ZeroPM removal workshop: Four year monitoring of PFAS levels in Thessaloniki water resources and drinking water

Nikoletta Xanthopoulou, Chemist MSc, PhD, Laboratory Manager, Thessaloniki Drinking Water Treatment Plant Laboratory, EYATH S.A. EUREAU, EU1 Drinking Water Committee Co-Chair 4-year monitoring of PFAs levels in Thessaloniki water resources and drinking water. PFAs levels in water using a Solid Phase Extraction coupled with LC/MS-MS analytical method. Monitoring the drinking water of Thessaloniki PFAs: Let’s meet the PFAs family Perand polyfluoroalkyl substances (PFAS) are a large family of thousands of synthetic individual compounds that have been used in many industrial and commercial products around the world since about the 1950s. They bear a very strong and stable carbon fluorine bond in their molecules. All PFAs compounds consist of two main components, a perfluorinated chain (tail) and a functional group (head) which is either a carboxylic acid or a sulfonate. Due to their perfluorinated tail, PFAS bear unique physicochemical properties that are drastically different to their hydrogenated counterparts. 2 PFAS are used for their non-sticking waterand stain-repellent qualities and their capacity to increase firefighting foam effectiveness (FIREFIGHTING RETARDANTS) The same chemical properties that make PFAS almost irreplaceable for several products, make them hard to remediate. These chemicals have very limited reactivity, and they are extremely persistent in the environment and bioaccumulative in human and animal tissues. This is especially true for “long-chain” PFAs. PFAs levels in water using a Solid Phase Extraction coupled with LC/MS-MS analytical method. Monitoring the drinking water of Thessaloniki PFAs: A dangerous everyday “buddy” Perand polyfluoroalkyl substances (PFAS) are used in aeronautics, the automotive industry, the chemical industry, construction, firefighting, the pharmaceutical industry, semiconductors, refrigerants, the textile industry, and wood products. They are also used in almost all consumer goods for everyday use, in food containers, cosmetics, non-stick cookware, microwave-safe packaging, fabrics with water-repellent and stain-resistant properties, in photography, paints and in pesticides. 3 PFAs: How are we exposed? 4 Human exposure to PFAs is substantial through many pathways: 5 PFAs: Why are we so concerned? Concerns about the public health impact of PFAS have arisen for the following reasons: 1. Widespread occurrence. Studies find PFAS in the blood and urine of people. According to data from the National Health and Nutrition Examination Survey (NHANES), PFAS were found in the blood of 97% of Americans!!!!!! 2. Numerous exposures. PFAS are used in hundreds of everyday products globally. 