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Nanofiltration is a promising solution for the removal of emerging and persistent micropollutants, but it is limited by operating expenses due to high membrane areas and operational pressures, dictated by the membrane's low molecular weight cut-offs (MWCO), and the formation of large amounts of concentrate to be treated, e.g. by advanced oxidation. In this paper, a simple solution is proposed to enhance membrane retention of micropollutants by adding cyclodextrins (CDs) for complexation. Complexation between micropollutants and hydroxypropyl β-CD resulted in higher rejections of ibuprofen (99.3%), bisphenol A (94.5%) and phenol (76.4%) compared to filtrations without addition of CDs (82.4%, 14% and 4%, respectively) using a 1 kDa MWCO membrane. The CD complexation allowed for filtration with ultrafiltration (UF) membranes, where nanofiltration (NF) membranes would normally be the best available membrane to retain the micropollutants. By complexation with β-CD polymers, retentions of IBU of 97.0 were even achieved using a 5 kDa MWCO membrane. Operation of larger MWCO membranes will potentially lead to less retentate formation, i.e. higher concentration factors as well as higher operational flux which results in lower membrane area and lower operational expenses. Therefore, the addition of CDs fixated on larger compounds (particles or polymers) may be an efficient and simple solution to increase micropollutant rejection and increase water recovery, while potentially reducing operational treatment expenses. This is of high significance, as it can serve as a simple way to polish contaminated waters by removing micropollutants in large scale wastewater treatment.

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 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 optimise 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 100µg/L of amoxicillin and acetaminophen at pilot plant scale.

New titania-reduced graphene oxide (TiO2-rGO) nanocomposites have been studied to assess their application in the solar assisted photodegradation of a complex mixing of pesticides (pyrimethanil, isoproturon, alachlor and methomyl) at solar pilot plant, opening the opportunity to extend the use of these hybrid photocatalysts to complex wastewater effluents. TiO2-rGO nanocomposites were prepared by hydrothermal method from two commercial TiO2, Hombikat UV-100 (HBK) and Aeroxide® P25 (P25). The effect of two different water matrices (simulated and natural) on TiO2-rGO solar photoefficiency with two pesticides concentrations (5 mg·L−1 and 200 μg·L−1), and the additional use of an electron scavenging as oxidant agent, such as hydrogen peroxide in a comparison with oxygen from air, has been studied in compound parabolic collectors (CPC) photoreactors. Best photocatalytic performances were always found with oxygen over both TiO2-rGO nanocomposites, regardless of the water matrix employed. The use of H2O2 as oxidant agent has not improved the final photocatalytic efficiency in any case. The generation of secondary highly reactive species in the reaction media from reaction of SO4●- /HO radicals, and the more negatively surface charge with low SBET of P25-rGO nanocomposite, besides its lower hydrodynamic size with lower particle aggregation in the reaction conditions, have been responsible to promote the photo-oxidation of the complex pesticides mix studied. Finally, HBK TiO2-reduced graphene oxide (HBK-rGO) nanocomposite has presented excellent solar photoefficiency in the photodegradation of 200 μg·L−1 of each pesticide with the oxygen form air, especially under natural water matrix, because of its large negatively charge surface area where probably recombination of electrons and holes is prevented.

The main objective of this work is to compare various Advanced Oxidation Processes based on solar photo-Fenton at circumneutral pH (by adding EDDS as iron complexing agent), such as solar photo-electro-Fenton process and solar ozonation in combination with Fenton like processes (O3/Fe2+/H2O2, O3/Fe3+/H2O2 and Solar/Fe3+/O3/H2O2), for the elimination of four microcontaminants (MCs) (Terbutryn, chlorfenvinphos, pentachlorophenol and diclofenac) at 200 μg/L each and in different water matrices. These compounds were selected as Priority Substances listed in European Commission directives (2013/39/EC and 2008/105/EC Directives). Research was carried out at pilot plant scale in a 30 L electrochemical system (cells made by an anode of boron-doped diamond thin film on a niobium mesh (Nb-BDD) and a carbon-polytetrafluoroethylene (PTFE) GDE as the cathode), a 20 L ozone reactor and three different solar photoreactors (39 L, 45 L and 120 L) based on compound parabolic collectors (CPC) and connected to the non-solar oxidation systems. Results showed successful elimination of at least 80% of MCs for all the technologies tested. However, solar photo-Fenton at circumneutral pH showed better performance than solar photo-electro-Fenton and even electro-Fenton processes. In addition, the combination of ozone with solar radiation showed promising results since almost a complete elimination of MCs was attained with a significant lower ozone consumption than when applying ozone in the dark (with or without the assistance of Fenton´s reagent).

