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Highlights: [•] Continuous and sequential iron dosage allowed micropollutants removal at natural pH. [•] Bicarbonates were detrimental to the process efficiency when using iron additions. [•] Iron addition mode affects reaction time and efficacy. [•] Continuous addition allows a better distribution of iron in the photo-reactor. [•] Acetamiprid, thiabendazole and imazalil degradation could be achieved in 15min. [Copyright &y& Elsevier]

Four biodegradability tests (Pseudomonas putida bioassay, Zahn–Wellens test, BOD5/COD ratio and respirometry assay) have been used to determine the biodegradability enhancement during the treatment of wastewater containing 200mgL−1 of dissolved organic carbon (DOC) of a five commercial pesticides mixture (Vydate, Metomur, Couraze, Ditumur and Scala) by an advanced oxidation process (AOP). A comparative study was carried out taking into account repeatability and precision of each biodegradability test. Solar photo-Fenton was the AOP selected for pesticide degradation up to three levels of mineralization: 20%, 40% and 60% of initial DOC. Intra- and interday precisions were evaluated conducting each biodegradability test by triplicate and they were applied three times on different dates over a period of three months. Fisher’s least significant difference method was applied to the means, P. putida and Zahn–Wellens tests giving higher repeatability and precision. The P. putida test requires a shorter time to obtain reliable results using a standardized inoculum and constitutes a worthwhile alternative to estimate biodegradability in contrast to other less accurate or more time consuming methods. [Copyright &y& Elsevier]

Abstract: In recent years, there has been a tremendous amount of research and development in the area of photocatalysis (heterogeneous and homogeneous), a process included in a special class of oxidation techniques defined as Advanced Oxidation Processes (AOPs), all characterized by the same chemical feature, production of ls. This paper reviews the use of sunlight to produce the ls by TiO2 photocatalysis and photo-Fenton process. The reacting systems necessary for performing solar photocatalysis are described. The paper also summarizes most of the research carried out related to solar photocatalytic degradation of water contaminants, and how it could significantly contribute to the treatment of persistent toxic compounds. It outlines how to enhance the process efficiency by integration with biotreatment. Various solar reactors for photocatalytic water treatment mainly based on non-concentrating collectors built during the last few years are also described in detail in this review, as well as the use of the solar photocatalytic processes to inactivate microorganisms present in water, placing special emphasis on experimental systems made to optimize this disinfection technique. [Copyright &y& Elsevier]

Abstract: A mixture of five pesticides commonly used in intensive agriculture in the southeast of Spain, Methomyl, Dimethoate, Oxamyl, Cymoxanil and Pyrimethanil, has been completely mineralized in a combined solar photocatalytic–biological pilot plant. Two advanced oxidation processes (AOPs: TiO2 and photo-Fenton) were employed for enhancing the biodegradability of wastewater and an aerobic immobilised biomass reactor (IBR) was used for the following continuous biological treatment. TiO2 photocatalysis experiments were performed in a 35-L solar pilot plant made up of three compound parabolic collectors (CPCs), whereas photo-Fenton tests were carried out in a 75-L solar pilot plant with four CPCs units. The initial pesticide concentrations in the mixture were 50mgL−1 each. The TiO2 catalyst concentration employed was 200mgL−1, and two different Fe2+ concentrations, 20mgL−1 and 55mgL−1, were used in the photo-Fenton tests. Toxicity (Vibrio fischeri) and biodegradability assays (Zahn-Wellens test) were also performed to monitor toxicity and biodegradability of samples at different stages of photo-Fenton treatment. Biodegradable compounds generated during the preliminary oxidative process were mineralized in a 60-L activated sludge biological reactor filled with 30L of propylene Pall Ring supports. Total disappearance of the parent compounds, more than 90% mineralization and complete nitrification were achieved by the combined system. [Copyright &y& Elsevier]

