A comprehensive review of integrated biological and chemical technologies for sustainable agroindustrial wastewater treatment

Agro-industrial wastewater presents a complex environmental challenge due to its variable composition, including high organic loads, nutrients, heavy metals, dyes, pesticides, and emerging micropollutants. This review synthesizes recent advances in biological and chemical treatment technologies, with emphasis on hybrid systems integrating anaerobic, aerobic, and advanced oxidation processes (AOPs) for improved efficiency and resource recovery. Case studies from dairy, snack-food, aquaculture, and olive oil processing industries demonstrate pollutant removal efficiencies of up to 95% chemical oxygen demand (COD) reduction under hydraulic retention times of approximately 12–24 h and operating temperatures between 30 and 37 °C, and up to 80% nutrient recovery using integrated processes such as anaerobic membrane bioreactor (AnMBR) + AOP and electrocoagulation (EC) + membrane bioreactor (MBR). Life-cycle assessment (LCA) insights highlight energy optimization potential, showing up to 30% operational cost savings and enhanced circular resource recovery. A decision matrix supports technology selection based on wastewater strength, contaminant profiles, regulatory discharge limits, and reuse goals. Furthermore, the integration of artificial intelligence (AI), Internet of Things (IoT), and predictive control systems is discussed as a pathway for smarter, more sustainable wastewater management. Despite their demonstrated effectiveness, the large-scale implementation of hybrid treatment systems remains constrained by high capital investment, operational complexity, membrane fouling, chemical consumption, and energy demands, requiring careful trade-offs between treatment performance, economic feasibility, and long-term sustainability. This analysis underscores the need for adaptive, sector-specific, and multi-functional treatment strategies to achieve regulatory compliance while enabling water reuse and energy recovery.