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PROBLEMS OF BIOLOGICAL REMEDIATION FOR TERRITORIES

A.D. Ukraintsev, A.N. Sinitsin*, T.K.Krasheninnikova

JSC "Biochimmash", * Military University RHBZ

Problems, connecting with the contamination of the environment with dioxins, oil and oil products are well-known. During the last 15-20 years these are the subject of constant scientific discussions, publications, versatile investigations, and the intensity of those does not decrease. At the same time, the volume of information gained (thousands of publications), scientific opinions expressed and tendencies developed, can be focused on the following main directions.

Determination of the list harmful compounds. It has appeared, that we should speak about the spectrum of harmful compounds, that only one of them (although the most toxic), is 2,3,7,8-tetrachlordibenzdioxin. For sure, this group includes polychlorinated biphenyls, halogen derivatives of dibenzfuranes, etc. As a whole, the UNO Program on the environment (YuNEP) combined these substances in the group of POC (persistent organic contaminants).

At the time being, YuNEP has selected twelve groups of POC, presenting a global problem. These are: pesticides, industrial chemical substances and unpremeditatedly produced side products and contaminants: aldryne, dyldrine, endryne, toxaphene, DDT, chlordane, heptachlor, myrax, PCB, hexachlorbenzene, dioxins, furanes. As could be seen from the list, the group under discussion, can number the hundreds of individual substances, the full list of those with their characteristics is not available at the present time.

The key word in the definition is "persistent", i.e. those that natural degradation in the environment takes place during dozen, hundreds, and even thousands years. Therefore, their influence will inevitably effect on the vital activity and health of many generations of live organisms, including people.

Complete discontinuance of coming technogenic POC into nature even if its significant reduction is an urgent direction to control POC, however, it is not real in the nearest time.

Other direction is the development of high-efficient technological methods of detoxification (destruction, liquidation) of POC, that came to the environment by some or other way.

As a whole, this direction can be considered as extremely urgent and important, allowing to a great extent to decrease the urgency of the problem at positive solution.

Of all POC, absolute leaders by its harmfulness and persistency in the environment are polychlorinated dibenzdioxins (in further, dioxins). We can conclude, that the most rapid and efficient way to solve this problem with POC is the developments of methods (technologies) of the destruction for dioxins and other halogen-containing harmful xenobiotics in the processing wastes and in the environmental objects.

Analysis of main directions of the investigations, and of scientific ideas and practical tendencies in this field has shown that mainly they have phenomenological, descriptive character with clear tendency of intimidating the unconversants. It is expressed in active attraction of mass-media by some scientists, numerous conferences, creation of special and industrial workshops and international organizations, issue of special materials, etc. Only extremely expensive methods of dioxin analysis in complicated natural objects are available, but in practice these methods have been monopolized by a small group of the specialized companies.

However, till no technologies, allowing to perform large-scale tests in practice have been proposed.

Methods of dioxin destruction are well known and can be easily grouped in 3 main directions:

These universal methods of the destruction are able to "process" not only specific products (e.g. 2,3,7,8-tetrachlorinedibenzdioxin), but the whole range of the aromatic hydrocarbons ,containing in aromatic nucleus such links, as carbon-oxygen, carbon- chlorine or simultaneously both types.

Photolysis and pyrolysis methods require great expenditures of power, and obviously are applicable only for the destruction of halogen-containing aromatic hydrocarbons in the processing wastes by direct burning or by using metallurgic processes available.

Therefore, lets consider the method of molecule destruction of chlorine-organic compounds under the influence of microorganisms. For simple vital activity of the microorganisms, and moreover, for the efficient processing by them the harmful admixtures, definite temperature, humidity, substrate composition are necessary. The process can take great time, can require the suppression or activation of aborigenal microflora. Biotechnological method can not be used directly to the media with high content of harmful substances (percents and dozen of percents). Or such process will require special technological approaches.