3. Growing numbers. The EPA toxicity database, DSSTox, lists 14,735 unique PFAS chemical compounds. Different organisations use different PFAs definitions and give estimates between 8,000 and 7 million. 2. Persistent. PFAS remain in the environment for an unknown amount of time!!!!!!! 2. Bioaccumulation. People may encounter different PFAS chemicals everyday. Over time, people may take in more of the chemicals than they excrete, a process that leads to bioaccumulation in human bodies. 6. Precursors. The human body is said to be able to produce enzymatically PFAs from several precursor compounds that bear perfluorooctyl-sulfonamide-based moiety. https://doi.org/10.3390/ijerph120606098, https://doi.org/10.1016/j.cej.2025.168618 6 TFA: Trifluoroacetic acid or trifluoroacetate – The “smallest” and “naughtiest” member of the PFAs family TFA is a degradation product of compounds that contain the group CF3Refrigerants (HFCs, HCFCs και HFOs) Long chain PFAs PFAs pesticides, fluorinated pharmaceuticals, fluoropolymers Wastewater Treatment Plants effluents Atmospheric deposition occurs onto the ground and surface waters, followed by diffusion into the groundwater Very persistent & mobile pollutant Not included in the DWD. Its targeted monitoring is mentioned in the technical guidelines of PFAs Total. Not removed from polluted water by any known removal method except for reverse osmosis. Toxicity data remain controversial; further research by independent, credible organizations is needed Its concentrations are continuously increasing in soil, plants, water, and the atmosphere 7 Aliakmonas River reaching Thessaloniki Water Treatment Plant 297 km Ilarionas Polyphytos Asomata Sfikia S. Barbara Grammos Mountain Thermaikos Gulf S. Barbara Water Treatment Plant 8 From Thessaloniki Water Treatment Plant to our glass of water!!! 9 Thessaloniki Water Treatment Plant (TWTP) Laboratory Since 2002 when TWTP was constructed Laboratory staff includes 10 scientists and technicians Initial purpose: TWTP Process control and optimization Today: Quality control Laboratory of all drinking water samples from Thessaloniki area, all water resources (Aliakmonas, Aravissos and several boreholes) and of TWTP process samples. Accredited to ISO-17025:2017 since 2017 for most of the analytical methods used. All the drinking water monitoring parameters included in the European/Greek Guidelines are analyzed in TWTP laboratory except for Radioactive Substances and Hexavalent Chromium which are determined in accredited labs. 16 Method Validation according to ISO 17025:2017 - LOQ PFHxA COMPOUND SPIKED DRINKING WATER SAMPLES SPIKED DRINKING WATER BLANK SAMPLES: 1 pptCONCENTRATION: RESULTDATESAMPLE NAME 1,1016/4/2024 LOQ DW 1 ppt 6.lcd 1,0216/4/2024 LOQ DW 1 ppt 5.lcd 0,9716/4/2024 LOQ DW 1 ppt 4.lcd 1,0716/4/2024 LOQ DW 1 ppt 3.lcd 1,1616/4/2024 LOQ DW 1 ppt 2.lcd 1,1416/4/2024 