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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 H 2 O 2 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., (© 2023. The Author(s).)

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/Fe 3+ -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 Fe 3+ -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 Fe 3+ -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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

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 H 2 O 2 is necessary to guarantee Fenton's reaction. Significant decrease in H 2 O 2 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 H 2 O 2 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 H 2 O 2 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 Fe 3+ :EDDS and consequent iron precipitation at neutral pH., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The aim of this work was to investigate the treatment of the artificial sweetener saccharin (SAC) in a solar compound parabolic collector pilot plant by means of the photo-Fenton process at pH 2.8. Olive mill wastewater (OMW) was used as iron chelating agent to avoid acidification of water at pH 2.8. For comparative purposes, Ethylenediamine-N, N-disuccinic acid (EDDS), a well-studied iron chelator, was also employed at circumneutral pH. Degradation products formed along treatment were identified by LC-QTOF-MS analysis. Their degradation was associated with toxicity removal, evaluated by monitoring changes in the bioluminescence of Vibrio fischeri bacteria. Results showed that conventional photo-Fenton at pH 2.8 could easily degrade SAC and its intermediates yielding k, apparent reaction rate constant, in the range of 0.64-0.82 L kJ -1 , as well as, eliminate effluent's chronic toxicity. Both OMW and EDDS formed iron-complexes able to catalyse H 2 O 2 decomposition and generate HO. OMW yielded lower SAC oxidation rates (k = 0.05-0.1 L kJ -1 ) than EDDS (k = 2.21-7.88 L kJ -1 ) possibly due to its higher TOC contribution. However, the degradation rates were improved (k = 0.13 L kJ -1 ) by increasing OMW dilution in the reactant mixture. All in all, encouraging results were obtained by using OMW as iron chelating agent, thus rendering this approach promising towards the increase of process sustainability., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Photo-Fenton is a solar disinfection technology widely demonstrated to be effective to inactivate microorganisms in water by the combined effect of photoactivated iron species and the direct action of solar photons. Nevertheless, the precipitation of iron as ferric hydroxide at basic pH is the main disadvantage of this process. Thus, challenge in photo-Fenton is looking for alternatives to iron salts. Polycarboxylic acids, such as Ethylendiamine-N',N'-disuccinic acid (EDDS), can form strong complex with Fe 3+ and enhance the dissolution of iron in natural water through photochemical process. The aim of this study was to evaluate the disinfection effectiveness of solar photo-Fenton with and without EDDS in water. Several reagent concentrations were assessed, best bacterial (Escherichia coli and Enterococcus faecalis) inactivation was obtained with 0.1:0.2:0.3 mM (Fe 3+ :EDDS:H 2 O 2 ) in isotonic water. The benefit of using EDDS complexes to increase the efficiency of kept dissolved iron in water at basic pH was proven. Solar disinfection and H 2 O 2 /solar with and without EDDS, and Fe 3+ :EDDS complexes were also investigated. Bacterial inactivation results in municipal wastewater effluents (MWWE) demonstrated that the competitive role of organic matter and inorganic compounds strongly affect the efficacy of Fe 3+ :EDDS at all concentrations tested, obtaining the fastest inactivation kinetics with H 2 O 2 /solar (0.3 mM)., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This work reports the treatment of a mature landfill leachate through the application of chemical-based treatment processes in order to achieve the discharge legal limits into natural water courses. Firstly, the effect of coagulation/flocculation with different chemicals was studied, evaluating the role of different initial pH and chemicals concentration. Afterwards, the efficiency of two different advanced oxidation processes for leachate remediation was assessed. Fenton and solar photo-Fenton processes were applied alone and in combination with a coagulation/flocculation pre-treatment. This physicochemical conditioning step, with 2 g L(-1) of FeCl3 · 6H2O at pH 5, allowed removing 63% of COD, 80% of turbidity and 74% of total polyphenols. Combining the coagulation/flocculation pre-treatment with Fenton reagent, it was possible to reach 89% of COD removal in 96 h. Moreover, coagulation/flocculation combined with solar photo-Fenton revealed higher DOC (75%) reductions than single solar photo-Fenton (54%). In the combined treatment (coagulation/flocculation and solar photo-Fenton), it was reached a DOC reduction of 50% after the chemical oxidation, with 110 kJ L(-1) of accumulated UV energy and a H2O2 consumption of 116 mM. Toxicity and biodegradability assays were performed to evaluate possible variations along the oxidation processes. After the combined treatment, the leachate under study presented non-toxicity but biodegradability increased., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In view of the inefficient elimination of micro-pollutants by today's conventional biological treatments and new legislation requiring elimination of at least 80 % of their concentration, the application of an advanced tertiary treatment must be studied. A good option would be advanced oxidation processes (AOPs), which have very often been combined with physicochemical pre-treatSments to increase efficiency or reduce operating costs. This study focused on the combination of membrane nanofiltration and solar photo-Fenton for the main purpose of removing five pharmaceuticals (sulfamethoxazole, ibuprofen, ofloxacin, carbamazepine and flumequine) from real MWTP effluents under realistic conditions (μg L(-1)). This research also included tests performed with modified photo-Fenton using a low iron concentration at circumneutral pH and a low hydrogen peroxide dose, in an attempt to reduce major treatment costs. Over 80 % of dissolved organic carbon, chemical oxygen demand and turbidity were also retained during nanofiltration, making pharmaceutical removal less efficient in terms of concentrate treatment time than direct treatment, i.e. the concentrate illumination time was around 150 min while direct treatment was around 40 min. Nevertheless, it should be highlighted that, although no savings in installation costs was observed for the combined system (nanofiltration/solar photo-Fenton), the reaction rate improved and so, there was a savings in reagent costs (mainly hydrogen peroxide and sulfuric acid).

