Responses of microorganisms to on-line chemical cleaning with sodium hypochlorite in membrane bioreactor

• Main Author: Cai, Weiwei
• Other Authors: Liu Yu
• Format: Theses and Dissertations
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Environmental engineering::Water treatment
• Online Access: http://hdl.handle.net/10356/72109
• Institution: Nanyang Technological University

On-line chemical cleaning with sodium hypochlorite (NaClO) has been commonly employed for maintaining a constant permeability in membrane bioreactor (MBR), during which activated sludge is inevitably exposed to NaClO. However, little information is currently available about the potential effects of NaClO on microorganisms in such a prevalent practice. This study, therefore, aims to investigate the diverse responses of microorganisms to NaClO at various dosages. Significant enhancement of microbial adherence on membrane surface was observed upon the exposure of microorganisms to NaClO, whereby the possible mechanism behind was also proposed. Meanwhile, substantial amount of dissolved organic matter (DOM) and halogenated byproducts were released into the liquid phase due to NaClO triggered bacterial lysis. Moreover, these emerging DOM and byproducts were further characterized, while their fate in MBR was also determined. Consequently, this study provides new insights into the current practice of on-line chemical cleaning with NaClO, and sheds lights on its potential negative impacts on MBR performance.