The challenge of providing good quality reclaimed water free from contaminants of emerging concern, even at small concentrations, i.e., microcontaminants (MCs), and pathogens are one of the main hot topics worldwide. UVC based advanced oxidation processes, using in situ production of strong oxidizing radicals, such as HO● and SO4●–, have shown high oxidation rates for MCs; however, few works have focused on the simultaneous removal of MCs and pathogens, like bacteria. Thus, the aim of this work was to assess the oxidation of six MCs: acetaminophen (ACT), caffeine, (CAF), carbamazepine (CBZ), trimethoprim (TMP), sulfamethoxazole (SMX), and diclofenac (DCF) in the presence of Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), and Salmonella enteritidis (S. enteritidis) in a simulated effluent from a municipal wastewater treatment plant by the application of UVC/H2O2 and UVC/S2O82– processes at pilot plant scale. The concentration of MCs and bacteria were monitored along the oxidation processes as well as their regrowth after 24, 48, and 144 h. UVC based processes were compared in terms of the required treatment time to remove at least 80% of the sum of MCs, regrowth assessment, and energy consumption. Despite UVC/H2O2 and UVC/S2O82– processes showed similar results, even though after using distinct molar concentrations, UVC/H2O2 process did not exhibit bacterial regrowth in dark conditions. A simple model has been also proposed in this work with the main objective of calculating the minimum concentration of oxidants as a function of the radiation absorption at 254 nm in a given photo-reactor setup.

The efficiency of solar photo-Fenton treatment is related to ambient conditions, as it depends on solar irradiance levels and operation temperature, consequently, it is highly influenced by plant location. In this context, solar photo-Fenton feasibility in three Sunbelt cities (Tabernas -Spain-, Arica -Chile- and Doha -Qatar-) for the treatment of industrial wastewater has been analysed. Process performance was simulated by means of a semi-empirical photo-Fenton model comparing the results obtained with yearly average ambient conditions and the most unfavourable monthly ambient conditions. This data was used with scaling-up purposes in order to determine the photoreactor size and reservoir tank volume needed for each case. Finally, an economical assessment was carried out. Doha presented the lowest total costs (TC), 2.23 €/m3, followed by Arica with 2.45 €/m3 and Tabernas with 2.67 €/m3 for the method based on yearly averages. For the most unfavourable ambient conditions method, the TCs were slightly higher resulting in 2.29, 2.55 and 3.11 €/m3, respectively. Cost breakdowns were analogous independently of scaling-up method and location, being amortization costs (ACs) more influenced by location than operation costs (OCs).

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.

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 NH

In this study, the use of a commercial iron fertilizer (Fe3+-EDDHA) employed to remediate iron chlorosis in agriculture has been investigated as a promoting bactericidal agent in solar wastewater disinfection processes. Two water matrices: isotonic water (IW) and synthetic fresh-cut wastewater (SFCWW) and two bacterial strains (E. coli O157:H7 and Salmonella enteritidis) have been investigated. The bacterial inactivation rates were compared with other solar processes (solar only, H2O2/solar, Fe3+/solar and Fe3+/H2O2/solar) at neutral pH and at laboratory scale (200 mL) under natural solar radiation. Reagents concentration tested was 0.5, 2.5 and 5 mg L−1 of Fe3+ or Fe3+-EDDHA and 1, 5 and 10 mg L-1 of H2O2. Microbial inactivation kinetics showed an improvement of the solar disinfection efficiency when using Fe3+-EDDHA/solar in comparison with Fe3+/H2O2/solar (conventional photo-Fenton) in both water matrices. Among all reagent concentrations tested, the best inactivation kinetic rate for both bacteria was obtained with 2.5/5 mg L−1 Fe3+-EDDHA/H2O2, reaching > 5-log reduction in 45 min of treatment or 31 Whm-2 of solar UVA-dose. In addition, an inactivation mechanism has been proposed based on changes in membrane permeability when Fe3+-EDDHA is present and on structural damages caused by hydroxyl radicals (HO•) for Fe3+-EDDHA/H2O2/solar process. Finally, this study highlights the possibility of efficient fresh-cut wastewater treat for further irrigation reuse in arid and semiarid regions using disinfected wastewater that already includes iron fertilizer, reducing water scarcity and with the additional advantage of diminished impact of iron chlorosis in crops.

