The performance of freshwater one-stage partial nitritation/anammox process with the increase of salinity up to 3.0

[Display omitted] •One-stage PNA process was operated until salinity up to 3.0%.•A high nitrogen removal rate was achieved even at salinity of 2.5%.•Keeping low nitrite in reactor was the key factor for desirable performance.•Freshwater microbial community was adapted to high salinity.•Nitrosomonas + Kuenenia were dominated functional microbes throughout the operation. The freshwater anammox-based process would usually experience performance fluctuation and need adoption period when subjected to saline wastewater according to previous studies. In this study, the performance of nitrite-limited freshwater one-stage partial nitritation/anammox (PNA) process subjected to saline wastewater was investigated. The results showed that the nitrite-limited freshwater system could smoothly adapt to the salinity of 0.25%. The stable nitrogen removal could be achieved until the salinity of 2.5%, at which the desirable average NRR of 0.74 ± 0.1 kg/m3/d was achieved. The microbial community analysis showed that during the whole experiment, the main functional microbes were from genus Nitrosomonas and genus Kuenenia, which were through to be the crucial factors for achieving the excellent performance. This study indicates the nitrite-limited strategy is admissible for stabilizing the performance of freshwater one-stage PNA process subjected to saline wastewater in actual application.