LOQ DW 1 ppt 1.lcd 0,07STANDARD DEVIATION Sr 0,25LIMIT OF DETECTION (LOD - ppt) 0,75LIMIT OF QUANTITATION (LOQ - ppt) 1,00LAB REPORTING LIMIT (ppt) ≤1,5 MAX LIMIT OF QUANTITATION ACCORDING TO EUROPEAN DRINKING WATER DIRECTIVE (ppt) PFHxA COMPOUND SPIKED DRINKING WATER SAMPLES SPIKED DRINKING WATER BLANK SAMPLES: 1 pptCONCENTRATION: RESULTDATESAMPLE NAME 1,14 16/4/2024 LOQ SURF 1 ppt 6.lcd 1,10 16/4/2024 LOQ SURF 1 ppt 5.lcd 1,12 16/4/2024 LOQ SURF 1 ppt 4.lcd 1,17 16/4/2024 LOQ SURF 1 ppt 3.lcd 1,19 16/4/2024 LOQ SURF 1 ppt 2.lcd 1,04 16/4/2024 LOQ SURF 1 ppt 1.lcd 0,05STANDARD DEVIATION Sr 0,18LIMIT OF DETECTION (LOD - ppt) 0,54LIMIT OF QUANTITATION (LOQ - ppt) 1,00LAB REPORTING LIMIT (ppt) - MAX LIMIT OF QUANTITATION ACCORDING TO EUROPEAN DRINKING WATER DIRECTIVE (ppt) COMPOUND LOD DW (ppt) LOQ DW (ppt) LOD SURF (ppt) LOQ SURF (ppt) LAB REPORTING LIMIT (?1,5 ng/L or ppt) PFBA 0,31 0,94 0,29 0,88 1,00 L-PFBS 0,11 0,33 0,15 0,44 1,00 PFPeA 0,22 0,66 0,18 0,55 1,00 PFHpA 0,20 0,60 0,18 0,54 1,00 PFHxA 0,25 0,75 0,18 0,54 1,00 L-PFHxS 0,19 0,56 0,53 1,59 1,00 PFOA 0,23 0,69 0,31 0,92 1,00 L-PFHpS 0,15 0,46 0,12 0,39 1,00 PFOS 0,25 0,74 0,36 1,09 1,00 PFNA 0,26 0,79 0,24 0,71 1,00 PFDA 0,19 0,56 0,18 0,55 1,00 L-PFDS 0,35 1,06 0,21 0,62 1,00 PFUdA 0,23 0,69 0,36 1,07 1,00 L-PFUdS 0,26 0,78 0,22 0,65 1,00 PFDoA 0,23 0,70 0,15 0,45 1,00 L-PFDoS 0,27 0,80 0,49 1,48 1,00 PFTrDA 0,27 0,82 0,28 0,85 1,00 L-PFTrDS 0,33 0,98 0,38 1,15 1,00 L-PFPeS 0,10 0,31 0,05 0,14 1,00 PFNS 0,21 0,63 0,20 0,61 1,00 Drinking Water LOQs range: 0,10-0,35ng/L Surface Water LOQs range: 0,14 -1,59 ng/L (ppt) Lab Reporting Limit: 1 ng/L 17 Method Validation according to ISO 17025:2017 – Repeatability ΠΑΡΑΜΕΤΡΟΣ ΕΠΙΠΕΔΟ: 1 ΕΠΙΠΕΔΟ: 2 ΕΠΙΠΕΔΟ: 3 ΣΤΟΙΧΕΙΑ ΔΕΙΓΜΑΤΟΣ ΕΛΕΓΧΟΥ: Εμβολιασμένο πόσιμο νερό με πρότυπο PFAs ΣΤΟΙΧΕΙΑ ΔΕΙΓΜΑΤΟΣ ΕΛΕΓΧΟΥ: Εμβολιασμένο πόσιμο νερό με πρότυπο PFAs ΣΤΟΙΧΕΙΑ ΔΕΙΓΜΑΤΟΣ ΕΛΕΓΧΟΥ: Εμβολιασμένο πόσιμο νερό με πρότυπο PFAs ΣΥΓΚΕΝΤΡΩΣΗ: 10 ppt ΣΥΓΚΕΝΤΡΩΣΗ: 50 ppt ΣΥΓΚΕΝΤΡΩΣΗ: 100 ppt ΗΜ/ΝΙΑ ΜΕΤΡΗΣΕΩΝ: 30/10/2022 ΗΜ/ΝΙΑ ΜΕΤΡΗΣΕΩΝ: 19/12/2022 ΗΜ/ΝΙΑ ΜΕΤΡΗΣΕΩΝ: 19/12/2022 ΑΝΑΛΥΤΗΣ: Ξανθοπούλου ΑΝΑΛΥΤΗΣ: Ξανθοπούλου ΑΝΑΛΥΤΗΣ: Γκεμεντζόγλου ΚΩΔΙΚΟΣ ΧΡΩΜΑΤΟΓΡΑΦ. (SAMPLE NAME) ΑΠΟΤΕΛΕΣΜΑ ΚΩΔΙΚΟΣ ΧΡΩΜΑΤΟΓΡΑΦ. (SAMPLE NAME) ΑΠΟΤΕΛΕΣΜΑ ΚΩΔΙΚΟΣ ΧΡΩΜΑΤΟΓΡΑΦ. (SAMPLE NAME) ΑΠΟΤΕΛΕΣΜΑ STD 10 ppb SPE SURF 11.lcd 10,58 STD 50 ppt SPE SURF 01.lcd 47,02 STD 100 ppt SPE SURF 01.lcd 99,39 STD 10 ppb SPE SURF 10.lcd 9,74 STD 50 ppt SPE SURF 02.lcd 45,53 STD 100 ppt SPE SURF 02.lcd 117,77 STD 10 ppb SPE SURF 08.lcd 10,75 STD 50 ppt SPE SURF 03.lcd 46,43 STD 100 ppt SPE SURF 03.lcd 97,22 STD 10 ppb SPE SURF 07.lcd 10,33 STD 50 ppt SPE SURF 04.lcd 38,35 STD 100 ppt SPE SURF 07.lcd 84,13 STD 10 ppb SPE SURF 05.lcd 8,72 STD 50 ppt SPE SURF 05.lcd 45,60 STD 100 ppt SPE SURF 05.lcd 108,57 STD 10 ppb SPE SURF 02.lcd 