This paper presents for the first time the treatment of contaminants of emerging concern (CECs) in a systematic study in different municipal wastewater treatment plants (MWWTPs) of the Mediterranean area, more than 1000 km away. Solar photo-Fenton process at neutral pH with Fe3+-EDDS has been demonstrated to be very efficient under controlled conditions and must be validated in realistic and variable conditions such as real MWWTP effluents of different composition. To this end, CEC removal was studied in effluents from 5 treatment plants in the Mediterranean area of Spain, the inorganic and organic composition varying in the range 161–641 mg L−1 (sulfate), 133–538 mg L−1 (chloride) and 10–20 mg L−1 (dissolved organic carbon). More than 45 CECs were quantified in MWW and results showed that the effect on CEC elimination of the concentration of anions and organic matter was interfered by the nature of the organic matter. However, origin and composition of MWW was not critic for attaining >80% degradation of CECs after 15 min of reaction. Moreover, conventional anions (sulfate, chloride) had a positive effect on CEC degradation rate. This paper demonstrates the consistency and predictability of the solar photo-Fenton process at circumneutral pH for treating CECs in simple and cheap photoreactors.

The main purpose of this pilot plant study was to compare degradation of five microcontaminants (MCs) (antipyrine, carbamazepine, caffeine, ciprofloxacin and sulfamethoxazole at 100 μg/L) by solar photo-Fenton mediated by EDDS and solar/Fe:EDDS/S2O82−. The effects of the Fe:EDDS ratio (1:1 and 1:2), initial iron species (Fe(II) or Fe(III) at 0.1 mM) and oxidizing agent (S2O82− or H2O2 at 0.25–1.5 mM) were evaluated. The higher the S2O82− concentration, the faster MC degradation was, with S2O82− consumption always below 0.6 mM and similar degradation rates with Fe(II) and Fe(III). Under the best conditions (Fe 0.1 mM, Fe:EDDS 1:1, S2O82− 1 mM) antipyrine, carbamazepine, caffeine, ciprofloxacin and sulfamethoxazole at 100 μg/L where 90% eliminated applying a solar energy of 2 kJ/L (13 min at 30 W/m2 solar radiation

The degradation of trimethoprim (TMP) was investigated in a compound parabolic collector (CPC) pilot scale reactor. P25 TiO2 was employed as the photocatalyst, while sodium persulfate (SPS) was activated by solar light to generate reactive radicals. Experiments were performed in three matrices, namely natural water, municipal wastewater treatment plant (MWTP) effluent and well water at SPS concentrations between 0.125 and 0.5 mM, initial solution pH between 4 and 7.5, in the presence of 1 mg/L TMP, 200 mg/L TiO2 and 10 mg/L humic acid. TMP degradation occurs by the combined action of semiconductor photocatalysis, persulfate oxidation and photolysis. The extent of TMP degradation generally increases with increasing SPS concentration and decreasing water matrix complexity, while the solution pH effect is dependent of the water matrix. SPS conversion is always slower than TMP degradation; for example, complete degradation of TMP occurs at ca 2.5 kJ/L accumulated energy with 0.125 mM SPS, whose complete conversion requires 9 kJ/L. The proposed process may be employed for the simultaneous decontamination and disinfection of water matrices. Experiments with well water in a laboratory scale reactor resulted in 5-log reduction of Enterococcus faecalis and complete removal of 1 mg/L TMP after 1 and 3.3 kJ/L accumulated energy, respectively.

The potential of polyphenols, present in olive mill wastewater (OMW), to act as iron chelators in photo-Fenton reaction without water acidification for the treatment of different microcontaminants in water has been studied. OMW containing 6.3 g/L of phenols has been dosed from 1:100 to 1:1500 in water containing 200 μg/L of terbutryn, chlorfenvinphos, pentachlorophenol and diclofenac. Experiments were performed in compound parabolic collector (CPC) solar pilot plant installed in Plataforma Solar de Almeria using Fe 0.1 mM and H2O2 50 mg L−1. The total irradiated area was 3.08 m2 and the total volume 39 L. Results indicated that iron was forming a stable complex with components of OMW along different pH values. > 90% degradation of the four microcontaminants was achieved with solar photo-Fenton at circumnetutral pH adding OMW 1:1200 for keeping iron in solution, allowing to operate a photo-Fenton process without acidifying wastewater. It leads to an alternative to using artificial-synthetic iron-complexing ligands.