Two advanced oxidation processes (AOPs/, ozonation and photo-Fenton, combined with a pilot aerobic biological reactor at field scare were employed for the treatment of industrial non-biodegradable saline wastewater (TOC around 200 mg L -1) containing a biorecalcitrant compound, α-methylphenylglycine (MPG), at a concentration of 500 mgL-1. Ozonation experiments were performed in a 50-L reactor with constant inlet ozone of 21.9 g m-3. Solar photo-Fenton tests were carried out in a 75-L pilot plant made up of four compound parabolic collector (CPC) units. The catalyst concentration employed in this system was 20mgL-1 of Fe2+ and the H2O2 concentration was kept in the range of 200-500mgL-1. Complete degradation of MPG was attained after 1, 020 min of ozone treatment, while only 195 mm were required for photo-Fenton. Samples from different stages of both AOPs were taken for Zahn-Wellens biocompatibility tests. Biodegradability enhancement of the industrial satine wastewater was confirmed (> 770% biodegradability). Biodegradable compounds generated during the preliminary oxidative processes were biologically mineralised in a 170-L aerobic immobilised biomass reactor (IBR). The global efficiency of both AOP/biological combined systems was 90% removal of an initial TOC of over 500 mg L-1. [ABSTRACT FROM AUTHOR]

Abstract: A coupled solar photocatalytic-biological pilot plant system has been employed to enhance the biodegradability and complete mineralization of a biorecalcitrant industrial compound, α-methylphenylglycine, dissolved in distilled water and simulated seawater at 500mgL−1. The pollutant was completely degraded by a solar photo-Fenton treatment in a 75-L pilot plant made up of four compound parabolic collector (CPC) units. The catalyst concentration employed was 2 and 20mgL−1 of Fe2+ and the H2O2 concentration was kept in the range of 200–500mgL−1. A Zahn–Wellens (Z–W) test applied to photo-treated samples demonstrated that intermediates produced within a short time of starting the photo-Fenton process were biodegradable. Consequently, the photocatalytic and biological processes were combined. Biodegradable compounds generated during the preliminary oxidative process were biologically mineralized in a 170-L aerobic immobilised biomass reactor (IBR), filled with 90–95L propylene Pall® Ring supports colonized by activated sludge. Almost total mineralization (90% overall total organic carbon removed) was attained in the combined treatment system (for both distilled and seawater experiments). Moreover, nitrification and denitrification phenomena were also observed. [Copyright &y& Elsevier]

The technical feasibility and performance of photocatalytic degradation of four water-soluble pesticides (diuron, imidacloprid, formetanate and methomyl) have been studied at pilot scale in two well-defined systems of special interest because natural-solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. The pilot plant is made up of compound parabolic collectors (CPCs) specially designed for solar photocatalytic applications. Experimental conditions allowed disappearance of pesticide and degree of mineralisation achieved in the two photocatalytic systems to be compared. In order to assure that the photocatalytic results are consistent, hydrolysis and photolysis tests have been performed with the four pesticides. The initial concentration tested with imidacloprid, formetanate and methomyl was 50 and 30 mg/l with diuron, and the catalyst concentrations were 200 mg/l and 0.05 mM with TiO2 and iron, respectively. Total disappearance of the parent compounds and 90% mineralisation have been attained with all pesticides tested, methomyl being the most difficult to be degraded with both treatments. First-order rate constants, initial rate, time necessary for mineralising 90% of the initial TOC and hydrogen peroxide consumption were calculated in all cases, enabling comparison both of treatments and of the selected pesticide reactivity. [Copyright &y& Elsevier]

