Assessment of antibiotic-resistant infection risks associated with reclaimed wastewater irrigation in intensive tomato cultivation.

Agricultural irrigation using reclaimed urban wastewater (RWW) represents a sustainable practice to meet the ever-increasing water stress in modern societies. However, the occurrence of residual antibiotics and antibiotic resistant bacteria (ARB) in RWW is an important human health concern. This study applied for the first time a novel Simple-Death dose-response model to the field data of Escherichia coli and Pseudomonas spp. collected from three greenhouses for cultivation of tomatoes irrigated with RWW. The model estimates the risk of infection by enteropathogenic E. coli associated with consumption of tomatoes and the risk of eye-infection caused by Pseudomonas aeruginosa in cultivation soil through hand-to-eye contacts. The fraction of antibiotic resistant (AR)-E. coli measured in irrigation water and AR-Pseudomonas spp. in soil was incorporated in the model to estimate the survival of ARB and antibiotic susceptible bacteria in the presence of trace level of antibiotics in human body. The results showed that the risk of E. coli infection through consumption of tomatoes irrigated with RWW is within the WHO and USEPA recommended risk threshold (<10-4); Pseudomonas aeruginosa eye-infection risk is at or below the acceptable risk level. The presence of residual antibiotic in human body reduced the overall risk probabilities of infections but selectively enhanced the survival of ARB in comparison to their susceptible counterparts, which resulted in antibiotic untreatable infection. Therefore, the outcomes of this study call for a new risk threshold for antibiotic untreatable infections and highlight the key importance of adopting work safety measures for better human health protection.

Solar photo-Fenton optimization at neutral pH for microcontaminant removal at pilot plant scale.

The increasing occurrence of micropollutants in natural water bodies has medium to long-term effects on both aquatic life and human health. The aim of this study is to optimize the degradation of two pharmaceutical pollutants of emerging concern: amoxicillin and acetaminophen in aqueous solution at laboratory and pilot scale, by solar photo-Fenton process carried out at neutral pH using ethylenediamine-N,N'-disuccinic acid (EDDS) as a complexing agent to maintain iron in solution. The initial concentration of each compound was set at 1 mg/L dissolved in a simulated effluent from a municipal wastewater treatment plant (MWTP). A factorial experimental design and its surface response analysis were used to optimize the operating parameters to achieve the highest initial degradation rate of each target. The evolution of the degradation process was measured by ultra-performance liquid chromatography (UPLC/UV), obtaining elimination rates above 90% for both contaminants. Statistical study showed the optimum concentrations of Fe(III) at 3 mg/L at an Fe-EDDS ratio of 1:2 and 2.75 mg/L H2O2 for the almost complete removal of the target compounds by solar photo-Fenton process. Validation of the experimental design was successfully carried out with actual MWTP effluent spiked with 100 µg/L of amoxicillin and acetaminophen, each at pilot plant scale.

Peroxymonosulfate/Solar process for urban wastewater purification at a pilot plant scale: A techno-economic assessment.

