Membrane processing for olive mill wastewater fractionation

The possibility of complete fractionation of olive mill wastewater (OMW) was investigated using membrane technology. Combinations of different membrane processes were used for the fractionation of OMW into by-products that may be further developed to achieve reduction of the expenses involved. Ultrafiltration (UF) in combination with nanofiltration (NF) and/or reverse osmosis (RO) were found to be very efficient for the treatment and fractionation OMW. An extended parametric study for the optimum fractionation yield of OMW involved variation of the operational system parameters including temperature, and the trans-membrane pressure. The final effluent obtained was a clean transparent with very low content of organic compounds and dissolved ionic salts. The chemical composition of the post-treatment effluent showed that it was suitable for disposal in aquatic receptors or for use for irrigation purposes. The ultrafiltration process resulted in the separation of high molecular weight constituents including suspended solid particles. Phenols present in the OMW were removed to an extent exceeding 95% of the initial value following the nanofiltration step. The concentrate obtained at this stage was very rich in phenols. Better efficiency of the OMW treatment was achieved applying RO after UF.

It is possible to achieve high levels of purification of OMW obtained from a typical olive mill in Western Greece using membrane technology. The parametric study included a number of operational parameter values of primary importance for the operation of UF, NF and RO units. Using the system of ultrafiltration, nanofiltration and/or reverse osmosis the OMW may be treated efficiently to obtain a permeate (water) fraction with quality characteristics that make it possible to be discharged in aquatic systems according to national or EU regulations or to be used for irrigation (~75–80% of the initial volume). The ultrafiltration process may be used to separate high molecular weight components and suspended solid particles. The UF concentrate was found to contain the largest portion of fats, lipids, solids, etc. Further processing with nanofiltration may be employed for the separation of the most part of phenols present. Clearly further research is needed in this direction, related with the sustainability