The use of rinse water (RW) from two-phase centrifugation in the olive-oil extraction industry has been studied in relation to the production of the microalga Scenedesmus obliquus (CCAP 276/3A). The characterization of the wastewater indicates that it is N deficient. The highest value of maximum specific growth rate, 0.044 h(-1) was registered in the culture with 5% RW. However, biomass productivity proved greater in the culture with 100% RW. The specific growth rates were adjusted to a model of inhibition by substrate. The content in normalized chlorophyll diminished with the duration of the cultures, reaching a minimum CHL'(min) value, which showed an inhibition type similar to that of the specific growth rate. The yield in protein indicates that the cultures were limited by N to approximately 50% RW. The greater specific rate of protein synthesis during the exponential phase was 3.7 mg/g h to 50% RW. It was found that the composition of the lipid fraction of the biomass depended on the percentage of wastewater used as the nutrient medium, reaching the highest percentages of monounsaturated, polyunsaturated, and essential fatty acids in the culture with 100% RW. (c) 2007 Elsevier Ltd. All rights reserved.