At the same time, working with low concentrations of the substrate, uniformly distributed in the medium, we can obtain the maximal efficacy of the method, that is undoubtedly higher than photolysis or thermal treatment.

At all diversity of microorganism metabolism, we can predict with sufficient certainty, the directions of biodegradation for halogen-containing xenobiotics. It is biological oxidation with molecular oxygen, in the course of which oxy-group produced as a result of the substitution or attachment reaction is included into the attacking molecule. Later on, further oxidation of the substrate is possible to mono- or poly-carbonic acid with the break of the hydrocarbon chain or opening of the aromatic ring. In the organisms of animals this scheme is realized as well as in biosynthesis (adrenaline) and also as a method to attach to xenobiotic the properties of water-solubility by its subsequent removal from the organism (cytochrome R-450). Non-specificity of microsome oxidation (mono-oxygenase) with respect to the oxidizing substrates and cascade mechanism of the oxidation give a wide possibility to an organism to survive in the conditions of diverse substances effect. It also should be outlined, that even on the first stage of microsome oxidation (introduction of oxi-group into aromatic nucleus) , the toxicity, e.g. of dioxins, decreases in dozen and hundreds times, physicochemical properties have been changing greatly, first of all, the hydrofobicity has been decreasing, chemical activity has been increasing and all degradation processes have been increasing.

In Federal Program "Dioxins- super-eco-toxicants of XХ1 century", adopted by the decree of the Government, RF in 1997, it was outlined that the method of bacterial destruction of polychlorinated dioxins has no practical application today. Mainly, it can be explained by small attention to the method of biodegradation itself, and in the second place, by the prolonged time of the microorganism effect to organic compounds of chlorine. As far as definite types of bacteria existing, under effect of those the destruction of the molecules of polychlorinated dioxins has been observed, then it is natural to suppose that at the selection of such bacteria and at the selection of the conditions, the production of strains and industrial preparations that could efficiently degrade polychlorinated dioxins in the acceptable terms is possible.

Preliminary studies on the problem of biodegradation of polychlorinated aromatic compounds have been performed by the specialists of JSC "Biochimmash" and ANO "NTO ETIN" with the participation of Military University RCB defense. The main results of studies are as follows:

  1. Low-hazard model substances for experimental work were selected:
    2-chlorine-phenol - for the selection of microorganism strains to the ability for biodegradation of polychlorinated aromatic compounds;
    2,4,6-tri-chlorine phenol - for the assessment of biodegrading ability of the selected strains to the stable contaminants.
  2. The methods for the infestation of water and soil samples with model substances were selected, that can really provide the reproduction of the results. The methods of HPLC for the determination of model substances in these media were selected.
  3. Efficient strain-destructor was chosen.
  4. It was established, that the selected microorganism degraded 2,4,6-tri-chlorine phenol for 60 days of incubation for 70 %; without microorganisms in the same conditions the reduction of TCP was 30 %.
  5. It was established in the experiments the fact of the consumption of trichlorine benz-dioxin by the selected strain.

Besides, "Biochimmash", ANO "NTO ETIN" and Lomonosov's MSU have developed the preparation "Rodart" that is used for the degradation of hydrocarbons with the aim of microbiological decontamination of soil and water surfaces contaminated with crude oil and oil products; it is also used for complex decontamination of analogous objects after the application of mechanical, adsorptive and chemical methods. The preparation "Rodart" provides the activation of the processes for the natural selection of the polluted soils and waters.

The preparation effects at the level of contamination with oil and oil products to 20 % by weight. By its main indices (degree of destruction at high 20% level of soil and water surfaces contamination, ability to degrade heavy and light fractions of hydrocarbons, rate of biodegradation, effect in a wide range of temperature), the preparation has no analogs and is competes with the best foreign preparations. In Table 1 main comparative characteristics of different domestic preparations and of the preparation "Rodart" are presented.

The preparation and products of oil destruction do not render harmful effect to the environment. At the reduction of the contamination to the level lower acceptable limits of concentration, bio-preparation loses its biological activity because of the absence of hydrocarbon as a source of nutrition and energy.

