airflow into and out of the treated soil, greatly slowing biodegradation.

[0102] The rate of biodegradation of pollutants such as DDT and its derivatives, as well as other large organic molecules, is highly dependent on earthworms, so it is important to increase the number of worms by adding leaves or other suitable organic material.

[0103] Make sure the material you use is actually good for the worms. Fresh straw such as corn does not work very well. Hay is much better. Hay can be pre-composted to break down the hard surface of the straw. Leaves, or a black compost soil mixed with grass and other leaves, may be the best to apply.

[0104] This explains why it is recommended to plant the largest trees possible in spots needing cleanup, as they will produce large amounts of leaves that are beneficial to earthworms.

[0105] Biodegradation can be further improved by planting or sowing trees, flowers, grasses, etc. (phytoremediation). This increases the number and abundance of fungi and earthworms through mycorrhizae (a symbiotic relationship between green plants and fungi), provides easily accessible water channels for plant roots, effective soil drainage, and good aeration of the soil.

[0106] To enhance the biodegradation of contaminants, additional cultured or other microorganisms can be added to the soil (bioaugmentation).

[0107] G. Continue the process and moisten the cropland Keep the soil moist at all times, but never submerge or flood the soil. The soil should be moist, but always well drained and do not leave water on it for long periods of time. Never prevent the soil from breathing, as this will kill the worms and make the process anaerobic.

[0108] The biodegradation process of DDT and other organic molecules is highly dependent on water. The amount of water for the soil depends on the soil type, with sandy soils needing more water than clay soils. The concentration of water in the soil should not be too high in heavy clay soils, as this can inhibit the free diffusion of oxygen into the soil.

[0109] Use a permanent watering system that gives the required amount of water (test the soil regularly) or use sensors in the soil that tell you when to water. This should preferably continue for a 12 month period.

[0110] H. Monitoring and Adjusting pH The pH should be checked and adjusted downwards if necessary to pH<7, preferably pH=3-6, more preferably pH=4.5-6.0, pH=2.0-4.0 for chemicals requiring very low pH, and pH=7.0-9.0 for chemicals requiring high pH.

[0111] In the laboratory, we know that the ideal pH for very rapid breakdown of organic molecules like DDT is between 2 and 4, but the pH in soil cannot be made so low that it kills earthworms. This means that any downward adjustment of pH must take into account the soil type, and only soils that are sufficiently supportive of worms can be adjusted substantially downward.

[0112] This means that in soils that cannot adequately support worms, the process slows down, so many soils require a higher pH (pH = 5.0-6.5).

[0113] The simplest way to adjust the pH downward is to use a mixture of regular hot composted manure and acid compost. The acid compost is obtained from anaerobic composting, and the air flow to the compost is adjusted during composting until the desired pH is reached.

[0114] Alternatively, chemicals can be used that do not pollute but lower the pH. + is added, but Cl - and S.O. 4 -- The same applies when adding iron salts, and contaminating anions should be avoided.

[0115] There are special circumstances where contaminants or pollutants are stable in an acidic environment. In this case, the pH of the treatment medium is adjusted to a pH of 7-9, preferably 7.5-8.5, to allow biodegradation.

[0116] I. Continuing the process The soil concentration of the organic chemical or group of chemicals you want to remove, such as DDTr, is measured again in the treated soil after one year to see if the process needs to continue. It is generally recommended to also measure the content in the layer 10 cm below the treated layer, but this is not strictly necessary since the probability of significant changes here is low.

[0117] Repeat the soil remediation process as many times as necessary. Dig down further only when the top layer has been adequately treated. Keep in mind that the half-life of a stable molecule like DDT, when bound to the soil, is typically 10-30 years. You will be satisfied if you can break down the majority of DDTr (or any other organic chemical you want to break down) in 2-3 years. Keep in mind that the process can take years if local factors slow it down, as mentioned above.

[0118] For effective biodegradation of organic pollutants, it is important to keep the soil viable.

[0119] So dig down slowly in appropriate stages, i.e. 10cm at a time, until you reach the depth you want to clean.

[0120] If you want to dig down further and treat the next layer (i.e. the layer 10-20 cm down), it is wise to turn the soil over, so that the process always proceeds in the upper layer of soil, which is well aerated. When you turn the soil, the lower 10-20 cm layer is lifted, and this layer now becomes the top 10 cm layer.

[0121] This process is repeated with the layer that was previously 10-20cm down and is now the top 10cm of soil. To access the layer 20-30cm down, the soil is then dug down 30cm and the top 10cm is again addressed.

[0122] Of course, if you want to treat a layer 15-30 cm below, you can start at the top 15 cm and dig down 30 cm of soil, or start at the top 20 cm and dig down 40 cm of soil to access a layer 20-40 cm below, etc.

[0123] It is important to understand that the process works much better in the upper layers of the soil than deeper in the soil.

