Investigacion

Environment International 31 (2005) 289 – 295
www.elsevier.com/locate/envint

Treatment of olive mill effluents
Part I. Organic matter degradation by chemical and biological
processes—an overview
Dionissios Mantzavinos*, Nicolas Kalogerakis
Department of Environmental Engineering, Technical University of Crete, Polytechneioupolis, GR-73100 Chania, Greece

Abstract
Olive mill effluentsconstitute a serious environmental problem in the Mediterranean Sea region due to the unique features associated with
this type of agro-waste (i.e. seasonal and localized production, high and diverse organic load, low flowrates). Therefore, it is not surprising
that research efforts have been directed towards the development of efficient treatment technologies including various physico-chemicaland
biological processes. This work reviews recent advances regarding olive mill effluent treatment with emphasis given on biological and
chemical degradation processes.
D 2004 Elsevier Ltd. All rights reserved.
Keywords: Advanced oxidation; Biological processes; Olive mill effluents; Treatment

1. Introduction
The foodstuff processing industry based on olive oil
extraction and table olivepreparation is an economically
important activity for many regions of the Mediterranean
Sea area. It is estimated (Brenes et al., 1999) that the
annual world production of olive oil and (black and green)
table olives is about 2.5 106 and 106 tons, respectively,
with Spain, Italy and Greece being the major producers.
Given that both processes result in large quantities of
strong effluents,increasing concern has been expressed
about their effective treatment and safe disposal in the
environment. The quantity of olive oil mill vegetation and
washing effluents (commonly referred to as olive mill
effluents or wastewaters (OME or OMW)) generated, and
consequently the environmental impact, depends on the
method of olive oil extraction used. The traditional cold
press methodtypically generates about 50% of OME
relative to the initial weight of the olives, while the
continuous centrifugation process generates 80–110% of
* Corresponding author. Tel.: +30 28210 37797; fax: +30 28210
37847.
E-mail address: mantzavi@mred.tuc.gr (D. Mantzavinos).
0160-4120/$ - see front matter D 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.envint.2004.10.005

OME due to thecontinuous washing of the olive paste with
warm water prior to oil separation from the paste. It is
estimated that the annual OME production in the Mediterranean Sea area exceeds 30d 106 m3. OME may have
COD values as high as about 220 g/l and the organic
matter mainly consists of polysaccharides, sugars, polyphenols, polyalcohols, proteins, organic acids and oil
(Cabrera et al., 1996). Moreover,OME contain considerable amounts of suspended solids that may reach up to
190 g/l (Zouari, 1998). The major concerns regarding OME
treatment are as follows:
(i)

concentration and composition; OME are strong
wastes containing high concentrations of phenolic
compounds (up to 10 g/l depending on the type and
origin of the effluent) that are difficult to biodegrade;
(ii) seasonal productionwhich typically lasts between
December and February;
(iii) olive oil manufacturing industries are small plants
with a daily OME flowrate between 10 and 100 m3
and are distributed over large areas.
OME treatment usually comprises a physico-chemical
method aiming at the removal of organic matter from the

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D. Mantzavinos, N. Kalogerakis / Environment International 31 (2005) 289–295liquid phase. This is usually done by means of lime
coagulation, lagooning for water evaporation and more
recently membrane separation (i.e. reverse osmosis and
ultrafiltration) (Borja et al., 1998). These processes, however, suffer from serious drawbacks such as high cost, low
efficiency and sludge-disposal problems. Therefore, several
degradation processes have gained a lot of attention...