The safe reuse of reclaimed water for agricultural irrigation has been considered as an alternative, feasible and sustainable option to address water scarcity. This work aims to validate the capability of the solar water photochemical process based on the synergistic effect between peroxymonosulfate (PMS) and natural solar radiation for actual urban wastewater (UWW) purification at a pilot plant scale using a solar Compound Parabolic Collector photo-reactor. The PMS/Solar process performance was assessed by monitoring simultaneously the inactivation of naturally occurring bacteria (Escherichia coli, Total coliforms, Enterococcus spp. and Pseudomonas spp.) as a potential tertiary treatment to fit the minimum bacterial requirements for UWW purification but also additional challenges have been in deep analysed simultaneously. In this regard, a global analysis including the degradation of three Contaminants of Emerging Concern (CECs) (Diclofenac-DCF, Sulfamethoxazole-SMX and Trimethoprim-TMP), the removal of antibiotic resistant elements, the residual toxicity and the treatment cost has been analysed. Different PMS concentrations (0-1 mM) were tested and an enhancement in the process performance was obtained with increasing oxidant load, obtaining the best results with 1 mM of PMS, at which detection limit (DL) of 2 CFU/mL was reached for all microbial targets after 15 min (1.1 kJ/L of accumulated solar UV-A radiation (QUV)) and 80 % of CECs removal was reached after 27 min (2.0 kJ/L of QUV) of solar treatment time. Inactivation of naturally occurring antibiotic resistant bacteria (ARB) and removal of 16S rRNA and selected antibiotic resistance genes (ARGs) (i.e., intI1, sul1, qnrS, blaTEM, blaCTX-M32, tetM) were also investigated. ARB was successfully inactivated to values below the DL, but the process was not able to completely remove ARGs. A total reduction of intI1 (30 %), 16S rRNA (19 %), sul1 (14 %), blaCTX-M32 (12 %), qnrS (10 %), blaTEM (8 %), and tetM (7 %), was obtained after 120 min (11.5 kJ/L of QUV). An absence of an eco and phytotoxic effect of treated samples was observed towards Aliivibrio fischeri and three seeds, respectively. Finally, an estimated treatment cost of 0.96 €/m3 for the simultaneous UWW disinfection and decontamination demonstrates the promising capability of this solar treatment for UWW reclamation and reuse in agriculture, especially in areas with a high solar radiation incidence.

Use of Fluorescence Spectroscopy and Chemometrics to Visualise Fluoroquinolones Photodegradation Major Trends: A Confirmation Study with Mass Spectrometry.

In this work, we employed EEM-PARAFAC (fluorescence excitation-emission matrices-parallel factor analysis) as a low-cost tool to study the oxidation pathways of (fluoro)quinolones. Amounts of 12.5 µM of enrofloxacin (ENR), ciprofloxacin (CIP), ofloxacin (OFL), oxolinic acid (OA), and flumequine (FLU), as individual solutions, were irradiated under UVA light. A 5-component PARAFAC model was obtained, four of them related to the parent pollutants, named as ENR-like (including CIP), OFL-like, OA-like, and FLU-like, and an additional one related to photoproducts, called ENRox-like (with an emission red-shift with respect to the ENR-like component). Mass spectrometry was employed to correlate the five PARAFAC components with their plausible molecular structures. Results indicated that photoproducts presenting: (i) hydroxylation or alkyl cleavages exhibited fingerprints analogous to those of the parent pollutants; (ii) defluorination and hydroxylation emitted within the ENRox-like region; (iii) the aforementioned changes plus piperazine ring cleavage emitted within the OA-like region. Afterwards, the five antibiotics were mixed in a single solution (each at a concentration of 0.25 µM) in seawater, PARAFAC being also able to deconvolute the fingerprint of humic-like substances. This approach could be a potential game changer in the analysis of (fluorescent) contaminants of emerging concern removals in complex matrices, giving rapid visual insights into the degradation pathways.

Individual and combined effect of ions species and organic matter on the removal of microcontaminants by Fe3+-EDDS/solar-light activated persulfate.

This work is focused on improving the understanding of the complex water matrix interactions occurring during the removal of a microcontaminants mixture (acetamiprid, carbamazepine and caffeine) by solar/Fe3+-EDDS/persulfate process. The individual and combined effects of sulfates (100-500 mg/L), nitrates (20-160 mg/L), bicarbonates (77-770 mg/L) and chlorides (300-1500 mg/L) were assessed by comparing the outcomes obtained in different synthetic and actual water matrices. In general, the results showed negligible effects of the different anions on Fe3+-EDDS concentration and PS consumption profiles, while the combination of bicarbonates and chlorides seemed to be the key for the MC removal efficiency decrease found when working with complex matrixes. Finally, the influence of dissolved organic matter on process performance was evaluated. It was concluded that there is neither any influence of this variable on Fe3+-EDDS concentration and PS consumption profiles. In contrast, there was a general negative effect on MC removal efficiency, which strongly depended on both the concentration and composition of the dissolved organic matter.

EEM-PARAFAC as a convenient methodology to study fluorescent emerging pollutants degradation: (fluoro)quinolones oxidation in different water matrices.

