Increasing use and release of titanium dioxide nanoparticles (TiO₂ NPs) into aquatic systems, including water compartments use to produce drinking water, represent a risk for human health through direct NPs ingestion. Since drinking water treatment plants (DWTPs) provide and guarantee the quality of the water for human consumption, in this study, the TiO₂ NPs removal efficiency of a conventional DWTP which provides drinking water for half million consumers is investigated. For that purpose, a pilot-scale DWTP is considered.

Experiments were first conducted without considering the coagulation process in order to evaluate the efficiency of the filtration processes (sand and granular activated carbon (GAC) filtration) and the specific impact of the coagulation (with Polyaluminum Chloride (PACl)) on TiO₂ NPs removal. Results show that filtration processes through sand and GAC achieve an overall TiO₂ NPs removal of 96.3% ± 1.0. The NPs removal was mainly attributed to straining and adsorption processes during filtration. Our results also indicate that the addition of coagulant significantly improves TiO₂ NPs removal with a global removal efficiency >99.5% ± 0.5. The higher removal efficiency in presence of coagulant is related to NPs surface charge reduction and aggregation, significantly increasing their retention and attachment in the filter media.