9,37 STD 50 ppt SPE SURF 06.lcd 38,55 STD 100 ppt SPE SURF 06.lcd 101,18 ΜΕΣΗ ΤΙΜΗ 9,92 ΜΕΣΗ ΤΙΜΗ 43,58 ΜΕΣΗ ΤΙΜΗ 101,38 ΤΥΠΙΚΗ ΑΠΟΚΛΙΣΗ Sr 0,78 ΤΥΠΙΚΗ ΑΠΟΚΛΙΣΗ Sr 4,01 ΤΥΠΙΚΗ ΑΠΟΚΛΙΣΗ Sr 11,31 ΟΡΙΟ ΕΠΑΝΑΛΗΨΙΜΟΤΗΤΑΣ r 2,84 ΟΡΙΟ ΕΠΑΝΑΛΗΨΙΜΟΤΗΤΑΣ r 14,59 ΟΡΙΟ ΕΠΑΝΑΛΗΨΙΜΟΤΗΤΑΣ r 41,11 % RSD r 7,89 % RSD r 9,21 % RSD r 11,15 Predicted %RSD r 89,34 Predicted %RSD r 77,86 Predicted % RSD r 70,18 Horrat (RSD/PRSD) (<2) 0,09 Horrat (RSD/PRSD) (<2) 0,12 Horrat (RSD/PRSD) (<2) 0,16 L-PFTrDS Compound REPEAT %RSDr DW 10PPT REPEAT %RSDr SURF 10PPT REPEAT %RSDr DW 50PPT REPEAT %RSDr SURF 50PPT REPEAT % RSDr DW 100PPT REPEAT %RSDr SURF 100PPT PFBA 2,89 6,30 13,39 15,17 18,14 7,73 L-PFBS 3,87 3,36 10,05 6,18 10,27 12,58 PFPeA 2,22 8,25 10,22 12,47 13,75 5,69 PFHpA 1,76 6,17 14,01 9,71 8,61 10,18 PFHxA 3,42 7,54 10,47 16,08 7,49 8,68 L-PFHxS 1,48 6,96 8,22 6,76 5,94 10,24 PFOA 1,96 3,75 12,62 3,88 8,16 4,84 L-PFHpS 2,44 6,25 10,98 6,58 4,39 4,75 PFOS 0,58 3,71 3,78 5,59 7,71 9,62 PFNA 1,93 3,82 12,85 7,89 8,43 10,87 PFDA 1,68 1,82 9,64 5,92 8,08 9,80 L-PFDS 4,90 5,37 11,12 8,73 15,87 9,30 PFUdA 0,76 1,73 11,26 6,40 10,72 9,69 L-PFUdS 3,80 9,40 4,83 6,35 13,29 12,66 PFDoA 3,83 4,36 12,13 5,86 11,15 11,05 L-PFDoS 13,36 6,96 5,83 8,79 13,63 12,49 PFTrDA 4,11 4,67 14,49 8,72 15,05 9,50 L-PFTrDS 1,67 7,89 10,04 9,21 10,28 11,15 L-PFPeS 6,91 8,04 10,56 9,10 16,45 12,27 PFNS 10,12 7,21 8,41 8,78 13,79 13,48 Maximum acceptable RSD for all method characteristics is ≤ 25% Repeatability range: 0,58 -18,14 % 18 Method Validation according to ISO 17025:2017 – Reproducibility PFAs RSDR 10 DW RSDR 10 SURF ) RSDR 50 DW RSDR 50 SURF RSDR 100 DW g RSDR 100 SURF PFBA 10,81 11,81 13,41 16,15 18,91 10,85 L-PFBS 13,43 5,53 10,63 6,32 10,75 13,43 PFPeA 9,02 15,59 10,42 13,38 14,91 9,69 PFHpA 10,62 9,74 14,47 10,15 10,03 10,60 PFHxA 7,92 14,31 11,03 17,74 8,36 10,02 L-PFHxS 4,84 9,40 10,23 7,09 7,34 11,35 PFOA 9,49 8,77 13,77 8,71 8,80 7,75 L-PFHpS 4,68 9,01 11,01 14,97 5,87 14,69 PFOS 12,21 9,30 4,06 6,00 7,79 11,55 PFNA 10,00 6,58 13,75 8,01 9,18 15,36 PFDA 9,91 5,72 13,04 9,82 8,23 14,02 L-PFDS 7,84 6,04 11,24 8,74 15,90 10,65 PFUdA 15,62 11,19 13,73 11,60 10,96 12,08 L-PFUdS 9,75 11,86 10,37 6,45 13,89 13,66 PFDoA 13,86 4,56 14,93 5,99 11,20 11,66 L-PFDoS 13,36 14,74 13,84 15,80 18,41 12,19 PFTrDA 7,82 7,82 15,08 9,30 16,34 10,94 L-PFTrDS 12,73 14,00 10,48 15,65 10,47 13,79 L-PFPeS 10,51 13,16 16,91 17,07 21,57 12,44 PFNS 10,48 9,22 8,77 10,59 14,20 15,37 Reproducibility range: 4,06 -21,57 % 19 Method Validation according to ISO 17025:2017 – Recovery PFAs R 10 DW SDR 10 DW R 10 SURF SD R 10 SURF R 50 DW SDR 50 DW R 50 SURF SD R 50 SURF R 100 DW SD R 100 DW R 100 SURF SD R 100 SURF PFBA 100 11 97 11 98 13 95 15 105 20 58 46 L-PFBS 103 14 110 16 94 10 95 6 100 11 87 12 PFPeA 103 9 124 22 97 10 99 13 95 14 93 9 PFHpA 