Impact of salinity on treatment of saline wastewater by sequencing batch biofilm reactor process

High salinity industrial wastewater is difficult to treat using biological treatment system because of the high concentrations of salt. The potential of a sequencing batch biofilm reactor (SBBR) process in treating synthetic high salinity wastewater was evaluated at laboratory scale during a 110-day operation. The reactor was operated in a 12 h cycle, and each cycle consisted of 0.25 h influent addition, 8 h aeration, 3 h anoxic reaction, 0.5 h sedimentation and 0.25 h effluent withdrawal. Gradual increase in salinity gradient was applied during the acclimatization period. The acclimated SBBR system was demonstrated to be an effective process to remove organic compounds and ammonia nitrogen under high salinity conditions with chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) removal efficiencies of 88% and 80%, respectively. The microscopic examination indicated that rather than rotifers or vorticella, the zoogloea, filamentous fungus mingled with a small quantity of swimming infusorians were dominant bacteria in SBBR system. The removal efficiencies close to 80% in COD and 75% in NH3-N were achieved at an organic loading rate (OLR) of 0.96 kg COD/(m(3)center dot d), pH of 7.0, salinity of 14 g/L and NH3-N of 30 mg/L.