Physicochemical Characterisation of Olive Mill Wastewaters Based on Extraction Methods and Filtration Levels

Olive mill wastewaters (OMWW) generated during olive oil extraction represent a significant environmental challenge due to their high organic matter content, acidic pH, phenolic content, and toxicity. Their composition varies widely depending on the extraction method and remains difficult to treat, particularly for small-scale producers lacking access to complex infrastructure. This study evaluates the combined effect of the extraction system (traditional vs. three-phase continuous) and filtration level (single vs. double) on the physicochemical and biological properties of OMWW. The methodologies employed included the analysis of water content, density, fatty acid composition, acidity, pH, total solids, chemical and biochemical oxygen demand, and biodegradability. The results indicate that traditional systems consistently produced OMWW with higher organic matter and phenolic loads, while filtration moderately reduced antioxidant potential and acidity, especially in traditional systems. The use of simple, low-cost filtration materials proved effective in improving effluent clarity and could serve as a practical pre-treatment option. This approach offers an accessible strategy for small producers aiming to valorise OMWW or reduce environmental impact. However, the study was conducted at the laboratory scale, and the long-term behaviour of filtered OMWW under real operating conditions remains to be evaluated.