In recent years, membrane technologies (nanofiltration (NF)/reverse osmosis (RO)) have received much attention for micropollutant separation from Municipal Wastewater Treatment Plant (MWTP) effluents. Practically all micropollutants are retained in the concentrate stream, which must be treated. Advanced Oxidation Processes (AOPs) have been demonstrated to be a good option for the removal of microcontaminants from water systems. However, these processes are expensive, and therefore, are usually combined with other techniques (such as membrane systems) in an attempt at cost reduction. One of the main costs in solar photo-Fenton comes from reagent consumption, mainly hydrogen peroxide and chemicals for pH adjustment. Thus, in this study, solar photo-Fenton was used to treat a real MWTP effluent with low initial iron (less than 0.2 mM) and hydrogen peroxide (less than 2 mM) concentrations. In order to work at neutral pH, iron complexing agents (EDDS and citrate) were used in the two cases studied: direct treatment of the MWTP effluent and treatment of the concentrate stream generated by NF. The degradation of five pharmaceuticals (carbamazepine, flumequine, ibuprofen, ofloxacin and sulfamethoxazole) spiked in the effluent at low initial concentrations (μg L(-1)) was monitored as the main variable in the pilot-plant-scale photo-Fenton experiments. In both effluents, pharmaceuticals were efficiently removed (>90%), requiring low accumulated solar energy (2 kJUV L(-1), key parameter in scaling up the CPC photoreactor) and low iron and hydrogen peroxide concentrations (reagent costs, 0.1 and 1.5 mM, respectively). NF provided a clean effluent, and the concentrate was positively treated by solar photo-Fenton with no significant differences between the direct MWTP effluent and NF concentrate treatments., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The photo-Fenton process has proven its efficiency in the removal of micropollutants. However, the high costs usually associated with it prevent a spread of this technology. An important factor affecting costs is the kind of photoreactor used, usually tubular with a reflecting surface. Tubular reactors like compound parabolic collectors, CPCs, involve high capital costs. In comparison, the application of less costly reactors such as the extensive raceway ponds (RPRs) would help to spread the use of the photo-Fenton process as tertiary treatment at commercial scale. As far as the authors know, RPRs have never been used in advanced oxidation processes (AOPs) applications. This work is aimed at studying the applicability of RPRs to remove micropollutants with solar photo-Fenton. For this purpose, a pesticide mixture of commercial acetamiprid (ACTM) and thiabendazole (TBZ) (100μg/L each) was used in simulated secondary effluent. Iron concentration (1, 5.5 and 10mg/L) and liquid depth (5, 10 and 15cm) were studied as process variables. TBZ was removed at the beginning of the treatment (less than 5min), although ACTM removal times were longer (20-40min for the highest iron concentrations). High treatment capacity per surface area was obtained (48mg/hm(2) with 5.5mg Fe/L and 15cm liquid depth), proving the feasibility of using RPRs for micropollutant removal., (Copyright © 2014 Elsevier B.V. All rights reserved.)