Abstract: The degradation of 15 emerging contaminants (ECs) at low concentrations in simulated and real effluent of municipal wastewater treatment plant with photo-Fenton at unchanged pH and Fe=5mgL−1 in a pilot-scale solar CPC reactor was studied. The degradation of those 15 compounds (Acetaminophen, Antipyrine, Atrazine, Caffeine, Carbamazepine, Diclofenac, Flumequine, Hydroxybiphenyl, Ibuprofen, Isoproturon, Ketorolac, Ofloxacin, Progesterone, Sulfamethoxazole and Triclosan), each with an initial concentration of 100μgL−1, was found to depend on the presence of CO3 2− and HCO3 − (hydroxyl radicals scavengers) and on the type of water (simulated water, simulated effluent wastewater and real effluent wastewater), but is relatively independent of pH, the type of acid used for release of hydroxyl radicals scavengers and the initial H2O2 concentration used. Toxicity tests with Vibrio fisheri showed that degradation of the compounds in real effluent wastewater led to toxicity increase. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to propose a municipal wastewater treatment method based on solar Advanced Oxidation Processes (AOPs) permitting reuse of the treated wastewater. Experiments were performed in a pilot compound parabolic collector (CPC) solar plant at the Plataforma Solar de Almería. Mineralisation was monitored by measuring the dissolved organic carbon (DOC), and the concentration profile of each compound during degradation was determined by HPLC–UV. Two different approaches, photo-Fenton (pH=2.8) and TiO2 were tested with 9 different emerging contaminants at 100μgL−1 each (acetaminophen, antipyrine, atrazine, caffeine, diclofenac, isoproturon, progesterone, sulfamethoxazole, and triclosan) at low iron and TiO2 concentrations. Photo-Fenton was by far more effective than TiO2 for degrading these contaminants, and was therefore selected for further study. The 9 contaminants were tested under the following conditions without pH adjustment: (i) Fe=5mgL−1, D.I. water; (ii) Fe=5, 15 and 55mgL−1, standard fresh water; (iii) Fe=5mgL−1, standard fresh water without NaHCO3. Initial amount of hydrogen peroxide was 50mgL−1, frequently analysed and added to maintain this concentration. It was demonstrated that low efficiency in some cases is mainly due to bicarbonates, and it is therefore proposed that the process be improved, either by increasing the iron concentration, or eliminating bicarbonates. [Copyright &y& Elsevier]

Olive mill wastewater (OMW), a highly polluted wastewater from the olive oil industry, was treated by solar photocatalysis and solar photo-Fenton. Among the tested systems the application of titanium dioxide alone was not successful. The addition of peroxydisulphate as an electron acceptor had only limited effect on degradation performance and led to high salt concentrations (30 g/l sulphate generated) and a pH value near zero. The photo-Fenton method successfully removed up to 85% COD and up to 100% of phenol index of OMW with different initial concentrations and from different sources. Two solar photocatalytic pilot-plant reactors were used; one of conventional CPC type and an open non-concentrating Falling Film Reactor. The latter, newly designed reactor worked properly and yielded comparable results to the CPC in terms of degradation rate referred to incident UV radiation energy per solution volume. The suspended solids in the OMW hinder light from entering the reactor. Therefore, flocculation induced by a commercial flocculation agent was successfully applied to remove suspended solids. Application of this pre-treatment led to considerable increase of degradation rates and decrease of hydrogen peroxide consumption. [Copyright &y& Elsevier]

Graphical abstract Highlights • The photodegradation of four micro-contaminants has been studied. • Hybrid magnetic materials have been employed in photo-Fenton like process. • TiO 2 homemade shown better performances than P25. • Micro-contaminants degradation has been attained under solar irradiation. Abstract This work reports on the light-induced heterogeneous photodegradation of four micro-contaminants (MCs): Carbamazepine (C), Flumequine (F), Ibuprofen (I), and Sulfamethoxazole (S), using two different heterogeneous advanced oxidation processes. The first one is the semiconductor photocatalysis, run in the presence of the suspension of a home prepared TiO 2 (TiO 2 HP); the second one is an heterogeneous photo-Fenton process run in the presence of a hybrid magnetic nanomaterial (MB3) with an iron oxides core and an organic shell made of bio-based substances (BBS) isolated from urban biowaste. The two materials work upon two different mechanisms and were already tested (and the action mechanism hypothesized) at the lab scale under model conditions: TiO 2 acts as photocatalyst through the photo-generation of hole/electron pairs able to give rise to oxidation and reduction reactions, whereas hybrid magnetic nanomaterial acts in the presence of H 2 O 2 by a photo-Fenton like mechanism. The results evidenced the better performances of TiO 2 HP (also better than the well-known reference TiO 2 P25). Preliminary photodegradation experiments carried out in a pilot plant under natural solar radiation confirmed the good results obtained with TiO 2 HP. Moreover, in the adopted experimental conditions, the Fe(II) leached from MB3 can be considered as responsible of the MCs degradation through a homogeneous photo-Fenton reaction, where MB3 act as iron reservoir. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This work aims to evaluate the applicability of EDDS (ethylenediamine-N,N′-disuccinic acid) as an iron chelating agent for photo-Fenton treatment of municipal wastewater spiked with organic contaminants at near-neutral pH. A series of laboratory scale experiments are conducted under simulated sunlight in accordance with a central composite experimental design in order to define the most favorable conditions in terms of initial iron concentration (maintaining a molar ratio 1:2 of Fe:EDDS), H 2 O 2 and pH. The system is evaluated in terms of degradation efficiency, H 2 O 2 consumption and iron availability. The simulated system has been compared in terms of degradation efficiency with a 60 L compound parabolic collector (CPC), and significant correlation has been observed. An approach for estimating near-optimal regions of operability is also demonstrated. [ABSTRACT FROM AUTHOR]

