Integrated biomass production and biodegradation of olive mill wastewater by cultivation of Scenedesmus sp

Abstract Biomass production and bio-treatment of olive mill wastewater (OMW) were simultaneously achieved by cultivation of Scenedesmus sp. The influence of medium composition was addressed by analyzing the effect of the addition of unsterilized OMW (9% v·v − 1 ) and of inorganic nutrients, and the use of tap water. Performance of implemented treatments was assessed by analysis of the following variables: biomass productivity, growth rate, content of target microalgal fractions (lipids and carbohydrates), and consumption of OMW organic carbon fractions (reducing sugars and phenols). The addition of unsterilized OMW (9% v·v − 1 ) caused darkening of microalgal cultures inducing transition to heterotrophic growth. Growth rate values attained in heterotrophic cultures (with OMW) (0.0181 and 0.023 h − 1 ) were comparable to those attained in autotrophic cultures (without OMW) (0.0272 and 0.0249 h − 1 ). Nonetheless, significantly lower biomass productions were achieved by heterotrophic growth (0.22 and 0.35 g·L − 1 vs. 0.56 and 0.51 g·L − 1 ). Even though leading to lower biomass productions, heterotrophic growth ensured carbohydrate productions comparable to those attained by autotrophic growth (0.1 and 0.16 vs. 0.12 and 0.17 g·L − 1 ). Biodegradation of OMW phenols was found to be significantly affected by the concentration of inorganic nutrients. The inhibition of microalgal growth induced by phenols, and the interaction between phenol biodegradation and biomass production were analyzed.