LT4593B - Process for biological reclamation of soil contaminated with oil or oil-products - Google Patents

Abstract

This invention is related to the field of environment protection, to be more precise - to biological treatment of soil polluted with oil or oil products, such as remnant (scarcely biodegrading) black oil, and it may be used for environmental protection. Biological treatment of soil polluted with oil or oil products is based on the insertion of organic and mineral fertilisers into polluted soil, tilling the polluted soil periodically ploughing and cultivating it, irrigating and mulching it, sowing into a mulch layer oil product resistant and less demanding for the soils upper plants - agricultural cultures, the rhizosphere of which immobilizes oil oxygenising micro-organisms, growing seeds, cultures, until the soil pollution decreases to a permissible level, and then the plant biomass is ploughed.

Description

The invention relates to the field of ecology, and more particularly to biological treatment of soil contaminated with petroleum or petroleum products such as fuel oil and may be used for environmental protection.

Fuel oil is a complex multi-component pollutant. According to our data (State Ground Cleaning Technology Report, 1996, 1997, 1998), it contains significant amounts of aromatic hydrocarbons and resins. The qualitative characteristic of fuel oil is,%: paraffin-naphthenic hydrocarbons - 15; olefins and cyclodio lefins - 5;

alkylmonoaromatic, alki 1d iaro mat i n la i. polyaromatic hydrocarbons 25, benzene resins 55. These are components which are severely degraded by oil-oxidizing micro-organisms (ΝΌΜ). The soil contaminated with such fuel oil is cleaned in a specially equipped biodegradation site. We use a primer for cleaning when its fuel oil pollution does not exceed 30000 - 35000mgkg of dry soil and at lower pollution. The surface of the site must be waterproof. The soil to be cleaned is laid on a water-permeable drainage layer, the soil to be cleaned is applied in a layer of 35-45 cm. It must contain an appropriate concentration of biogenic elements (C, N, P, S. Ca, etc.) and trace elements (Mn, Cu, Mo, Br, Co, J, etc.). As a result, the soil is periodically fertilized with mineral fertilizers, aerated during cultivation and, if necessary, watered.

The soil to be cleaned by oil oxidizing microorganisms should contain O, 9x10 '- 3.5x10 ^{, s} (depending on the time of year). Such concentration is maintained by biotechnological means. With soil contamination of 35000 mg / kg dry soil, after 30 days (to our knowledge), the NOM in the soil destroys all paraffins and naphthenes. 30% aromatic hydrocarbons and only 12% benzene resins, which are the most difficult to decompose. When cleaning the soil contamination with fuel oil still up to 6000 g / kg of dry soil is mNroorganizmų various physiological groups of content (colonies / g soil) Heterotroph (bacteria growing on MPA) - 4.1 10 ⁷ χ aerobic azotofiksatorių - 0.5 xl0 ⁴ aerobic cellulose-degrading bacteria - 2.2 χ 10 ³ oil-oxidizing microorganisms - 0.9 χ 10 ⁶ total bacterial count - 9.1 x 10 ^s actinomycetes - 6.1 χ 10 ³ micromycetes - 2.8 x 100 ² GB 4593 B

In known ways, further cleaning of the soil in the final stage of cleaning up to the permissible level or before the final degradation of the pollutants is complicated, time consuming and does not allow efficient use of the soil cleaning sites.

According to our research, some fuel oil-resistant wild flora grows in areas polluted with fuel oil. We have recorded 38 such wild plant species belonging to various systematic groups. These plants have a well-developed root system. They also include plants with rhizomes, which, thanks to the rhizomes, not only retain viability during the fuel oil spill, but also spread rapidly to the contaminated area from the remaining live diasporas and penetrate into the contaminated area from the non-contaminated area. 50-100 times more microorganisms accumulate in the rhizosphere of the oil-resistant plants roots and branch hairs, compared to the soil located further from the roots. The roots of the plants have a well-expressed extracellular activity of 1 m bar. As a result, nitrogen in organic compounds, which is hardly available to microorganisms, becomes easily absorbed. The phosphatase activity of plant roots activates the transformation of both soil organophosphates and superphosphate fertilizers. Phosphorus becomes more accessible to soil and oil oxidizing microorganisms. In addition to absorbing free solutions of the soil solution, as well as colloidal sorbed cations and anions, the plants release into the soil some organic compounds (organic acids, enzymes), which, as a food source for microorganisms, ensure their rapid growth.

