Improved nutrient removal from saline wastewater in an SBR by Halobacter supplemented activated sludge

High salinity synthetic wastewater was treated in a four-step sequencing batch reactor (SBR) for nutrient removal at different salt (NaCl) concentrations by using Halobacter-added and Halobacter-free activated sludge cultures. Salt (NaCl) concentration was varied between 0 and 6% (w/v). The sequencing batch operation for nutrient removal consisted of anaerobic, oxic, anoxic, and oxic phases with hydraulic residence times (HRT) of 1/3/1/1 h and a settling phase of 45 min. Sludge age (SRT) was kept constant at 10 days in all experiments. Effects of salt content on percent removals of COD, NH4-N and PO4-P were investigated for both cases. Percent COD, NH4-N and PO4-P removals decreased with increasing salt content for both cultures, resulting in high effluent nutrient levels and high sludge volume indexes (SVI) at high salt contents. However, Halobacter-added activated sludge culture resulted in considerably higher percent nutrient removals, especially at salt contents above 2%. Nearly, 73% COD, 51% NH4-N, 31% PO4-P were removed from 5% salt containing wastewater with the Halobacter-added activated sludge, whereas percent removals were 47% COD, 36% NH4-N, and 21% PO4-P for the Halobacter-free culture in the SBR.