Response of activated sludge to high concentration salt

• Main Author: Tan, Joyce Hui Ling.
• Other Authors: Liu Yu
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Environmental engineering::Water treatment
• Online Access: http://hdl.handle.net/10356/15940
• Institution: Nanyang Technological University

The effect of sodium chloride (NaCl) on the yield of biological solids and the ability of microbial populations to remove substrate was assessed by varying the salt concentration added to the activated sludge. In order to quantify the adverse effects of salt on biological treatment of saline wastewater, activated sludge was cultivated under aerobic condition in lab scale batch reactors. Sodium chloride concentrations ranging from 0 to 30 g/L were added to each of the batch reactors. Acetate was used as the main carbon source for substrate. Variations in the biomass production, TOC removal rate and the efficiency with salt concentration were determined. It was found that sodium chloride concentrations of up to 10 g/L would not have negative effect on the removal efficiency of substrate. When salt concentration was increased up to 30 g/L, an adverse effect on the substrate removal was observed in the batch culture of activated sludge. This is probably due to the fact that high salt concentrations in wastewater would cause plasmolysis and loss of cell activity, thereby resulting in low TOC removal efficiency. Lower biomass concentrations were also observed at higher salt concentrations, compared to the control culture without addition of sodium chloride. Optical microscopy and scanning electron microscopy indicated morphological changes in the microbial population. From this study, it was concluded that microbial culture from wastewater facilities could be acclimated to treat wastewater containing sodium chloride concentrations of up to 15 g/L.