Use of ultrafiltration ceramic membranes as a first step treatment for olive oil washing wastewater

Olive oil is a food product in great demand throughout the world, its production generating large volumes of wastewater with a high organic load, where phenolic compounds are present. These compounds have outstanding antioxidant characteristics, so their recovery is of great interest. In this way, the treatment of these wastewaters should be based on reusing water and, at the same time, on recovering valuable compounds. Ultrafiltration with ceramic membranes (5, 15 and 50 kDa) is proposed as a first treatment step for olive oil washing wastewater (OOWW) from the continuous two-phase centrifugation process. The effect of cross flow velocity and transmembrane pressure was evaluated against permeate flux values and the removal of turbidity, colour, chemical oxygen demand (COD), sugars and the phenolic compounds recovery. The CFV had a great influence on the removal of colour and turbidity. COD rejection increased with increasing TMP, being the highest rejection obtained under the most extreme conditions. The rejection of phenolic compounds and sugars did not show great variation between conditions. The 50 kDa membrane was the one that presented the largest permeate flux decline and the lowest permeability recovery after the cleaning, confirming the great fouling that this membrane suffered. The 15 kDa membrane at the operating conditions of 3 m.s-1 and 3 bar was observed as a good option to eliminate much of the colour (72%) and turbidity (99%) and to reduce considerably the organic load (54%) without greatly affecting the concentration of phenolic compounds (rejection of 21%) for future recovery.