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).

Solar zerovalent iron (ZVI) was studied at circumneutral pH in combination with hydrogen peroxide and persulfate for removal of imidacloprid as a model contaminant in natural water. Three commercial ZVI sources, steel wool (ZVI-SW) and two iron micro-powders (ZVI-MS and ZVI-S) were independently evaluated. First, different ZVI corrosion conditions were tested in contact with air, exposed to natural solar radiation and with addition of oxidants, such as H2O2 and S2O82−, demonstrating the importance of released iron. Then, the technical feasibilities of solar/H2O2/ZVI and solar/S2O82−/ZVI were assessed for the elimination of 1 mg/L of imidacloprid. In general, H2O2 concentrations and treatment times were high. Only ZVI-MS (1 mM) reached 80% imidacloprid degradation after 157 min and 3 mM (102 mg/L) of H2O2. Solar/S2O82−/ZVI performance was better, reaching >80% imidacloprid degradation in

The application of electrochemical processes for wastewater treatment has increase significantly in the last two decades. However, most of the works are focused on lab-scale systems testing in saline simulated solutions spiked with a reference organic compound, evidencing the scarcity of studies on actual wastewaters through a more realistic practical approach. The aim of the present work is assessing the performance of electrochemical treatments in actual matrices, considering the formation of different oxidants species, apart from hydroxyl radicals, from dissolved ions contained in target effluents as well as both, the regeneration of Fe2+ and their combination with a light irradiation source. The degradation of a mix of microcontaminants in water matrices with different complexity by solar photoelectron-Fenton at natural pH and at pilot scale has been carried out at Plataforma Solar de Almeria. Higher degradation rates were obtained when focusing on the more complex and saline matrices. In addition, complex industrial wastewaters mineralization was also studied by means of solar assisted electro-oxidation, showing the crucial role of ammonium concentration in the effluent, since it acts as a competitor for active chlorine species and so reducing the mineralization rate.

[EN] 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 mu M 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., This work is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 765860 (AQUAlity). The paper reflects only the authors view and the Agency is not responsible for any use that may be made of the information it contains.

This review explored the latest progress (since 2017) in solar photocatalysis for water decontamination and disinfection, including three sections focused on decontamination by heterogeneous photocatalysis, decontamination by solar photo-Fenton and disinfection. Semiconductor (SC) heterogeneous photocatalysis is still the most extended area of research covering classical issues as single materials (TiO2 is majoritarian) but also a combination of SC, doping and composites, suspended or supported, applied to water decontamination and disinfection. Other matters are gaining interest for decontamination and disinfection as metal-free, natural and biologically synthesized photocatalysts, photocatalysis with additional (different to oxygen) oxidants, the synergy between active carbon adsorption and photocatalysis, and composites based on graphitic carbon nitride or graphene. Disinfection by homogeneous solar photocatalysis (mainly photo-Fenton at circumneutral pH and low iron concentration) with and without iron chelates and/or additional oxidants is also an extended area of research. Microcontaminants (contaminants of emerging concern) removal by homogeneous photo-Fenton at circumneutral pH and low iron concentration was also studied, very often in combination with disinfection for permitting municipal wastewater reuse. Photo-Fenton and photo-Fenton like processes are already established as a relevant research area, including electro processes and heterogeneous photocatalysts. Interesting studies in classical photo-Fenton (acidic pH) were mainly focused on industrial wastewater and leachates.

[EN] 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(Ill):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., This paper is part of a project that received funding from the European Union's Horizon 2020 Research and Innovation Programme under Marie Sklodowska-Curie Grant Agreement No 765860. Dennis Deemter would like to thank the staff at the Plataforma Solar de Almeria. The authors wish to thank the Spanish Ministry of Science, Innovation and Universities (MCIU), AEI and FEDER for funding under the CalypSol Project (Reference: RTI2018-097997-B-C32 and RTI2018097997-B-C31).

