**3.1 Three-phase olive mill wastes**

276 Olive Oil – Constituents, Quality, Health Properties and Bioconversions

reduced fresh water consumption in the centrifugation phase. The two-phase process has attracted special interest in countries where water supplies are restricted. The quantity of water required to carry out the two-phase process is much lower than in the three-phase process and a considerable reduction in generated two-phase olive mill wastewaters (2POMWW) is achieved. However, the two-phase process led to a slight increase in solid wastes. The quantities of two-phase olive mill solid wastes (2POMSW) are 60% higher

Over 2.9 million tonnes of virgin olive oil are produced annually worldwide, of which 2.4- 2.6 million tonnes are produced in the European Union (IOOC, 2009). Currently, both elaboration systems, three- and two-phase, coexist in the Mediterranean area (Niaounakis & Halvadakis, 2004). Spain, the largest producer of olive oil in the world, currently uses the two-phase system in 98% of its olive mills. Over the past few years, Spain has produced between 1,412,000 tonnes (2003/2004 season) and 1,028,000 tonnes (2008/2009 season) of olive oil, which meant 57.7% and 53% of European production (IOOC, 2009). Croatia uses the two-phase system in 55% of its mills and produces 4,500 tonnes of olive oil (2008/2009 season). In olive oil producing countries such as Cyprus, Portugal and Italy, only around 5% of the mills use the two-phase system (Roig et al., 2006). Other large producers such as Greece or Malta have continued using mainly the three-phase system although the twophase system is being introduced slowly. The high quantities of wastes produced in both

3POMSW are produced in a proportion of 500 kg per ton of olives and are basically made

3POMWW are the main wastes generated in the three-phase olive mill system (1,200 L ton-1 milled olives). The annual 3POMWW production of Mediterranean olive-growing countries is estimated between 7-30 million m3. The chemical composition of 3POMWW is complex due to the water from the milled olives (vegetation water) and the soft tissues from the olive fruit. Typical composition of three-phase olive mill wastewaters is: pH 5.04, COD 43.0 g L-1 (COD: Chemical Oxigen Demand), total sugars 17.4 g L-1, total phenols 2.5 g L-1 and lipids

The change from the three-phase to the two-phase elaboration system reduces the high generation of wastewaters produced in the three-phase process. The two-phase elaboration process generates 800 kg of 2POMSW per ton of olives processed. 2POMSW have a 60%-70% humidity content, 13%-15% lignin, 18%-20% cellulose and hemicellulose and 2.5%-3% oil (Borja et al., 2002). In a similar way to 3POMWW, the composition of 2POMSW is complex due to the vegetation water. Consequently, 2POMSW and 3POMWW are the main

2POMWW are a mixture between the water used for olive washing before the milling process and the water coming from washing the oil in a vertical centrifuge. Initial studies gave volumes of 2POMWW of around 250 L ton-1 of olives in total. However, current studies have suggested a significant reduction in the amount of water to be added to the vertical

than those generated in the three-phase system (3POMSW).

systems makes sustainable treatments necessary.

**2.2 Waste quantities and characteristics** 

up of dry pulp and stones.

0.75 g L-1 (D'Annibale et al., 2006).

problematic streams.

centrifuge.
