Intensive use of engineered nanoparticles (NPs) in daily products ineluctably results in their release into aquatic systems and consequently into drinking water resources. Therefore, understanding NPs behavior in various waters from naturel to mineral waters is crucial for risk assessment evaluation and the efficient removal of NPs during the drinking water treatment process. In this study, the impact of relevant physicochemical parameters, such as pH, water hardness, and presence of natural organic matter (NOM) on the surface charge properties and aggregation abilities of both NPs and nanoplastic particles is investigated. TiO2, CeO2, and Polystyrene (PS) nanoplastics are selected, owing to their large number applications and contrasting characteristics at environmental pH. Experiments are performed in different water samples, including, ultrapure water, three bottled mineral waters, Lake Geneva, and drinking water produced from Lake Geneva. Our findings demonstrate that both water hardness and negatively charged natural organic matter concentrations, which were measured via dissolved organic carbon determination, are playing important roles. At environmental pH, when negatively charged nanoparticles are considered, specific cation adsorption is promoting aggregation so long as NOM concentration is limited. On the other hand, NOM adsorption is expected to be a key process in NPs destabilization when positively charged PS nanoplastics are considered.

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Microplastics have been detected all around the globe in freshwaters which are frequently used to produce drinking water. Therefore, the contamination of raw water with microplastics that supplies drinking water treatment plants, and their removal efficiency is raising more concern and interest. In the present study, we evaluated the microplastic contamination in a conventional drinking water treatment plant (Geneva, Switzerland) and the contribution of coagulation on the efficiency of the filtration systems (sand and activated carbon filtrations) in the removal efficiency of microplastics (MPs) and synthetic fibres. This work was performed in a pilot station that replicates the main drinking water treatment process. Raw water and effluents of each filtering processes were analysed for the presence of MPs and synthetic fibres with sizes ≥ 63 μm using infrared spectroscopy. The contamination of MPs in raw water and in drinking water ranged from 19.5 to 143.5 MPs/m3 and from 0 to 8 MPs/m3 (in presence and absence of coagulant), respectively. On the other hand, concentration of synthetic fibres ranged from 7.7 to 23.8 synthetic fibres/m3 in raw water and from 0 to 3 synthetic fibres/m3 in drinking water. Results show that on average 89% of microplastics and 81% of synthetic fibres (≥63 μm) are retained in water treatment in absence of coagulant. Better final removal efficiency of microplastics (97%) and synthetic fibres (96%) was observed in drinking water with coagulation treatment. The chemical composition of microplastics and synthetic fibres is found more heterogeneous in raw water than after sand filtration and activated carbon filtration.

Intensive use of engineered nanoparticles (NPs) results in their release into aquatic systems and consequently into drinking water resources. Therefore, it is important to evaluate how NPs can be effectively removed through water treatment processes, such as coagulation, to control environmental and health risks associated with NP exposure. This work investigates the effect of two conventional coagulants, polyaluminum chloride (PACl) and iron chloride (FeCl3), on NPs. Three bottled mineral and Lake Geneva waters, currently used as drinking water resources, were considered to get an insight into coagulation efficiency. TiO2, CeO2 NPs, and polystyrene (PS) nanoplastics were selected, owing to their large number of applications and contrasting surface charge and aggregation behavior at environmental pH. Our findings indicate that PACl is more efficient compared with FeCl3 since lower dosages are required to coagulate all nanoparticles. On the other hand, nanoplastic coagulation is found less efficient compared with TiO2 and CeO2 NPs. This is an important outcome indicating that nanoplastic stability and dispersion state will be more pronounced and therefore more challenging to eliminate. Results highlight the key role of NP and PS nanoplastic surface charge, as well as water properties, coagulant type, and dosage on nanoparticle elimination from aquatic systems. Practitioner Points pH, water hardness, and NOM are playing roles in final coagulant dosage concentration. PACl is more efficient than FeCl3 in most conditions. Positively charged nanoplastics are more difficult to eliminate by coagulation. NP surface properties in bottled mineral and surface waters are controlled by pH, divalent cations, and NOM. NP surface charge and coagulation efficiency depend on water properties.