Title
#PRA2124
Ecologically Safe Technology for Bioremediation of Soils Polluted by Toxic Chemical Substances
Short Title:
Bioremediation of Soils Polluted by Toxic Chemical Substances
Technology Area:
Remediation and Decontamination / ENV-RED
Person for Contact:
V.I.Varenik
Address: Obolensk 142279, Serpukhov District, Moscow Region, Russian Federation
Tel.: 7 (095) 190 0725
Fax: 7 (095) 190 0725
R.V.Borovick
Address: Obolensk 142279, Serpukhov District, Moscow Region, Russian Federation
Tel.: 7 27 75 9738
Fax: 7 27 75 9738
Research Institute Where the Above Persons Belong:
Research Centre for Toxicology and Hygienic Regulation of Biopreparations at Ministry of Health of Russian
Federation, Serpukhov, Russia (RCT&HRB)
Present Status of Research:
Pollution of the environment by toxicants presents a severe hazard to health and to nature. Self-purification of soil
from high concentrations of pollutants and its stabilisation do take place, but they are very slow and require active
human intervention. Processes of soil forming proceed even slower: 1 cm of soil humus is formed, under natural
conditions, in the course of 300-400 years. In our opinion, the use of biological methods for remediation sound the
most ecologically friendly and promising, because the fertility and properties are not destroyed.
The Department for Ecological Biotechnology at the RCT&HRB develops biological methods for removal or
decomposition of environmental xenobiotics as the main direction of its activity. Three main methods form the basis
of our approaches: 1) microbiological destruction using natural strains, as the primary method; 2) the use of
earthworms for intensification of microbial decomposition of pollutants and restoration of natural soil microflora
with microrganisms-symbionts, and; 3) application of various biological products (biohumus, chitin powder from
crustaceous, bentonite clay, etc.) as sorbents.
We consider the developed approach to be a complex system of soil bioremediation.
Processes of soil remediation are carried out under obligatory control over integral toxicity using animals-biotests,
and the appropriate techniques have been developed.
At the Toxicological Centre, a collection of natural microorganisms-degraders of oil products, polycyclis
hydrocarbons, phenols, polychlorinated biphenyls, heptyl, etc. has been organized and is constantly supplemented.
The most promising strains of biodegraders are subjected to comprehensive toxicological examination on albino
mice and rats to determine safety for warm-blooded animals and humans.
The collection of animals-biotests (daphnia, infusoria, guppi fish and earthworms) has been created and maintained
in vital activity. The developed express-technique for biotesting allows the assessment of pollution and integral soil
toxicity before and after remediation, and permits ecological monitoring and mapping of polluted territories
according to toxicity level well before the xenobiotic content in the soil has been ascertained.
Under financial support of the ISTC (Project #228), manifold investigations on development of biotechnology for
remediation of soil polluted by polyphenyls are carried out. These substances have been used in the electrotechnical
industry to impregnate condensers, because they are excessively stable. They are not exposed to photolitical,
chemical or biological decomposition. It has been established, through the toxicological examinations, that
polyphenyls are highly toxic, accumulate in the human body, have a carcinogenic effect, and cause disruption of the
reproductive function and dermatides.
For 60 days rats were given soil extract containing TCD (trichlorodiphynyl) – 1 mg/ml, copper – 1,5 mg/ml, zinc –
4,6 mg/ml, lead – 0,4 mg/ml. Leukopenia, eosinophilia and an increasing relative content of something relating to
stab leukocytes. The hepatotoxic effect has manifested as increasing transaminase activity. However, the most
important manifestation of toxicity of given xenobiotic combination has been the serious disruption to the function of
males’ gonads, manifested by severe dystrophia and, on frequent occasion, by atrophia of seminiferous structure.
More than a hundred natural strains of microorganisms-PCB-degraders have been isolated from the soils near the
“Condensator” plant (Serpukhov district), which have been polluted by polyphenyls over a long period. After control
over bioactivity and safety for warm-blooded animals, two most effective biodegraders have been determined:
bacteria Alcaligenes latus (TCD-13 strain) and yeast Hansenulla californica (AT-strain). The indicated strains have
been deposited into the International Collection of Industrial Microorganisms (Moscow) and two international PCT
Records of Invention have been submitted.
According to the developed biotechnology, a suspension of microorganisms-PCB degraders is introduced directly
into polluted soil. To speed up the processes of polyphenyl decomposition and remediation of original soil
microflora, specially selected earthworms are used on the second bioremediation stage.
The role of the earthworms is multifunctional: on the one hand they continue and accelerate the processes of
microbiological destruction through aeration and, on the other hand, powerful fermentation systems of the
earthworms’ digestive tract intensify processes of xenobiotic decomposition. One more role of the earthworms
should be noted – removal of microorganisms-degraders from soil. For ecological safety reasons, the need may arise
to reduce microbial concentration in soil up to threshold point (10 2–103 per 1 gram). Species features of the
earthworms’ biology and their technological possibilities are widely diversified, and may form the subject of another
report. Control over the processes of PCB decomposition is carried out by biotesting on daphnia - in this case LD50
was 2,8 mg/kg of soil TCD. A field trial of the developed biotechnology has shown that during the summer season
PCB concentration in remediated soils has reduced from 279 to 171-160 mg/kg of soil, that is to say by 42-47%.
Integral toxicity of remediated soils determined by biotesting has shown its reduction.
Experiments with use of warm-blooded animal (albino rats) have shown that toxic products of PCB decomposition
have not formed after biological remediation.
We have not studied the chemical processes, concerned with the biological destruction of polychlorinated
compounds because these fermentative processes have been well studied and described. (Tetsuya Kumamari et al.
1998, О.E. Zaberina et al., 1997; F. Fava et al., 1997; Q. Wu et al., 1998). At the same time, a progressive reduction
of PCB concentration with formation of mono-and dichlorobiphenyls, which are less toxic, takes place.
Further, we have conducted investigations on the application of new types of biosorbents for binding heavy metals,
chemical and radioactive pollutants in soil. In experiments with the soils polluted by salts of heavy metals and
radionuclids (strontium-90 and cesium-137), it has been shown that biohumus, chitin powder (the reprocessing
product of marine crustaceous chitin) and grey bentonite clays, activated by a special method, have high sorbing
properties.
Our investigations on the seminar devoted to ecological problems of elimination of chemical weapons are of
relevance, because the described methods – microbiological destruction, vermicomposting, biosorption – may be
used for remediation of soil, polluted by a wide spectrum of organic compounds, including PS (poison substances).
Such reports appear in increasing frequency. The application of biological methods in combination with
physico-chemical methods have unexpected and positive results for soil bioremediation.