Compound Parabolic Collector Reactor Research Articles

Effective removal of paracetamol in compound parabolic collectors and fixed bed reactors under natural sunlight.

Removal of persistent organic pollutants from water is quite challenging using biological treatment processes in waste water treatment plants. In order to improve the wastewater treatment quality for water reuse, many techniques are developed and the most commonly used is heterogeneous photocatalysis. This work studies the degradation of paracetamol (PAR), which is one of the most persistent pharmaceutical drugs in water, and widely used as an analgesic and antipyretic drug in Algeria. The paracetamol degradation has been carried out via heterogeneous photocatalysis, in a suspended solution of catalyst using a Compound Parabolic Collectors (CPC) reactor and in a fixed bed with immobilized catalyst under natural solar radiation. The degradation performance has been studied under various parameters such as substrate concentration and pH of solution. The degradation efficiency decreased when the initial paracetamol concentration increased from 2.5 mg/L to 20 mg/L. In addition, the selected reactors were found to be competent for the paracetamol degradation with an almost 98-99% removal of PAR. For the CPC reactor with suspended TiO2, the paracetamol elimination reached 98% after 300 min; however, for the fixed-bed reactor, TiO2 immobilized on cellulose-based paper was utilized, which yielded an almost 99% reduction in the PAR concentration after 90 min only of solar irradiation.

The solar photo-Fenton process at neutral pH applied to microcystin-LR degradation: Fe2+, H2O2 and reaction matrix effects.

Microcystins are a group of cyanotoxins with known hepatotoxic effects, and their presence in drinking water represents a public health concern all over the world. The main objective of this work was to evaluate the solar photo-Fenton process at near-neutral pH in the degradation of microcystin-LR (MC-LR) under conditions close to those found in bloom episodes, with a high concentration of cell debris and natural organic matter (NOM). The influence of experimental parameters such as Fe2+ and H2O2 concentrations, reaction matrix, and the presence of scavenger ions, as well as ecotoxicity before and after treatment, was also evaluated. The reaction matrix was obtained from Microcystis aeruginosa cultivated in ASM-1 medium (ACE1 and ACE2 extracts). H2O2 and Fe2+ concentrations were optimized by 22 factorial design with the central point in a bench-scale solar reactor, using ACE1 extract, and the improved condition was applied in a compound parabolic collector (CPC) reactor, for the ACE2, natural water (RVW) and natural water with M. aeruginosa crude extract (RVCE). Matrix effect assays indicated that radical scavengers present in the medium were responsible for the decrease in the mineralization rates. The solar photo-Fenton process in the CPC reactor achieved COD (75%) and MC-LR (70%) reduction after 120 min at pH = 7.8, [H2O2]/COD = 3.18 and [H2O2]/[Fe2+] = 10 for the ACE2 sample. When the same conditions were applied to the RVCE sample, the process removed 77% of DOC and up to 99% of MC-LR after 45 min of the reaction. Sinapis alba bioassays showed that there was no increase in ecotoxicity after the solar photo-Fenton treatment. These results demonstrate the potential of the solar photo-Fenton process at neutral pH as an additional step in the treatment of natural matrices contaminated with microcystins. In addition, the work reinforces the importance of bioassays in treatment process monitoring.

Reclamation of Real Urban Wastewater Using Solar Advanced Oxidation Processes: An Assessment of Microbial Pathogens and 74 Organic Microcontaminants Uptake in Lettuce and Radish.

In this study, disinfection of urban wastewater (UWW) with two solar processes (H2O2 -20 mg/L and photo-Fenton 10 mg/L-Fe2+/20 mg/L-H2O2 at natural water pH) at pilot scale using a 60 L compound parabolic collector reactor for irrigation of two raw-eaten vegetables (lettuce and radish) has been investigated. Several microbial targets (total coliforms, Escherichia coli, Salmonella spp., and Enterococcus spp.) naturally occurring in UWW and 74 organic microcontaminants (OMCs) were monitored. Disinfection results showed no significant differences between both processes, showing the following inactivation resistance order: Salmonella spp. < E. coli < total coliforms < Enterococcus spp. Reductions of target microorganisms to concentrations below the limit of detection (LOD) was achieved in all cases with cumulative solar UV energy per volume (QUV) ranged from 12 to 40 kJ/L (90 min to 5 h). Solar photo-Fenton showed a reduction of 66% of OMCs and solar/H2O2 of 56% in 5 h treatment. Irrigation of radish and lettuce with solar treated effluents, secondary effluents, and mineral water was performed for 6 and 16 weeks, respectively. The presence of bacteria was monitored in surfaces and uptake of leaves, fruit, and also in soil. The bacterial concentrations detected were below the LOD in the 81.2% (lettuce) and the 87.5% (radish) of the total number of samples evaluated. Moreover, uptake of OMCs was reduced above 70% in crops irrigated with solar treated effluents in comparison with secondary effluents of UWW.

