Use of solar distillation for olive mill wastewater drying and recovery of polyphenolic compounds.

Olive mill wastewater (OMW) is characterized by its high organic load and the presence of phenolic compounds. For first time, a solar distillator was used to investigate the simultaneous solar drying of OMW and the recovery of phenolic compounds with antioxidant properties in the distillate. Two experiments were conducted and the role of thermal insulation on the performance of the distiller was studied. The use of insulation resulted to higher temperatures in the distillator (up to 84.3 °C and 78.5 °C at the air and sludge, respectively), shorter period for OMW dewatering (14 days), while it increased the performance of distillator by 26.1%. Chemical characterization of the distillate showed that pH and COD concentration gradually decreased during the experiments, whereas an opposite trend was noticed for conductivity and total phenols concentration. Almost 4% of the total phenols found initially in OMW were transferred to the distillate when an insulated solar distillator was used. Gas chromatographic analysis of collected distillates confirmed the presence of tyrosol in all samples; whereas hydroxytyrosol was found only in fresh collected distillate samples. Further experiments should be conducted to optimize the process and quantify the concentrations of recovered phenolic compounds.