This study compares two different solar photo-Fenton processes, conventional photo-Fenton at pH3 and modified photo-Fenton at neutral pH with minimal Fe (5 mg L⁻¹) and minimal initial H₂O₂ (50 mg L⁻¹) concentrations for the degradation of emerging contaminants in Municipal Wastewater Treatment Plants effluents in solar pilot plant. As Fe precipitates at neutral pH, complexing agents which are able to form photoactive species, do not pollute the environment or increase toxicity have to be used to keep the iron in solution. This study was done using real effluents containing over 60 different contaminants, which were monitored during treatment by liquid chromatography coupled to a hybrid quadrupole/linear ion trap mass analyzer (LC-QTRAP-MS/MS) operating in selected reaction monitoring (SRM) mode. Concentrations of the selected contaminants ranged from a few ng L⁻¹ to tens of μg L⁻¹. It was demonstrated in all cases the removal of over 95% of the contaminants. Photo-Fenton at pH3 provided the best treatment time, but has the disadvantage that the water must be previously acidified. The most promising process was photo-Fenton modified with Ethylenediamine-N,N'-disuccinic acid (EDDS), as the pH remained in the neutral range., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The photo-Fenton degradation of paracetamol (PCT) was evaluated using FeSO(4) and the iron complex potassium ferrioxalate (FeOx) as iron source under simulated solar light. The efficiency of the degradation process was evaluated considering the decay of PCT and total organic carbon concentration and the generation of carboxylic acids, ammonium and nitrate, expressed as total nitrogen. The results showed that the degradation was favored in the presence of FeSO(4) in relation to FeOx. The higher concentration of hydroxylated intermediates generated in the presence of FeSO(4) in relation to FeOx probably enhanced the reduction of Fe(III) to Fe(II) improving the degradation efficiency. The degradation products were determined using liquid chromatography electrospray time-of-flight mass spectrometry. Although at different concentrations, the same intermediates were generated using either FeSO(4) or FeOx, which were mainly products of hydroxylation reactions and acetamide. The toxicity of the sample for Vibrio fischeri and Daphnia magna decreased from 100% to less than 40% during photo-Fenton treatment in the presence of both iron species, except for D. magna in the presence of FeOx due to the toxicity of oxalate to this organism. The considerable decrease of the sample toxicity during photo-Fenton treatment using FeSO(4) indicates a safe application of the process for the removal of this pharmaceutical., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

This work reports on pulp mill wastewater (PMW) tertiary treatment by Fenton (Fe(2+)/H(2)O(2)) and solar photo-Fenton (Fe(2+)/H(2)O(2)/UV) processes in a pilot plant based on compound parabolic collectors (CPCs). Solar photo-Fenton reaction is much more efficient than the respective dark reaction under identical experimental conditions. It leads to DOC mineralisation, COD and total polyphenols (TP) removal higher than 90%. The solar photo-Fenton experiment with 5mg Fe L(-1) reaches 90% of DOC mineralisation with 31kJ L(-1) of UV energy and 50mM of H(2)O(2). The initial non-biodegradability of PMW, as shown by respirometry assays and BOD(5)/COD ratio, can be changed after a solar photo-Fenton treatment. Experiments with 20 and 50mg Fe L(-1) revealed that solar photo-Fenton can reach the same DOC degradation (90%), however, consuming less H(2)O(2) and time. Diluting the initial organic load to 50% also diminishes the dosage of H(2)O(2) and the necessary reaction time to achieve high DOC removals. Accordingly, solar photo-Fenton can be considered an alternative or complementary process to improve the performance of a biologic treatment and, subsequently, achieve legal limits on discharge into natural waters., (Copyright © 2012 Elsevier B.V. All rights reserved.)

This study evaluated the formation of chlorinated transformation products during photo-Fenton treatment of pyrimethanil (PYR-20 mg L(-1)) in two water matrices, demineralised water (DW) and water containing 5 g L(-1) of NaCl (DW(NaCl)). All experiments were carried out in compound parabolic collectors (CPC) at an initial Fe(2+) concentration of 5 mg L(-1) and H(2)O(2) concentration of 150-350 mg L(-1). Dissolved Organic Carbon (DOC), High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD), Liquid Chromatography-Time-Of-Flight Mass Spectrometry (LC-TOF-MS), toxicity and biodegradability tests were conducted to control the photocatalytic treatment. In DW, PYR was completely eliminated after 11.8 min of illumination and initial DOC was reduced 50% after 79 min of illumination with 33 mM of H(2)O(2) consumed. On the other hand, in DW(NaCl) water matrix, the same reduction in DOC took 110 min of illumination and H(2)O(2) consumption of 39 mM, and total degradation of PYR was observed at 12 min of illumination. PYR transformation products (TPs) were identified by LC-TOF-MS. It was demonstrated that photo-Fenton in a DW(NaCl) produces some chlorinated TPs in addition to the non-chlorinated TPs identified during degradation in the DW. All TPs formed were eliminated during photo-Fenton. Additionally, the presence of chlorinated TPs does not increase the toxicity of the water, and TPs formed are more biodegradable than PYR., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The goal of this paper was to develop a modified photo-Fenton treatment able to degrade micro pollutants in municipal wastewater treatment plant (MWTP) effluents at a neutral pH with minimal iron and H(2)O(2) concentrations. Complexation of Fe by ethylenediamine-N,N'-disuccinic acid (EDDS) leads to stabilization and solubilization of Fe at natural pH. Photo-Fenton experiments were performed in a pilot compound parabolic collector (CPC) solar plant. Samples were treated with solid phase extraction (SPE) and analyzed by HPLC-Qtrap-MS. The rapid degradation of contaminants within the first minutes of illumination and the low detrimental impact on degradation of bicarbonates present in the water suggested that radical species other than HO(•) are responsible for the efficiency of such photo-Fenton process. Disinfection of MWTP effluents by the same process showed promising results, although disinfection was not complete.

