A remarkable step in the aerobic biological treatment of Olive Mill Wastewater (OMW): A combination of selected microbial strains that enhance their decolorization and depollution

Natural Resources and Sustainable Development Laboratory, Department of Biology, Faculty of Sciences, Ibn Tofaïl University, BP 133, 14000 Kenitra, Morocco

^* Corresponding author: hassan.bouigua@uit.ac.ma

Abstract

The olive industry extracts oil from olives but also generates solid co-products called pomace and liquid wastes known as Olive Mill Wastewater (OMW). With global annual production exceeding 30 million tons and approximately 685,000 tons in Morocco alone, these wastes pose environmental challenges due to their high acidity, organic load, and phenolic compounds. Our research aims to depollute and recycle OMW using aerobic biological treatment methods. Samples were collected from various ecological sites across four Moroccan regions. We isolated and purified several strains of molds, yeasts, and bacteria capable of decolorizing OMW. Decolorization experiments revealed promising results, with a combination of seven selected molds showing significant reductions in chemical oxygen demand (COD) by 71.44%, biochemical oxygen demand (BOD5) by 69.91%, and polyphenols content by 84.22%. Encouraged by these findings, we propose further treatment using sourdoughs composed of combinations of different pure strains, including yeasts and selected bacteria such as Bacillus subtilis and Pseudomonas aeruginosa. This approach demonstrates a practical and cost-effective method for depolluting and recycling OMW, contributing to environmental protection and human health preservation. By mitigating the risks associated with untreated OMW discharge, this study offers a viable solution to the environmental challenges posed by olive processing industries globally, particularly in regions like Morocco where olive cultivation is significant.