101 11 100 8 93 13 98 10 95 10 84 9 PFHxA 96 8 98 15 89 10 93 17 95 8 76 8 L-PFHxS 110 5 113 5 94 10 92 7 97 7 82 9 PFOA 103 10 98 10 91 13 100 9 96 8 86 7 L-PFHpS 104 5 108 11 100 11 104 16 99 6 90 13 PFOS 107 13 107 11 102 4 102 6 101 8 103 12 PFNA 108 11 105 7 95 13 95 8 100 9 87 13 PFDA 101 10 104 6 93 12 92 9 98 8 88 12 L-PFDS 101 8 114 8 87 10 102 9 89 14 100 11 PFUdA 105 16 106 13 95 13 99 11 100 11 86 10 L-PFUdS 103 10 109 14 94 10 99 6 93 13 97 13 PFDoA 109 15 111 6 95 14 96 6 103 12 85 10 L-PFDoS 96 13 96 15 93 13 88 14 93 17 82 10 PFTrDA 105 8 106 8 102 15 97 9 98 16 80 9 L-PFTrDS 96 12 125 10 108 11 107 17 99 10 101 11 L-PFPeS 101 11 100 15 95 16 89 15 92 8 77 10 PFNS 96 10 134 10 75 7 106 11 73 10 102 21 Recovery acceptable range: 70-125% Maximum acceptable RSD: 25% Drinking Water Recovery range: 73-110% Surface Water Recovery range: 58-134% % RSDs for all levels and both matrices are below 22% with one exception 20 Method Validation according to ISO 17025:2017 – Uncertainty PFAs UNCER 10 DW UNCER 10 SURF UNCER 50 DW UNCER 50 SURF UNCER 100 DW UNCER 100 SURF PFBA 52 41 28 17 31 51 L-PFBS 29 16 29 24 26 30 PFPeA 18 34 44 48 41 37 L-PFPeS 27 32 39 42 45 30 PFHxA 20 33 24 39 19 22 L-PFHxS 12 20 25 20 23 26 PFHpA 24 33 33 29 25 27 L-PFHpS 11 20 28 35 16 33 PFOA 29 29 43 42 29 29 PFOS 27 21 10 14 17 25 PFNA 30 25 49 49 43 50 PFNS 25 22 26 26 33 37 PFDA 23 15 32 27 20 32 L-PFDS 18 14 27 26 37 26 PFUdA 35 27 30 25 24 26 L-PFUdS 43 29 30 20 30 50 PFDoA 30 10 33 23 25 26 L-PFDoS 31 35 36 38 41 28 PFTrDA 18 18 34 23 27 25 L-PFTrDS 29 34 24 35 23 30 <50% Maximum acceptable uncertainty for DW 100 ng/L level is 50% according to Greek/European Guidelines Uncertainty range for DW 100 ng/L level : 16-45% Uncertainty range for all levels and both matrices: 10-52% 21 3-year PFAs Monitoring in Thessaloniki raw and drinking water Sampling Points 6/9/2021 16/12/2021 31/1/2022 4/2/2022 21/2/2022 14/3/2022 11/4/2022 9/5/2022 6/6/2022 4/7/2022 22/8/2022 26/9/2022 17/10/2022 23/11/2022 12/12/2022 Poliphitos Lake <10 TWTP Inlet Water <10 <10 <10 <10 <10 <10 <10 16,6 (PFDoA+ PFTrDA) <10 <10 <10 <10 <10 9,5 (PFOA) Aravissos Springs 11,4 (PFOA) TWTP Finished Water <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 Dendropotamos Pumpstation <10 <10 <10 <10 <10 Diavata Pumpstation <10 City sampling point (various) <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 City sampling point (various) <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 Raw WaterFinished Water City sampling points Sampling Points 9/1/2023 6/2/2023 6/3/2023 3/4/2022 8/5/2023 29/5/2023 26/6/2023 24/7/2023 27/7/2023 21/8/2023 11/9/2023 9/10/2023 31/10/2023 13/11/2023 11/12/2023 Poliphitos Lake <10 TWTP Inlet Water 38.06 (PFBA) <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 Aravissos Springs <10 TWTP Finished