Assessment of polyphenols decomposition during olive mill wastewaters drying in storage basin

Olive mill wastewaters (OMW) are considered as a serious pollutant in Mediterranean countries due to their high level of toxicity and the huge quantities generated yearly. However, satisfying treatment to such a threat has yet to be proven and the evaporation ponds remain the most used technique and the ultimate path for OMW. The OMW phenolic compounds decomposition during drying in basin using qualitative survey was little investigated. This research was undertaken to study OMW evolution during drying in storage basin. Three OMW samples were collected from storage basin: liquid (L), sludge (S), and dry OMW (D). pH, electrical conductivity (EC), Na⁺, K⁺ and Ca²⁺ contents, oil content, and organic matter content (OM) were analyzed. The phenolic compounds were investigated by high performance liquid chromatography (HPLC) method. Results showed decreases of pH, electrical conductivity (EC), mineral Na⁺, K⁺ and Ca²⁺ contents, oil content, organic matter (OM), and total polyphenol compounds. The HPLC analysis showed that fresh liquid OMW contains five phenolic compounds (hydroxytyrosol, tyrosol, vanilic acid, ferulic acid, and coumaric acid). In the sludge OMW only hydroxytyrosol, tyrosol, and ferulic acid were detected. In dry OMW, two phenolic compounds were identified (hyroxytyrosol and tyrosol).