SEQUENCING BATCH REACTOR FOR TREATMENT OF HIGH SALINE WASTEWATER

The performance of sequencing batch reactors (SBR) for treating high saline wastewater (NaCl concentration ranging from 0 to 60 g/L) using microbial culture derived from a municipal wastewater treatment plant was investigated. The salt tolerance ability (0 to 150 g/L of NaCl) of these microorganisms was also studied using batch tests. Synthetic wastewater comprised of acetate as the carbon source with a mixture of nutrients and NaCl in tapwater or seawater was used. It was found that low sodium chloride concentrations of up to 10 g/L could stimulate acetate removal. The SBR study showed that acetate removal efficiency decreased from 96% in the absence of NaCl to 86% when the wastewater contained 60 g/L of NaCl. Effluent turbidity was found to be an issue for treatment of wastewater with a sodium chloride concentration equal to or greater than 30 g/L. No clear relationship was observed between sludge volume index and NaCl concentration. Study using seawater (˜20 g/L total dissolved solids) showed that SBR could achieve an organic removal efficiency of 95% with a low effluent turbidity. From the salt tolerance tests, it was found that microbial culture could tolerate up to 110 g/L of NaCl concentration and yet still achieving acetate removal. When salt concentration was greater than 110 g/L, the final TOC concentration, after 150 hours, was found to be higher than its initial concentration due to organics contributed from cell lysis. From this study, it was concluded that the biomass in the SBR could be acclimated for treating wastewater with NaCl concentration of up to 60 g/L. However, removal efficiencies and effluent turbidity would be deteriorated when operated under a high level of salinity.