The widespread use of wild plants to clean fuel oil contaminated soil is difficult because of the difficulties of planting and cultivating them, the difficulty of collecting their seeds and their narrow adaptation to soil conditions.

Known method for microbiological cleaning of water, soil or other surfaces contaminated with petroleum products, described in patent specification RU 2007372, where

3.5 - 6. treated with a suspension of micromycetes Candida giddsnnondii ΒΚΠΜ Y-241 cells and mineral additives, nitrogen and phosphorus fertilizers.

The disadvantage of this method is that it can be applied to the surface treatment of soil contaminated with petroleum or petroleum products and is ineffective when it is necessary to treat a larger amount of contaminated soil before its complete revitalization, thereby also treating the soil after 40 days of oil degradation. the intensity decreases and remains virtually unchanged and the residual soil contamination by oil products amounts to 2.2 kg / m ^ of soil.

³ LT 4593 B

Also known is a method for cleaning oil-contaminated soil, which is described in RU 2 <) G266y, in which the contaminated soil is aerated and watered with a suspension of nitrogen and phosphorus mineral fertilizers and microorganisms association.

The disadvantage of this method is that microorganism associations actively degrade petroleum products until the soil temperature exceeds S - 10 ° C. At lower temperatures, microorganism activity is greatly slowed down and fractions remaining at the end of the process, such as aromatic hydrocarbons, benzene resins, spirit-benzene resins are difficult to destroy microorganisms.

SUMMARY OF THE INVENTION The object of the present invention is to increase the cleaning efficiency of a large amount of soil contaminated with residual (hardly biodegradable) fuel oil in the final stage of biological treatment, to improve the physiological-biochemical activity and biological activity of soil microorganisms and to reduce its cost.

The problem is solved by the present invention, where organic and mineral fertilizers are added to the soil polluted with small amounts of fuel oil, the soil is aerated several times by plowing, harrowing, cultivating, irrigating the soil, mulching the treated area with fertile and structural soil layer. seeds of higher crops - agricultural crops, in which the rhizosphere immobilizes oil-oxidizing microorganisms (NOMs) - are cultivated until the soil contamination is reduced to an acceptable level, after which the plant biomass is degraded. As 50 to 100 times more microorganisms accumulate in the rhizosphere of plants compared to the soil further away from the roots, the plants not only absorb free cations and anions of soil solution but also colloid sorbed cations and release some organic compounds into the soil, which ensures rapid microorganisms reproduce and stimulate their activity. Plants accumulate mineral substances from the soil in their biomass, therefore, after the soil cleaning is completed, the plant biomass decomposes, which effectively helps to restore the natural microbiocenosis and autoregeneration mechanisms of the cleaned soil.

Before applying, the fuel oil-contaminated soil is applied with mineral fertilizers in a layer of organic fertilizers, such as rye straw chopper, about 2 cm, after which the cultivated soil is mulched with about 5 cm of fertile soil or peat. Rye straw, when incorporated into the soil to be cleaned, increases its porosity, oxygen delivery to the soil, and the mulch layer helps maintain the required soil moisture and has a positive effect on plants during their germination phase.

⁴ LT 4593 B

Prepared for sowing with fuel oil contaminated soil, with soil oil contamination concentration not exceeding 6000-7001) mgAg dry soil, depending on the time of year and air temperature, seed of higher crops - agricultural crops - is sown in the mulch layer.

In the temperate zone, winter rye seeds are sown in the oil-polluted soil during the first half of September, when the soil temperature is at least 1-2 ° C.

In temperate climates, oilseed-contaminated soil in early spring, when the soil temperature is at least 4-5 ° C, sows better seeds of oat-vetch mixture or meadow mist-vetch mixture.

Seeds of oat-vetch mixture, vetch-meadow mist mixture or rye seed are sown in a layer of mulch at a depth of about ten seed diameters.

May. end of June. in the first half the crop biomass is harnessed. The mineral content of the plant biomass enriches the soil and can be further used as a compost fertilizer.