This work assessed the solar photo-Fenton degradation of nalidixic acid (NXA), a quinolone antibacterial agent, in several different aqueous solutions. It has been proven that the composition of the water clearly affects the efficiency of the photo-Fenton process. The presence of chlorine ions induces the concurrence of different mechanisms involving Cl() and Cl(2)(-) radicals, which slow down the process. Up to 35 transformation products (TPs) were identified and their structures characterized by accurate LC-TOF-MS mass measurements during treatment of the different model waters. Photocatalytic degradation was thus observed to proceed mainly through the attack of the hydroxyl radicals on the double bond C((2))C((3)) which induce further ring opening. All the TPs identified persisted after total degradation of NXA. NXA in real pharmaceutical effluent was treated by photo-Fenton as a first stage before biological treatment. As NXA has been demonstrated to be recalcitrant to biological treatment, photo-Fenton treatment of the effluent was continued until its total degradation. Although NXA was efficiently degraded, LC-MS analyses demonstrated that some of the TPs identified after the photo-Fenton treatment were also recalcitrant to biological treatment, persisting after the combined treatment. These results show that analytical assessment of photocatalytic water treatments is essential to assure they are functioning as intended., (© 2010 Elsevier Ltd. All rights reserved.)

The influence of iron species on amoxicillin (AMX) degradation, intermediate products generated and toxicity during the photo-Fenton process using a solar simulator were evaluated in this work. The AMX degradation was favored in the presence of the potassium ferrioxalate complex (FeOx) when compared to FeSO(4). Total oxidation of AMX in the presence of FeOx was obtained after 5 min, while 15 min were necessary using FeSO(4). The results obtained with Daphnia magna biossays showed that the toxicity decreased from 65 to 5% after 90 min of irradiation in the presence of FeSO(4). However, it increased again to a maximum of 100% after 150 min, what indicates the generation of more toxic intermediates than AMX, reaching 45% after 240 min. However, using FeOx, the inhibition of mobility varied between 100 and 70% during treatment, probably due to the presence of oxalate, which is toxic to the neonates. After 240 min, between 73 and 81% TOC removal was observed. Different pathways of AMX degradation were suggested including the opening of the four-membered β-lactamic ring and further oxidations of the methyl group to aldehyde and/or hydroxylation of the benzoic ring, generating other intermediates after bound cleavage between different atoms and further oxidation to carboxylates such acetate, oxalate and propionate, besides the generation of nitrate and ammonium., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Remediation of pharmaceutical wastewater, containing nalidixic acid (NXA; 38 mg/L), a quinolone antibacterial agent commonly used in human and veterinary medicine, and characterized as having mainly 725 mg/L dissolved organic carbon (DOC), 3400 mg/L chemical oxygen demand, and around 4 g/L NaCl, was studied. A prior biodegradability study (Zahn-Wellens test) had demonstrated that the matrix was biodegradable after a rather long biomass adaptation period. After 4 days of treatment in an immobilized biomass reactor (IBR), 96% of the original DOC was removed by the biological treatment however, more than 50% of NXA was adsorbed on the biomass. As development of chronic toxicity in the IBR is possible after long exposure to NXA, adsorption and biomass stability during continuous exposure to NXA were studied in different cycles for one month. Afterthe biotreatment, the effluent was treated by solar photo-Fenton. Total degradation of NXA and reduction in toxicity were observed. The intermediates formed during degradation by biotreatment and subsequent photo-Fenton were studied by liquid chromatography-time-of-flight mass spectrometry.

