Specific nutrient removal rates in saline wastewater treatment using sequencing batch reactor

Effects of salt concentration (0–6%, w/v) on specific nutrient removal rates from saline wastewater in a sequencing batch reactor (SBR) were investigated. The sequencing batch operation consisted of anaerobic, oxic, anoxic and oxic phases with hydraulic residence times (HRT) of 1/3/1/1 h and a settling phase of 3/4 h. Solids retention time (SRT) was kept constant at 10 days in all experiments. Specific nutrient (COD, NH4-N and PO4-P) removal rates decreased with increasing salt concentration due to adverse effects of salt on microorganisms. A salt tolerant organism, Halobacter halobium was added to the activated sludge culture (1/1, v/v) in order to improve the nutrient removal performance of the SBR. Nutrient removal performances of Halobacter-free and Halobacter-added activated sludge cultures were compared for all salt contents tested. Specific rates of nutrient removal obtained with the Halobacter-added culture were higher that those of Halobacter-free activated sludge, especially at high salt contents.