Commercial (fluoro)quinolones ((F)Qs), ciprofloxacin (CIP), enrofloxacin (ENR), ofloxacin (OFL), oxolinic acid (OA) and flumequine (FLU) (3 µM each), were degraded with solar-photo-Fenton in a compound parabolic concentrator photoreactor (total volume 5 L) in ultra-pure water at pH = 5.0, salty water at pH = 5.0, and simulated wastewater at pH = 5.0 and 7.5. Iron speciation (its hydrolysis and the complexation with (F)Qs 15 µM and/or chlorides 0.5 M) was calculated at pH 5.0, observing, negligible formation of Fe(III)-chloride complexes, and that >99 % of the total (F)Qs are forming complexes stoichiometry 1:1 with Fe(III) (which also increases the percentage of Fe(OH)2+), being minoritarian the free antibiotic form. On the other hand, EEM-PARAFAC (fluorescence excitation-emission matrices-parallel factor analysis) was employed to simultaneously study the behaviour of: i) 4 structure-related groups corresponding to parent pollutants and slightly oxidised by-products, ENR-like (including CIP), OFL-like, OA-like, FLU-like; ii) intermediates still showing (F)Q characteristics (exhibiting analogous fluorescent fingerprint to ENR-like one, but shifted to shorter wavelengths); iii) humic-like substances. The scores from the 4 PARAFAC components corresponding to the parent pollutants were plotted vs. accumulated energy, exhibiting slower decay than their individual removals (measured with HPLC-UV/vis) due to the contribution of the aforementioned by-products to the overall fluorescence. Moreover, thiabendazole (TBZ) 3 µM was added as fluorescence interference. The presence of (F)Qs greatly enhanced TBZ degradation due to (F)Q-Fe(III) complex formation, keeping iron active at pH = 5.0 for Fenton process. The EEM-PARAFAC model was able to recognise the former six components plus an additional one attributable to TBZ-like.

Natural solar activation of modified zinc oxides with rare earth elements (Ce, Yb) and Fe for the simultaneous disinfection and decontamination of urban wastewater.

This study investigates the capability of modified zinc oxides (ZnO) with Ce, Yb and Fe towards the simultaneous inactivation of pathogenic bacteria (Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa) and Contaminants of Emerging Concern (CECs, Diclofenac, Sulfamethoxazole and Trimethoprim) under natural sunlight. Several catalyst loads (from 0 to 500 mg/L) were assessed as proof-of principle in isotonic solution followed by the evaluation of organic matter effect in simulated and actual urban wastewater (UWW), using bare TiO2-P25 as reference. The order of photocatalysts efficiency for both bacterial and CECs removal was: ZnO-Ce â‰… TiO2-P25 > ZnO-Yb > ZnO-Fe > photolysis > darkness in all water matrices. The best photocatalytic performance for water disinfection and decontamination was obtained with 500 mg/L of ZnO-Ce: 80% of ∑CECs removal after 45 min (4.4 kJ/L of accumulated solar UV-A energy (QUV)) and the total inactivation of bacteria (Detection Limit of 2 CFU/mL) after 120 min (14 kJ/L of QUV) in UWW. The microbial and CECs abatement mechanism was described based on the generation of hydroxyl radicals, which was experimentally demonstrated for ZnO-Ce. Additionally, no significant release of Zn2+ and Ce was detected after the solar exposure. These results point out for the first time the capability of ZnO-Ce for the simultaneous UWW disinfection and decontamination under natural sunlight.

Simultaneous disinfection and microcontaminants elimination of urban wastewater secondary effluent by solar advanced oxidation sequential treatment at pilot scale.

