Abstract Microalgae are primary producers of aquatic ecosystems that are capable of living in complex habitats with difficult conditions. In this study, the green microalgae Scenedesmus quadricauda was cultured in molasses and alcohol factory effluent using a two-stage culture method with the aim of determining growth, biomass, and biochemical compositions and eva‎luating bioremediation. The experiment was conducted in two 14-day culture stages, in 13 treatments including; molasses effluent 1, 5, and 10%, alcohol factory effluent 1, 5, and 10%, molasses effluent without insoluble solid particles 1, 5, and 10%, and alcohol factory effluent without insoluble solid particles 1, 5, and 10%, and a control, each of which was performed in 3 replicates. The highest phosphate and nitrate consumption was measured in 1% alcoholic effluent without insoluble solid particles. The nitrite content in all samples, except 1% alcoholic effluent without insoluble solid particles and 1% alcoholic effluent, increased significantly. In dilute alcoholic effluent without insoluble solid particles; the highest phosphate and nitrate removal rate, the highest dye absorption and the lowest chlorophyll a and b and carotenoid contents were obtained. The highest chlorophyll a and b contents were obtained in 1% molasses effluent treatment and the lowest contents were obtained in 1% alcoholic effluent without insoluble solid particles. The highest COD removal efficiency (99.46%) was obtained in 10% molasses effluent without insoluble solid particles. The highest BOD5 removal efficiency (99.19%) was obtained in 5% molasses effluent without insoluble solid particles. The highest biomass was obtained in 10% molasses effluent without insoluble solid particles, and the biomass production trend was increasing with increasing concentration from 1 to 10% in molasses without insoluble solid particles, respectively. The biomass produced by 1 and 5% molasses was almost equal and higher than the control, but at a concentration of 10%, the amount of biomass produced was significantly reduced. The highest amount of saturated fatty acid (SFA) was measured in 5% molasses effluent, the highest amount of monounsaturated fatty acid (MUFA) was measured in 10% molasses effluent and the highest amount of polyunsaturated fatty acid (PUFA) was also measured in 5% alcoholic effluent. The highest amount of saturated fatty acid formed was related to C16:0, the highest amount of monounsaturated fatty acids was related to C18:1, and the highest amount of polyunsaturated fatty acids was related to C18:2. In general, the results show that biomass from microalgae S. quadricauda combined with two-stage cultivation in the effluent studied in this research has many advantages, including; short reproduction cycle, higher photosynthesis, higher and more optimal nutrient utilization efficiency, higher fat content for biofuel production and effluent bioremediation. Keywords: biorefining, molasses effluent, alcoholic effluent, Scenedesmus quadricauda, biomass, fatty acids

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اميد بيرقدار كشكولي , نوراله ميرغفاري