Effect of increasing salinity to adapted and non-adapted Anammox biofilms.

The Anammox process is an efficient low energy alternative for the elimination of nitrogen from wastewater. The process is already in use for side stream applications. However, some industrial wastewaters, e.g. from textile industry are highly saline. This may be a limit for the application of the Anammox process. The aim of this study was to evaluate the effects of different NaCl concentrations on the efficiency of adapted and non-adapted Anammox biofilms. The tested NaCl concentrations ranged from 0 to 50 g NaCl*L-1. Concentrations below 30 g NaCl*L-1 did not significantly result in different nitrogen removal rates between adapted and non-adapted bacteria. However, adapted bacteria were significantly more resilient to salt at higher concentrations (40 and 50 g NaCl*L-1). The IC50 for adapted and non-adapted Anammox bacteria were 19.99 and 20.30 g NaCl*L-1, respectively. Whereas adapted biomass depletes the nitrogen in ratios of NO2- / NH4+ around 1.20 indicating a mainly Anammox-driven consumption of the nitrogen, the ratio increases to 2.21 at 40 g NaCl*L-1 for non-adapted biomass. This indicates an increase of other processes like denitrification. At lower NaCL concentrations up to 10 g NaCl*L-1, a stimulating effect of NaCl to the Anammox process has been observed.