Continuous UV-C/H2O2 and UV-C/Chlorine applied to municipal secondary effluent and nanofiltration retentate: removal of contaminants of emerging concern, ecotoxicity, and reuse potential
Abstract
As global effects of water scarcity raise concerns and environmental regulations evolve, contemporary wastewater treatment plants (WWTPs) face the challenge of effectively removing a diverse range of contaminants of emerging concern (CECs) from municipal effluents. This study focuses on the assessment of advanced oxidation processes (AOPs), specifically UV-C/H2O2 and UV-C/Chlorine, for the removal of 14 target CECs in municipal secondary effluent (MSE, spiked with 10 μg L−1 of each CEC) or in the subsequent MSE nanofiltration retentate (NFR, no spiking). Phototreatments were carried out in continuous mode operation, with a hydraulic retention time of 3.4 min, using a tube-in-tube membrane photoreactor. For both wastewater matrices, UV-C photolysis (3.3 kJ L−1) exhibited high efficacy in removing CECs susceptible to photolysis, although lower treatment performance was observed for NFR. In MSE, adding 10 mg L−1 of H2O2 or Cl2 enhanced treatment efficiency, with UV-C/H2O2 outperforming UV-C/Chlorine. Both UV-C/AOPs eliminated the chronic toxicity of MSE toward Chlorella vulgaris. In the NFR, not only was the degradation of target CECs diminished, but chronic toxicity to C. vulgaris persisted after both UV-C/AOPs, with UV-C/Chlorine increasing toxicity due to potential toxic by-products. Nanofiltration permeate (NFP) exhibited low CECs and microbial content. A single chlorine addition effectively controlled Escherichia coli regrowth for 3 days, proving NFP potential for safe reuse in crop irrigation (<1 CFU/100 mL for E. coli; <1 mg L−1 for free chlorine). These findings provide valuable insights into the applications and limitations of UV-C/H2O2 and UV-C/Chlorine for distinct wastewater treatment scenarios.
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SUPPLEMENTARY MATERIAL Continuous UV-C/H2O2 and UV-C/Chlorine applied to municipal secondary effluent and nanofiltration retentate: removal of contaminants of emerging concern, ecotoxicity, and reuse potential Fernando Rodrigues-Silvaa, Carla S. Santosb,c, Joaquín A. Marreroc,d, Rosa Montese, José Benito Quintanae, Rosario Rodile, Olga C. Nunesc,d, Maria Clara V.M. Starlinga, Camila C. Amorima*, Ana I. Gomesb,c*, Vítor J.P. Vilarb,c* a Research Group on Environmental Applications of Advanced Oxidation Processes (GruPOA); Department of Sanitary and Environmental Engineering, The Federal University of Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil. b Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials (LSRELCM), Faculty of Engineering University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal c Associate Laboratory in Chemical Engineering (ALiCE), Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. d Laboratory for Process and Reaction Engineering, Environment, Biotechnology and Energy (LEPABE), Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal e Department of Analytical Chemistry, Nutrition and Food Sciences, Institute of Research on Chemical and Biological Analysis (IAQBUS), Universidade de Santiago de Compostela, Constantino Candeira S/N, 15782, Santiago de Compostela, Spain *Authors to whom all correspondence should be addressed (corresponding authors): [email protected] (Camila C. Amorim); [email protected] (Ana I. Gomes); [email protected] (Vítor J.P. Vilar)
1 MATERIAL AND METHODS Chemicals Table SM-1. List of the target CECs selected for testing and respective abbreviations and chemical composition. CAS no. Contaminant Acronym Molecule structure Organic functional group* Chemical composition MW (g mol -1 ) pKa Log KOW PNEC (µg L -1 ) 29122-68-7 Atenolol ATNL C14H22N2O3 266.336 9.6 0.43 150.0 66722-44-9 Bisoprolol BSPL Aromatics: arene, benzene ring; CHN-containing: amine, amine secondary; CHO-containing: alkanol, ether; C18H31NO4 325.443 9.5 2.20 92.0 298-46-4 Carbamazepine CBZ Aromatics: arene, benzene ring; CH only: alkene; CHNO-containing: urea CHO-containing: carbonyl C15H12N2O 236.269 13.94 2.77 2.00
2 36507-30-9 Carbamazepine 10,11-epoxide CBZ-EPX Aromatics: arene, benzene ring; CHN-containing: iminyl; CHO-containing: epoxide, ether C15H12N2O2 252.268 - 1.97 2.57 134-62-3 N.N-diethyl-meta- toluamide DEET C12H17NO 191.274 - 2.50 88.0 15307-86-5 Diclofenac DCF Aromatics: aniline, arene, benzene ring; CHN-containing: amine, amine secondary; CHO-containing: carbonyl, carboxilic acid; Halogen-containing: aryl chloride, aryl halide, leaving group C14H11Cl2NO2 296.148 4.15 4.26 0.05 330-54-1 Diuron DRN Aromatics: arene, benzene ring; CHNO-containing: urea; CHO-containing: carbonyl; Halogen-containing: aryl chloride, aryl halide, leaving group C9H10Cl2N2O 233.1 13.55 2.53 0.07 73334-07-3 Iopromide IOP Aromatics: arene, benzene ring; CHNO-containing: carbomaxamide, carboxamide secundary, carboxamide tertiary CHO-containing: alkanol, carbonyl, 1,2-diol, ether; Halogen-containing: aryl halide, aryl iodide, leaving C18H24I3N3O8 791.112 9.9 -0.44 0.14
3 group 138402-11- 6 Irbesartan ISTN Aromatics: arene, azarene, benzene ring, heteroarene CHN-containing: amidine, amine, aminyl; CHNO-containing: carboxamide, carboxmide tertiary; CHO-containing: carbonyl; C25H28N6O 428.53 4.12 5.39 700 124750-99- 8 Losartan LSTN Aromatics: arene, azarene, benzene ring, heteroarene; CHN-containing: amine, amine tertiary; CHO-containing: alkanol; Halogen-containing: aryl chloride, aryl halide, leaving group C22H23ClN6O 422.91 4.9 5.00 0.0019 137862-53- 4 Valsartan VSTN C24H29N5O3 435.519 4.73 5.27 560.0 93413-69-5 Venlafaxine VLX Aromatics: arene, benzene ring; CH only: alkene; CHN-containing: amine, amine tertiary; CHO-containing: alkanol, ether; C17H27NO2 277.402 9.4 2.74 0.88
4 723-46-6 Sulfamethoxazole SMX Aromatics: aniline, arene, azarena, arene, benzene ring, heteroarene; CHN-containing: amine, amine primary; S-containing: sulfonamide; C10H11N3O3S 253.279 3.92 0.79 0.60 108-78-1 Melamine MLN Aromatics: aniline, arene, azaarene, heteroarene CHN-containing: amine, amine primary; C3H6N6 126.12 5.00 -0.59 3.54 *Organic functional group was determined by an open online tool – ACE functional group finder [https://epoch.uky.edu/ace/public/fnalGroups.jsp].
