In this study, biodegradation of petrochemical wastewater and production of single cell protein from it as carbon source was investigated using several process parameters. The process parameters such as carbon source, type of phosphorus source, phosphorus source concentration, type of nitrogen source, nitrogen source concentration, and temperature were considered. In order to investigate the influence of process parameters, a factorial design using Taguchi method was applied with six factors at four levels. The optimum medium composition for single cell protein production was found to contain petrochemical wastewater 8%, peptone 0.2%, and K 2 HPO 4 0.008% at temperature 37 • C. The percentage ratio of single cell protein to cell dry weight in optimal conditions was 76.4%. In conclusion, Haloarcula sp. IRU1 can degrade petrochemical wastewater and use it as carbon source for single cell protein production in different conditions.