Application of electrical resistivity tomography method for the assessment of olive mill wastewater infiltration in storage basin site (southeastern Tunisia)

The production of olive in several Mediterranean countries, including Tunisia, stands for a basic trait marking the agricultural field. However, this activity generated large quantities of by-wastes and residues during the process of olive oil extraction. However, solid (pomace) or liquid wastes (olive mill wastewater (OMW)) exhibit an adverse polluting effect on air, surface water, soil, and water table. The objective of this work is to explore the impact of OMW on the quality of the storage site by investigation of OMW storage infiltration and permeability using geochemical and geophysical analysis. A control core (CC) is considered as uncontaminated soil, a core (C1) in OMW is from the receiving basin, and another core (C2) is from the drying basin. Geochemical analysis demonstrated the enrichment of soil with nutrient substances (organic matter, nitrogen, phosphorus, and potassium) with an increase of phenolic compound contents. The results derived from high-performance liquid chromatography (HPLC) entailed the appearance of five types of polyphenols, homogentisic acid, catechin, tyrosol, hydroxybenzoic acid, and caffeic acid, along 600-cm depth. Electrical resistivity tomography results showed a vertical OMW infiltration for about 22.5 m. It was also revealed that storage site is characterized by low resistivity and low permeability corresponding to clay substratum as confirmed by the recorded high electrical conductivity (EC) values. Electrical resistivity tomography is a quick technique that allows following propagation of OMW in storage basin. Thus, this technique can be useful for soil management for estimating either OMW infiltration or permeability.