The effect of different times of Fe:Ethylenediamine-N, N'-disuccinic acid (EDDS) dosing and H2O2 as well as different Fe:EDDS concentrations in the sequential treatment sunlight/H2O2 followed by sunlight/H2O2/Fe:EDDS at circumneutral pH was investigated for the first time focusing both in contaminants of emerging concern (CECs) and bacteria removal in urban wastewater treatment plant effluents. Process efficiency was evaluated in terms of (i) degradation of five CECs (namely caffeine, carbamazepine, diclofenac, sulfamethoxazole and trimethoprim) at the initial concentration of 100 µgL-1 each and (ii) bacteria inactivation (Escherichia coli (E. coli) and Salmonella spp). The effect of H2O2, Fe and EDDS concentration and Fe:EDDS dosing time was evaluated. 60% removal of the sum of total CECs and pathogens inactivation below the detection limit (DL) were observed by the sequential treatment with Fe:EDDS additions at 60 min and 45 min in simulated urban wastewater effluent. Sequential treatment was validated in actual urban wastewater effluent, being able to remove 60% of the target CECs and inactivate bacteria below the DL. Increasing EDDS concentration negatively affected Salmonella spp inactivation. Sequential treatment based on 120 min of sunlight/H2O2 (50 mg L-1) and subsequent SPF with Fe:EDDS (0.1:0.1 mM) was chosen as best operation conditions for full scale treatment in urban wastewater treatment plants.

Valorization of UWWTP effluents for ammonium recovery and MC elimination by advanced AOPs.

The main objective of this study was to generate ready-to-use revalorized irrigation water for fertilization from urban wastewater treatment plant (UWWTP) effluents. The focus was on controlled retention of NH4+ and microcontaminants (MC), using nanofiltration. Retentates generated were treated by solar photo-Fenton at circumneutral pH using Ethylenediamine-N, N'-disuccinic acid (EDDS) iron complexing agent. Solar photo-Fenton degradation efficacy was compared with electrooxidation processes as anodic oxidation, solar-assisted anodic oxidation, electro-Fenton and solar photoelectro Fenton. Finally, phytotoxicity and acute toxicity tests were performed to demonstrate the potentially safe reuse of treated wastewater for crop irrigation. Nanofiltration was able to produce a ready-to-use permeate stream containing recovered NH4+. (valuable nutrient). Solar photo-Fenton treatment at circumneutral pH would only be of interest for rapid degradation of contaminants at less than 1 mg/L in nanofiltration retentates. Other alternative tertiary treatments, such as electrooxidation processes, are a promising alternative when a high concentration of MC requires longer process times. Anodic oxidation was demonstrated to be able to eliminate >80% of microcontaminants and solar-assisted anodic oxidation significantly reduced the electricity consumption. Electro-Fenton processes were the least efficient of the processes tested. Phytotoxicity results showed that irrigation with the permeates reduced germination, root development was mainly promoted and shoot development was positive only at low retention rate (concentration factor = 2). Acute and chronic Daphnia magna toxicity studies demonstrated that the permeate volumes should be diluted at least 50% before direct reuse for crop irrigation.

Solar-driven free chlorine advanced oxidation process for simultaneous removal of microcontaminants and microorganisms in natural water at pilot-scale.

Contamination of natural water (NW) by emerging contaminants has been widely pointed out as one of the main challenges to ensure high-quality drinking water. Thus, the effectiveness of a solar-driven free chlorine advanced oxidation process simultaneously investigating the elimination of six organic microcontaminants (OMCs) and three bacteria from NW at a pilot-scale was evaluated in this study. Firstly, the solar/free chlorine process was studied at lab-scale using a solar simulator to evaluate the effect of free chlorine concentration (0.5-10 mg L-1) on OMC degradation and generation of toxic oxyanions (e.g., ClO3- ions). Thus, the best free chlorine concentration observed was applied for the simultaneous removal of OMCs and pathogens under natural solar light at pilot scale. At lab-scale, the solar/free chlorine (2.5 mg L-1) process achieved 80% of total degradation in 5 min (1.4 kJ L-1 of accumulative UV energy) with an oxidant consumption of 0.3 mg L-1 and without ClO3- generation. Similar results were attained under natural solar irradiation at a pilot-scale. For all bacteria strains, the legally required detection limit (DL = 1 CFU 100 mL-1) for reclaimed water reuse was attained in a short contact time. Still, more importantly, the solar/free chlorine (2.5 mg L-1) process effectively avoided the possible bacterial regrowth in the post-treated sample after six days. Finally, the combination of free chlorine with solar irradiation provided a simple and energy-efficient process for OMC and bacteria removal in NW at a pilot-scale.

