Influence of pH on the culture of Scenedesmus obliquus in olive-mill wastewater

Olive-mill wastewater (OMW), an agro-industrial by-product from olive-oil milling (with the three-phase extraction method), was used experimentally as 5% (v/v) of the medium to culture Scenedesmus obliquus CCAP 276/3A. The characterization of the wastewater indicated a nitrogen deficiency. The highest specific growth rate of S. obliquus μm = 0.022 h−1 was found when the medium was maintained at a constant pH value of 7.0. The biomass productivity, Pb was determined by the influence of pH on the speciation of the dissolved CO2. The greatest elimination of BOD5 occurred at extreme pH values. The protein and chlorophyll contents presented a maximum value close to pH = 7.0. The highest crude-protein content in the biomass was 25.6%. The polyunsaturated and essential fatty acids presented a clear trend to increase with the pH, at pH 9.0, representing 26.2 and 19.4%, respectively, of the total fatty-acid content of the biomass.