RU2225271C2 - Method of purification of soils from underground pollution by phenols - Google Patents

Abstract

FIELD: biological purification of soils. SUBSTANCE: the invention presents a method of purification of soil from underground pollution by phenols, that provides for irrigation of a soil surface over the center of the underground pollution by a suspension, containing a microorganism-biodestructor and biogenic elements, infiltration of the suspension in the soil and extraction of the underground pollutions by it, a liquid pumping-out from a water-bearing bed through the special wells and following purification from pollutions using an aeration filter and aeration by air (the pumped out air is purified from vapors of pollutions by the air filter). In the capacity of a microorganism - biodestructor in the irrigation liquid, in the aeration filter and the air filter the strain of bacteria - Aureobacterium saperdae 6-204 is used, and the nozzle of the aeration filter with a porosity of 0.4-0.9 is made out of inert materials (excelsior, peat). The method allows for 65 days to purify the soil from the underground pollution by phenols by more than 99 % without any overburden operations and excavation of the polluted underground soil up to the surface. EFFECT: the method allows within rather short period of time to purify phenol polluted soils by 99 % without any overburden or excavation operations. 5 tbl, 2 dwg

Description

 The invention relates to the biological cleaning of the soil from underground pollution with phonols, using microorganisms and can be used in the chemical industry, energy, utilities and in accidents in transport.

 In recent years, the use of microorganisms-biodestructors in the treatment of soils and sediments contaminated with organic substances has attracted more and more attention of researchers and technologists [1].

 Closest to the claimed purpose and combination of essential features is a method of biological soil treatment based on microbiological oxidation of organic pollutants (phenols) in a surface-type bioreactor (biofilter). In this case, extraction of contaminants from the soil by water entering through the infiltration trench, pumping out of groundwater and subsequent biodegradation of the contaminants contained in it by native microflora in the biofilter are carried out [2].

 The main disadvantages of the known method adopted for the prototype are the low intensity of pollution degradation associated with the use of native microflora, as well as significant evaporation of organic pollution from well water in the bioreactor. In addition, the method is associated with a change in the natural landscape, since the flow of wash water into the soil is carried out through an infiltration trench.

 The claimed invention solves the problem of increasing the efficiency of cleaning underground soil pollution. The proposed method is also based on the extraction of groundwater with subsequent biodegradation of the contaminants contained in them, and further extraction of the contaminated water with purified water from the soil, however, unlike the prototype, not native microflora, but the bacterial strain Aureobacterium saperdae 6- 204, immobilized on the nozzle of the air filter, provides biooxidation of vapors of organic pollution (phenol) in the air filter (see Fig. 1).

 The technical result achieved by the implementation of the invention is ensured by the fact that the soil surface is irrigated with a liquid containing from 0.05 to 0.2 g-ion / l ammonium, from 0.005 d6 0.05 g-ion / l phosphates, as well as Aureobacterium saperdae 6-204 biodestructor microorganism; the liquid pumped out of the wells with the impurities dissolved in it is fed to the air filter with a flow rate that ensures the concentration of pollution at the exit of the air filter in the range 0.1-0.3 mg / l; aeration of the air filter is carried out by pumping air from under the nozzle layer, the evacuated air is cleaned of fumes from the air filter, also filled with a nozzle with a bioorganic microorganism; The bacterial strain Aureobacterium saperdae 6-204 is used as a biodestructor microorganism in the air filter and air filter, and the air filter nozzle with a porosity of 0.4-0.9 is made of inert materials.

 The elimination of underground pollution is carried out by extracting them into the wash water, pumping the latter out of the wells and biodegradation of the pollution by an air filter. Wash water is applied to the surface of contaminated areas by sprinkling. Pumping from wells is carried out by borehole pumps so that the groundwater level in the area drops to a minimum compared to the usual level. After pumping, sprinkling of the site is performed to restore the groundwater level. Pumping and sprinkling procedures are repeated until the concentration of pollutants in groundwater is reduced to acceptable values.

 The pumped water from the wells through a system of pressure pipelines laid on the surface of the earth is fed to a phenol washing water purification system in an air filter equipped with a drainage grate, on which a nozzle layer is placed. In the air filter, wash water circulates through the nozzle with immobilized cells of the microorganism-biodestructor, which consume phenols contained in the water. Water is circulated through the air filter until the phenol concentration in the water drops to the level of 0.1-0.3 mg / l. The design of the installation for processing contaminated water excludes the possibility of their getting into the underground horizons. Utilization of phenol vapors is ensured by draining the latter from the air filter into a special air filter with a nozzle from horse peat with immobilized cells of the bioorganic microorganism, where they are captured and biodegradable.

 In the claimed technology uses a phenol-oxidizing bacteria strain Aureobacterium saperdae 6-204. Microorganisms are non-pathogenic, non-toxic, non-invasive (not taking root in humans and warm-blooded animals).