A Rational Analysis on Key Parameters Ruling Zerovalent Iron-Based Treatment Trains: Towards the Separation of Reductive from Oxidative Phases.

The development of treatment trains for pollutant degradation employing zerovalent iron has been attracting a lot of interest in the last few years. This approach consists of pre-treatment only with zerovalent iron, followed by a Fenton oxidation taking advantage of the iron ions released in the first step. In this work, the advantages/disadvantages of this strategy were studied employing commercial zerovalent iron microparticles (mZVI). The effect of the initial amount of mZVI, H2O2, pH, conductivity, anions and dissolved oxygen were analysed using p-nitrobenzoic acid (PNBA) as model pollutant. 83% reduction of PNBA 6 µM into p-aminobenzoic acid (PABA) was achieved in natural water at an initial pH 3.0 and 1.4 g/L of mZVI, under aerobic conditions, in 2 h. An evaluation of the convenience of removing mZVI after the reductive phase before the Fenton oxidation was investigated together with mZVI reusability. The Fenton step against the more reactive PABA required 50 mg/L of H2O2 to achieve more than 96% removal in 15 min at pH 7.5 (final pH from the reductive step). At least one complete reuse cycle (reduction/oxidation) was achieved with the separated mZVI. This approach might be interesting to treat wastewater containing pollutants initially resistant to hydroxyl radicals.

Solar processes and ozonation for fresh-cut wastewater reclamation and reuse: Assessment of chemical, microbiological and chlorosis risks of raw-eaten crops.

In this study, a full cycle of agricultural reuse of agro-food wastewater (synthetic fresh-cut wastewater, SFCWW) at pilot plant scale has been investigated. Treated SFCWW by ozonation and two solar processes (H2O2/solar, Fe3+-EDDHA/H2O2/solar) was used to irrigate two raw-eaten crops (lettuce and radish) grown in peat. Two foodborne pathogens (E. coli O157:H7 and Salmonella enteritidis) and five organic microcontaminants (OMCs: atrazine, azoxystrobin, buprofezin, procymidone and terbutryn) were monitored along the whole process. The three studied processes showed a high treatment capability (reaching microbial loads < 7 CFU/100 mL and 21-90 % of OMC reduction), robustness (based on 7 or 10 analysed batches for each treatment process) and high suitability for subsequent treated SFCWW safe reuse: non-phytotoxic towards Lactuca sativa and no bacterial regrowth during its storage for a week. The analysis of the harvested crop samples irrigated with treated SFCWW in all the studied processes showed an absence of microbial contamination (< limit of detection, LOD; i.e., < 1 CFU/99 g of lettuce and < 1 CFU/8 g of radish), a significant reduction of OMC uptake (in the range 40-60 % and > 90 % for solar treated and ozonated SFCWW, respectively) and bioaccumulation in both crops in comparison with the results obtained with untreated SFCWW. Moreover, the chlorophyll content in the harvested lettuces irrigated with SFCWW treated by Fe3+-EDDHA/H2O2/solar was twice than that irrigated with SFCWW treated by H2O2/solar and ozone, indicating the additional advantage of using Fe3+-EDDHA as an iron source to reduce the risk of iron chlorosis in crops. Finally, the chemical (dietary risk assessment for the combined exposure of the 5 OMCs) and quantitative microbiological risk assessment (QMRA) of the harvested crops showed the capability of the studied processes to reduce the risk associated with untreated SFCWW reuse by more than 50 % and more than 4 orders of magnitude, respectively.

UV-C Peroxymonosulfate Activation for Wastewater Regeneration: Simultaneous Inactivation of Pathogens and Degradation of Contaminants of Emerging Concern.