Microbiological method of oil and oil products biodegradation advantageously differ from chemical, physical methods and their combinations by small capital investments, low power consumption, absence of the secondary wastes, ability to self-keeping and self-regulation, ecological safety.

Biopreparation "Rodart" of pilot -scale production represents dried powder of light-brown color with specific odor, it comprises the cells of bacteria, non-pathogenic for human beings, animals and plants, residues of nutrient medium and components of the protective medium. Composition of the preparation is "know-how" of the researchers. The preparation is characterized by a wide range of resistance to temperature regime (from +8 to +35 °C) with temperature optimum 15-30 °C and can be used efficiently in different climate conditions. Biopreparation is easily and completely suspended in water. The consumption of the preparation is 10 kg per 1 hectare of soils; 1,0 kg per 1 hectare of water surface. Number of treatments depends on climatic, geophysical conditions and on the level and character of the contamination.

On the last stage of soil re-mediation from the pollution with xeno-biotics, the seeds of plants should be seeded. The growth of the plants on the decontaminated territories is as a rule an indicator of the decontamination degree and the presence of toxic semi-products of destruction. Proper selection of the plants allows to add the stage of purification, that is called phyto-remediation. For the intensification of plant growth process, JSC "Biochimmash" developed the preparation- plant growth stimulant under the name "Mycepfit", the basis of this preparation is biologically active substances, produced by endo-mycorrhizal fungi at suspension culturing in the reactors. This technology is unique, there no analogs in the world.

On the basis of the indicated above, and by the results of long-term studies, performed at JSC "Biochimmash" jointly with Military Chemical University, the preparation can be created- biodegradant of xeno-biotics of wide range of effect. Now, it is possible to develop such preparation, comprising the association of microorganisms that destroys oil, oil products, dioxins, etc. on the basis of the microorganism collection available in JSC "Biochimmash".

Our proposals are to perform complex experimental studies with the final aim to develop the preparation for bio-destruction of territories contaminated with different xeno-biotic.

Table 1. Comparative Analyses of the Efficiency of the Degree of Oil Consumption for Different Preparations- Biodegradants of Oil

Name of the preparation

Content of oil, % 1 treatment 2 treatment 3 treatment Object of contamination

Total time of effect, days

    Time, days Oil consumption,% Time, days Oil consumption,% Time, days

Oil consumption, %

   
Devoroil
(dry com. preparation)
10
10
3
3
12-14
12-14
12-14
12-14
23,7
12,3
36,4
32,3
12-14
12-14
12-14
12-14
42,3
24,5
60,8
54,2
12-14
12-14
12-14
12-14
52,4
35,6
81,2
75,8
Soil
Water
Soil
Water
36-42
36-42
36-42
36-42
Putidoil
(dry commercial preparation)
10
10
3
3
10
10
10
10
30,4
24,8
40,9
42,4
10
10
10
10
45,8
39,4
52,1
54,7
10
10
10
10
65,3
69,3
75,9
86,4
Soil
Water
Soil
Water
30
30
230
30
Roder
(liquid commercial preparation)
10
10
3
3
10
10
10
10
24,9
32,7
45,8
52,4
10
10
10
10
37,5
40,9
68,3
72,4
10
10
10
10
49,1
52,6
90,5
92,3
Soil
Water
Soil
Water
30
30
30
30
Rodart
(liquid preparation, experimental batch)
10
10
3
3
5-7
5-7
5-7
5-7
43,8
40,2
65,4
63,7
5-7
5-7
5-7
5-7
67,9
62,1
80,6
79,3
5-7
5-7
5-7
5-7
81,9
74,2
99,4
96,5
Soil
Water
Soil
Water
15-21
15-21
15-21
15-21

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Proceedings of First Russian Workshop on Biological Security
Copyright © Committee of Scientists for Global Security and Arms Control