Treatment of Olive Mill Wastewater through Integrated Pressure-Driven Membrane Processes

Abstract

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.

Recovery of Polyphenols from Agri-Food By-Products: The Olive Oil and Winery Industries Cases

“…Membrane separation processes can be used at large scale, with three main objectives: (i) to remove suspended and colloidal matter in the extraction stage by using pressuredriven membrane techniques as microfiltration (MF 0.1-5 µm, 1-10 bar) and/or ultrafiltration (UF 0.5-100 nm, 1-10 bar); (ii) to selectively separate polyphenols from other families of compounds co-extracted in the extraction (e.g., sugars, proteins, lipids) by using pressure-driven membrane techniques as ultrafiltration (UF) and/or nanofiltration (NF) and; (iii) to reduce the volume of the polyphenols rich streams by using pressure-driven membrane techniques as nanofiltration (NF 5-10 nm, 10-30 bar) and/or reverse osmosis (RO < 0.5 nm, 35-100 bar) [20,[105][106][107][108][109][110][111][112][113].…”

Treatment of Hydrothermal-Liquefaction Wastewater with Crossflow UF for Oil and Particle Removal

“…However, this would not be applicable for real HTL-WW without a pretreatment step, since it would lead to colloidal organic fouling followed by a rapid decrease in the permeate flux and membrane selectivity [ 13 ]. As an example, the pretreatment of wastewater resulting from olive-oil production via MF showed an efficient retention of suspended materials and production of a clarified permeate that was further treated via RO in order to separate the dissolved substances from water [ 14 ]. Among the above mentioned pressure-driven membrane processes, UF is one of the most effective pretreatment methods for oily wastewater in comparison with the traditional separation methods (mechanical separation, filtration, and chemical de-emulsification) [ 15 ].…”

A Single Step Preparation of Photothermally Active Polyvinylidene Fluoride Membranes Using Triethyl Phosphate as a Green Solvent for Distillation Applications

“…In this context, membrane distillation (MD) has recently gained increasing attention because of its theoretical ability completely reject non-volatile solutes, even when treating highly concentrated feed streams such as reverse osmosis brines [1] and industrial wastewaters [2,3].…”