This study explores the capability of Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs) for the simultaneous disinfection and decontamination of urban wastewater. Sulfate and hydroxyl radicals in solution were generated activating peroxymonosulfate (PMS) under UV-C irradiation at pilot plant scale. The efficiency of the process was assessed toward the removal of three CECs (Trimethoprim (TMP), Sulfamethoxazole (SMX), and Diclofenac (DCF)) and three bacteria (Escherichia coli, Enterococcus spp., and Pseudomonas spp.) in actual urban wastewater (UWW), obtaining the optimal value of PMS at 0.5 mmol/L. Under such experimental conditions, bacterial concentration ≤ 10 CFU/100 mL was reached after 15 min of UV-C treatment (0.03 kJ/L of accumulative UV-C radiation) for natural occurring bacteria, no bacterial regrowth was observed after 24 and 48 h, and 80% removal of total CECs was achieved after 12 min (0.03 kJ/L), with a release of sulfate ions far from the limit established in wastewater discharge. Moreover, the inactivation of Ampicillin (AMP), Ciprofloxacin (CPX), and Trimethoprim (TMP) antibiotic-resistant bacteria (ARB) and reduction of target genes (ARGs) were successfully achieved. Finally, a harmful effect toward the receiving aquatic environment was not observed according to Aliivibrio fischeri toxicity tests, while a slightly toxic effect toward plant growth (phytotoxicity tests) was detected. As a conclusion, a cost analysis demonstrated that the process could be feasible and a promising alternative to successfully address wastewater reuse challenges.

Direct oxidation of peroxymonosulfate under natural solar radiation: Accelerating the simultaneous removal of organic contaminants and pathogens from water.

This study investigates the effectiveness of non-activated peroxymonosulfate (PMS) as oxidative agent for water purification in the presence and absence of natural solar radiation. The inactivation of three pathogens (Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa) and degradation of three Contaminants of Emerging Concern (CECs) (Trimethoprim-TMP, Sulfamethoxazole-SMX and Diclofenac-DCF) was simultaneously assessed in isotonic water (IW) by testing a wide range of PMS concentrations (from 0.0001 to 0.01 mM). A significant oxidative effect of PMS in darkness was obtained for both bacteria and CEC abatement, but when irradiated with solar light, results demonstrated a great enhancement on all bacterial kinetic rates, reaching >5 Log reduction in 30 min (1.5 kJL-1 of QUV) with 0.005 mM of oxidant as the best concentration. For CECs, higher degradation performance was obtained with 0.01 mM, 80% removal of DCF, SMX and TMP was achieved in 16 min (1.5 kJL-1), 27 min (9.4 kJL-1) and 150 min (16.8 kJL-1), respectively. Besides, the influence of inorganic species on the global PMS/solar system performance was assessed by testing its effectiveness in distilled water (DW), natural well water (WeW) and diluted well water (d-WeW) at 0.01 mM. Results revealed that (i) high chloride concentration (IW) has an important positive effect, (ii) the presence of a complex inorganic chemical water composition reduced the system efficiency (WeW), and (iii) no differences were obtained from the presence of low or high contents of carbonates/bicarbonates (WeW versus d-WeW), obtaining the following global PMS/solar efficiency performance order: IW > DW > WeW = d-WeW.

Sunlight advanced oxidation processes vs ozonation for wastewater disinfection and safe reclamation.

Solar processes (sunlight/H2O2, solar photo-Fenton with EDDS at neutral pH) were compared to a consolidated technology (ozonation) in the inactivation of target bacteria (E. coli, Salmonella spp. and Enterococcus spp.) under realistic conditions (real secondary treated urban wastewater (WW), pilot scale reactors, natural sunlight) to evaluate their possible industrial application. The highest bacteria inactivation rate (all the target pathogens were inactivated below the detection limit (DL) (100 CFU/100 mL) within 45 min treatment) was observed for ozonation (83 mgO3/L h). Similar inactivation behavior for all bacteria was observed for sunlight/H2O2 (50 mg/L) and solar photo-Fenton (SPF) with EDDS (1:1 molar ratio, 0.1 mM of Fe and 50 mg/L of H2O2). Although the DL was not reached, faster inactivation kinetics (0.007, 0.013 and 0.002 1/min for E. coli, Salmonella spp. and Enterococcus spp., respectively) and lower bacterial concentration after a 180 min treatment were observed for sunlight/H2O2 process compared to SPF (0.005, 0.01 1/min and no inactivation, respectively), Enterococcus spp. being the higher resistance microorganism. The negative effect of carbonates on disinfection performance was also evaluated. Quantitative microbial risk assessment for the ingestion of lettuce irrigated with untreated and treated WW was estimated. Disinfection by ozonation and sunlight/H2O2 processes were found to drastically decrease the associated microbiological risk (the mean risk of illness decreased from 0.10 (untreated) to 1.35 × 10-4 (treated) for E. coli and from 0.03 to 2.21 × 10-6 for Salmonella).

