Abstract

The rising discharge of agro-industrial effluents rich in nitrogen and phosphorus compounds poses significant threats to aquatic ecosystems, including eutrophication, algal blooms, and loss of biodiversity. Conventional biological treatments often struggle with fluctuating organic loads, recalcitrant compounds, and nutrient imbalance, necessitating the development of more resilient and efficient treatment systems. This study reviews recent advances in hybrid chemical-biological treatment technologies aimed at optimizing nutrient removal from agro-industrial wastewater. Emphasis is placed on integrated systems that combine chemical precipitation, ion exchange, or advanced oxidation processes (AOPs) with biological methods such as activated sludge, anaerobic digestion, and constructed wetlands. These hybrid configurations enhance nutrient recovery, reduce sludge production, and improve process stability under variable influent conditions. For instance, the pre-application of chemical coagulation or AOPs can break down complex organic matter and enhance biodegradability, thereby improving the performance of subsequent biological units. Moreover, the use of biofilm reactors and microbial consortia with specific denitrification or phosphorus uptake capacities has led to improved nutrient removal efficiency and reduced hydraulic retention times. The review also highlights the role of operational parameters, such as pH, carbon-to-nitrogen ratio, and redox conditions, in influencing process outcomes. Pilot-scale and field studies demonstrate that hybrid systems can consistently achieve total nitrogen and phosphorus removal efficiencies above 85%, even in high-strength effluents from dairy, slaughterhouse, and food processing industries. Despite the promising results, challenges such as cost, system complexity, and long-term stability remain. The integration of real-time monitoring tools and data-driven process control is recommended to enhance operational efficiency. This paper concludes that hybrid chemical-biological systems represent a robust and scalable solution for sustainable agro-industrial effluent management, with significant potential for resource recovery and environmental protection.