Abstract
Problem statement: Olive Mill Wastewater (OMW) is an ambivalent by-product of the olive oil production, which appears in huge amounts every year after the olive-harvest in the production countries, mainly in the Mediterranean region. OMW is characterized by a high organic load and i.a. contains considerable amounts of phytotoxical polyphenols, which cause important environmental problems. Approach: Due to their antioxidant properties the use of these polyphenols is also popular in several industry branches, which results in high sale values for this group of chemicals. The removal of polyphenols from biological wastewaters like OMW does not only reduce the pollutant load but also shows great potential for a beneficial recovery of these antioxidants. This is the reason why a growing number of studies deal with a combined wastewater treatment, which, besides water purification, also regards the ability of recovering polyphenols. This article is an overview of reports concerning polyphenol recovery from OMW via membrane technologies. Results: Patents and studies, which appeared in literature, are reviewed in order to identify the potential of membranes as well as making comparisons possible. Some pretreatments, feasible for membrane processes, are covered. Depending on the initial wastewater and its polyphenol content the concentration in the obtained solution ranges from 0.5-19.3 g L-1 polyphenols. An example mentioned in WO2005/123603 even obtains a concentration of 30 g L-1. Polyphenols such as hydroxytyrosol, protocatechuic acid, tyrosol, caffeic acid and oleuropein were found in this concentrate and make it suitable for the use in industry. Conclusion: The membrane processes in sequential design in particular show good results and offer an alternative to other OMW treatments especially in terms of polyphenol recovery.
Highlights
The production of olive oil, extracted from the olive fruit, involves the generation of several wastes of solid, liquid and semi-solid type
The liquid fraction, called Olive Mill Wastewater (OMW), causes adverse effects on the environment, due to its phytotoxical compounds and because it occurs in great quantities and in a short period of time after the oliveharvest in November (Torrecilla, 2010)
That is sequent membrane processes allow adjusting this why it is reasonable to achieve a reduction of the treatment with regard to the particular wastewater, Chemical Oxygen Demand (COD) by retaining the whose characteristics vary with olive origin, extraction suspended solids for instance via micro- or ultrafiltration
Summary
The production of olive oil, extracted from the olive fruit, involves the generation of several wastes of solid, liquid and semi-solid type. Apart from purifying the wastewater, there have been attempts to make use of the polyphenols contained in the OMW. While these components are the main reason for the wastewater’s phytotoxicity, they show useful characteristics as antioxidants (Marco et al, 2007). Sci., 8 (3): 195-201, 2012 phenols can be found e.g., in varnishes, pesticides and treatment of OMW including polyphenol recovery and in the production processes of drugs, cosmetics and to allow comparisons between diverse plants and synthetics. That is sequent membrane processes allow adjusting this why it is reasonable to achieve a reduction of the treatment with regard to the particular wastewater, Chemical Oxygen Demand (COD) by retaining the whose characteristics vary with olive origin, extraction suspended solids for instance via micro- or ultrafiltration
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