Characterization and treatment of a real pharmaceutical wastewater containing 775 mg dissolved organic carbon per liter by a solar photo-Fenton/biotreatment were studied. There were also many inorganic compounds present in the matrix. The most important chemical in this wastewater was nalidixic acid (45 mg/L), an antibiotic pertaining to the quinolone group. A Zahn-Wellens test demonstrated that the real bulk organic content of the wastewater was biodegradable, but only after long biomass adaptation; however, the nalidixic acid concentration remained constant, showing that it cannot be biodegraded. An alternative is chemical oxidation (photo-Fenton process) first to enhance biodegradability, followed by a biological treatment (Immobilized Biomass Reactor--IBR). In this case, two studies of photo-Fenton treatment of the real wastewater were performed, one with an excess of H2O2 (kinetic study) and another with controlled H2O2 dosing (biodegradability and toxicity studies). In the kinetic study, nalidixic acid completely disappeared after 190 min. In the other experiment with controlled H2O2, nalidixic acid degradation was complete at 66 mM of H2O2 consumed. Biodegradability and toxicity bioassays showed that photo-Fenton should be performed until total degradation of nalidixic acid before coupling a biological treatment. Analysis of the average oxidation state (AOS) demonstrated the formation of more oxidized intermediates. With this information, the photo-Fenton treatment time (190 min) and H2O2 dose (66 mM) necessary for adequate biodegradability of the wastewater could be determined. An IBR operated in batch mode was able to reduce the remaining DOC to less than 35 mg/L. Ammonium consumption and NO3- generation demonstrated that nitrification was also attained in the IBR. Overall DOC degradation efficiency of the combined photo-Fenton and biological treatment was over 95%, of which 33% correspond to the solar photochemical process and 62% to the biological treatment.

The purpose of this work was to determine the degradation products and pathway of chlorfenvinphos (CFVP) in water treated by photo-Fenton driven by solar irradiation, as well as to develop an analytical procedure for the degradation experiments. Degradation products and pathway were determined in a laboratory experimental setup. Routine water sample analysis was done by standard laboratory wet chemistry procedures and the use of laboratory equipment such as HPLC-UV and ionic chromatography (IC). Solid-phase extraction (SPE) was used to extract analytes from an aqueous matrix, and GC-MS was used to identify intermediate degradation products. The use of an HPLC-TOF-MS provided more results on degradation products and more insight was gained into how degradation takes place. In all experiments, strong mineralisation and degradation of CFVP was observed. CFVP and its degradation products, like 2,4-dichlorophenol, 2,4-dichlorobenzoic acid and triethylphosphate were decomposed into organic substances like acetate, formate, maleate, and inorganic ions like chloride and phosphate, within the detection limits (12.5 microg/L for CFVP in the GC-MS and 40 microg/L in HPLC-UV) of the equipment used. In fact, Cl(-) emerges in nearly stoichiometric concentrations and PO(4)(3)(-) is precipitated as FePO(4). The remarkably complete absence of chlorinated aliphatic substances and chlorinated acids leads to the conclusion that chlorine is removed very quickly, and that residual DOC does not correspond to any chlorinated compound.

A coupled solar photo-Fenton (chemical) and biological treatment has been used to remove biorecalcitrant diuron (42 mg l(-1)) and linuron (75 mg l(-1)) herbicides from water at pilot plant scale. The chemical process has been carried out in a 82 l solar pilot plant made up by four compound parabolic collector units, and it was followed by a biological treatment performed in a 40 l sequencing batch reactor. Two Fe(II) doses (2 and 5 mg l(-1)) and sequential additions of H2O2 (20 mg l(-1)) have been used to chemically degrade the initially polluted effluent. Next, biodegradability at different oxidation states has been assessed by means of BOD/COD ratio. A reagent dose of Fe=5 mg l(-1) and H2O2=100 mg l(-1) has been required to obtain a biodegradable effluent after 100 min of irradiation time. Finally, the organic content of the photo-treated solution has been completely assimilated by a biomass consortium in the sequencing batch reactor using a total suspended solids concentration of 0.2 g l(-1) and a hydraulic retention time of 24h. Comparison between the data obtained at pilot plant scale (specially the one corresponding to the chemical step) and previously published data from a similar system performing at laboratory scale, has been carried out.

