TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Strain: In the strain, the degraded hydrocarbons comprise number of carbon atoms ranging from 1 carbon to more than 60 carbon atoms. The cells of the strain are oval shaped approximately 7.5 mu m average diameter and 6.4 mu m medium height; fascicular formation as 2 to 8 cells connected together in the nuclei of these cells do not coincide with the axis of the form; and every cell is duplicated at a rate of approximately 1 division per day. The strain grows in a temperature range between 20 and 30 degrees C, a pH range between 7 and 8.5, and a light intensity range between 30 and 700 mu mol/m2-second. It grows at 22 degrees C, pH 8.2, and a light intensity of 60 mu mol/m2-second. It grows in a medium containing oil from petroleum as sole carbon source. The strain is a clone that was obtained by a process comprising: (a) obtaining a sample in a natural environment that has received petroleum hydrocarbons; (b) selection of a clone of Scenedesmus obtusus in the sample obtained in step (a); and (c) isolation of that cell selected in step (b) and transferring to selected cell culture medium. The natural environment where strain can be obtained is an aquatic environment such as a river, lake, reservoir, aquifer or marine environment. The strain is a clone of the strain of Scenedesmus obtusus called SoP3 that is deposited in the National Bank of Algae with reference D3309 BNA, or its genetically modified mutant or variant. Preferred Device: In the device, the hardware comprises at least a siliceous material, plastic, cellulose or synthetic. The material comprises at least one compound from polyurethane, polyester, polysulfonate, polyvinyl, polyamide, cellulose acetate, epoxy resins, carrageenan, agar, alginate or collagen. Preferred Method: Bioremediation of petroleum hydrocarbons comprises: (a) fitting the contaminated medium; and (b) inoculation of the medium with at least one strain of Scenedesmus obtusus for degrading petroleum hydrocarbons; or bioremediation of petroleum hydrocarbons comprises: (a) fitting the contaminated medium; and (b) contacting the contaminated medium with a device containing an inoculum of the strain of Scenedesmus obtusus for degrading petroleum hydrocarbons, in a confined space or hardware. The environmental conditioning step includes adjusting one or more parameters from the pH, temperature, dissolved oxygen concentration, lighting, pressure or flow rate. Conditioning step includes adjusting the pH to 8.2, temperature 22 degrees C and 60 mu mol/m2-second enlightenment. The method further comprises inoculating 103 or 106 cells/ml of the strain of Scenedesmus obtusus. It comprises one or more cycles involving the deletion of microalgal biomass produced in the culture and inoculation of new clones of the strain. The medium to be treated includes a river, a reservoir of water, a swamp, a lake, an aquifer, a marine, a tank or receptacle for the storage of liquid, storage tank water supplies for human use, a tank or reservoir of a water treatment plant, a receptacle or conduit for water treatment in a wastewater treatment plant, a reactor for waste treatment, industrial effluent or sewage, surface soil surfaces and solid media. EXAMPLE - No suitable example given.