Advancing anammox pathways for wastewater treatment: A focus on conventional carrier challenges and innovations of 3D printed biocarrier

Anammox (AMX) has become one of the most promising nitrogen removal technologies applicable in wastewater treatment, leading to sustainability and energy efficiency compared to conventional methods. Despite its efficiency, AMX in treating mainstream wastewater was challenging because of the slow growth rate of the anammox bacteria (AnAOB). This review paper explores the AMX pathways, including partial nitrification and anammox (PN/AMX), partial denitrification and anammox (PD/AMX), and simultaneous partial nitrification anammox and denitrification (SNAD), highlighting their mechanisms, advantages, and critical factors affecting them. In addressing the AMX and its pathways limitations, this paper emphasizes the critical role of different carriers and carrier enhancement techniques in stabilizing AnAOB, improving biofilm formation, and enhancing overall process efficiency. It also discusses the limitations of the conventional carrier and carrier enhancement methods, such as limited surface area, mechanical instability, clogging, etc., and emphasizes explorative innovation solutions. As a promising solution, 3D-printed carriers stand out due to their customizable designs, improved porosity, and enhanced surface area. By leveraging these advancements, this review underscores the potential of 3D-printed carriers to overcome key AMX challenges, paving the way for more efficient and sustainable nitrogen removal in wastewater treatment.