In this paper, we present the photo-Fenton treatment in a solar pilot-plant scale of several EU priority hazardous substances (Alachlor, Atrazine, Chlorfenvinphos, Diuron and Isoproturon) dissolved in water. The results have been evaluated not only from the point of view of contaminant disappearance and mineralisation, but also of toxicity reduction and enhancement of biodegradability. Degradation was monitored by total organic carbon, pesticide concentration by HPLC-UV, inorganics released by ion chromatography, and biodegradability by the Zahn-Wellens (Z-W) test. The total volume of the solar photoreactor, composed of compound parabolic collectors with a total area of 4.16m2, was between 70 and 82 L. The treatment was shown to be effective, mineralising all of the pesticides tested, both alone and in mixtures. In order to find out the conditions for biocompatibility using the photo-Fenton reaction as a pre-treatment step, wastewater inoculated with unacclimated municipal sludge containing pesticides after certain degradation time was evaluated by the Z-W test. Biodegradability was enhanced (70% considered biodegradable) by the photo-Fenton treatment after 12-25min. It may be concluded that the photo-Fenton treatment consistently enhances biodegradability of wastewater containing pesticides.

Phenolic compounds are known to be present in high concentrations in various types of agro-industrial wastes. As they are highly biorecalcitrant, the possibility of treatment by advanced oxidation processes should be investigated. In this work, six model phenolic compounds (vanillin, protocatechuic acid, syringic acid, p-coumaric acid, gallic acid and L-tyrosine) were chosen for a demonstration of degradation by photo-Fenton reaction, under artificial light in laboratory experiments in Vienna and under sunlight in pilot-plant experiments at the Plataforma Solar de Almería in Spain. All compounds were completely mineralised. No non-degradable intermediates were produced, either in experiments with single substances or in a more complex matrix of a mixture of phenolic compounds. The expected selectivity of the photo-Fenton reaction for aromatic compounds was proven by comparison of the decrease in total organic carbon with the removal of total phenolic content.

Solar photo-Fenton process has been extensively reported to be highly efficient in the remediation of complex industrial wastewater containing several families of pollutants such as pharmaceuticals, dyes, pesticides, derivatives of wine, etc. Moreover, solar photo-Fenton mathematical modelling regarded as a powerful tool for scaling-up and process control purposes is hindered by the complexity and variability of its reaction mechanism which depends on the particular wastewater under study. In this work, non-biodegradable cork boiling wastewater has been selected as a case study for solar photo-Fenton dynamic modelling by using MATLAB® software. First of all physic-chemical pretreatment was applied attaining chemical oxygen demand (COD) reductions between 43 and 70 % and total suspended solid (TSS) reductions between 23 % and 59 %. After solar photo-Fenton treatment, COD decreased between 45 and 90 % after consumptions of HO varying around 1.9 and 2.4 g/L. Individual calibration of the semi-empirical model by using experimental results made it possible to perfectly predict hydrogen peroxide variations throughout the treatment. It must be highlighted that slight deviations between predictions and experimental data must be attributed to important changes in wastewater characteristics. [ABSTRACT FROM AUTHOR]

SUMMARY Artificial neural networks (ANN) were proposed as a multivariate experimental design tool for monitoring a photo-Fenton treatment of wastewaters containing a synthetic mixture of pesticides. ANN and Nelder-Mead simplex methods were used to find out the optimum operating parameters of a photo-Fenton pilot plant. ANN was developed to predict the most important operating parameters (e.g., the total organic carbon and the initial mineralization kinetic rate constants of the reactions), which determine the photo-catalytic degradation efficiency in photo-Fenton processes. Experimental measurements of temperature, pH, hydrogen peroxide (H2O 2) consumption, initial concentration of Fe2+, and the AE were used as input data for the ANN learning. A feed-forward with one hidden layer, a Levenberg-Marquardt learning algorithm, a hyperbolic tangent sigmoidal transfer function and a linear transfer function were used to develop the ANN model. The best fitting of the training database was obtained with an ANN architecture constituted by seven neurons in the hidden layer. The simulated results were validated with experimental measurements, showing an acceptable agreement ( R2 > 0.99). The ANN was subsequently coupled with a Nelder-Mead simplex method to obtain the optimum operating parameters of the photo-Fenton pilot plant. The H2O2 consumption was used as key variable for evaluating the optimization procedure. Errors less than 1% between simulated and experimental data were found. The obtained results showed that the use of ANN provides an excellent predictive performance tool with the additional capability to assess the influence of each operating parameter on the removal process of water pollutants. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Titanium dioxide photocatalysis, using 200 mgl−1 of TiO2, and photo-Fenton, using 20 mg l−1 of iron, were applied to the treatment of dimethoate dissolved in water at 50 mg l−1. A heterogeneous photocatalysis test was performed in a 35-l solar pilot plant with Compound Parabolic Collectors (CPCs) under natural illumination. A homogeneous photocatalysis test was performed in a different solar pilot plant with four CPC units and a total volume of 75 l. In this work total disappearance of dimethoate and 90% of mineralization were attained in both solar treatments. Treatment time, hydrogen peroxide consumption and ferric phosphate precipitation during photo-Fenton treatment were discussed. [ABSTRACT FROM AUTHOR]

