This chapter explores advanced wastewater treatment (AWT) processes that extend beyond conventional biological treatment to achieve high-quality effluents. It emphasizes nutrient removal, particularly nitrogen and phosphorus, through integrated nitrification, denitrification, and biological phosphorus removal pathways. Various process configurations, such as the Modified Ludzack–Ettinger (MLE) process, post-anoxic denitrification, and two-sludge systems, are discussed in detail, along with mass balance approaches to quantify nutrient transformations. The chapter also highlights the role of alkalinity, electron donor availability, and sludge age in governing system performance. Emerging technologies like the Pho-Strip process are presented, illustrating innovative strategies for phosphorus recovery. Together, these concepts provide the foundation for designing sustainable treatment systems that meet stringent environmental discharge standards.