Fluorescence Spectroscopy and Chemometrics: A Simple and Easy Way for the Monitoring of Fluoroquinolone Mixture Degradation.

In this work, fluorescence excitation-emission matrices (EEMs), in combination with the chemometric tool and parallel factor analysis (PARAFAC), have been proposed as an unexplored methodology to follow the removal of the fluorescent contaminants of emerging concern, fluoroquinolones (FQs). Ofloxacin, enrofloxacin, and sarafloxacin were degraded by different advanced oxidation processes employing simulated sunlight (hν): photolysis, H2O2/hν, and photo-Fenton. All experiments were performed in ultrapure water at three different pH values: 2.8, 5.0, and 7.0. With the obvious advantage of multivariate analysis methods, EEM-PARAFAC allowed the monitoring of degradation from the overall substances (original and formed ones) through simultaneous, rapid, and cost-efficient fluorescence spectroscopy determinations. A five-component model was found to best fit the experimental data, allowing us to (i) describe the decay of the fluorescence signals of the three parent pollutants, (ii) follow the kinetics profile of FQ-like byproducts with similar EEM fingerprints than the original FQs, and (iii) observe the formation of two families of reaction intermediates with completely different EEMs. Results were finally correlated with high pressure liquid chromatography, total organic carbon, and toxicity tests on Escherichia coli, showing good agreement with all the studied techniques.

Simultaneous removal of contaminants of emerging concern and pathogens from urban wastewater by homogeneous solar driven advanced oxidation processes.

Simultaneous removal of contaminants of emerging concern and bacteria inactivation in simulated municipal wastewater effluent (SMWW) through solar advanced oxidation processes, namely sunlight/H2O2 and solar photo-Fenton with Ethylenediamine-N,N'-disuccinic acid (EDDS) at neutral pH was investigated. Process efficiency was evaluated in terms of (i) degradation of five contaminants of emerging concern (CECs, namely caffeine, carbamazepine, diclofenac, sulfamethoxazole and trimethoprim) at the initial concentration of 100 µgL-1 each and (ii) bacteria inactivation (E. coli, S. enteritidis and E. faecalis), at the initial concentration of 103 CFU mL-1 each. Solar photo-Fenton process was first investigated at lab scale in a solar simulator to evaluate the effect of iron concentration (0.1 mM and 0.05 mM) and Fe:EDDS ratio (1:2 and 1:1). Subsequently, sunlight/H2O2 and solar photo-Fenton with EDDS (molar ratio 1:1, Fe(III) 0.1 mM) at neutral pH were singularly and sequentially investigated at pilot scale in a raceway pond reactor. Sunlight/H2O2 (50 mg L-1) tests resulted in total bacteria inactivation in 60 min (0.69 kJ L-1) but low CECs removal efficiency. On the opposite, solar photo-Fenton was effective in the removal of the total CECs (87% removal after 20 min and 0.14 kJ L-1) but not in E. faecalis inactivation (the initial concentration did not change even after 180 min). However, when the two processes were operated sequentially, a complete bacteria inactivation was observed in 15 min (0.17 kJ L-1), 20 min (0.23 kJ L-1) and 60 min (0.70 kJ L-1) of treatment for E. coli, S. enteritidis and E. faecalis, respectively and 80% removal of total CECs was achieved after 10 min of Fe:EDDS addition. Sequential combination of sunlight/H2O2 and solar photo-Fenton would be an effective solution for simultaneous CECs removal and bacteria inactivation in the same photo-reactor.

Effect of salinity on preconcentration of contaminants of emerging concern by nanofiltration: Application of solar photo-Fenton as a tertiary treatment.