One of the most important factors affecting the application of advanced oxidation processes (AOPs) at full scale are the high operating costs, especially those associated with the cost of the reagents. Therefore, the optimization of operating parameters, such as a reduction in reagent consumption to achieve the partial or complete decontamination of waters, is crucial in AOP application. The present study is focused on the comparison of solar and UV photo-Fenton technologies (by using H 2 O 2 or S 2 O 8 2− ), for the removal of five micro-contaminants (antipyrine, caffeine, carbamazepine, ciprofloxacin and sulfamethoxazole) from simulated freshwater at very low concentrations (100 ppb each one). In addition, economic assessment of the implementation of UV/H 2 O 2 , UV/S 2 O 8 2− , solar/Fe(II)/H 2 O 2 and solar/Fe(II)/S 2 O 8 2− was also carried out. The total costs obtained were 0.42 €/m 3 for solar/Fe(II)/H 2 O 2 with 50 mg/L of initial H 2 O 2 , 0.72 €/m 3 for solar/Fe(II)/S 2 O 8 2− with 50 mg/L of initial S 2 O 8 2− , 0.43 €/m 3 for UV/H 2 O 2 with 50 mg/L of initial H 2 O 2 , 0.49 €/m 3 for UV/S 2 O 8 2− with 50 mg/L of initial S 2 O 8 2− and 0.61 €/m 3 for UV/S 2 O 8 2− with 25 mg/L of initial S 2 O 8 2− . It was concluded that consumption of reagents and electricity costs coming from lamp operation in the UV process had a significant impact on the total operating cost of both technologies. Furthermore, it must be stressed that solar and UV processes promoted by H 2 O 2 are more cost-effective than when employing S 2 O 8 2− . [ABSTRACT FROM AUTHOR]

Abstract: The appropriate catalyst concentration for industrial wastewater treatment is several hundred milligrams per liter in solar photoreactors. Nonetheless, when the purpose of eliminating emerging contaminants in municipal wastewater treatment plant effluents is for reuse of the water, and they are present at extremely low concentrations, a tertiary treatment with a much lower photocatalyst concentration might be possible. TiO2 concentrations of only tens of mgL−1 were selected to evaluate the influence of catalyst load, initial hydrogen peroxide dose and radiation intensity on the degradation rate of five emerging contaminants (100μgL−1 of ofloxacin, sulfamethoxazole, flumequine, carbamazepine, and 2-hydroxy-biphenyl) spiked in a real municipal wastewater treatment plant effluent. Response surface methodology based on a spherical central composite design was used to optimize the parameters to find the maximal degradation rate. The experiments were carried out using an Evonik P-25 titanium dioxide suspension in a Suntest solar simulator. It has been demonstrated that the use of hydrogen peroxide is highly recommendable for working with TiO2 at low concentrations and high photon flux must be avoided. It has also been demonstrated that too low (less than 40mgL−1) TiO2 concentration is not recommendable. [Copyright &y& Elsevier]

Simulations and real decomposition experiments with hydrogen peroxide induced by dissolved iron and solar illumination were performed in a solar pilot plant with compound parabolic collectors designed for photo-Fenton wastewater treatment. The structure of a gray-box linear model aimed at reproducing system dynamics with parameters dependent on operating conditions when operating around prescribed set-points is proposed. This simple model relates the changes in hydrogen peroxide concentration due to changes in hydrogen peroxide injection, dissolved iron, and solar illumination. Based on this model, control of the hydrogen peroxide concentration at set points between 200-900 mg/L±10 mg/L under dynamic conditions (simultaneous decomposition and addition of hydrogen peroxide by a dosage pump), was achieved. Different basic approaches for controller actuation upon the frequency of the dosage pump were tested, ranging from a simple PI controller to a PI controller plus antiwindup action and feedforward control. From these basic approaches, conclusions can be drawn about the process's behavior under closed-loop control. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructured iron-doped TiO2 catalysts with anatase structure and two different iron contents (0.7 and 3.5wt.%) have been prepared by a combined sol–gel/microemulsion method and examined with respect to their behaviour for photocatalytic degradation of aqueous phenol with H2O2 under solar light. The activity results are compared with those obtained for similarly prepared undoped systems as well as Degussa P25 reference catalyst and have been complemented with structural/morphological and electronic characterization analyses achieved by XRD, TEM, Raman, S BET, UV–vis DRS and XPS techniques. In contrast to typically observed results, the highest photoactivity is obtained for the catalyst with highest iron loading while that with 0.7% Fe displays lower photoactivity than undoped samples. Such unusual behaviour has been attributed to the contribution of new photoactive iron complexes generated on the surface of the catalyst as a consequence of iron leaching and readsorption processes taking place during the course of phenol photodegradation process. [Copyright &y& Elsevier]

