Integrated Bioreactor and Wetland-Based Approaches for Agricultural Drainage Treatment: A Comprehensive Review of Design, Performance, and Field Applications

Agricultural drainage water is a significant contributor to a broad spectrum of pollutant loads, including nitrates, ammonium, organic matter, phosphorus, and emerging substances, and thus poses an important environmental and human health concern. This review aims to integrate existing knowledge on bioreactors and natural and constructed wetlands in the treatment of agricultural drainage water. It covers bioreactors from a perspective on categorization, principles, and performance with respect to treatment efficiency. It provides a critical evaluation of constructed wetlands as passive treatment systems, in addition to their importance as nature-based service providers. Some significant issues in bioreactors, such as media durability, greenhouse gas production, and the elimination of emerging pollutants, will be critically described, and this critique will conclude with proposals for possible path methods in bioreactors toward a suitable convergence with a nature-related water treatment system.