 The selected strain Aureobacterium saperdae 6-204 was isolated from the accumulative culture of a sample of soils in Chuvashia, where in 1996 a freight train with phenol crashed. This soil is characterized by a phenol content of 0.14 g / kg to 1.754 g / kg.

 Characterization of Aureobacterium saperdae 6-204 strain.

 Storage medium: MPA (meat-peptone agar).

 Cultural and morphological characteristics: yellow, small, shiny, drop-shaped, whole colonies form on meat-peptone agar, the edge is smooth, the colony has a uniform structure, the diameter of the young colony is 2-2.5 mm, and the old is 3-3.5 mm. . The pigment does not diffuse on Wednesday. Bacteria are gram-positive, non-spore-forming, non-acid-resistant, sticks 1.05 x 2.5-1.0 x 3.0 microns. Single, some in pairs, a V-shaped configuration or palisade in the form of parallel-lying rods, cocciform cells 0.7x0.7-1.05x1.05 μm are found. In old cultures, sticks are usually short, they do not form mycelium. Cells are weakly mobile.

Physiological and biochemical characteristics: aerobes, respiratory metabolism with the formation of a small amount of acid, but not gas from glucose, sucrose, maltose, mannose. The bacteria are catalase-positive, they do not dilute gelatin, they do not curl milk and do not peptone. Nitrates do not recover. Abundant growth with a beige-yellow pigment on a slice of potato. In the BCH, the mucous membrane, moderate turbidity, the precipitate is sparse. It grows well in the pH range of 6.8-7.4, at a temperature of 15-20 ^o C, indole and hydrogen sulfide does not form. The strain Aureobacterium saperdae 6-204 was deposited in the collection of microorganisms OOO PKF "Bigor".

 In the process of biodegradation of phenols, no substances are produced that have a negative impact on the environment. When phenols are exhausted, the cells of the biological product-destructor are replaced by natural microflora.

 Example 1. Experiments were conducted to study the developed method for cleaning the soil with a phenol content of ≈1000 mg / kg using the bacterial strain Aureobacterium saperdae 6-204. The experiments were carried out on a model installation; wood shavings were used as an air filter nozzle.

 The installation shown in FIG. 2, consists of: a 550-liter wash column, five 3-liter air filters, five 2-liter tanks, eight gear pumps, a fan, a 50-liter storage tank, a 5-liter purified water tank, an air filter, hoses, an instrumentation system and A. Air filters and containers are made of plexiglass and polyethylene. Communications are made of silicone hoses.

 The first purification step — the extraction of contaminants from soil samples — was carried out in a wash column (1) with a diameter of 0.45 m and a height of 3.5 m made of plexiglass.

 Multistage extraction of soil samples was carried out, the number of extraction stages in the experiments varied from 2 to 4.

A soil sample was irrigated with water from a distribution head with an intensity of 0.1 m ³ / m ² • h or with a flow rate of 1 l / h.

 The initial and residual (after extraction) content of contaminants in the soil samples was measured. In the experiments, the degree of phenol extraction from the soil at each extraction stage was determined.

 Based on the obtained material balance of the process of phenol extraction from the soil, the degree of extraction of these substances in weight percent was determined.

где φ - степень "недоизвлечения" экстрагируемого вещества;
а - отношение потоков: масса отделяемого раствора к массе раствора, удерживаемого твердым веществом;
n_с число ступеней экстрагирования.The treatment was carried out with a pure solvent - water, so the degree of "under-extraction" of the extracted substance (the ratio of the amount of extracted substance in the residue to the amount in the starting material) was calculated by the formula

where φ is the degree of "under-extraction" of the extracted substance;
a is the ratio of flows: the mass of the separated solution to the mass of the solution retained by a solid;
n _{with the} number of stages of extraction.

 The experimental results presented in Table 1 showed that during water extraction of phenol from soil, on average, phenol is almost completely washed out after 3 extraction steps - the final degree of extraction reaches ≈100%, the residual phenol concentration in the soil does not exceed the allowable phenolic index.

 Depending on the initial concentration of phenols in the soil, multistage extraction from the soil is provided.

The second stage of purification - biodegradation of contaminants - was carried out according to the following scheme. Each of the five air filters (6) was loaded with a nozzle layer 150 mm high on a substrate of a vasopron sheet. The nozzle consisted of wood shavings. A sprinkler was located above the surface of the nozzle, and a device for venting air under the nozzle. Flow sensors (5) monitored the flow of solution into the sprinklers on each air filter. Air was pumped out of the unit. Air was taken by an exhaust fan (8) from under the nozzle at each stage. Wash water from the wash column (1) containing phenols extracted from the soil entered the storage tank (2), in which a suspension was prepared containing:
- water with a phenol content of 150 mg / l;
- biological product (strain of bacteria Aureobacterium saperdae 6-204) - 10 mg of ASB / l
- (NH ₄ ) ₂ SO ₄ - 191 mg / l;
- KH ₂ PO ₄ - 30 mg / l;
- MgSO ₄ - 10 mg / l;
- trace elements - 12.5 mg / l.

