**1. Introduction**

The rapid growth of industrial activities in recent years and non-obedience with environmental laws accompanied by discharging of various pollutants from petrochemical industries cause increase of contaminants into the environment [1, 2]. Wastewater comprises many organic and inorganic pollutants, and settling them into received waters causes to serious environmental problems [3]. The entrance of huge amounts of contaminants such as oil compounds and heavy metals via the wastewaters of industries to the coastal and aquatic ecosystems has created serious problems [4, 5].

#### **Figure 1.**

*Summary of global water pollution worldwide and geographical distribution of water pollution based on the type of main pollutant [5].*

The presence of pollutants in water bodies above their acceptable levels set by the World Health Organization (WHO) and Environmental Agencies may have enormous effects [6]. Most of wastes discharged to the environment contain toxic contaminants such as aromatic compounds and heavy metals which can cause major damage to marine ecosystems and living organisms such as neuronic toxicity, carcinogenicity and reproduction abilities [7, 8]. Therefore, it is necessary to reduce the levels of pollutants below the standard range (**Figure 1**) [9].

Many methods have been offered for treatment of contaminated water environments, but they may be non-effective or expensive. However, bioremediation is an effective technology with a range of advantages rather than traditional methods [10, 11]. Bioremediation of waste materials which contain hydrocarbons and heavy metals is based on the microorganism's potential such as bacteria and fungi to absorb them from polluted wastewater or change them to non-toxic products [11–13].

The microorganisms could be native to a polluted area or isolated from another place and moved to the contaminated position. PAHs and heavy metals in the environment can influence microbial communities and form new microbial communities with the purpose of adapt to the hazardous environment so the strains screened from these contaminated areas usually show high capacity to tackle with the pollution of PAHs and heavy metals [11, 14].
