Perfluoroalkyl substances (PFAS) represent one of the most recalcitrant class of compounds of emerging concern and their removal from water is a challenging goal. In this study, we investigated the removal efficiency of three selected PFAS from water, namely, perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA) and pefluorooctanesulfonic acid (PFOS) using a custom-built non-thermal plasma generator. A modified full factorial design (with 2 levels, 3 variables and the central point in which both quadratic terms and interactions between couple of variables were considered) was used to investigate the effect of plasma discharge frequency, distance between the electrodes and water conductivity on treatment efficiency. Then, the plasma treatment running on optimized conditions was used to degrade PFAS at ppb level both individually and in mixture, in ultrapure and groundwater matrices. PFOS 1 ppb exhibited the best degradation reaching complete removal after 30 min of treatment in both water matrices (first order rate constant 0.107 min⁻¹ in ultrapure water and 0.0633 min⁻¹ in groundwater), while the degradation rate of PFOA and PFHxA was slower of around 65% and 83%, respectively. During plasma treatment, the production of reactive species in the liquid phase (hydroxyl radical, hydrogen peroxide) and in the gas phase (ozone, NO_x) was investigated. Particular attention was dedicated to the nitrogen balance in solution where, following to NO_x hydrolysis, total nitrogen (TN) was accumulated at the rate of up to 40 mg^N L⁻¹ h⁻¹.

Pharmaceuticals and hormones (PhACs) enter the aquatic environment in multiple ways, posing potential adverse effects on non-target organisms. They have been widely detected in drinking water sources, challenging water companies to reassure good quality drinking water. The aim of this study was to evaluate the concentration of sixteen PhACs in both raw and treated drinking water sources in the Metropolitan Area of Turin—where Società Metropolitana Acque Torino (SMAT) is the company in charge of the water cycle management—and evaluate the potential human health risks associated to these compounds. Multivariate spatial statistical analysis techniques were used in order to characterize the areas at higher risk of pollution, taking into account the already existing SMAT sampling points’ network. Health risks were assessed considering average detected concentrations and provisional guideline values for individual compounds as well as their combined mixture. As reported in the just-issued Drinking Water Directive 2020/2184/UE, in order to establish priority substances, a risk assessment of contaminants present in raw drinking water sources is required for monitoring, identifying potential health risks and, if necessary, managing their removal. The results showed negligibly low human health risks in both raw water sources and treated water.

Per and polyfluoroalkyl substances (PFASs) are a huge class of Contaminants of Emerging Concern, well-known to be persistent, bioaccumulative and toxic. They have been detected in different environmental matrices, in wildlife and even in humans, with drinking water being considered as the main exposure route. Therefore, the present study focused on the estimation of PFAS in the Metropolitan Area of Turin, where SMAT (Società Metropolitana Acque Torino S.p.A.) is in charge of the management of the water cycle and the development of a tool for supporting “smart” water quality monitoring programs to address emerging pollutants’ assessments using multivariate spatial and statistical analysis tools. A new “green” analytical method was developed and validated in order to determine 16 different PFAS in drinking water with a direct injection to the Ultra High Performance Liquid Chromatography tandem Mass Spectrometry (UHPLC-MS/MS) system and without any pretreatment step. The validation of this analytical method resulted in really low Quantification Limits (5 ng L⁻¹), in satisfying recoveries (70%–102%) and in a good linearity (R² = 0.99) for every compound. Among the results, only 4 compounds and only 6% of the samples showed a pollution level higher than the limits of and Quantification (LOQ). Finally, the correlation study between the assessment findings and the industrial sites which serve as potential sources of pollution in the monitored area was carried out.

In the last 20 years, several articles related to the use of fluorescence excitation–emission matrices—parallel factor analysis (EEM-PARAFAC) to monitor dissolved organic matter (DOM) in drinking- and wastewater treatment plants were published. Noteworthy, its use in respective quality control laboratories remains scarce. To extend its popularisation, in this work, EEM-PARAFAC was employed to analyse the DOM composition changes along the different stages of the drinking water treatment plant administrated by Società Metropolitana Acque Torino. The best PARAFAC model was the one of three components, indicating that the Po River is constituted, mainly, by humic acid-like (HA-L) and tryptophan-like (Try-L) substances, the tyrosine-like ones being negligible (Tyr-L). Results indicated that physical treatments (sedimentation) did not produce a reduction in the PARAFAC scores; however, a 50% decay in 254 nm absorbance was observed. Fluorescent DOM was only removed with chemical treatments, obtaining ca. 70% HA-L scores decay with ozonation and 40% with chlorination. Furthermore, although ozonation degraded HA-L substances, the Try-L scores increased by 25%, indicating the transformation of HA-L into smaller molecules. On the contrary, total organic carbon measurements only exhibited a significant change when comparing the treatment plant’s inlet and outlet (approximately a 45% decrease), but not within intermediate processes.

This study was aimed at developing statistically based model equations capable of predicting chlorite and chlorate formation during the primary oxidation/disinfection treatment using data collected on two real scale treatment plants. In this phase many operational parameters, raw water quality as well as the second oxidant dose applied, sodium hypochlorite, importantly influence the chlorite and chlorate formation. The operational parameters and the raw water quality correlated with chlorite and chlorate formation were: contact time, chemical doses, temperature, turbidity, organic substances (non-purgeable organic carbon and UV254nm absorbance), pH, iron and ammonium concentration. Given the high numbers of variables two models have been developed. The first one (complex) includes all the studied parameters; the other model (simplified) takes into account only the parameters that gave a significant correlation (>0.55) with the dependent variable. Nearly 60% of the predictions for chlorite formation were observed to be within ±40% of the measured levels and the found key parameters were the water organic content and the physico-chemical characteristics (pH and temperature). Nearly 85% of the predictions for chlorate formation were observed to be within ±40% of the measured levels and the found key parameters were again the chemical physical water characteristics (pH and temperature) and the applied chemicals doses.