Start-up of a full-scale two-stage partial nitritation/anammox (PN/A) process treating reject water from high solid anaerobic sludge digestion (HSAD)

•d), with a total nitrogen removal efficiency of over 90%. Compared to the traditional nitrification-denitrification process, the PN/A process remarkably reduces the addition of organic chemicals and aeration energy consumption, saving approximately 4.2 million yuan (RMB) in operational costs annually. In summary, this research provides a full-scale reference for the start-up of the PN/A process treating sludge HSAD reject water.