Study on the in Situ Enzymatic Self-Cleansing of Microfiltration Membrane for Valorization of Olive Mill Wastewater Abaynesh Yihdego Gebreyohannes, †,‡ Rosalinda Mazzei,* ,† Efrem Curcio, †,‡ Teresa Poerio, † Enrico Drioli, † and Lidietta Giorno † † Institute on Membrane Technology ITM-CNR, Via P. Bucci CUBO 17C, 87036 Rende (CS), Italy ‡ Dipartimento di Ingegneria per l’Ambiente e il Territorio e Ingegneria Chimica, University of Calabria, via P.Bucci CUBO 45A, 87036 Rende (CS) Italy ABSTRACT: In this study intensified removal of pectins was integrated with microfiltration step to develop in situ self-cleansing biocatalytically active membranes. This method was developed to reduce the severe fouling that occurred during microfiltration (MF) of olive mill wastewater (OMWW) for the recovery of bioactive compounds using integrated membrane processes. As a proof-of-concept, pectinase has been immobilized on the MF membrane surface and flux performances as a function of time has been monitored and compared with inert membrane. For the experiments real OMWW has been used. The steady-state flux through the enzyme immobilized on the membrane surface solo was 50% higher than inert membrane. The mechanism for the better performance of the biocatalytically active on the surface has been explained as based on both degradation of deposited pectins (in situ self-cleansing) and overcome of product inhibition as it is continuously removed from the reaction site. The inhibitory effect has been clearly identified from kinetic study of pectinase. For all types of used membrane systems, analysis of cake resistance, membrane resistance, and membrane fouling index indicated surface biofunctionalized membranes with the least fouling tendency and significantly improved flux. 1. INTRODUCTION Olive oil production generates dark acid wastewater with more than 300 times polluting capacity compared to that of municipal sewage. This wastewater called olive mill wastewater (OMWW) comes from the large amounts of water added during the basic stage of olive process. The annual environ- mental release is estimated to be about 30 million m 3 /year with a very high organic load especially rich in more than 30 different types of biophenolic compounds. 1-3 These com- pounds are phytotoxic with strong antibacterial effect. 2,4-6 Serious environmental damages have been caused over the years due to the continuous damping of OMWW reach in the environmentally toxic biophenolic compounds. 7 As a matter of fact, most of the processing facilities are located close to sea resorts and places of high tourist interest. This situation makes the negative socioeconomic and environmental impacts of this industrial activity more than obvious. Nowadays expansion of olive oil production from Mediterranean to other part of the world as evidenced by emerging olive oil producers like the US, Australia, and South America transfer the environmental concern related to this process from a regional to an international concern. Especially increased awareness on the health preventing capacity of the olive oil raised the worldwide consumption abruptly. In recent years many management options have been proposed for the treatment of OMWW; mostly aimed at reducing the phytotoxic nature of the biophenols in order to reuse OMWW for agricultural purposes. 8 On the other hand the biophenolic compounds existing in OMWW though recalcitrant they are also compounds of interest in the food, pharmaceutical, or cosmetic industries due to their high antioxidant and other important bioactivities. 1,6 Therefore focusing on the recovery of these high added value compounds has the potential to increase the material resource efficiency of handling such environmentally detrimental waste stream. This in turn would result in significant economic value increase of OMWW that otherwise could represent only a disposal cost in the mill industry. Recently, there is a growing research activity in the use of integrated membrane system for valorization of olive mill wastewater. 9-13 Rationalizing industrial wastewater treatment by the use of integrated membrane process can benefit from the synergistic effect of individual units in terms of product quality, plant compactness, environmental impact, and energy con- sumption. 14 However until now none of the membrane process for treatment of OMWW is yet industrialized due to huge fouling phenomena that reduced the economical feasibility. All the integrated membrane process for valorization of OMWW involves sequence of pretreatment steps like acid- ification, enzymatic treatment, centrifugation, or classical filtration 10-12 to make the wastewater easily processable with the subsequent membrane process, but not all the foulants can be removed using the mentioned pretreatment. Indeed the pectins are one of the strong foulants present in the wastewater that survives the traditional pretreatment. Hence membrane treatment of olive mill wastewater is highly restricted by accumulation of these pectic and other extracellular materials on the surface and/or inside the pores of the membrane. Special Issue: Enrico Drioli Festschrift Received: January 25, 2013 Revised: April 17, 2013 Accepted: April 17, 2013 Article pubs.acs.org/IECR © XXXX American Chemical Society A dx.doi.org/10.1021/ie400291w | Ind. Eng. Chem. Res. XXXX, XXX, XXX-XXX