5 CECs Quantification by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Analysis was performed by direct injection of 45 μL of the sample into the chromatographic system Acquity UPLC® H class interfaced to a Xevo TQD triple quadrupole mass spectrometer (Waters, Milford, MA, USA). Separation took place in a Luna C18 100A column (50 mm × 2 mm, 3 µm particle size) supplied by Phenomenex (Torrance, CA, USA), with constant temperature of 30 °C and 0.2 mL min-1 flow rate. The mobile phases consisted of (A) 1 mM ammonium fluoride in ultrapure water and (B) 1 mM ammonium fluoride in MeOH. The gradient was as follows: 0-1 min, 0% B; 1-8 min, linear gradient to 100% B; 7-13 min, 100% B and finally 13-20 min, 0% B. Nitrogen was used as nebulising and drying gas and Argon was used as collision gas. The analyses were determined in the ESI positive and negative polarities, and the acquisition mode was multiple-reaction monitoring (MRM). Two MRM transitions were used as a quantifier (Q) and qualifier (q) for each compound (Table SM-2). The quantification of CECs was performed by the standard addition method spiking each real matrix with the target CECs at 5 different concentration levels (LOQ-50 µg/L). Linearity, in terms of R2 was higher than 0.990 for all analytes in both matrices and repeatability, in terms of RSD (%) was lower than 15 % (5 consecutive injections of the 10 µg/L spiked level in each matrix). The method limits of quantification (LQ) are shown in Table SM-3 and were estimated by extrapolating the signal to noise (S/N) obtained from the chromatographic peaks at the specific native concentration in real samples (or the lowest addition level if the CECs were not present) to a S/N of 10.
6 Table SM-2. Instrumental LC-MS/MS parameters. CECs Retention time (min) Precursor ion (m/z) Product ion (m/z) Collision energy (V) Cone voltage (V) ESI mode ATNL 5.7 267 145 (Q) 190 (q) 30 16 38 + BSPL 7.5 326 116 (Q) 204 (q) 20 18 45 + CBZ 7.9 237 194 (Q) 179 (q) 20 38 40 + CBZ-EPX 7.1 253 180 (Q) 210 (q) 25 12 39 + DCF 8.7 294 296 250 (Q) 252 (q) 10 10 33 - DEET 8.2 192 119(Q) 91(q) 15 25 25 + DRN 8.4 233 72 (Q) 160 (q) 20 20 30 + IOP 5.2 792 559 (Q) 573 (q) 25 15 50 + ISTN 8.6 434 179 (Q) 350 (q) 65 28 50 - LSTN 8.3 421 127 (Q) 157 (q) 30 25 30 - VSTN 8.4 434 179 (Q) 350 (q) 25 20 35 + MLN 1.5 127 85 (Q) 69 (q) 15 20 45 + SMX 6.2 254 92 (Q) 156 (q) 25 15 35 + VLX 7.9 278 58 (Q) 260 (q) 20 10 25 + Note: Capillary voltages: 3.5 and 1.5 kV in positive and negative polarities, respectively. Source temperature: 350 ºC. Desolvation gas (N2) flow: 650 L h-1. Cone gas (N2) flow: 5 L h-1. Collision energy (CE) and cone voltage (CV) were adjusted for every transition. (Q) quantifier transition; (q) qualifier transition.
7 Table SM-3. LC-MS/MS method LQs in municipal secondary effluent and nanofiltration retentate CECs Municipal Secondary Effluent LQ (µg L-1) Nanofiltration Retentate LQ (µg L-1) ATNL 0.15 0.18 BSPL 0.15 0.22 CBZ 0.03 0.05 CBZ-EPX 0.02 0.10 DCF 0.25 0.40 DEET 0.03 0.05 DRN 0.08 0.08 IOP 0.80 1.0 ISTN 0.20 0.30 LSTN 0.80 1.0 VSTN 0.44 0.17 MLN 0.75 1.0 SMX 0.10 0.10 VLX 0.15 0.20
8 RESULTS AND DISCUSSION Figure SM-1. Removal percentage for the 14 target CECs spiked in MSE (10 µg L-1 for each) under UV-C irradiation (3.3 kJ L-1) without oxidant dosage (–□–) and under dark conditions with H2O2 (–□–) or NaClO (–□–) dosage. Figure SM-2. Consumption of the oxidants for the photo-treatment tests performed with MSE. Conditions: treatment time 3.4 min, UV-C dose of 3.3 kJ L-1.