Large-scale study for the photocatalytic degradation of paracetamol using Fe2O3/TiO2 nanocomposite catalyst and CPC reactor under natural sunlight radiations

Heterogeneous photocatalysis is a promising advanced oxidation process for the degradation of emerging contaminants. In this regard, Hematite (α-Fe2O3) doped TiO2 nanocomposite catalyst was synthesized via sol-gel method. The catalyst was prepared in large quantities (225 g) comparatively with other studies and characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray (EDX), and nitrogen gas physisorption studies. The bandgap of the synthesized catalyst was determined using UV–vis diffused reflectance spectroscopy (DRS), and the point of zero charge (PZC) was identified by measuring the zeta potential (ζ-potential) of the nanoparticles. A large-scale study was conducted using a modified Compound Parabolic Collector Reactor (CPCR) for the degradation of paracetamol under natural sunlight irradiations. The operating parameters including the initial concentration of paracetamol, initial pH of the solution, and catalyst loading were optimized using face-centered central composite design (FCCD) based on response surface method (RSM) to obtain the maximum degradation efficiency of paracetamol.•The simplified and direct sol-gel method described helps in the synthesis of a novel nanocomposite catalyst (Fe2O3/TiO2) in large quantities while maintaining good characteristics compared to other methods.•The described treatment method using the modified CPCR will allow the degradation of paracetamol in a more sustainable and green manner.•Optimizing the operating parameters that have a significant influence on the degradation of paracetamol will contribute towards higher degradation rates.

Combination of solar disinfection (SODIS) with H2O2 for enhanced disinfection of marine aquaculture effluents

Technologically advanced recirculation aquaculture systems (RAS), developed for intensive farming, allows to recycle about 90–99% of water. As a result, accumulation of pathogenic bacteria in water often occurs and possesses threat of infectious fish diseases. The goal of this study was to evaluate feasibility of solar disinfection in combination with hydrogen peroxide for seawater and real marine aquaculture effluent. Specific roles of solar disinfection (SODIS), hydrogen peroxide and highly reactive oxidizing species (experiments conducted in presence of tert-butyl alcohol), generated in combined SODIS/H2O2 process were investigated. Natural consortia of Vibrio spp., known as highly resistant pathogen, present in seawater and real marine aquaculture effluent were chosen as target microorganisms. The SODIS/H2O2 process significantly enhances inactivation of natural Vibrio consortia (Vibrio harveyi, Vibrio owensii and Vibrio alfacsensis) in seawater in comparison with individual SODIS and H2O2 treatment. The best results in terms of Vibrio spp. inactivation efficiency was obtained with SODIS/H2O2 conducted using open channel raceway reactor. The efficiency of Vibrio spp. inactivation by SODIS/H2O2 in raceway and compound parabolic collector (CPC) reactors was found to be similar, requiring the dose of 28–29 Wh m−2 for complete inactivation of Vibrio spp. present in seawater. Absence of toxic effect of residual H2O2 for Nannochloropsis gaditana, as well as absence of Vibrio spp. regrowth (48 h) indicate suitability of SODIS/H2O2 process for inactivation of pathogenic bacteria in aquaculture effluent and following nutrients removal by microalgae. Moreover, feasibility of SODIS/H2O2 performed in raceway reactor for disinfection of real aquaculture effluent, containing more than 5⋅103 CFU mL−1 of Vibrio harveyi, was demonstrated requiring the dose of 34.4 Wh m−2 for complete Vibrio spp. inactivation. The annual operation and maintenance cost of aquaculture effluent disinfection using CPC and raceway reactors were evaluated.