This study evaluates the use of the Fe(III)-EDDS complexing agent as an alternative to conventional acidic pH photo-Fenton for the treatment of the pesticide imidacloprid in natural water. The main objective is to estimate whether Fe(III)-EDDS is a viable alternative when treating waters containing high concentrations of contaminants. To this end, the mode of action of Fe(III)-EDDS is examined in the presence of carbonates, at different aeration conditions and at different temperatures. The role of HO 2 /O 2 − radical species and some aspects of the Fe(III)-EDDS complexation mechanism are discussed. Degradation kinetics and toxicities of generated intermediates are compared between Fe(III)-EDDS and conventional photo-Fenton treatment. An overview of the benefits and limitations of the process is presented. [ABSTRACT FROM AUTHOR]

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 kJ UV 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. [ABSTRACT FROM AUTHOR]

Abstract: Conventional municipal wastewater treatment plants are not able to entirely degrade some organic pollutants that end up in the environment. Within this group of contaminants, Emerging Contaminants are mostly unregulated compounds that may be candidates for future regulation. In this work, different advanced technologies: solar heterogeneous photocatalysis with TiO2, solar photo-Fenton and ozonation, are studied as tertiary treatments for the remediation of micropollutants present in real municipal wastewater treatment plants effluents at pilot plant scale. Contaminants elimination was followed by Liquid Chromatography/Quadrupole ion trap Mass Spectrometry analysis after a pre-concentration 100:1 by automatic solid phase extraction. 66 target micropollutants were identified and quantified. 16 of those contaminants at initial concentrations over 1000 ng L−1, made up over 88% of the initial total effluent pollutant load. The order of micropollutants elimination efficiency under the experimental conditions evaluated was solar photo-Fenton > ozonation > solar heterogeneous photocatalysis with TiO2. Toxicity analyses by Vibrio fischeri and respirometric tests showed no significant changes in the effluent toxicity after the three tertiary treatments application. Solar photo-Fenton and ozonation treatments were also compared from an economical point of view. [Copyright &y& Elsevier]

Abstract: The applicability of photo-Fenton to degrade a mixture of emerging pollutants (EPs) namely amoxycillin, acetaminophen, acetemiprid, caffeine, clofibric acid and carbamazepine has been studied at different scenarios. At high concentrations, acidic photo-Fenton was able to achieve a fast removal of the EPs. Although, complete mineralization was not reached, the toxicity of the solution was decreased according to the respiration of activated sludge and luminescence of Vibrio fischeri assays, although according to this last assay a transitory enhancement of the toxicity was found, attributable to the formation of toxic by-products such as phenols, chlorophenols and chlorinated pyrydines. Experiments carried out with 5mg/l of each EP showed that at neutral media the process was two orders of magnitude less efficient than at acidic pH, although it was still able to remove the EPs. The aqueous matrix has a remarkable effect on the process as the presence of humic acids increased the reaction rate and inorganic salts played an inhibitory role. Finally, experiments performed with 10μg/l of each EP showed that under those experimental conditions nearly complete removal of the EPs was reached with neutral photo-Fenton after 120min of irradiation; in this case, humic substances played a disfavorable role. [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: This study evaluates the solar photo-Fenton decontamination of wastewater containing a highly polluted mixture of two common herbicides, one of them partially dissolved. The mixture was composed by the commercial formulations Hierbamina® (479.5g/L 2,4-dichlorophenoxyacetic acid, 2,4-D) and Gesaprim® (90% atrazine, ATZ), in a 5:9 (v/v) ratio, as they are commonly dosed in Mexico. All solar photo-Fenton experiments were performed in a Compound Parabolic Collector (CPC) pilot-plant with a total volume of 35L (22L illuminated volume). The influence of some operating variables (e.g., iron concentration, matrix salinity and initial pollutant concentration) and their relationship to photo-Fenton process efficiency were studied. Experiments were performed at three iron concentrations (5, 10 and 20mg/L), in two types of waters (demineralized and fresh) and at two initial herbicides amounts (90 and 170mg/L of ATZ and 50 and 100mg/L of 2,4-D). Solution ecotoxicity and biodegradability during the photo-treatment was also evaluated, since it has been demonstrated that some photo-degradation by-products of ATZ and 2,4-D can be more toxic and/or persistent than the parent compounds. It was found that 10mg/L of iron was a suitable concentration, the use of fresh water did not reduce photo-Fenton efficiency and H2O2 consumption becomes more efficient with higher starting pollutant concentration. Moreover, the study of toxicity and biodegradability during photo-Fenton degradation allowed the selection of the most favourable design parameters for the detoxification of the water. [Copyright &y& Elsevier]