World is facing an environmental crisis and industrial awareness regarding their wastewaters is gaining strength. By treating them, water footprint can be reduced allowing their recycle and reuse, as well as recovering substances with added value. This work reports the pre-treatment of non-biodegradable elderberry agro-industrial wastewater at pilot plant scale by different oxidative processes (solar photo-Fenton, solar electrochemistry and ozonation). An economical approach has been addressed for improving biodegradability for a subsequent lower-cost biological treatment. Solar photo-Fenton process attained biodegradability in 30 min entailing 0.22 € m−3 of operation costs. Solar photoelectro-Fenton treatment turned industrial wastewater biodegradable after 20 min costing 0.11 € m−3, while solar-assisted anodic oxidation required 60 min and 0.12 € m−3. Solar processes combined with electrooxidation showed to be more promising options than ozonation for reducing water footprint of biorecalcitrant industrial wastewaters and moderate organic content, if an engagement between treatment time and operating costs is prioritized.

Solar photo-Fenton (SPF) at circumneutral pH with ethylenediamine-N,N'-disuccinic acid (EDDS) in raceway pond reactor was compared to a well-stablished process (ozonation) in the degradation of five contaminant of emerging concern (CECs, namely Caffeine, Carbamazepine, Diclofenac, Sulfamethoxazole and Trimethoprim) at the initial concentration of 100 μg/L each in urban wastewater treatment plant secondary effluent (UWWE) at pilot scale with natural sunlight. Both were found to be effective in the removal of the target CECs. Ozonation treatment was faster being able to degrade 80% of each CEC in UWWE within the early 15 min (18.0 mgO3/L consumed). Acute (using activated sludge, Vibrio fischeri and Daphnia magna) and chronic (using activated sludge at 72 h of sample contact and V. fischeri at 24 h of sample contact) toxicity were also evaluated. Acute toxicity evaluated by activated sludge did not show any toxic effect. V. fischeri gave less sensitive results compared to D. magna tests. Lower toxicity levels for SPF were observed. Highest acute toxicity was observed for D. magna in UWWE treated by ozonation. Relevant chronic toxicity assessed by activated sludge and V. fischeri was observed in almost all analysed samples, despite 80% of the CECs were eliminated. Successful performance of AOPs for CECs removal is not a guarantee of obtaining safe alternative water sources.

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.

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.

During the last decades, many water treatment processes have been proposed to deal with the increasing water quality requirements demanded for the urban wastewater effluents (UWWE). Among them, the so-called Advanced Oxidation Processes (AOPs) include a wide range of technologies based on the generation of very reactive and non-selective radical species with a strong oxidation potential that can readily remove not only PhACs but also other organic micropollutants. Together with ozone-based processes, these technologies constitute promising alternatives to be used as final barrier to remove these contaminants before the discharge of the effluents to the environment. This chapter focuses on the processes with higher potential to be implemented at large scale for the removal of PhACs in urban wastewater treatment plants: ozone-based, Fenton, and UV/H2O2 processes. Along the chapter, the fundamentals of these processes are introduced, including some of the more relevant modifications from the basic processes, and the more recent studies about their application for the removal of PhACs from UWWE at pilot and full scale are reviewed. From a scientific and technical point of view, the results from these researches confirm the successful removal of a wide range of PhACs and other micropollutants, although the absolute efficiency depends on the water matrix and the specific substances monitored along the treatment. As final remarks, other aspects are also included, such as the need to control the potential formation of by-products during the process and the required optimization of the processes to become competitive in economic terms.

Cork boiling wastewater is a very complex mixture of naturally occurring compounds leached and partially oxidized during the boiling cycles. The effluent generated is recalcitrant and could cause a significant environmental impact. Moreover, if this untreated industrial wastewater enters a municipal wastewater treatment plant it could hamper or reduce the efficiency of most activated sludge degradation processes. Despite the efforts to treat the cork boiling wastewater for reusing purposes, is still not well-known how safe these compounds (original compounds and oxidation by-products) will be. The purpose of this work was to apply an HPLC-high resolution mass spectrometry method and subsequent non-target screening using a multivariate analysis method (PCA), to explore relationships between samples (treatments) and spectral features (masses or compounds) that could indicate changes in formation, degradation or polarity, during coagulation/flocculation (C/F) and photo-Fenton (PhF). Although, most of the signal intensities were reduced after the treatment line, 16 and 4 new peaks were detected to be formed after C/F and PhF processes respectively. The use of this non-target approach showed to be an effective strategy to explore, classify and detect transformation products during the treatment of an unknown complex mixture.

