As OOMW are produced only in the Mediterranean region, EU policy has not brought into force any common guidelines for their management. EU Council Directive 91/271/EEC on “Urban Wastewater Treatment” concerns the protection of the environment from the adverse effects of the discharge of urban and agro-food industry wastewaters. Effective treatment should be therefore applied before wastewaters are discharged into receiving waters, while treated wastewaters should be reused whenever appropriate (Zaharaki and Komnitsas, 2009).
The practices currently applied include land disposal, discharge into nearby rivers, lakes or seas and storage/evaporation in lagoons, causing thus serious environmental problems such as water resources contamination. The second significant problem to highlight has to do with the lack of a framework for separating soil from water receivers. The presence of organic matter as well as many inorganic compounds (nitrogen, phosphorus, potassium) causes severe pollution when OOMW are disposed of into water bodies, but when disposed of in soil erosion is prevented and can be beneficial to soil fertility (Rinaldi et al., 2003; Kapellakis et al., 2008).
The experience gained through the PROSODOL project indicates that in the three major olive oil productive countries in Europe (i.e. Spain, Italy and Greece), different management systems of the OOMW have been developed, adopted and are implemented. In Italy, the management of OOMW is ruled by the law No 574 of 1996 and the Ministry Degree of 6th July 2005 with the majority of the mill owners already conformed to them. In Spain the wastes of the olive oil industry are mainly used for the production of heat and energy, they are also composted; however large amounts are still deposited in evaporation ponds. In Greece, due to the lack of specific legislative framework and effective monitoring by the responsible governmental, regional and local authorities, OOMW are mainly disposed in evaporation ponds, on soil and in water systems. Thus, it is believed and was proved during the PROSODOL project, that soils in Greece or elsewhere, where OOMW are disposed uncontrolled on soil or without taking the appropriate protective measures, are under different degree of degradation threat. In general and as it has been detected during the sampling campaigns of this project, if a soil system had accepted the disposal of waste in the past, it is very likely to maintain some of its physic-chemical properties increased for many years after the incident. In Greece there are no specific regulations regarding the discharge of OOMW. The main principles for OOMW management are based on the Greek Law 1650/86 ‘‘For the Protection of the Environment’’ according to which, olive mill owners are obliged to provide an environmental impact assessment study. The updated circular letter ΥΜ/5784/23-1-1992 (No 4419/23-10-1992) refers to the problems encountered due to OOMW disposal, the need for an efficient pre-treatment and the care required in order to avoid disposal to various water resources. Each Prefecture is responsible for adopting proper OOMW management practices encouraging different waste management approaches.
The issue of an olive-mill operation permit is subject to measures taken to treat OOMW, such as pre-treatment with lime before disposal, pre-treatment/fractionization by natural sedimentation and separate management of the individual fractions or disposal in constructed open ponds. However, there is no single technical solution that can ensure satisfactory treatment efficiency with an application cost within the economic means of each individual olive-mill owner, given its geographical distribution and the size of its olive-mill plants (Paraskeva and Diamadopoulos, 2006).
In the island of Crete south of Greece where PROSODOL is implemented, OOMW were discharged until 1987 uncontrolled into the environment. About 80-90% of the total OOMW produced were disposed of in ephemeral rivers (Voreadou, 1994). Since then, local public authorities prohibited uncontrolled disposal in water bodies and obliged mill owners to construct treatment units (involving mixing with Ca(OH)2, sedimentation and grease removal) and evaporation lagoons with low construction, operation and maintenance costs. To avoid potential downward OOMW leakage, a compacted clay liner should be placed at the bottom of the pond; after evaporation of OOMW, the remaining sludge may be landfilled (Kapellakis et al., 2002; 2006).
- EU Council Directive 91/271/EEC (1991) concerning Urban Wastewater Treatment, OJ NO L135/40 of May 30.
- Greek Law 1650/86 ‘‘For the Protection of the Environment’’, Government Gazette: 160/Α/16-10-86.
- Kapellakis I.E., K.P. Tsagarakis, Ch. Avramaki, J. Crowther and N. Hytiris (2002). Potential for olive mill wastewater reuse: the case of Messara Basin in Crete. In Proc. of IWA-regional symposium on water recycling in Mediterranean Region, vol 1, 515–524, Iraklion, Greece, 26–29 September.
- Kapellakis I.E., K.P. Tsagarakis, Ch. Avramaki and A.N. Angelakis (2006). Olive mill wastewater management in river basins: A case study in Greece, Agr Water Manage 82, 354–370.
- Kapellakis I.E., K.P. Tsagarakis and J.C. Crowther (2008). Olive oil history, production and by-product management, Rev Environ Sci Biotechnol 7, 1–26.
- Paraskeva P. and E. Diamadopoulos (2006). Technologies for olive mill wastewater (OMW) treatment: a review, J Chem Technol Biotechnol 81, 1475–1485.
- Rinaldi M., G. Rana and M. Introna (2003). Olive-mill wastewater spreading in southern Italy: effects on a durum wheat crop, Field Crops Res 84, 319–326.
- Voreadou K. (1994). Olive mill wastewater-impacts on natural water ecosystems in Crete. Current management practices and future perspectives. Int. meeting on olive mill wastewater management, Sitia, Lassithi, Greece, 16–17 June, 9–14 (in Greek).
- Zaharaki D. and K. Komnitsas (2009). Existing and emerging technologies for the treatment of olive oil mill wastewaters, International Conference AMIREG 2009 “Towards sustainable development: Assessing the footprint of resource utilization and hazardous waste management”, Athens, 7-9 September.
The Italian Law n° 574 of 1996 defines the terms for the reutilization in field of the olive oil waste waters (OOWW) and of the olive husks.
- Olive husks can be used as amendments with no specific limits if they comply with Italian Law n° 748 of 1984 regulating the use of amendments;
- The law sets the limit that can be applied each year on a soil according to the following thresholds:
- 50 m3/ha for OOWW obtained from discontinuous extraction systems
- 80 m3/ha for OOWW obtained from continuous extraction systems
- The application of the OOWW on a soil should be previously communicated to the mayor of the city, at least thirty days in advance;
- The law specifies the soil categories on which the OOWW must not be applied:
soils which are less than 300 meters away from the preservation areas for the water collection destined to the human consumption;
soils which are less than 200 meters away from the inhabited areas;
soils which are cultivated with vegetable crops;
soils where water tables are at less the ten meters depth;
soils which are frozen, covered by snow, awashed or saturated with water.
- The OOWW can be stocked no more than thirty days before their utilization;
- The law defines also the authorities which are responsible for the control of OOWW application.
The Legislative Decree n° 152 of 1999, transposition of the European Directives 91/271/CEE and 91/676/CEE, regulates the waters safeguard from pollution. The article 38 of this act makes reference to the Italian Law n°574 of 1996 with regards to agronomic use of sewage sludge and other wastes such as OMWW. The same law regulates the disposal of wastes directly in the sewage system setting the thresholds of the chemical and physical parameters the wastes must comply with (Table 5 – Annex 5).
References to Italian law can be found at the following page (in Italian): 1 (more specifically referred to olive wastes) - 2 (more in general also regarding water preservation from different pollution sources) - Both pages are in Italian language.