INNOVATIVE APPROACHES TO NITROGEN REMOVAL: EXPLORING THE MECHANISMS AND CHALLENGES OF HETEROTROPHIC NITRIFICATION AND AEROBIC DENITRIFICATION (HNAD) IN WASTEWATER MANAGEMENT

Abstract Nitrogen pollution in wastewater presents significant environmental and health hazards due to the presence of refractory substances, including phenolic compounds, polycyclic aromatic hydrocarbons, and heterocyclic nitrogenous compounds. Conventional treatment methods are often insufficient for successfully removing these pollutants. This review article provides a comprehensive overview of recent advancements in the treatment of nitrogen-rich wastewater, focusing on heterotrophic nitrification and aerobic denitrification (HNAD) processes. In spite of the potential of HNAD processes, they face challenges related to environmental influences and operational conditions. Conformist methods characteristically necessitate extensive capacity and precise conditions, often leading to inefficiencies. This review outlines the recent developments in HNAD processes and explores their mechanisms, metabolic pathways, and influencing factors, including carbon/nitrogen ratio, dissolved oxygen, temperature, pH, shaking speed, heavy metals, salinity, and antibiotics. The review also highlights the intricacy of treating coking wastewater due to its intractable nature and discusses how biological methods, especially bioaugmentation, can improve biodegradability. Integrated treatment methods are emerging as comprehensive solutions, combining various approaches to enhance efficiency and effectiveness. Furthermore, innovative technologies such as microwave irradiation show assurance for treating coking wastewater. Finally, this review identifies future research directions, emphasizing the need for further inquiry into the HNAD process and its application in real-world wastewater treatment facilities. By consideration the relations between various metabolic activities and optimizing environmental conditions, HNAD processes can be additional developed to offer sustainable and resourceful solutions for nitrogen removal from wastewater.