In this work, the oxidation of phenolic compounds was accompanied by shift in the wavelength and change in the colour such as the oxidation of phenol to catechol by Volvox aureus, Nostoc Linckia and Oscillatoria rubescens. The oxidation of β-naphthol by Volvox aureus, Lyngbya lagerlerimi and Nostoc linckia, and the oxidation of catechol by Chlorella vulgaris and V. aureus were suggested. The degradation of polycyclic aromatic hydrocarbons by different algae seems to be related to the molecular structures of the compound and physiological metabolism of the algae. The highest percentage of degradation of naphthalene by N. linckia after 7 days was 47.71%, while the highest percentage of degradation of anthracene by E. viridis after 7 days was 92.28%. The highest percentage of degradation of 2-methythie 3-phenyl quinazlin-4-3H (one) by V. aureus after 7 days was 83.39%, and the highest percentage of degradation of 2-phenyl 3,1benzexazin-4 one by E. viridis after 7 days was 79.74%. The obtained results suggest that microbial biodegradation of pollutants can be used to clean up contaminated environments. Biotreatment of wastes using living organisms is an environmentally friendly, relatively simple and cost-effective alternative to physico-chemical processes. Algae can convert benzo pyrene to peroxides, dihdrodiols and oxides [10,11]. When benzo pyrene was incubated with algae, a greater percentage of the benzo pyrene was first degraded and mineralized (broken down to carbon dioxide and water). These findings that algae in conjunction with bacteria may lead to more complete degradation of large PAH s like benzo pyrene [12]. Biodegradation of Phenolic andRecently, [13][14][15][16] studied the ability of some algae for biodegradation of phenolic compounds in the light and dark. The aim of this investigation was to study the ability of some algae isolated from different polluted sites, on the degradation of different phenolic compounds, polycyclic and heterocyclic aromatic compounds. Materials and Methods Algae and growth conditionsThe following algae are isolated from different polluted sites and purified in axenic cultures (bacterial free) and used in this investigation