Currently, the disposal of waste from the oil and gas industry is becoming important. Oil contaminated soils, resulting from the extraction, processing and transportation of crude oil, now occupy landfills with areas reaching tens of km2. This is especially true for enterprises that own such landfills due to the tightening of environmental legislation aimed at increasing fees for negative environmental impacts . At the present stage of development of the oil and gas industry in the RK, the following methods for the processing of oil sludge have been applied.
Usually, refineries use a set of measures that includes several of the listed methods for processing oil sludge to achieve the best effect.
World practice uses many techniques aimed at neutralizing oil-polluted soils. All techniques can be divided into several groups.
The first group should include techniques that include the excavation of contaminated soil and subsequent measures for the disposal of pollution:plowing of oil-contaminated soil into the soil on uncomfortable lands. This technique involves the rehabilitation of oil-contaminated soil, distributing loosened soil (10 kg / m2) over the surface of the earth. This amount of soil polluted with oil is plowed to a depth of 30-35 cm, and land usually falls into the category of average land pollution. Plowing is repeated after a month, gradually decreasing to one per season after 2 years. Most often, the period of detoxification of soil contaminated with oil does not exceed 3 years, but with the use of bioremediation it can be reduced to 1 year [2-3];removal to a remote landfill. Oil contaminated soil can be added to the waste of urban landfills no more than 1-2% of the total waste.
The general term of utilization usually does not exceed - 3-5 years;export of soil contaminated by oil to specialized sites, providing for the distribution of contaminated soil over the area followed by aeration loosening and forced ventilation, irrigation, the introduction of nutrients and microorganisms into the soil. The total disposal period is 1 year;rehabilitation, involving the removal of contaminated soil and placing it in a kagat with a height of up to 2 m. Further irrigation of the laid kagat with a suspension of biomass of microorganisms with the addition of nutrients. Kagat gardening is often used.
The general term of recycling is 2 years;processing of soil contaminated by oil on stationary block lines for coarse and fine cleaning, which allows the maximum to bring oil to the specified parameters. At the same time, the soil with the content of oil products not exceeding 15 g / kg goes back to the site. This is followed by remediation (GenECO technology).
The second group of techniques is devoted to bioremediation measures directly at the site of contamination:
- treatment of oil-polluted soil with oil-oxidizing strains of microorganisms with simultaneous application of mineral fertilizers to the soil;
- treatment of polluted soil with preparations to stimulate the growth of native oxidizing microflora. This technology is currently the most widely used biotechnology for the elimination of oil pollution of the soil;
- burning of oil at the site of the spill, which allows you to utilize oil pollution only on the soil surface. Ecologically unfavorable is the destruction of natural biocenoses in places of annealing, as well as air pollution by combustion products.
There are other techniques for sanitizing the soil. Such as soil separation, high-temperature soil firing, steam treatment and other methods. These methods are rarely used due to the complexity of implementation. The analysis of methods of processing and disposal of oil-polluted soils, carried out by the authors, made it possible to identify the most relevant set of measures in the conditions of the Saratov region: the localization of the oil-polluted part of the territory; selection of commodity oil products, oil contaminated plant residues and garbage for subsequent disposal; chemical melioration using minerals (bentonite clays, bauxite ores and other materials); bioremediation - cleaning of oil-contaminated soil and water using preparations of hydrocarbon oxidizing microorganisms, biogenic additives that provide them with additional nutrition; as well as special preparations necessary for the stimulation of native oiloxidizing microflora. At the final stage of cleaning of oil-contaminated soils, it is advisable to use oligochaetes Eisenia foetida, E. Irregularis; biological recultivation (phytomelioration) of lands that are intended for farmland (introduction of crop rotations with plants used as siderite; mulching and other methods). The most environmentally friendly are biological methods for processing oil sludge. And although at present their use is limited by a number of factors, such as the range of activity of biological products, temperature, acidity, thickness of the oil-contaminated layer, aerobic conditions, there is no doubt that the potential uses of biological methods for processing oil sludge [4-5].
The improved technology for processing oil sludge used in oil-producing enterprises of the Saratov region, includes a method of biological delamination with subsequent disposal of the resulting residues. In this case, the oil sludge, which settles to the bottom of the tank capacity, is pumped not to the sludge storage tank, but to the anaerobic reactor. The reactor is equipped with a heating system and a specialized device that secures the anaerobic association of microorganisms. The normal vital activity of microorganisms is ensured by feeding the oil sludge nutrient into the anaerobic reactor in parallel with the pumping of oil sludge from the tank. After pumping the oil sludge and nutrient medium into the anaerobic reactor, the process of microbiological separation takes place in it. The process of stratification is accompanied by the development of the vital activity products of microorganisms - gas, surfactants, contributing to the separation of petroleum from mechanical impurities. Oil products accumulate in the upper part of the reactor tank, and the water drains down. As the accumulation of oil from the upper block of the anaerobic reactor by gravity into the tank, and the water goes into the sewer. The complete process of biological delamination in the anaerobic reactor lasts for 10-15 days. Next, the residual oil sludge treated in the anaerobic reactor with a percentage of up to 6-8% of oil product sludge is pumped to a biological stabilizer, where it is treated under aerobic conditions. The normal vital activity of microorganisms in a biological stabilizer is ensured by the supply of air and nutrient nitrogen- and phosphorus-containing additives. At the end of the stabilization process, the oil sludge contains petroleum products within 0.5%. After that, the oil sludge is pumped to specialized sites for subsequent drying. At the same time installations of biological utilization of oil slime work round the clock. The design capacity of each of them reaches 3,500 m3 / year. Waste to the installation in the form of oil sludge is a viscous dark-colored liquid with the smell of petroleum products. Oilsludgeisclassifiedashazardclass 3..
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