[Characterisation and environnemental impacts of olive oil wastewater disposal].

The management of wastewater issued from olive oil extraction (locally named margine), continues to cause enormous problems due to the great quantities annually produced, and the contamination risks related to their high level of pollution and toxicity. The nearness of Agareb zone to the main olive oil production zone of Sfax and the existence of clayey outcrops are the main factors influencing the choice of this zone for the implantation of a site for the margine evaporation. The investigation and sampling works developed on the site have established the geological, hydrogeological, geotechnical and environmental characteristics. The permeable silty and sandy layers in the site favorized the infiltration of margine through and below the storage basins. This infiltration is particularly observed in the south part of the site where it has reached a depth of 4m at a distance of 20 m laterally. The chemical analysis of the substratum and infiltrated margine showed that the latter constituted a polluting source, its acidity may affect physical and geotechnical clay layer properties and causes pollutant migration in the subsoil. The wastewater infiltration in the underlying layers has caused the dissolution of salts and the modification of pH, nutrients contents and phenolic compound concentrations. The geotechnical investigations conducted on the site showed the instability of the embankments slopes separating the margine storage basins and the presence of sliding which may cause margine flow out from the storage basins and consequently the spreading of pollution on great areas.