The effect of TiO₂ nanoparticles removal on drinking water quality produced by conventional treatment C/F/S

Nanoparticles, namely titanium dioxide (TiO₂), are emerging contaminants widely used to commercial and industrial applications, are a potential hazard and can cause damage to environment and human health due to their toxicity. Therefore, their removal from the water is urgent to minimize or eliminate the adverse environmental and human effects. This work, investigates the efficiency of conventional coagulation/flocculation/sedimentation (C/F/S) from drinking water treatment to remove TiO₂ nanoparticles (NPs) from surface waters, and pretends to understand if the removal of TiO₂ NPs affects the ability of C/F/S to remove natural organic matter (NOM) and turbidity, and consequently affects the quality of the treated water. Results show that TiO₂ NPs removal is high (>90%) for all the waters studied (hydrophobic and hydrophilic waters) and the treated water quality is not compromised (turbidity, Ti and Al concentrations, pH and conductivity are below the national and international guidelines). In addition, TiO₂ initial concentrations, ranging between 0.2 and 10 mg/L, have not a significant impact on NPs removal by C/F/S. Therefore, the widely used polyaluminium based coagulants are effective in the removal of TiO₂ NPs by conventional C/F/S treatment, but removal is strongly influenced by the water characteristics. Hydrophobic waters need a higher coagulant dose than hydrophilic waters to achieve the same TiO₂ NPs removals, as well as water with higher UV_254nm values. The principal mechanism involved in TiO₂ NPs removal is charge neutralisation.