Industrial cleaning of soil contaminated with residual amounts of fuel oil and complete revitalization of the soil is carried out using experimentally selected crop plants resistant to fuel oil effect: oat-vetch mixture, vetch-meadow mist mixture or winter rye. These plants are introduced into fuel oil contaminated soil when it is biologically cleaned on a special site, poured in a layer of 35 - 45 cm, and when soil contamination does not exceed 6000 - 7000 mg'kg of dry soil. The soil contamination level is adjusted, if necessary, it is supplemented with the required amount of unpolluted soil, determines soil moisture, soil porosity. the amount of mineral fertilizers in it. Add to the contaminated soil mineral fertilizers in the following quantities: ammonium nitrate - 19.5 g. m ² , superphosphate 6.5 g / m ² , potassium chloride 3.25 g / m ² . Together with mineral fertilizers, apply a layer of organic fertilizers up to 2 cm, for example, rye straw choppers, periodically (every 3 days) plow, cultivate (harrow), water to maintain normal soil moisture. The prepared soil is mulched with about 5 cm of fertilizer soil or crushed peat. Soil mulch is prepared in the temperate zone in early spring, when the soil temperature is at least 4-5 ° C, sowing seeds of either oat-vetch mixture or vetch moss mixture. The seed is inserted at a depth of approximately ten seed diameters. If necessary, the irrigated area is measured to measure residual contamination. When the residual contamination reaches the allowable level and is reached within about 40 to 45 days, the crop biomass is degraded.

The present invention relates to the use of higher crop crops for cleaning soil contaminated with residual oil or petroleum products, in particular difficult to degradable fuel oil resins. They were selected on the basis of the morphological and physiological properties of fuel oil-resistant wild plants. The selection of plants resistant to fuel oil was performed under ground conditions. Thirteen plant species were selected for the test: Elytrigia repais, Phragmites mistralis, Lupine luteus, Festuca pratensis, Typhoides arundinacea, Linum sativum Phleum pratense), blue-green alfalfa (Medicago sativa), meadow mist (Poa trivialis), white clover (Trifolium repens), oats (/ 1 vena sativa), vetch (Vida sativa), winter rye (Secale cereale).

example

The test area was 120 m ² . Removed 45 cm deep soil. In its place was placed a fuel oil-polluted sandy soil. Fuel oil pollution - 18000-25000 mg kg dry soil. Fuel oil qualitative characteristics (in this test and later),%, paraffin-naphthenic hydrocarbons - 15, olefins and cyclodiolefins - 5, alkylmonoaromatic, alkyldiaromatic, polyaromatic hydrocarbons - 25, benzene resins - 55 m. rye straw chop - 2 cm thick and nailed 20 cm deep. The test site (120 m ² ) is divided into 12 segments - plots of 10 m ² area. Eight test plants or groups of plants were planted there, 2 plots for the penis (with and without soil reparation), and 2 plots for control (with and without soil reparation).

Test started May 20th.

Part of the soil contaminated with fuel oil was covered with a 5 cm thick soil layer. The seed placement depth of the plants used for the experiments was equal to 10 seed diameters.

the plant used in the herd was evaluated for growth in heavy fuel oil contamination soil, left for further tests oat-vetch mixture, bell-tree, yellow-throated lupine, fescue, meadow mist, spring rape. In the test, fuel oil pollution is reduced in individual variants to 10g'kg; 12g / kg; 15 g / kg dry soil.

Concentration of fuel oil in excess of 10 g of dry soil was found to strongly inhibit the formation of all investigated plants and their root system.

Coating soil contaminated with fuel oil with a 5 cm layer of clean soil (mulching) improves the formation of test plants and their roots.

The test showed that oats, vetches, meadow mist, mixtures of the above plants, burbot as well as winter rye are the most resistant to fuel oil. The bell as a weed is not accepted for further evaluation.

example

The test was carried out on 3 plant species, namely oats, vetches and meadow mist. Soil - sandy loam. which under experimental conditions is contaminated with fuel oil at lower concentrations (4320 mg kg - 4770 mg'kg dry soil) and higher (8020 - 9440 mg / kg dry soil). Used plastic containers, the bottom of the containers is filled with a layer of gravel (drainage) 3 - 5 cm thick. The tanks are filled with 13 kg of test soil with the specified fuel oil contamination, the area of the test plot is 95 cm ² . Mulching with 5 cm of unpolluted soil was also tested (separate variants).

