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21 Descri tion of Technoloov Microorganisms are ubiquitous in nature and contaminated sal may already support a community of bacteria and fungi which possess the capability of degrading aliphatic and aromatic hydrocarbons (Table 1) Even many of the chemically stable substances such as paraffin and mineral oil can be metabolized by microorganisms TABLE 1 TYPE OF ORGANISMS THAT ARE ABLE TO DECOMPOSE HYDROCARBONS ' BACTERIA MYCELIAL BACTERIA FUNGI Achromobacter Actinomyces Acremonium Alcaligenes iMicromonospora Aspergillus Bacillus Mycobactenum Candida ' Bacterium Nocardia Citromyces Brevibactenum Streptomyces Penicillium Corynegacteruwm Torula Flavobactenum Pseudomonas Specific microorganisms are specialized in the decomposition of the various hydrocarbons and ' polyaromatic hydrocarbons Amongst the bacteria, it is mainly the pseudomonas that are capable of decomposing hydrocarbons rapidly It is clear from the data provided for the Jahant Road site that the main group of contaminants belong to the fuel-gas hydrocarbon category This suggests that microbial decontamination is a feasible option for the soil restoration However, the degradation rates of these compounds are ' strongly influenced by many environmental conditions such as temperature, water activity, available electron acceptors as well as the availability of nutrients in the soil matrix Microbial degradation achieves different rates depending on the dominant composition of oil hydrocarbons Thus, rapid degradation of aliphatic hydrocarbons such as the non-branched chain paraffins, can be achieved ' The oxidation is catalyzed by B-oxidase enzymes and involves the inclusion of molecular oxygen Slower reaction is known for long chain alkanes, naphthenes, cycloparaff ins, polyaromatics The main obstacle to effective biodegradation of some of these compounds lies not only in their inherent ' molecular recalcitrance but also in their exceedingly low water solubility, e g , Chrysene 6 ugL-1 and 1,2,5,6-dibenzanthracene Q 6 ugL-1 The oxidation of the aromatic compounds is catalyzed by mono and di-oxygenases and the utilization of oxygen is imperative for the complete oxidation of these compounds into H2O and CO2 Bioremediation processes do not usually result in the accumulation of toxic intermediary products ' Only particular groups of microorganisms are capable of decomposing specific hydrocarbons For successful soil restoration, the growth of the appropriate species should be stimulated by the manipulation of environmental conditions such as improving the bioavailability of nutrients, oxygen, etc This would allow the indigenous active population to proliferate and result in faster rate of ' decontamination For degradation of recalcitrant compounds, efficiency can often times be improved if pollutant-degrading organisms have a competitive advantage over the other organisms present If deemed necessary, this can be achieved by the reintroduction into the soil of ' appropriate consortia or inocula of specific microorganisms responsible for key transformations in the biodegradation of the xenobiotic compounds These microorganisms can be isolated and selected from the soils by straightforward procedure, if necessary, grown to sufficient density and used for inoculation to enhance the overall biodegradation activity within the contaminated soil 3