Water <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 Dendropo tamos Pumpstat ion <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 Diavata Pumpstat ion <10 <10 <10 <10 City sampling point (various) <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 City sampling point (various) <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 PFAs findings are rare and found ONLY in raw water samples (surface and ground water) Only 2 surface water samples and one ground water sample had PFAs varying between 11,4 to 38,06ng/L. PFOA, PFBA, PFDoA and PFTrDA were identified The low PFAs concentrations are attributed to the lack of industrial activity near Thessaloniki drinking water catchment areas No PFAs concentration > 10ng/L (Sept 2021 to Jan 2024) was detected in any of the drinking water samples Only two drinking water samples had PFAs concentrations ranging between 1-10 ng/L (Feb 2024 to Oct 2025). PFOA, PFBA, PFDoA and PFTrDA were identified 22 LC-MS/MS TFA Analysis LCMS Instrument Analytical PreSolvent Delay Column Column Injection Volume LC Flow Rate Mobile Phase A Mobile Phase B Isocratic Run / Acquisition Interface Interface Desolvation Line Heat Block Heating Gas Flow Drying Gas Flow Nebulizing Gas Method LoQ (μg/L) Cal Curve Range (μg/L) 0,1 0,14 Conditions: 85% Mob Phase B MRMs monitored 113,0 → 68,7 (quantifier) 113,0 → 112,7 (qualifier) LCMS system and instrument conditions - Method Characteristics 200 o C 15 L/min 5 L/min 3 L/min Less than 22 minutes all 49 PFAS Electrospray Ionization (ESI) 300 o C 100 o C 50 µL 0.3 mL/min 5 mM Ammonium Formate + 0,1% formic acid in LCMS-grade Water Shimadzu LCMS-8050 - Restek Raptor Polar X 2.7um 100 x 2.1mm Multi Mode 40 o C LCMS-grade Acetonitrile LCMS Instrument Analytical PreSolvent Delay Column Column Injection Volume LC Flow Rate Mobile Phase A Mobile Phase B Isocratic Run / Acquisition Interface Interface Desolvation Line Heat Block Heating Gas Flow Drying Gas Flow Nebulizing Gas Method LoQ (μg/L) Cal Curve Range (μg/L) 0,1 0,14 Conditions: 85% Mob Phase B MRMs monitored 113,0 → 68,7 (quantifier) 113,0 → 112,7 (qualifier) LCMS system and instrument conditions - Method Characteristics 200 o C 15 L/min 5 L/min 3 L/min Less than 22 minutes all 49 PFAS Electrospray Ionization (ESI) 300 o C 100 o C 50 µL 0.3 mL/min 5 mM Ammonium Formate + 0,1% formic acid in LCMS-grade Water Shimadzu LCMS-8050 - Restek Raptor Polar X 2.7um 100 x 2.1mm Multi Mode 40 o C LCMS-grade Acetonitrile Direct injection of water sample after filtration through Nylon syringe filter 23 •My Deepest Thanks to: •The staff of TWTP Laboratory Dept •The staff of the Dept of Process and Maintenance of TWTP in charge of water sampling •Our manager of Water Supply Installations of EYATh SA •The CEO and the General Manager of EYATh SA •All of you for your attention!