Abstract: This work evaluates the technical feasibility of large-scale combined solar photo-Fenton/aerobic biological treatment targeting the treatment of a real industrial wastewater polluted with commercial pesticides. Photo-Fenton experiments were carried out under sunlight in a CPC-based plant (150m2 of solar collectors and the total photo-reactor volume 1060L). The biological reactor was an immobilized biomass reactor (IBR, 2× 1230L) filled with Pall®Ring supports colonized by activated sludge from a municipal wastewater treatment plant. The first study performed was focused on the decontamination of wastewater containing a selected mixture of five commercial pesticides (Vydate®, Metomur®, Couraze®, Ditimur-40® and Scala®) at 500mg/L of initial dissolved organic carbon (DOC). Real wastewater containing pesticides was tested at two different initial DOCs (200 and 500mg/L). The solar photo-Fenton was always performed in batch mode at pH adjusted to 2.8 and with 20mg/L of Fe2+, while the biological reactor was operated both in batch and continuous mode. Mineralization was followed by measuring DOC and chemical oxygen demand (COD) and the composition of the real wastewater was determined by liquid chromatography electrospray time-of-flight mass spectrometry (LC-TOF-MS). It has been demonstrated that photo-Fenton is able to enhance biodegradability of real wastewaters containing biorecalcitrant compounds at concentrations up to 500mg/L but it has been also pointed out that the process should be optimized by a proper selection of treatment time and H2O2 dose. [Copyright &y& Elsevier]

A new approach to assess biocompatibility of an effluent, based on combination of different bioassays and chemical analyses, has been tested using a mixture of four commercial pesticides treated by a solar photo-Fenton as target effluent. A very fast elimination of the pesticides occurred (all of them were below detection limit at t 30W =36min), but mineralisation was a more time-consuming process, due to the formation of organic intermediates and to the presence of solvents, as shown by GC–MS analysis. Measurements based on activated sludge indicated that detoxification was coincident with the removal of the active ingredients, while more sensitive Vibrio fischeri bacterium showed significant toxicity until the end of the experiment, although the effluent might be compatible with biological processes. Biodegradability of the solutions was enhanced by the photochemical process, to reach BOD5/COD ratios above 0.8. Longer time bioassays, such as the Zahn–Wellens'' test, support the applicability of coupling photochemical with activated sludge-based biological processes to deal with these effluents. [Copyright &y& Elsevier]

Abstract: Characterization and treatment of a real pharmaceutical wastewater containing 775mg 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 (45mg/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 190min. In the other experiment with controlled H2O2, nalidixic acid degradation was complete at 66mM 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 (190min) and H2O2 dose (66mM) 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 35mg/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. [Copyright &y& Elsevier]

Abstract: Titanium dioxide photocatalysis (200mg/L) and photo-Fenton were applied to the treatment of several different pesticides considered priority substances (PS) by the European Commission dissolved in water at 50mg/L or at maximum water solubility (alachlor, atrazine, chlorfenvinphos, diuron, isoproturon and pentachlorophenol) alone (20mg/L of iron) and as a mixture (10mg/L of iron). All tests were performed in new twin 75-L compound parabolic collector (CPC) pilot plants driven by solar energy. Total organic carbon (TOC) mineralisation, disappearance of the parent compound and inorganic ion release are discussed as a function of treatment time. Photo-Fenton treatment was found to be shorter than TiO2 and more appropriate for these compounds and mixtures of them. [Copyright &y& Elsevier]

