Batch membrane treatment of olive vegetation wastewater from two-phase olive oil production process by threshold flux based methods

Abstract

The more efficient continuous centrifugation-based olive oil extraction processes brought as drawback a significant increment of the generated effluents, highlighting olive vegetation wastewater (OVW) as the most polluted. In this work, OVW from a two-phase olive oil extraction process (OVW-2) was treated by means of batch membrane operations in sequence comprising UF, NF and RO. This treatment is capable of successfully removing the organic matter and other pollutants from the wastewater, but membrane fouling can limit drastically membranes operation and longevity. Threshold flux-based methods represent a reliable tool to avoid fouling problems and were formerly applied to treat OVW streams coming from a three-phase production line (OVW-3). Below threshold flux conditions, no relevant rates of fouling are observed, thus making the treatment process technically and economically feasible. In order to increase the threshold flux values, some pretreatment processes were conducted on the feedstock, such as pH-T flocculation and successively photocatalysis by novel lab-made titanium dioxide nanoparticles. The latter provided 22.3%, 17.6% and 20.4% further threshold flux increase to UF, NF and RO, respectively. At the end, a permeate with COD equal to 121mg/L was successfully obtained, respecting both Italian and Spanish standards for discharging purified OVW-2 in municipal sewers.