Monitoring the stability of an Anammox reactor under high salinity conditions

Abstract

The effects of high salinity conditions (up to 30 g NaCl L −1) on the efficiency and activity of the Anammox process were studied in a sequencing batch reactor. The use of the estimated maximum Specific Anammox Activity (SAA) was evaluated as a monitoring parameter of the performance of the process. The SAA values obtained from biomass adapted under the same salinity conditions and collected from the reactor could be used to calculate the maximum capacity of the system and, therefore, to predict its efficiency at a certain operation condition. Batch assays carried out with non-adapted and adapted Anammox biomass at different salt concentrations indicated a stimulatory effect on the SAA at concentrations up to 6 and 15 g NaCl L −1 while higher salt concentrations caused a decrease in the activity. The addition of salt enhanced the aggregation of Anammox biomass in granules with a consequent decrease in the Sludge Volumetric Index from 80 to 25 mL g VSS −1. The system was able to treat a nitrite loading rate around 0.32 g NO 2 −-N L −1 d −1 when salt concentrations of 15 g L −1 of NaCl were present in the feeding, with nitrogen removal efficiencies of 99%. The Anammox process exhibited high resistance to the presence of high NaCl concentrations being then recommended to remove nitrogen from effluents with high salt concentrations.