**8. Conclusion**

Biodegradation is very fruitful and attractive option to remediating, cleaning, managing and recovering technique for solving polluted environment through microbial activity. The speed of undesirable waste substances degradation is determined in competition with in biological agents like fungi, bacterial, algae inadequate supply with essential nutrient, uncomfortable external abiotic conditions (aeration, moisture, pH, temperature), and low bioavailability. Bioremediation depending on several factors, which include but not limited to cost, site characteristics, type and concentration of pollutants. The leading step to a successful bioremediation is site description, which helps create the most suitable and promising bioremediation technique (ex-situ or in-situ). Ex-situ bioremediation techniques tend to be more costly due to excavation and transportation from archeological site. However, they can be used to treat wider range of pollutants. In contrast, in-situ techniques have no extra cost for excavation; however, on-site installation cost of equipment, attached with effectively and control the subsurface of polluted site can reduce some ineffective in-situ bioremediation methods. Geological characteristics of polluted sites comprising soil, pollutant type and depth, human habitation site and performance of every bioremediation technique should be integrated in determining the most appropriate and operative bioremediation technique to successfully treatment of polluted sites.