[0124] The method may further comprise analyzing the concentration of one or more contaminating / polluting chemicals in the soil before adding the fertilizer and analyzing the concentration of the substances again after predetermined periods of time, each predetermined period being preferably 12 months, and if the concentration is stable above the predetermined threshold, repeating the treatment process for the same soil or layer of material until the contaminant / pollutant has degraded to a concentration below said predetermined threshold.

[0125] The steps of the method can be repeated for the subsoil layer below the already treated soil layer. The subsoil layer to be treated is ploughed up to provide the top soil layer with the iron and pH modifier prior to the addition of the fertilizer. The soil is ploughed up, preferably to a depth of 20-30 cm, so that the first treated soil layer is lowered to a position below the soil layer to be treated, and optionally additional sublayers are then treated by ploughing the soil deeper, preferably an additional 10-20 cm for each layer, until the concentration of contaminating / polluting compounds in the soil reaches the desired level.

[0126] Practical Considerations Saving money by measuring indicators rather than total pollution In complex contamination cases, it is often sufficient to measure the concentrations of just a few of the major contaminants, as they are broken down together. This strategy can save significant project costs that are often spent on repeating chemical tests for the concentrations of dozens of compounds.

[0127] Legal restrictions on fertilizer use and processing times The most significant single factor limiting the time it takes to treat soil in the manner presented is the amount of compost / thermally composted manure that can legally be added to the soil in a year.

[0128] In Sweden, the use of 22 kg P / ha / year, or 1.6 kg P per tonne of thermally composted horse manure with wood chips, is permitted, which equates to a total of 69 t / ha over each 5-year period.

[0129] The 10% (by weight) organic substrate was used in the 10,000 m 2 This is a considerable amount, considering that the soil has a mass of 450 kg / m 2, i.e. 4500 tons. 10% of this is 450 tons. If thermally composted horse manure is applied to its maximum extent, the abovementioned 69 tons / ha can be used in Sweden for 5 years, assuming that the land is under cultivation and there are crops that can utilize all the nitrogen (N) as soon as it is released. This allows 15% of the cultivated land to be treated to a depth of 30 cm in each 5-year period. In this way, the cultivated land can be purified in 6.5 periods, i.e. 33 years.

[0130] Fortunately, the situation is usually not that serious. In many cases, it is only necessary to clean up the surface soil, such as the top 10 cm of soil. This is often the case with DDT contamination, where the DDTr concentration needs to be reduced to a threshold value. If the DDTr concentration is 50% above the threshold, it takes about two periods, or six years, to clean up agricultural land if you act as quickly as possible.

[0131] In a worst-case scenario where the entire agricultural land is highly contaminated, the thermal composting manure capacity would be 69,000 / 15 kg / m 2 =4600m 2 This is limited to treating only half of the top soil layer of the cultivated land, i.e. the top 10 cm. The next half must wait until the next 5-year period begins. After 10 years, the deeper half (10-20 cm down) can be treated (by plowing down the soil and treating the layer that is now the top layer), and so on.

[0132] It would take years to completely rid land of DDT in this way, but then again, this is only in situations where you want to use the soil for growing potatoes or another crop that could pick up DDT and supply it to consumers.

[0133] If you want to use the farmland for a sports area and want to have clean soil for a lawn, you can treat the top 5 cm of the entire farmland in the first year, which will already be enough to ensure a safe place to play football the following year.

[0134] It is important to understand that 69 tons per hectare of land is a lot of manure. Such an amount can only be used if the land has crops such as large trees that can utilize this amount of fertilizer, or if you are lucky enough to have good clay soil that can bind the minerals released from the fertilizer.

[0135] Again, the manure must be hot composted so that the phosphorus and nitrogen are tightly chemically bound and not released immediately, but over a period of 2-3 years, as is the case with fresh manure.

[0136] Fortunately, biodegradation often occurs very effectively in some parts of a field and much more slowly in other parts of the same field, for reasons that are often not yet understood. This means that highly contaminated "hot spots" of a field can be treated, while parts of the same field where the levels of contaminants are not significant can be left to natural degradation processes. Spot treatment often allows the spot to be effectively treated, and, if necessary, treated more deeply each year, making it possible to remove DDTr or another contaminant / pollutant from the field in just a few years.

Claims

1. 1. A method for treating soil in situ or ex situ to reduce the concentration of contaminating or polluting organic chemical compounds in said soil, comprising: a) determining the contaminated / contaminated area in which the soil should be treated; b) adding fertilizer in the form of thermally composted manure or other compost having a nutrient content comparable to that of thermally composted manure, the nutrients being correspondingly tightly bound to the compost, to the layer of soil in the area to be treated, said fertilizer being added in an amount of at least 10% (percentage by weight) of the soil of the layer to be treated, and repeated annually if necessary; c) iron, preferably in an amount of 1 to 4 kg Fe per ton of applied compost, unless the soil to be treated already contains at least 2 kg iron per ton of soil; ２＋ or Fe ３＋ , more preferably in an amount of 1.5 to 2.5 kg of Fe per ton of compost ２＋ , most preferably 1.5 to 2.2 kg of Fe ２＋ adding d) adjusting the soil pH to an acidic pH (pH<7), preferably to a pH of 3 to 6, more preferably to a pH of 4.5 to 6.0, or to a pH of 2 to 4; e) keeping the soil moist by adding water as needed for a predetermined period of time, preferably 12 months. A method comprising:

2. 10. The method of claim 1, wherein the manure in the form of hot composted manure comprises chicken, cow or horse straw or wood chip litter.

