7. Characterize the process of surface and groundwater contamination by oil and petroleum products

The most obvious consequences of oil pollution include the death of waterfowl and several species of animals, living in marine and fresh waters, pollution of beaches, reduction or cessation of fishing in the polluted waters. However, the greatest danger is the impact of petroleum products on the ecology of water bodies.

The oil by the contact with the water forms a layer on the surface, and the light hydrocarbons begin to evaporate. Gradually the oil is drawn into the turbulent motion of water, mixing with them, and after a while most of the oil is concentrated in the water masses. The content of dissolved oil in water can reach 10 mg / l. Meanwhile, MPC of petroleum products in recreational waters is 0.3 mg / l, and in fisheries - only 0.05 mg / l. First, fat, carbon, and naphthenic acid and phenols, cresols become in form of an aqueous solution. A few days after the receipt of petroleum products in water as a result of chemical and biochemical decomposition other soluble compounds are formed - oxygenated hydrocarbons, the toxicity of which is significantly higher than that of unoxidized.

7. Characterize the process of soil pollution by oil and petroleum products

Crude oil is a naturally liquid with a complex mixture of organic molecules, mostly hydrocarbon with varied chemical and physical properties. A precise description of the chemical composition of crude oil is not practicable because of its complexity. There are different operations in the petroleum industry in the onshore as well as in the offshore that can cause soil pollution and aquifer contamination with petroleum products, such as drilling operations, leakages from wellheads and pipelines and overflows at gathering stations, improper disposal of petroleum wastes and leakage from underground storage tanks.

Exploration and production of petroleum, however, have caused detrimental impacts to soils, surface and groundwaters, and ecosystems. According to statistics, every year there are more than 800 million tons of oil into the world environment, contaminated soil, groundwater, rivers and oceans, including oil pollution of the soil is mainly destruction of soil structure affect soil permeability, damage to plant roots, prevent root respiration and absorption, eventually leading to plant death. Second, the oil contaminated the soil aromatic substances on human and animal toxicity of a larger, of which benzene, toluene, xylene, phenols and other substances, if a larger concentration of exposure by the longer period of time will cause nausea, headaches, dizziness and other symptoms.

7. Describe the In situ bioremediation process

In situ bioremediation

Bioremediation method has gained acceptance worldwide as an in situ treatment of contaminated sites. Bioremediation can be also applied with the help of spreading units in case the contamination occurs at the surface. However, the degradation of oil in the in-situ process requires availability of sufficient amount of oxygen. Therefore, the selection of any method of this technique depends also on the penetration depth of the hydrocarbon into the soil and on the nature of the soil if it is groundwater saturated or unsaturated and if the contaminants in the subsoil are biodegradable. Figure 1 shows an example, in which nutrients and oxygen are injected into the contaminated area to stimulate the indigenous bacteria to break down the hydrocarbons as a nutrient source. Feeding oxygen and nutrients into the soil can accelerate the process of clean up. This method is suitable to treat contaminated sites of petrol stations and refinery sites as well as to treat areas, where the water table is close to the surface. Figure 2 shows the growth of microorganisms on soil surface in present of oil and water phases.