Abstract: Dissolved oxygen concentration variations have been investigated during the photo-Fenton process. Using Paracetamol as a model pollutant and dissolved organic carbon (DOC) removal as the priority objective, we have studied the effects of irradiance intensity (13–87W/m2), iron concentration (0.09–0.45mM), hydrogen peroxide concentration (9–45mM) and finally DOC concentration (4–25mM) on the relationship between the mineralization rate, the H2O2 reaction rate and the oxygen generation rate. A high level of oxygen generation is indicative of inefficient conditions whereas a decrease in dissolved oxygen concentration (i.e. generation rates near to zero) indicates a lack of hydrogen peroxide. As a consequence, dissolved oxygen monitoring has been presented as an easy, measurable tool for studying the evolution of the photo-Fenton process and its efficiency. [Copyright &y& Elsevier]

Abstract: Nowadays the potential of photo-Fenton process for decontamination of biologically persistent wastewater is widely recognized. In this process, hydrogen peroxide consumption could be considered as one of the factors that considerably affects costs. This highlights that an automatically hydrogen peroxide dosing system to keep the concentration optimized throughout the process would be a valuable tool for industrial wastewater remediation plants. Automatic H2O2 dosing during photo-Fenton would require a precise online measuring device. Today, several expensive and unreliable in complicated wastewater hydrogen peroxide probes are commercially available. This study focuses on considering dissolved oxygen concentration (DO) as a reaction stage indicator related to H2O2 concentration and consumption during photo-Fenton wastewater treatment. First, specific experiments designed to find out the DO–H2O2 related behavior during photo-Fenton at different possible operating conditions were carried out with manual addition of H2O2. Afterwards, a following set of experiments was performed with automatic H2O2 dosing according to DO concentration maintaining this parameter between desirable set points during the photo-Fenton reaction. The obtained results demonstrated the potential for making use of the DO profile for monitoring photo-Fenton, automatically dosing H2O2 and determining the end point of the treatment. The active participation of oxygen in the first stages of the process by Dorfman-mechanism was confirmed. [Copyright &y& Elsevier]

Abstract: A mixture of five commercial pesticides (Vydate®, Metomur®, Couraze®, Ditimur-40® and Scala®) commonly used in intensive agriculture has been selected as an example of highly toxic, non-biodegradable wastewater to be treated by solar Photo-Fenton. The effect of the total concentration of organics as dissolved organic carbon (100–500mg/L), operating temperature (25–50°C), dissolved iron concentration and their relationship to different process efficiency parameters (mineralization rate, hydrogen peroxide consumption and treatment time) were evaluated. Experiments were carried out under sunlight in a pilot plant. It consists of four compound parabolic collectors (CPCs) and a total volume of 75L. From the results of the study it can be concluded that solar plants should be designed for operating at temperatures below 45°C to avoid significant loss of iron. H2O2 should be carefully dosed during the photo-Fenton treatment to avoid its continued excess and inefficient use. [Copyright &y& Elsevier]

Abstract: Photo-Fenton experiments were performed using alachlor as a model compound (initial concentration 100mg/L) in a compound parabolic collector solar pilot-plant. Three process parameters were varied following a central composite design without star points (temperature 20–50°C, iron concentration 2–20mg/L, illuminated volume 11.9–59.5% of total). Under all experimental conditions, complete alachlor degradation, mineralisation of chloride and 85–95% mineralisation of dissolved organic carbon (DOC) was achieved. An increase in temperature, iron concentration and illuminated volume from minimum to maximum value reduced the time required for 80% degradation of initial DOC by approximate factors of 5, 6 and 2, respectively. When process parameter changes were made simultaneously, these factors multiplied each other, resulting in degradation times between 20 and 1250min. Models were designed to predict the time necessary to degrade 50 or 80% of the initial DOC applying response surface methodology (RSM). Another model based on the logistic dose response curve was also designed, which predicted the whole DOC degradation curve over time very well. The three varied process parameters (temperature, iron concentration and illuminated volume) were independent variables in all the models. Mass balances of hydrogen peroxide consumption showed that the same amount of hydrogen peroxide was always needed to degrade a certain amount of DOC regardless of variations in the process parameters within the range applied. Possible applications of the models developed for automatic process control are discussed. [Copyright &y& Elsevier]