3. 3. A method according to claim 1 or 2, wherein the area to be treated is covered with a layer of organic material suitable for attracting earthworms, preferably comprising leaves, hay, composted straw, etc., having a thickness of 1 to 20 cm, preferably 3 to 6 cm.

4. 3. The method of claim 1 or 2, wherein the area to be treated is covered with a 1 to 20 cm thick layer of mulch / wood chips, sawdust, or other cellulose-containing material that covers the soil, retains moisture without restricting air exchange, and is not significantly attractive to earthworms.

5. 3. The method according to claim 1 or 2, wherein the fertilizer is added in an amount of 10-100% or more by weight of the soil of the soil layer to be treated, in order to enable the treatment of soils with high concentrations of contaminants / pollutants or to enable more rapid decomposition.

6. 3. The method according to claim 1, wherein the soil to be treated is agricultural soil, horticultural or fruit garden soil, garden soil, building foundation soil, roadside soil containing contaminated asphalt tar, or forest soil, or ex situ soil.

7. 3. The method of claim 1 or 2, wherein the soil to be treated consists essentially of sand, gravel, clay, or carbonaceous material.

8. 3. A method according to claim 1 or 2, wherein the material to be treated is not a solid material but a mud, i.e. a sludge or a contaminated liquid, which is mixed with manure / compost / fertilizer / bacteria nutrients, iron is added and the pH is adjusted, and said mud or contaminated liquid is added to fresh manure before or during the hot composting of the manure, thereby reducing the concentration of said contaminants or contaminating organic chemical compounds in the solid phase, after which the resulting compost can be used as normal compost or for further biodegradation, or said contaminated mud or liquid is added to a biogas plant and the biogas-producing liquid is used to remove contaminants or pollutants from said contaminated mud or liquid.

9. 3. The method according to claim 1 or 2, further comprising analyzing the concentration of one or more contaminant / polluting chemicals in the soil before adding the fertilizer in step b), and analyzing the concentrations of said substances again after predetermined periods, each predetermined period being preferably 12 months, and if the concentrations are stable above a predetermined threshold, repeating steps b) to e) on the same soil or material layer until the contaminant / pollutant has degraded to a concentration below said predetermined threshold.

10. 3. The method of claim 1 or 2, wherein steps b) to e) are repeated for sub-soil layers below an already treated soil layer, including a sub-soil layer to be treated, which is preferably ploughed up with a plough to provide a top soil layer to be treated with iron and pH adjuster before adding the fertilizer in step b), the ploughed up soil layer preferably having a depth of 0 to 30 cm, more preferably 0 to 20 cm, whereby the initially treated soil layer descends to a position below the sub-soil layer to be treated, and optionally further sub-layers are subsequently treated by ploughing the soil deeper, preferably a further 10 to 20 cm for each layer, until the concentration of contaminating / contaminating compounds in the soil reaches a desired level.

11. 3. A method according to claim 1 or 2, in which additional trees, flowers, grasses etc. are planted or sown to support biodegradation (phytoremediation), in particular by increasing the number of fungi and earthworms through mycorrhizae (a symbiotic relationship between green plants and fungi), which provide easily accessible water channels for plant roots, effective soil drainage and good soil aeration.

12. 3. The method according to claim 1 or 2, wherein cultured or other microorganisms are additionally added to the soil (bioaugmentation), thereby promoting biodegradation of contaminants.

13. 3. A method according to claim 1 or 2, wherein the substances to be analysed and decomposed are pesticides such as one or more of the substances DDT, DDD, DDE and / or DDTr.

14. 3. The method of claim 1 or 2, wherein the material to be analyzed and decomposed is one or more of gasoline, petroleum, or other polycyclic and aromatic materials from the petrochemical industry.

15. The size of the area to be processed is a) assessment of the N, P and K content in the fertilizer used; b) the amount of fertilizer available; c) Rules established by the relevant regulatory authorities regarding the addition of NKP fertilizers to said soil. The method of claim 1 or 2, wherein the determination is based on one or more of the following:

16. 3. The method according to claim 1 or 2, wherein the adjustment of the pH in step e) is replaced by adjusting the treatment medium, preferably the soil to be treated, to a specific pH other than the pH mentioned in step e) of claim 1, if required for a specific biodegradation process, preferably to a pH between 7 and 9, preferably between 7.5 and 8.5, to allow biodegradation of contaminants or pollutants that are stable in an acidic environment.