Denitrifying phosphorus and glycogen accumulating organisms in organic-mediated anammox systems: A review toward advanced nitrogen and phosphorus removal

The convergence of biological nitrogen and phosphorus removal within a single, energy-efficient platform remains a challenge in wastewater treatment. Organic-mediated anammox systems emerged as a promising solution, wherein heterotrophic and autotrophic processes are coupled through internal carbon and nitrogen fluxes. Denitrifying polyphosphate-accumulating ­organisms (DPAOs) and denitrifying glycogen-accumulating organisms (DGAOs) play pivotal yet underexplored roles in orchestrating simultaneous nitrogen and phosphorus removal (SNPR). Here, we synthesize the functional ecology and metabolic plasticity of key DPAOs and DGAOs, with particular emphasis on their carbon utilization ­spectra—from volatile fatty acids to complex organics—and their differential denitrification phenotypes under anoxic conditions. We propose that these organisms form a dynamic regulatory hub that governs endogenous partial denitrification (EPD), thereby enabling sustained nitrite provisioning for anammox while synchronizing phosphorus uptake. By disentangling synergistic and competitive interactions among functional guilds, we reveal how carbon partitioning, electron competition, and intracellular storage dynamics collectively determine system-level performance. Key environmental and operational drivers—including carbon composition, C/N ratio, temperature, pH, and phosphorus loading—are evaluated as selective pressures shaping microbial assembly and metabolic routing. Persistent challenges, particularly the coexistence of slow-growing anammox bacteria with rapidly proliferating heterotrophs, are discussed alongside emerging strategies for phenotype-oriented enrichment and process stabilization. Finally, we advance a unifying microbe–metabolism–mediation framework that links community structure to metabolic function and process outcomes. This framework provides a mechanistic basis for the rational design and precise control of organic-mediated anammox systems, paving the way toward robust, low-carbon SNPR technologies adaptable to diverse wastewater matrices.