This study focused on the effect of salinity on the performance of a pilot-scale nanofiltration (NF) for preconcentration of microcontaminants (MCs) in combination with solar photo-Fenton or photo-Fenton-like treatment for their elimination from NF permeate and concentrate streams. Photo-Fenton was carried out in a solar simulator at pH of 3 and at natural pH using Ethylenediamine-N, N'-disuccinic acid (EDDS) as an iron complexing agent. Degradation efficacy was tested with MCs commonly found in urban wastewater treatment plant effluents (caffeine, imidacloprid, thiacloprid, carbamazepine and diclofenac). Hydrogen peroxide and persulfate were compared in solar processes. Increase in salinity and pressure had a negligible influence on MC permeability order and NF selectivity. Solar photo-Fenton was able to degrade MCs present in the concentrated stream, and rapidly eliminate any residual MCs that might finally be present in permeate streams. Persulfate used instead of hydrogen peroxide was shown to be inefficient for the selected MCs. Fe(III):EDDS at circumneutral pH was able to remove MCs as quickly as classical photo-Fenton at acid pH, or even faster. This effect supports use of Fe(III):EDDS at natural pH for treating NF concentrates or polishing NF permeates when NF membranes are operated under extreme conditions of salinity.

Aluminized surface to improve solar light absorption in open reactors: Application for micropollutants removal in effluents from municipal wastewater treatment plants.

This work proposes the evaluation of an aluminized surface on the bottom of open reactors to perform a photo-Fenton process, at circumneutral pH (using Fe III-Ethylenediamine-N,N'-disuccinic acid complex), for elimination of micropollutants (MPs) in real effluents from municipal wastewater treatment plants (EMWWTP). Firstly, the strategy was to initially investigate the real EMWWTP spiked with several MPs (acetaminophen, diclofenac, carbamazepine, caffeine, trimethoprim and sulfamethoxazole) with 20 and 100 µg L-1 in a laboratory scale (evaluated by HPLC-UV) using a solar simulator. Finally, the removal of all MCs present in the real EMWWTP was monitored (evaluated by HPLC-MS) in a pilot-scale (90 L) in a raceway pond reactor (RPR). The treatment time required for degradation above 80% for the investigated MPs was over 30 min, and the predominant effect could be mainly associated with organics present in the real EMWWTP due to the light attenuation and scavenging of radical species. Moreover, the results confirmed that chloride and sulfate would most likely equally not affect the process. The use of an aluminized surface on the bottom of RPRs has been confirmed as a suitable option to improve the photo-Fenton reaction, enabling the use of lower doses of iron. Up to 60 different MPs found in EMWWTP have been successfully degraded using 0.1 mM of Fe at circumneutral pH with a consumption of 30 mg L-1 H2O2 with less than 45 min.

Olive mill wastewater reuse to enable solar photo-Fenton-like processes for the elimination of priority substances in municipal wastewater treatment plant effluents.

Olive mill wastewater (OMW) appears as an interesting and innovative natural alternative to synthetic chelating agents of iron in solar photo-Fenton processes at circumneutral pH due to its high polyphenol content, valorizing wastewater typically found in sunny countries. The aim of this work was the reuse of OMW for the elimination of other recalcitrant microcontaminants: terbutryn, chlorfenvinphos, diclofenac, and pentachlorophenol. Highly diluted OMW (1:1500) was employed to keep the iron in solution at circumneutral pH. Eighty percent degradation of microcontaminants was achieved, although the reaction rate was slow compared with conventional photo-Fenton process, due to Fe-polyphenol complex instability at neutral pH. At pH around 4 (considerable superior to the photo-Fenton optimal pH 2.8), Fe-polyphenol complex stability was promoted: solar UV energy required was 25 times lower to reach the objective of 80% microcontaminants degradation, which was attained in a single step, without coupling with other processes. Operating photo-Fenton at slightly acidic pH was proposed for the first time for possible reuse of treated wastewater in crop irrigation, requiring minimum pH adjustment by simply mixing it with natural wastewater. Graphical abstract.