The Feasibility and Sustainability of Microcystis aeruginosa Removal with Nanobubble-Assisted Coagulation Using Polyaluminum Chloride (PACl) under Real Drinking Water Conditions

Abstract

Inorganic coagulants such as polyaluminum chloride (PACl) are widely used in conventional drinking water treatment systems to effectively reduce turbidity and remove contaminants across diverse water matrices; however, they are associated with high chemical demand, operational costs, and potential health and environmental concerns. This study demonstrates that integrating nonmodified nanobubbles (NBs) during the rapid-mixing stage of the coagulation process (NB-assisted coagulation) considerably enhances treatment performance compared to using PACl alone. Experiments were conducted in water samples collected from Lake Ontario to evaluate the performance of NB-assisted coagulation in real-water matrices. Microcystis aeruginosa was employed as a model contaminant due to its relevance as an emerging issue in water treatment systems and its ability to indicate intracellular cyanotoxin release via potential cell lysis. Results showed that cyanotoxin concentrations in NB-assisted systems were comparable to those in conventional coagulation, confirming that NBs do not disrupt cells or induce toxin release. Moreover, NB-assisted coagulation achieved equivalent or improved contaminant removal efficiency at reduced coagulant dosages, thereby lowering chemical consumption and the environmental footprint. The sustainability and economic benefits were further evaluated through a life cycle assessment and cost analysis for a hypothetical water treatment system incorporating an NB generator.