Implementation of membrane filtration and melt crystallization for the effective treatment and valorization of olive mill wastewaters

The olive oil extraction process is of vital importance for the farmers at Mediterranean countries. However, olive oil production is directly associated with the co-production of large quantities of Olive Mill Wastewater (OMW), which are considered as wastes but at the same time can also be considered as byproducts enriched in high added value constituents, such as phenolic compounds. The idea in the present work is firstly to separate and isolate the low molecular size phenolic compounds from other organic compounds, of high molecular size, using a combination of membrane processes (Ultrafiltration, UF, Nanofiltration, NF, Reverse Osmosis, RO). Further exploitation of the RO concentrate with vacuum distillation and freeze drying leads to the recovery of solid mixtures of the phenolic compounds and sugars. The implementation of cooling crystallization as a next treatment process is suggested for the separation of the phenolic compounds from sugars based on their solubility differences as a function of temperature. Further isolation and purification of phenolic compounds, may be achieved using melting crystallization and each compound may be selectively crystallized at its respective freezing point. To test the purification system proposed here, model “synthetic solutions” were used. The model solutions were made up using compounds with different molecular sizes including phenolic compounds. In the present study, recovering and purification of phenolic compounds was examined by experiments in synthetic OMW, where sucrose and tyrosol were served as model compounds for sugars and phenolics respectively.