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  • Development of drinking water treatment processes for nanoparticles removal
    Publication . Sousa, Vânia Sofia Serrão de; Teixeira, Margarida Ribau
    The ability of drinking water treatments (DWT) to remove ENPs from water is crucial to ensure the safety of public water supply. This thesis assessed the removal of three comercial metal-based nanoparticles, titanium dioxide (TiO2), silver (Ag) and copper oxide (CuO) in DWT, exploring and comparing the potential of conventional and advanced processes. To understand the removal mechanisms, individual ENPs and mixtures of the three ENPs, dispersed in synthesised and natural surface waters were used. Conventional coagulation/ flocculation/ sedimentation (C/F/S) process alone and enhanced with powdered activated carbon (PAC) were studied, and the advanced membrane filtration processes, ultrafiltration (UF) and nanofiltration (NF), were integrated with conventional C/F/S (hybrid water treatment) or used alone (NF). These technologies were evaluated under typical DWT operational conditions. Overall, results show that optimised treatments are able to remove ENPs, without hampering other DWT target compounds. Residual turbidity, dissolved organic carbon, specific UV absorbance and aluminium were below the guidelines and similar to those found in actual DWTP. C/F/S removed 93% and 98% of the tested ENPs, depending on water characteristics. C/F/S+PAC and C/F/F→UF treatments improved the removal of single and multiple ENPs in approximately 10% compared with C/F/S alone, with Ti and Cu undetected in the C/F/S→UF treated water. However, due to AgNPs dissolution, residual Ag concentrations were present in the C/F/S→UF treated water. Using NF, the dissolved Ag was eliminated from treated water to undetectable values (depending on water characteristics). The main mechanisms responsible for the removal were charge neutralisation (C/F/S), size exclusion (UF and NF), adsorption and complexation with salts and adsorption on NOM (PAC and NF). This study contributes to the advancement of knowledge on the removal of emerging contaminants from drinking water, demonstrating that the processes optimisation for the ENPs removal is a key factor to ensure safe water, reducing the potential hazards associated to the ingestion of these contaminants and meeting the drinking water quality guidelines.
    2020-06-01Doctoral thesis Open access Show more