The disposal of wastewater resulting from olive oil production (olive mill wastewater, OMW) is a major issue for olive oil producers. This wastewater is among the most polluting due to the very high concentration of organic substances and the presence of hardly degradable phenolic compounds. The systems proposed for OMW treatment are essentially based either on conventional chemical-physical, biological and thermal processes, or on membrane processes. With respect to conventional methods, membrane processes allow to separate different species without the use of chemicals or heat. This work deals with the use of the integrated pressure-driven membrane processes for the treatment of OMW. They consist of a first stage (microfiltration, MF) in which a porous multichannel ceramic membrane retains suspended materials and produces a clarified permeate for a second stage (reverse osmosis, RO), in order to separate (and concentrate) dissolved substances from water. Laboratory scale experiments with different small flat sheet RO membranes were first carried out in order to select the most appropriate one for the successive bench scale tests with a spiral wound module having a large membrane surface. The aim of this test was to concentrate the dissolved substances and to produce water with low salinity, chemical oxygen demand (COD), and reduced phytotoxicity due to a low content of phenolic compounds. The trend of the permeate flux and membrane retention as a function of the volume concentration ratio was investigated. The influence of OMW origin and its aging on the membrane performance was also studied.
Structural and surface properties of two commercial polysulfone ultrafiltration membranes have been evaluated by different techniques. Pore size distributions have been determined by Liquid-Liquid Displacement Porosimetry (LLDP) as well as by image analysis performed onto Field Emission Scanning Electron Microscopy (FESEM) images of the membrane surfaces. Fourier Transform Infrared Spectroscopy (FTIR) has been used to investigate membrane composition, and in particular, to obtain proper information on the presence of additive within the membrane structure.Porosimetric results obtained by the two independent techniques compared reasonably well and the Molecular Weight Cut Off (MWCO) of the two membranes estimated from LLDP pore size distribution were found to be in good agreement with the nominal values given by manufacturers.
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