The soil to be tested was initially wetted once with tap water, then (7 times) with a solution containing 1.5 g / l ammonium nitrate, 5 g / l superphosphate and 0.25 g / l potassium chloride. .

Test run is August. Dec. 22 - October month. June 06

The room and soil temperatures during the test ranged from 17.5 to 22.0 ° C. The biometric characteristics of oats and vetches grown together (mixture) under laboratory conditions are shown in Table 1.

Plant Biometrics

Number of seedlings, units

Stem length, cm Root length, cm Ground weight, g Root weight, g Gross weight, g

At a contamination of 4320 - 4770 g / kg of dry soil, inoculated:

oats wikis 25 · 46th 17th 26th 9th 7, is 12-26 1,350 8,982 0.600 2,396 1,950 11,378

table

In the case of pollution 8020 - 9440 g / kg dry soil inoculated:

oats wikis 26th 51 17th 23rd 9th 5-7 3,930 4,489 1.050 1,950 4,980 6,439

At the end of the test period, the oil pollution in the oat-vetch mixture variant and the vetch-meadow hazel variant decreased from 7000 mg / kg dry soil to 832 mg / kg dry soil. Meadow mist germinated abundantly, however, considering the specific structure of this plant, its stem and root length was not measured, and its total biomass weight in case of soil contamination with fuel oil 4320 - 4770 g'kg was 5,241 g dry soil and 8020 - 9440 g with soil contamination. 'kg dry soil comprised 1.072 g'kg dry soil.

example

Similar studies were conducted in the field during August. 29th October 10 The surface area of the tanks is 130 cm ² .

The results of the studies are presented in Table 2.

table

Biometric characteristics of plants (grown on 130 cm ² )

Number of seedlings, units

Stem length, cm Root length, cm Mixture:

ground weight, g root weight, g total weight, g

At a contamination of 4320 - 4770 g'kg dry soil added:

oats wikis 74 47 14th 19th 18th 22.54 19.70 42.24 22nd

In the case of pollution 8020 - 9440 g / kg dry soil inoculated:

oats wikis 40 21st 11th 17th 16th 17.03 13.00 30.03 17th

The obtained results show that oat and vetch plants grown in the mixture develop well, their growth is influenced by the lighting and moisture content, and the plants biodegradable fuel oil, which during the test period decreases to the allowable level. During the trial period, the plants produced a significant total weight of biomass, which is higher at lower soil oil pollution but high enough at higher oil pollution.

Winter rye has been tested for resistance to fuel oil. Under field conditions, rye sown in the first decade of September in oil-polluted soil - on average 6000 - 8000 mg kg dry soil - germinated and grew in the same way as in the control variant.

The agrotechnology of seed oil resistant plants is as follows.

Oats (Avena sativa) - a non-volatile plant, loves moisture, has a well-developed root system, can be sown early in spring when it is 4-5 ° C, important for cleaning fuel oil contaminated soil, because fuel oil oxidizing microorganisms begin to decay at soil temperature 8-10 ° C heat. By the time the soil reaches that temperature, the oat sprout system has already developed. Oat seed rate - 180 - 2 LO kg / ha. Seeds shall be treated.

Vetches (P / cv'fl scitiva) - A non-volatile plant that germinates when the soil temperature is 2 ° C and requires a lot of moisture. Vine seed rate - 150 kg / ha.

The oat-vetch mixture is better suited for cleaning oil-polluted soil. It is estimated that the optimum seed output rate for the oat-vetch mixture is 250 kg / ha, which is made using equal proportions of oats and vetch. Oat seed must have a minimum purity of 07% and a germination of 00%. Vetch seeds must have a minimum purity of 03% and a germination of 85%.

Mineral fertilizers (ammonium nitrate, superphosphate and potassium chloride) must be present in the fuel oiled soil, which is biologically treated. These plants accumulate these fertilizers in their biomass and do not leach into the environment. As the oat-vetch mixture grows, a strong root system is formed within 3 to 4 weeks. Organic acids secreted by its roots dissolve low soluble minerals and, by means of enzymes, dissolve organic compounds of various molecular sizes, including fuel oil, which it makes more accessible to oil-oxidizing microorganisms.

Meadow mist (Poa prcitensis} dwarf rhizome, densely wound, forms a stable turf, is good for both flooding and drought. Meadow mist seed rate - 14 kg ha. It is recommended to sow it with vetches, then meadow mist seed rate - 7 - 8 kg / ha, vetch - 8 8 kg / ha.

