Many methods or techniques have been used to control these pollutants, including chemical, physical, and biological, and the most successful of these is the biological technique called the biodegradation process. This method is one of the alternative and widely successful methods for removing pollutants and causes little harm to the environment. Some studies have shown that the biodegradation process takes place in three basic steps, which include: A small and simple change occurs in these organic compounds, fragmentation of the hydrocarbon chains into parts while preserving the chemical composition of the basic compound before fragmentation, and finally metallization of the organic parts and changing their composition from organic molecules to inorganic molecules, and that the microorganisms decomposing hydrocarbon compounds constitute less than 1% of the soil microbial community. These numbers increase when polluted to reach 10%. They produce some substances that affect surface tension and work to break up and analyze oil spills.                                                                            

       They are chemically heterotrophic and heterotrophic  Many of them were isolated from areas contaminated with crude oil and its derivatives, and their ability to analyze hydrocarbon compounds was studied. It was found that they are environmentally friendly bacteria that work to rid the environment of these pollutants, whether on the surface of the water or soil, and provide a safe option for treating pollution. As described by others  it is characterized by its ability to break down most of the components of oil, is genetically stable, has the ability to reproduce quickly, possesses decomposition enzymes and the ability to compete with other organisms naturally present at the site of pollution, and finally, it is distinguished by not causing negative side effects, and it also Unsatisfactory or producing toxic metabolites. Many researches have indicated the possibility of isolating and identifying different types of bacteria that have the ability to represent different types of hydrocarbon compounds  Most of the hydrocarbons belong to gram-negative bacteria, and these genera include Aeromonas media, Pseudomonas putida, Serratia liquefaciens Aeromonas media, Flavobacterium breve, Sphingobacterium spiritivorum, many of which were isolated from  Some researchers were able to identify (Acinetobacter baumanni, Klebseilla oxytoca) aerobic and facultative anaerobic bacteria and anaerobic bacteria in oil pollution sites and in wells as well as soil contaminated with hydrocarbons. In another study, some found that Bacillus species that have the ability to form spores are highly efficient in decomposition in polluted environments With oil, in addition to isolating various types of it from deep areas of polluted sea water, sediments and soil

        There are factors that affect the decomposition of oil  It was stated in some sources that environmental factors play an important role in the process of biodegradation of these pollutants, including the abundance of oxygen, pH, and temperatures. And the concentration and composition of contaminated hydrocarbons, relative humidity, and mineral salts. It was noted that the ability of Micrococcus roseus isolates to grow on diesel was observed by measuring the live numbers and optical absorbance of these isolates and using the dilution method  under aerobic conditions, given that this species needs oxygen for the process Biodegradation and the isolates that showed increasing growth from the beginning to the end of incubation reflects the ability of bacteria and their consumption of hydrocarbon compounds as a source of energy and carbon

         There are factors related to microorganisms, the mechanism of biodegradation depends on the presence of Bacteria with the ability to grow, reproduce, and decompose hydrocarbons in contaminated areas, depending on the abundance of nutrients needed for their growth in addition to environmental factors. Another factor is that the bacteria contain plasmids that carry the genes responsible for the biodegradation process. Some researchers   studied the effect of adding nutrients and an aeration agent on the biodegradation of polycyclic aromatic hydrocarbons using a mixture of bacteria. They concluded that biodegradation increased in the presence of the aeration agent, the addition of nutrients, and the presence of the bacterial mixture. In another study  on the effectiveness of biology Microbes naturally endemic to oil-contaminated soils. Analysis of crude oil derivatives in the presence of nitrogenous and phosphorous nutrients showed their ability to digest 80.8% of crude oil within 21 days.

         The efficiency of biodegradation of these pollutants was tested upon microbial injection using new active bacteria. 4.Bact No. Also, injection with a mixed culture of 4.Bact.No bacteria, White .rot fungus, and Streptomyces. Also, biological decomposition was estimated upon microbial injection using the complete microbial flora, as it was able to remove 99% of the crude oil