Abstract: The technical feasibility and performance of photocatalytic degradation of six water-soluble pesticides (cymoxanil, methomyl, oxamyl, dimethoate, pyrimethanil and telone) have been studied at pilot-plant scale in two well-defined systems which are of special interest because natural solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. TiO2 photocatalysis tests were performed in a 35L solar pilot plant with three Compound Parabolic Collectors (CPCs) under natural illumination and a 75L solar pilot plant with four CPC units was used for homogeneous photocatalysis tests. The initial pesticide concentration studied was 50mgL−1 and the catalyst concentrations employed were 200mgL−1 of TiO2 and 20mgL−1 of iron. Both toxicity (Vibrio fischeri, Biofix®) and biodegradability (Zahn–Wellens test) of the initial pesticide solutions were also measured. Total disappearance of the parent compounds and nearly complete mineralization were attained with all pesticides tested. Treatment time, hydrogen peroxide consumption and release of heteroatoms are discussed. [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]

Abstract: Pilot plant experiments applying solar titanium dioxide photocatalysis and solar photo-Fenton treatment at different pH and iron concentrations with an initial diclofenac concentration of 50mgL−1 are described. In preliminary experiments absence of hydrolysis and slow photolysis under solar irradiation of diclofenac solutions were observed. Solar photo-Fenton treatment with freshly precipitated iron at pH around 7 showed first order kinetics, the reaction taking place on the surface of the iron precipitate. Simultaneous oxidation, precipitation and re-dissolution processes of diclofenac governed photo-Fenton decomposition kinetics at pH 2.8. The use of different iron concentrations (0.03–0.75mM) showed no influence on the reaction rate in a neutral medium due to reactor geometry. Similar behaviour (no influence of iron concentration) was observed at pH 2.8, due to precipitation problems. A pH of around 4, close to the pK a of diclofenac, showed promising results, partly overcoming both iron and diclofenac precipitation. Solar titanium dioxide photocatalysis with Degussa P-25 followed first order kinetics and no precipitation or adsorption occurred. Decomposition of diclofenac took around 100min under all photo-Fenton treatment conditions employed. Decomposition by titanium dioxide photocatalysis took about 200min. In photo-Fenton treatment, hydrogen peroxide consumption to diclofenac decomposition was about 80–110mM at pH 2.8 and 40mM in the other two treatments (neutral pH and pH=4). [Copyright &y& Elsevier]

Abstract: Several different pesticides (alachlor, atrazine, chlorfenvinphos, diuron, isoproturon and pentachlorophenol) considered PS (priority substances) by the European Commission and dissolved in water at 50mg/L (or at maximum water solubility) have been degraded at pilot-plant scale using photo-Fenton and TiO2 photocatalysis driven by solar energy. Two different iron concentrations (2 and 55mg/L) and TiO2 at 200mg/L have been tested and discussed, using mainly TOC mineralisation for comparison of treatment effectiveness. Vibrio fischeri (Microtox®) toxicity assays were also employed for evaluating the photocatalytic treatments, and comparison between these results and parent compound disappearance, TOC evolution and anion (or ammonia) release were discussed. Almost complete mineralisation and total detoxification were always attained. It has been demonstrated that evolution of chloride could be a key-parameter for predicting toxicity of chlorinated compounds. [Copyright &y& Elsevier]

The technical feasibility and performance of photocatalytic degradation of aqueous methomyl (50 mg/L) have been studied at pilot scale in two well-defined systems of special interest because natural-solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. The pilot plant is made up of compound parabolic collectors specially designed for solar photocatalytic applications. Experimental conditions allowed pesticide disappearance, degree of mineralisation and toxicity achieved in the two photocatalytic systems to be compared. Total disappearance of methomyl is attained by photo-Fenton in 60 min and by TiO2 in 100 min. Hundred percent of nitrogen and sulphur are recovered as ammonium and sulphate. By contrast, complete mineralisation of total organic carbon (TOC) is not achieved even after quite a long time (more than 300 min). Three different bioassays (Vibrio fischeri, Daphnia magna and a Microalga) have been used for testing the progress of toxicity during treatment. All remained toxic down to very low-pesticide concentrations and in some bioassays were still toxic after total disappearance of the pesticide. Only if treatment is maintained throughout enough mineralisation (i.e. TOC disappearance), the toxicity is reduced to below the threshold (EC50%). [Copyright &y& Elsevier]