Winter rye (Secaie cereale) is sown on oil-polluted soil (over 6000 mg / kg dry soil) in autumn September. Winter rye can germinate at 1 - 2 ° C soil temperature, does not need much moisture to germinate, has strong, deep penetrating roots, can tolerate severe frost. In spring, as soon as the germs leave, strong stem growth begins, further root formation. Because of these properties, winter rye is well suited for the biological completion of fuel oil-contaminated soil, where the fuel oiled soil has been cleaned on site in 35-45 cm layers from May. It is recommended to sow in winter rye until autumn, when the soil temperature drops to 8 - 10 ° C and oil pollution remains about 6000 - 7000 mgkg of dry soil. In the spring (late May or early June), the soil is already fully decontaminated with fuel oil, the contamination does not exceed 832 mg / kg of dry soil, winter rye plants are harvested and this fertilizer soil can be used as compost soil. Winter rye seed should have 97% purity, 90% germination and an average seed weight of 30 g. Seeds shall be treated.

Plants sown in soil contaminated with fuel oil can be used as green-sidcral fertilizer when the fuel oil is destroyed. Due to the abundant use of mineral fertilizers in the biological treatment process, the soil has the same nutritional qualities as compost soil when it is completed and the plants are decapitated. It can be successfully used for fertilizing degraded soil and for quarrying. When the primary cleaning of oil-contaminated soil is carried out in special sites by applying a layer of 35 - 45 cm and cleaning from May. until autumn (until the soil temperature drops to 8 - 10 ° C), the residual soil contamination by fuel oil is over 6000 - 7000 mg / kg dry soil, and at low temperatures the fuel oil degradation slows down significantly, winter rye, which can germinate at 1 - 2 ° C soil temperature, they do not need much moisture to germinate. Rye has strong, deep-penetrating roots and can withstand severe frost. In the spring, as soon as the germs leave, rapid growth of the stem begins, and further root formation begins. At the end of May or the first half of June, rye is recommended as the soil is already completely cleaned of fuel oil and can be used as fertilizer in compost soil. If rye was not used in the autumn, then oat-vetch or meadow-vetch mixtures can be sown in the spring ready for cleaning. These plants germinate at 4-5 ° C and root well in a short period of time, and as early as late May or early June, the oil-soaked soils can be decomposed as compost soil and freed from contaminated soil treatment. continue to use the site for its intended purpose.

Once cleaned and ecologically reclaimed, the complex biological restoration of fuel-contaminated soil described herein can be removed and used rationally for planting and fertilization of quarries, quarrying and the biodegradation site by filling it with cleaning soil at short intervals.

Claims (7)

DEFINITION OF INVENTION 1. Biological treatment of soil contaminated by petroleum or petroleum products by applying mineral fertilizers to the soil, by periodically digging and cultivating the contaminated soil, by adding organic fertilizer to the soil prior to plowing with mineral fertilizers. , and cultivates seeds, crops and crops of oil-resistant and less demanding soils - crops whose rhizosphere immobilizes oil-oxidizing microorganisms, till the soil contamination is reduced to the permissible level, and then the plant biomass . 2. A method according to claim 1, characterized in that up to 2 cm of rye straw chopped layer is applied to the soil as an organic fertilizer, and the cultivated contaminated soil is mulched with a layer of fertile soil or peat of approximately 5 cm. 3. A process according to claims 1 and 2, wherein at a concentration of up to 6000 - 7000 mg / kg of dry soil contamination in oil products, depending on the time and ambient temperature, the higher plants - seeds of agricultural crops. 4. A method according to claim 3, characterized in that winter rye seeds are sown in the oil-polluted soil in the temperate zone in the first half of September, when the soil temperature is at least 1-2 ° C. 5. A method according to claim 3, characterized in that in the temperate zone the oil-polluted soil in early spring, when the soil temperature is not lower than 4-5 ^: C. sow seeds of oat-vetch mixture or grass-seed vetch mixture. 6. A method according to claims 1 and 4 or 5, characterized in that the seed is sown into the soil at a depth equal to ten seed diameters. 7. A method according to claim 1 and 4 or 1 and 5, wherein end of June. in the first half the crop biomass is harnessed.