A photocatalytic Ce-Y-ZrO2/TiO2 ultrafiltration membrane was successfully prepared on a ZrO2/SiC support by a modified sol-gel process. The top active layer is 2 μm thick, uniform and defect-free. The membrane presented a molecular weight cut-off (MWCO) of 19 kDa (equivalent to a pore size of 6 nm) and a high pure water permeability, 160 Lm-2h-1bar-1. The high hydrophilicity and negative surface charge of the membrane favoured its great retention of proteins (bovine serum albumin, whey protein, and hemoglobin), indigo dye, and humic acid. The membrane was effective in photodegrading phenol and humic acid under simulated sun light irradiation. During humic acid filtration tests, the membrane presented better anti-fouling properties (smaller flux decline) and higher permeate flux under irradiation compared to the filtration in the dark. Moreover, self-cleaning properties were observed by irradiating the membrane, which enabled recovering up to 97% of the original flux. Consequently, a longer operation without chemical cleaning is possible, reducing costs and the process footprint. Further investigation would allow the development of innovative treatments for dinking and wastewaters by combining filtration and advanced oxidation processes for the abatement of contaminants of emerging concern in the presence of natural organic matter.

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 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.

Autopsy of carbon-PTFE cathodes was performed by addressing their degradation in a commercial plate-and-frame cell equipped with a Nb-BDD anode. Cell is arranged within an electrochemical pilot plant designed for treating wastewaters by electrochemical Fenton-like processes, thus an efficient electrocatalytic production of H2O2 is necessary to guarantee Fenton’s reaction. Significant decrease in H2O2 electrogeneration occurred during pilot plant operation, hindering the efficient performance of Fenton-like processes. Two cathodes were studied, first was operated at pH 3 and second at neutral pH by using EDDS as complexing agent to maintain iron in solution. Electrogenerated H2O2 decreased from 43 mg L−1 to 16 mg L−1 in the first cathode after 50 h of operation and from 49 mg L−1 to 24 mg L−1 in the second one after 26 h of operation. Both were cleaned with 30% (v/v) solution of HCl/water for 24 h and H2O2 production was recovered only in the second cathode (able to generate 39 mg L−1). Autopsy of the cathodes was tackled by scanning electron microscopy (SEM) and X-ray energy dispersive (EDX), evidencing a strong degradation of first cathode surface and iron oxide inlays in second one due to the decomposition of Fe3+:EDDS and consequent iron precipitation at neutral pH.

Application of photo-Fenton for wastewater reuse is a hot-topic research activity for defining alternative water sources. In sunny water-stressed countries, solar irradiation is under study as a sustainable pollution-free energy source for powering photo-Fenton water treatment. In solar photo-Fenton, water containing iron and H2O2 is irradiated to promote generation of hydroxyl radicals, which can degrade pharmaceuticals and other pollutants of emerging concern. As homogeneous photo-Fenton has several disadvantages, such as its narrow pH operating range compared with other well-studied AOPs, photo-Fenton-like processes working at circumneutral pH have been widely investigated. Heterogeneous photo-Fenton is considered effective because of its wide working pH range and cyclability. Nevertheless, design of efficient heterogeneous catalysts remains the major challenge. This article discusses key photo-Fenton parameters as well as its limitations and future perspectives for real implementation.

Two different types of Carbon-containing TiO 2 photocatalysts were studied in depth. A hybrid TiO 2 -C spherical material was prepared by solvothermal synthesis from furfural and titanium isopropoxide and compared to a binary TiO 2 -activated carbon composite prepared using the slurry method. A systematic study of the catalyst concentration, type of pollutant molecule, the concentration of H 2 O 2 and the type of irradiation (simulated solar irradiation and pilot-scale photoreactors) was performed. The influence of catalyst weight and H 2 O 2 concentration was verified by following the kinetics of phenol (PH), imidacloprid (IM) and dichloroacetic acid (DCA) photodegradation. It may be concluded from the results that activated carbon promotes higher efficiency in the photoactivity of TiO 2 than the hybrid TiO 2 -C photocatalyst. The basic surface chemistry and significant contribution of micropores in the binary TiO 2 -AC composite seem to be responsible for their higher TiO 2 photoactivity than the TiO 2 -C hybrid materials which are characterized by a mesopore structure and an acid surface pH. This study shows the advantage of using a solar simulator to elucidate the efficiency of carbon materials in a thorough comparison including various photocatalytic reactions with several different substrates before testing at pilot scale.