Start-up and community analysis of simultaneous partial nitrification and anammox (SNAP) process by immobilization

In this study, partial-nitrification and anammox biomass were co-immobilized by polyvinyl alcohol and sodium alginate (PVA-SA) to treat the ammonium-rich wastewater. The enriched partial nitrification and anammox sludge entrapped in the beads. The beads were round in shape with 4-5 mm in diameter and not agglomerated with each other. The ammonium removal efficiency of 80% achieved within ten days. The nitrogen loading rate varied from the start (37 mg/L/d) to the end of experiment (75 mg/L/d). The enriched sludge, suitable environment inside of the beads for growth of bacteria, and low diffusion constraints were the possible reasons for the fast start-up of PN-anammox system. The necrosis/apoptosis analysis confirmed that there was no observed death phenomena inside of the gel beads in a normal operation of the reactor. The microbial community analysis showed that the dominance of phyla Proteobacteria (35.35%) while the abundance of phyla Planctomycetes was 2.42%. Likewise, at the genus level, Candidatus Brocadia accounts for 1.33% while Nitrosomonas was 0.89%, but the highest shared observed from the genus Burkholderia. The use of immobilization technology in the application of the SNAP process may represent a valuable alternative to other technologies such as granulation, suspended cell growth and biofilm system.