Degradation of emerging contaminants diclofenac, sulfamethoxazole, trimethoprim and carbamazepine by bentonite and vermiculite at a pilot solar compound parabolic collector

This study was aimed at evaluating bentonite (BEN) and vermiculite (VER) clays as photoactive materials for photodegrading a low-concentration (100 μg L−1) mixture of four emerging contaminants (ECs): trimethoprim (TMP), sulfamethoxazole (SMX), carbamazepine (CBZ) and diclofenac (DCF), using a solar advanced oxidation process. The experiments were performed in a stirred magnetic batch reactor (SMBR) and a solar pilot plant compound parabolic collector (CPC). The effect of mass, type of catalyst clay and H2O2 dose were evaluated, and the photodegradation of ECs was followed by Ultra Performance Liquid Chromatography (UPLC) and Dissolved Organic Carbon content (DOC). The results showed that the optimal dose of clays for EC degradation in both SMBR and CPC reactors was 0.2 g L−1. The photodegradation of ECs at optimal conditions by BEN and VER in the CPC decreased in the following order: DCF > TMP > SMX > CBZ and DCF > SMX > TMP > CBZ, respectively. The photodegradation rate constants for VER were 2, 32 and 1.1 times higher than those for BEN when SMX, CBZ and DCF were photodegraded with the optimal dose of clay, correspondingly. The percentage removal of DCF and SMX in experiments using BEN or VER was similar to TiO2. The TMP, SMX, CBZ and DCF degradation rate constants increased 9.05, 18.9, 2.08 and 23 times by adding [H2O2] = 200 mg L−1 and VER. The percentage removal of DOC was 16, 40 and 48% when VER and 50, 100 or 200 mg L−1 of hydrogen peroxide were added into the system, respectively. Similar results were obtained by adding BEN.

Solar photoreactor design by the photon path length and optimization of the radiant field in a TiO2-based CPC reactor

The photon path length inside the radiant field of a photocatalytic solar reactor (with a compound parabolic collector (CPC)) crossing a slurry fluid with suspended particles of TiO2 was studied. The modeling included three sub-models: a ray-tracing algorithm to determine the boundary conditions in the absorber wall, a boundary layer to calculate the path length of the photon before its extinction and finally, the six-flux scattering-absorption model (SFM) to estimate the absorbed energy profiles. A simple expression for the average of the local volumetric rate of photon absorption (LVRPA) in terms of a reference state was proposed.The recent concept of a radiant boundary layer was extended to CPC reactors, and a new calculation of the photon path length is proposed. We found that a catalyst load higher than the optimum value leads to a shorter photon path length causing a dark zone within the absorber where the catalyst activation does not occur. Optimal conditions for six different commercial TiO2 catalysts were determined. The best catalysts are the Fluka and Fischer catalysts, with 20% of radiant energy absorption over the total irradiated energy. The efficiency is independent of the diameter if the optimal catalyst load is guaranteed. The load-diameter optimal pairs share an absorber optical thickness (τa,opt=13.18 for the Degussa catalyst), which can be used to scale-up the reactor. The path length at maximum photon absorption was 3/4 of the absorber diameter. Reactor diameters of 1–5 cm had optimum catalyst loads of 230–46mg/l. The turbulent regime favors 〈LVRPA〉. The angle between the normal axis to the reactor surface and the sun position may vary up to 10° with minor losses of up to 0.5%.

Modeling the Photocatalytic Mineralization in Water of Commercial Formulation of Estrogens 17-β Estradiol (E2) and Nomegestrol Acetate in Contraceptive Pills in a Solar Powered Compound Parabolic Collector

Endocrine disruptors in water are contaminants of emerging concern due to the potential risks they pose to the environment and to the aquatic ecosystems. In this study, a solar photocatalytic treatment process in a pilot-scale compound parabolic collector (CPC) was used to remove commercial estradiol formulations (17-β estradiol and nomegestrol acetate) from water. Photolysis alone degraded up to 50% of estradiol and removed 11% of the total organic carbon (TOC). In contrast, solar photocatalysis degraded up to 57% of estrogens and the TOC removal was 31%, with 0.6 g/L of catalyst load (TiO2 Aeroxide P-25) and 213.6 ppm of TOC as initial concentration of the commercial estradiols formulation. The adsorption of estrogens over the catalyst was insignificant and was modeled by the Langmuir isotherm. The TOC removal via photocatalysis in the photoreactor was modeled considering the reactor fluid-dynamics, the radiation field, the estrogens mass balance, and a modified Langmuir–Hinshelwood rate law, that was expressed in terms of the rate of photon adsorption. The optimum removal of the estrogens and TOC was achieved at a catalyst concentration of 0.4 g/L in 29 mm diameter tubular CPC reactors which approached the optimum catalyst concentration and optical thickness determined from the modeling of the absorption of solar radiation in the CPC, by the six-flux absorption-scattering model (SFM).

Comparison of the solar photocatalytic activity of ZnO-Fe2O3 and ZnO-Fe(0) on 2,4-D degradation in a CPC reactor.

