**5. Types of bioremediations**

There are far more than nine types of bioremediation, but the following are the most common ways in which it is used.

#### **5.1 Biopile**

Bioremediation includes above-ground piling of dug polluted soil, followed by aeration and nutrient amendment to improve bioremediation by microbial metabolic activities. This technique comprises aeration, irrigation, nutrients, leachate collection and treatment bed systems. This specific ex-situ technique is progressively being measured due to its useful features with cost effectiveness, which allows operative biodegradation conditions includes pH, nutrient, temperature and aeration are effectively controlled. The biopile use to treat volatile low molecular weight pollutants; it can also be used effectively to remediate polluted very cold extreme environments [12–14]. The flexibility of biopile allows remediation time to be shortened as heating system can be integrated into biopile design to increase microbial activities and contaminant availability thus increasing the rate of biodegradation [15]. Additionally, heated air can be injected into biopile design to deliver air and heat in tandem, in order to facilitate enhanced bioremediation. Bulking agents such as straw saw dust, bark or wood chips and other organic materials have been added to enhance remediation process in a biopile construct. Although biopile systems connected to additional field ex-situ bioremediation techniques, such as land farming, bioventing, biosparging, robust engineering, maintenance and operation cost, lack of power supply at remote sites, which would facilitate constant air circulation in contaminated piled soil through air pump. Additional, extreme heating of air can lead to soil drying undertaking bioremediation, which will inhibit microbial activities and which stimulate volatilization than biodegradation [16].
