Olive Oil Mill Contamination in Geo-science: Impact on Groundwater and Soil

This review explores the geotechnical and environmental effects of olive oil mill wastewater (OMWW) on soil and groundwater, emphasizing contaminant behavior, detection methods, and treatment technologies. OMWW, a residue from olive oil production, is rich in phenolic compounds, organic matter, and salts, making it a persistent and phytotoxic pollutant whose improper disposal causes soil acidification, reduced permeability, microbial inhibition, and long-term groundwater contamination. Analysis of existing studies shows that intrusive methods such as lysimetry and soil coring, combined with non-intrusive geophysical tools like Electrical Resistivity Tomography (ERT) and Time Domain Reflectometry (TDR), provide the highest accuracy for monitoring contaminant movement. Treatment methods including bioremediation, phytoremediation, adsorption, and integrated hybrid systems have demonstrated high efficiencies, with bioremediation removing up to 96% of phytotoxic compounds, phytoremediation achieving >90% phenolic reduction, and integrated pretreatment–biological processes reaching >85% COD removal. Critical research gaps remain in predictive contamination modeling, pilot-scale validation, seasonal variability studies, and socio-economic integration, highlighting the need for multi-pronged approaches that combine advanced monitoring, modeling, and low-cost, sustainable remediation strategies tailored to resource-limited olive-producing regions.