Moderately quaternized starch-derived polymers for synchronous bacterial removal and sustained inactivation:...

The escalating bacterial contamination in underdeveloped regions poses serious health challenges, necessitating heavy reliance on disinfectants and increasing the risk of disinfection by-products (DBPs). As flocculation precedes disinfection, its potential to enhance downstream efficacy deserves systematic investigation. Quaternized starch-derived polymers (QSPs) have attracted attention due to their flocculation and bactericidal properties. However, the effects of QSPs on disinfection and their potential synergistic interactions remain unclear. Herein, we synthesized a series of QSPs with varying quaternization degrees and systematically evaluated their combined performance with chlorine disinfection. QSPs with moderate quaternization effectively decreased both E. coli concentration and viability in effluent and significantly reduced the release of intracellular organic matter, thereby mitigating chlorine demand and DBPs formation by 93.32 % and 56.20 %. QSPs also sustained bacterial regrowth, promoting stability and supernatant reuse. Density functional theory and XDLVO analyses revealed the release and re-aggregation of cellular organic matter exerted dual roles: promoting adsorption-bridging effects but hindering QSPs-cell interactions when excessive. Mechanistic studies revealed that through optimal regulation of quaternization, QSPs simultaneously achieved prolonged contact-bactericidal activity and flocculation-constraining effects. Real-water tests confirmed the practicality of QSPs, highlighting their potential as an efficient, affordable, and implementable on-site solution for treating bacteria-laden water in resource-limited regions.