Performance and microbial features of the partial nitritation-anammox process treating fish canning wastewater with variable salt concentrations

The partial nitritation-anammox (PN-AMX) process applied to wastewaters with high NaCl concentration was studied until now using simulated media, without considering the effect of organic matter concentration and the shift in microbial populations. This research work presents results on the application of this process to the treatment of saline industrial wastewater. Obtained results indicated that the PN-AMX process has the capability to recover its initial activity after a sudden/acute salt inhibition event (up to 16 g NaCl/L). With a progressive salt concentration increase for 150 days, the PN-AMX process was able to remove the 80% of the nitrogen at 7–9 g NaCl/L. The microbiological data indicated that NaCl and ammonia concentrations and temperature are important factors shaping PN-AMX communities. Thus, the NOB abundance (Nitrospira) decreases with the increase of the salt concentration, while heterotrophic denitrifiers are able to outcompete anammox after a peak of organic matter in the feeding. •Partial nitritation-anammox process treating industrial effluent with variable salt.•Sudden increase to 16 g NaCl/L: anammox inhibited but quickly recovered in 4 days.•After 150 adaptation days: good N removal values (80%, 0.2 gN/L·d) at 7–9 g NaCl/L.•Nitrite oxidizing activity suppressed for NaCl concentrations higher than 4–5 g/L.•A peak of organic matter developed heterotrophic bacteria that outcompeted anammox.