 The storage tank was fed with fresh nutrient medium once a day.

 From the storage tank, the liquid was pumped (5) sequentially to the five stages of the air filter through the receiving tanks (3). Irrigation nozzles in air filters were carried out through sprinklers. After passing through the nozzle layer, the liquid was collected in the receiving tank of this stage and returned to the air filter for recirculation. When the phenol content in the liquid of a given level is reached, the flow was directed by gravity to the receiving tank of the next purification stage, while the flow from the previous stage entered the receiving tank of this stage.

 Upon reaching a predetermined phenol content in the liquid leaving the last stage, the flow was directed to the collection of purified water (7), and a new portion of the liquid from the previous stage of purification entered the last stage. The purified water from the collection was pumped to irrigation in the wash column. Thus, the installation worked in a closed mode.

 During the operation of the installation, air containing phenol pairs was vented from under the nozzle layer of all air filters, which was directed to an air filter (9), where vapor condensate was biodegradable using the same microorganism Aureobacterium saperdae 6-204.

 For 65 days, the soil was cleaned in a closed process, consisting of washing the contaminated soil in the column and biological treatment of the wash water in the cascade of air filters. During the experiments, it was found that when the soil with phenols ≈1000 mg / kg was treated for 65 days, the phenol concentration in the water did not exceed the phenolic index for drinking water (0.25 mg / l), while the degree of soil purification from phenols amounted to 99.94%. In the table. 2 shows the characteristics of biocatalysts immobilized on wood chips and peat.

The hydraulic load on the wood chip nozzle was:
at the first stage - 30 m ³ / m ² • day;
on the 2nd-5th steps - 10 m ³ / m ² • day.

 Example 2. Experiments were conducted on cleaning the soil using horse peat as a nozzle air filter. The experiments were carried out on the setup described in example 1.

 According to the results of the experiment (Table 3), it is seen that when peat is used as a nozzle, more intensive oxidation of contaminants by biological product cells occurs.

The hydraulic load on the peat nozzle does not exceed 2.1 m ³ / m ² • day.

 Example 3. Experiments were conducted to optimize the nutrient medium, the effect of the concentration of introduced ammonium on the activity of phenol-degrading microorganisms was studied. The experiments were carried out on the setup described in example 1, using wood shavings as a nozzle.

 According to the results of the experiment (Table 4), it can be seen that when the content in the nutrient medium is 0.05-0.2 g-ion / l ammonium, a sufficiently high activity of the biocatalyst cells is ensured, and a high degree of purification of the soil from phenols is achieved.

 Example 4. The optimization of the nutrient medium by the amount of phosphates in the same conditions as previous experiments.

 The biocatalyst is characterized by a rather high activity when using a nutrient medium containing 0.005-0.05 g-ion / l of phosphates (Table 5).

 The examples presented show that the proposed method provides for 65 days the degree of soil purification above 99% without stripping and removing contaminated underground soil to the surface.

Sources of information
1. A. Yu. Vinarov, VN Smirnov and others. Biotechnological methods of environmental protection. Overview. M., 1999, 46 p.

 2. Morgan P., Watkinson R.J. (1989) Microbiological methods for the cleanup of soil and ground water contaminated with halogenated organic compounds. FEMS Microbiol. Rev. 63, p. 277-300.

Claims (1)

A method of cleaning the soil from underground pollution with phenols, including irrigating the surface of the soil above the core of the underground pollution with a suspension containing a bioorganic microorganism and biogenic elements, infiltrating the suspension into the soil and extracting underground pollution, pumping the liquid out of the aquifer through special wells and then cleaning it from pollution air filter with aeration, characterized in that the soil surface is irrigated with a liquid containing from 0.05 to 0.2 g-ion / l ammonium, from 0.005 to 0.05 g-ion / l phosphate s, as well as the microorganism-biodestructor Aureobacterium saperdae 6-204; the liquid pumped out of the wells with the impurities dissolved in it is fed to the air filter at a flow rate that ensures the concentration of pollution at the outlet of the air filter in the range of 0.1-0.3 mg / l; aeration of the air filter is carried out by pumping air from under the nozzle layer, the pumped-out air is cleaned of fumes from the air filter, also filled with a nozzle with a bioorganic microorganism; The bacterial strain Aureobacterium saperdae 6-204 is used as a biodestructor microorganism in the air filter and air filter, and the air filter nozzle with a porosity of 0.4-0.9 is made of inert materials.

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