Sustainable Actinomycete Biofilters Enable Optimized Phenol Removal and Agricultural Reuse of Olive Mill Wastewater within a Circular Economy Framework

Olive mill wastewater (OMW) is characterized by high phenolic content, posing environmental challenges due to its toxicity and persistence. This study evaluated a pilot-scale biofilter system combining biological degradation by a selective actinomycete consortium (OMC EMCC2006) with passive physicochemical stabilization for OMW treatment. Wastewater was sourced from the El-Fayrouze Olive Mill in North Sinai, Egypt, an arid region facing severe water scarcity. A 2⁴ factorial design in microcosm experiments was used to optimize phenol removal, testing nitrogen supplementation, inoculum size, support media, and activated carbon. Under optimized conditions, a continuous-flow biofilter operated for three months achieved a 63.9% reduction in Chemical Oxygen Demand and a 43.6% reduction in total phenols, with limestone enhancing buffering and microbial performance. The treated effluent was reused for irrigation of Jatropha curcas , increasing plant height by 15% and nearly doubling fruit yield. Life cycle assessment showed that the biofilter reduced energy demand and greenhouse gas emissions by up to 77% and 80% compared with electrocoagulation and Fenton oxidation. Water and material circularity indices improved 3–5 fold. The system offers a low-carbon, resource-efficient alternative to conventional treatments, providing a scalable model for sustainable agro-industrial effluent management in water-limited environments.