Treatment of Two-Phase Olive Mill Wastewater and Recovery of Phenolic Compounds Using Membrane Technology.

Varvara Sygouni,Iakovos C Iakovides,Polychronia I Bogdou,Alexis G Pantziaros,Evangelia Sfetsa,Emilia A Christoforou,Christakis A Paraskeva

doi:10.3390/membranes9020027

Varvara Sygouni, Iakovos C Iakovides + Show 5 more

Open Access

https://doi.org/10.3390/membranes9020027

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Abstract

The semi-solid wastes (pomace or alperujo) produced in the two-phase olive oil extraction process contains extremely high organic load and phenolic substances. Efficient treatment of such kinds of wastes using membrane filtration, should be sought to reduce the hazardous effects to the environment. On the other hand, phenolic compounds can be isolated and purified up to a level of commercial exploitation using the membrane technology. Firstly, the extraction process with mixtures of water and ethanol was optimized by testing extraction parameters (e.g., solvent’s mixture, duration, and temperature) at laboratory scale. Next, extraction was conducted using larger volumes and the treatment was continued in a pilot membrane filtration system, consisted of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes. The extracted solution from the olive oil pomace was fed to the pilot membrane filtration system, where all fat, lipids, and solids were removed while the phenolic compounds were concentrated in the retentate streams of NF and/or RO. Total phenolic content (TPC) at the RO’s concentrate stream was 225 mg/L and at the final effluent was lower than 10 mg/lt. The chemical oxygen demand (COD) value at the final effluent was much lower (~280 mg/L) than in the feed stream (>32,000 mg/L).

Highlights

The main products from olive trees are table olives and olive oil, which are essential components for a healthy nutrition and are related to the Mediterranean dietary
Investigation of the Extraction the optimum conditions for the extraction ofProcedure the maximum quantity of Total phenolic content (TPC) from the two-phase olive mill semi solid waste
Thephenols effect of from the semi-solid pomace was obtained in a series experiments with different percentages of the type of the solvent used during the extraction wasof investigated

Summary

Introduction

The main products from olive trees are table olives and olive oil, which are essential components for a healthy nutrition and are related to the Mediterranean dietary. Among the compounds that make olive oil an important ingredient in a human’s diet, are the contained polyphenol compounds, which show antioxidant activity. The most important phenols present in olive oil are tyrosol, oleuropein, caffeic acid, vanillic acid, and hydroxytyrosol [1,2]. During the production of oil, a large amount of waste is produced which is phytotoxic due to its high content in fat, lipids, and polyphenols [3]. The most used types of olive oil mills are the two- and the three-phase decanter systems. An overview of the olive mill wastes, and their valorization methods is given in [4,5] while in [6] a summary of the results achieved in composting experiments of two- or three-phase olive mill wastes is presented

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