Leonilde Marchão

The potential for bioremediation of olive mill wastewaters with different origins—olive washing (OWW) and olive oil extraction (OMW)—among four species of microalgae (Chlorella vulgaris, Auxenochlorella protothecoides, Scenedesmus obliquus, and Arthrospira maxima) was evaluated. All microalgae could grow in the wastewaters, but C. vulgaris and C. protothecoides showed the best performances. The highest biomass productivities of 165.8 mg L⁻¹ day⁻¹ for OMW and 107.9 mg L⁻¹ day⁻¹ for OWW were achieved with C. vulgaris and A. protothecoides, respectively. Moreover, with both species, COD and nitrate contents of the two wastewaters were reduced by 60 and more than 50%, respectively. However, significant removal of polyphenols was verified only in OWW (~45%). Overall, these findings demonstrate the potential of C. vulgaris and A. protothecoides species to be used in a biological olive mill wastewater treatment process.

Agro-industrial wastewaters are characterized by the presence of multiple organic and inorganic contaminants of environmental concern. The high pollutant load, the large volumes produced, and the seasonal variability makes the treatment of these wastewaters an environmental challenge. A wide range of wastewater treatment processes are available, however the continuous search for cost-effective treatment methods is necessary to comply with the legal limits of release in sewer systems and/or in natural waters. This review presents a state-of-the-art of the application of advanced oxidation processes (AOPs) to some worldwide generated agro-industrial wastewaters, such as olive mill, winery and pulp mill wastewaters. Studies carried out just with AOPs or combined with physico-chemical or biological treatments were included in this review. The main remarks and factors affecting the treatment efficiency such as chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), total organic carbon (TOC), and total polyphenols removal are discussed. From all the studies, the combination of processes led to better treatment efficiencies, regardless the wastewater type or its physico-chemical characteristics.