In this work a comparative study of the catalytic activity of ZnO-Fe2O3 and ZnO-Fe(0) 0.5 wt% materials was carried out in the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) as a commercial formulation Hierbamina®, using a compound parabolic collector (CPC) reactor. The catalysts were synthesized by the sol-gel method and characterized by X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. The textural properties of solids were determined from N2 adsorption isotherms using the Brunauer-Emmett-Teller (BET) method. The incorporation of Fe(0) onto ZnO was demonstrated by X-ray photoelectron spectroscopy analysis. The photocatalytic tests were performed at pH 7, using 10 mg L(-1) of herbicide and 0.5 g L(-1) of catalyst loading. The decay in herbicide concentration was followed by reversed-phase chromatography. A complete degradation of 2,4-D was achieved using ZnO-Fe(0) while 47% of herbicide removal was attained with ZnO-Fe2O3 mixed oxide for an accumulated energy QUV ≈ 2 kJ L(-1). The removal percentage of total organic carbon (TOC) during the solar photocatalytic process was superior using ZnO-Fe(0), achieving 45% compared to the 15% obtained with the mixed oxide catalyst.

Investigation of optimum conditions and costs estimation for degradation of phenol by solar photo-Fenton process

In this study, solar photo-Fenton reaction using compound parabolic collectors reactor was assessed for removal of phenol from aqueous solution. The effect of irradiation time, initial concentration, initial pH, and dosage of Fenton reagent were investigated. H2O2 and aromatic intermediates (catechol, benzoquinone, and hydroquinone) were quantified during the reaction to study the pathways of the oxidation process. Complete degradation of phenol was achieved after 45 min of irradiation when the initial concentration was 100 mg/L. However, increasing the initial concentration up to 500 mg/L inhibited the degradation efficiency. The dosage of H2O2 and Fe+2 significantly affected the degradation efficiency of phenol. The observed optimum pH for the reaction was 3.1. Phenol degradation at different concentration was fitted to the pseudo-first order kinetic according to Langmuir–Hinshelwood model. Costs estimation for a large scale reactor based was performed. The total costs of the best economic condition with maximum degradation of phenol are 2.54 €/m3.

Urban wastewater disinfection for agricultural reuse: effect of solar driven AOPs in the inactivation of a multidrug resistant E. coli strain

The occurrence of antibiotics in urban wastewater treatment plants (UWTPs) may result in the development of antibiotic resistance and subsequently in the release of multidrug resistant bacteria (MDR) and genes into the effluent. Conventional disinfection processes are only partially effective in controlling ARB spread, so advanced oxidation processes (AOPs) have been investigated as alternative option in this work. In particular, the aim of this work was to comparatively assess the efficiency of solar disinfection and solar driven AOPs (namely H2O2/sunlight, TiO2/sunlight, H2O2/TiO2/sunlight, natural photo-Fenton) for the inactivation of a multidrug (namely ampicillin, ciprofloxacin and tetracycline) resistant E. coli strain isolated from the effluent of the biological process of an UWTP. Different concentrations of H2O2 (0.588–1.470–2.205mM), TiO2 (50–100mgL−1), H2O2/TiO2 (0.147mM/50mgL−1, 0.588mM/100mgL−1) and Fe2+/H2O2 (0.090/0.294, 0.179/0.588, 0.358/1.176mM) were evaluated at pilot-scale (in compound parabolic collector reactor) in real biologically treated wastewater. All investigated processes resulted in a complete inactivation (5-log decrease) of bacteria until detection limit, but the best disinfection efficiency in terms of treatment time (20min to reach the detection limit) and required energy (0.98kJL−1) was observed for photo-Fenton at pH 4 (Fe2+/H2O2:0.090/0.294mM). Antimicrobial susceptibility was tested by Kirby-Bauer disk diffusion method. Ampicillin and ciprofloxacin (to which the selected strain is resistant), cefuroxime and nitrofurantoin were chosen as tested antibiotics. None of the investigated processes affected antibiotic resistance of survived colonies.

