A novel control strategy for the partial nitrification and anammox process (PN/A) of immobilized particles: using salinity as a factor

Abstract The impact of the addition of salinity on partial nitrification and anammox (PN/A) was investigated in this study. The sludge was immobilized by polyethylene glycol (PEG)-modified polyvinyl alcohol (PVA)-sodium alginate (SA) immobilization technology, and the effective diffusion coefficient (De) of the immobilized particles was measured to be 0.313×10-9 m2·s-1, indicating that the system has excellent mass transfer performance. An experiment was carried out by adding NaCl to create a salinity gradient. It was found that the initiation of partial nitrification was achieved at a concentration of 10 g·L-1 NaCl and the nitrite accumulation rate (NAR) reached 81.03%, which could provide sufficient NO2--N for subsequent anammox. Additionally, an anammox reactor operating at the same salinity maintained a stable state after acclimation, and the removal rates of NH4+-N and NO2--N reached 80%. The dominant population in the anammox system was Planctomycetes. Salinity is a feasible factor for controlling the PN/A process.