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Membranes 2017, 7(3), 36;

On Operating a Nanofiltration Membrane for Olive Mill Wastewater Purification at Sub- and Super-Boundary Conditions

Department of Chemical Engineering, University of Rome “La Sapienza”, Via Eudossiana, 18, 00184 Rome, Italy
Chemical Engineering Department, University of Granada, 18071 Granada, Spain
Balliol College, University of Oxford, Broad Street, Oxford OX1 3BJ, UK
Author to whom correspondence should be addressed.
Received: 15 June 2017 / Revised: 10 July 2017 / Accepted: 11 July 2017 / Published: 14 July 2017
(This article belongs to the Special Issue Membranes and Water Treatment 2016)
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In the last decades, membrane processes have gained a significant share of the market for wastewater purification. Although the product (i.e., purified water) is not of high added value, these processes are feasible both technically and from an economic point of view, provided the flux is relatively high and that membrane fouling is strongly inhibited. By controlling membrane fouling, the membrane may work for years without service, thus dramatically reducing operating costs and the need for membrane substitution. There is tension between operating at high permeate fluxes, which enhances fouling but reduces capital costs, and operating at lower fluxes which increases capital costs. Operating batch membrane processes leads to increased difficulties, since the feed fed to the membrane changes as a function of the recovery value. This paper is concerned with the operation of such a process. Membrane process designers should therefore avoid membrane fouling by operating membranes away from the permeate flux point where severe fouling is triggered. The design and operation of membrane purification plants is a difficult task, and the precision to properly describe the evolution of the fouling phenomenon as a function of the operating conditions is a key to success. Many reported works have reported on the control of fouling by operating below the boundary flux. On the other hand, only a few works have successfully sought to exploit super-boundary operating conditions; most super-boundary operations are reported to have led to process failures. In this work, both sub- and super-boundary operating conditions for a batch nanofiltration membrane process used for olive mill wastewater treatment were investigated. A model to identify a priori the point of transition from a sub-boundary to a super-boundary operation during a batch operation was developed, and this will provide membrane designers with a helpful tool to carefully avoid process failures. View Full-Text
Keywords: membranes; membrane fouling; boundary flux; critical flux; threshold flux membranes; membrane fouling; boundary flux; critical flux; threshold flux

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Stoller, M.; Ochando-Pulido, J.M.; Field, R. On Operating a Nanofiltration Membrane for Olive Mill Wastewater Purification at Sub- and Super-Boundary Conditions. Membranes 2017, 7, 36.

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