Assessing the validity of solar membrane distillation for disinfection of contaminated water

Together with desalination, reuse of wastewater is considered as a solution to mitigate the water deficit in many areas. Membrane distillation (MD) is a technology increasingly proposed for desalination and water treatment. The process is supposed to produce pure distillate, and this is what this paper evaluates. Biologically contaminated water was used in a commercial prototype of spiral-wound liquid-gap MD coupled with solar thermal energy to assess the suitability of the process for removing pathogens. Tests were done during several hours for different operating conditions. The produced distillate, the rejected concentrated solution and the feed water were monitored through time and samples were taken for microbiological analysis. Results proved the efficiency of solar MD to produce a contaminant-free distillate when Escherichia coli, Fusarium solani and Clostridium sp spores were present in the feed water. Furthermore, in the first two cases the population of biological contaminants in the concentrated decreased below the detection limit during the experiments. However, in the case of Clostridium sp spores, these were not totally inactivated in the concentrated solution. Therefore, it was necessary to apply a post treatment before reclaiming the concentrated solution. The technology used was a photo-Fenton process carried out in a compound parabolic collector reactor. The combination of MD and photo-Fenton achieved complete abatement of Clostridium sp. spores, which was not accomplished in previous experiments when photocatalysis alone was applied to wastewater.

Assessment of solar photo-Fenton, photocatalysis, and H2O2 for removal of phytopathogen fungi spores in synthetic and real effluents of urban wastewater

Abstract Scarcity of fresh water is a major environmental problem, and properly treated wastewater could be an alternative renewable water resource, especially for agriculture as the final point-of-use. But before wastewater can be reused, it must be treated to meet chemical and biological quality standards, which depend on the final use and legislation. Advanced Oxidation Processes (AOPs) have been demonstrated to be very efficient in decreasing the pathogen load in contaminated water. This study presents the experimental evaluation of several solar-driven AOPs, i.e., photo-Fenton (Fe2+, Fe3+) at low reagent concentration, heterogeneous photocatalysis (TiO2), and solar photoassisted H2O2 treatment for removal of the spores of Fusarium sp., a worldwide phytopathogen. The experimental work was done in a pilot solar photoreactor with Compound Parabolic Collector (CPC). Disinfection of Fusarium solani spores by all treatments was excellent in distilled water, in simulated municipal wastewater effluent (SMWWE), and in real municipal wastewater effluents (RMWWE). Degradation of dissolved organic carbon (DOC) was also evaluated. The inactivation rates varied depending on the water matrix, and disinfection was fastest in distilled water followed by SMWWE, and RMWWE. The best F. solani inactivation rate was with photo-Fenton treatment (10/20 mg/L of Fe2+/H2O2) at pH 3, followed by H2O2/Solar (10 mg/L) and finally TiO2/Solar was the slowest. These results underline the importance of solar AOPs and the CPC reactor technology as a good option for waterborne pathogen removal.

Comparing the photocatalytic oxidation of Metoprolol in a solarbox and a solar pilot plant reactor

Abstract The aim of this work is to study and compare the removal of Metoprolol (MET) “1-(isopropylamino)-3-[p(β-methoxyethyl)phenoxy]-2-propanol” by photolysis, photocatalysis/TiO 2 , UV–Vis/H 2 O 2 and UV–Vis/H 2 O 2 /TiO 2 processes using two different experimental devices: solarbox (SB) with a Xe lamp and a solar pilot plant reactor with compound parabolic collectors (CPCs). Photolysis shows low MET removal (14% and 8%) with SB and CPCs respectively, and TOC almost negligible. Different TiO 2 concentrations (0.05, 0.1 and 0.4 g/L) were used in both devices and the best results were obtained for 0.4 g/L, after 360 min of irradiation ( Q = 19 kJ/L) with complete MET elimination and 55% of TOC removal in SB. Tests done with real matrix water show a decrease in MET removal to 21% due the competition of the organic matter present for light and catalyst. The UV–Vis/H 2 O 2 /TiO 2 process represents an improvement with respect to the photocatalytic process (without H 2 O 2 ) and times required to achieve the same MET o TOC removal are shortened in both devices, for instance, 120 min for total MET removal in SB. The best mg H 2 O 2 /mg MET ratio was 3. The MET photocatalysis (in solarbox) increases biodegradability and the treated solutions can be coupled to biological process after 360 min of irradiation and the solution treated in CPC reactor, after 270 min, remains not biodegradable. A pseudo-first order kinetics in photocatalytic processes were calculated in SB and CPC reactors. The toxicity, measured by Vibrio Fischeri method, decreases when MET is degraded by photocatalysis/TiO 2 and UV–Vis/H 2 O 2 /TiO 2 processes in both devices. The major reaction intermediates in UV–Vis/H 2 O 2 /TiO 2 process were identified by ionization/mass spectrometry and a MET photo-degradation pathway was proposed. Finally, in photocatalysis (0.4 g/L TiO 2 ) the energy needed to degrade 1 mg of MET, at 240 min was evaluated, being 0.275 and 0.065 kJ/mg MET for SB and CPCs respectively.

Solar CPC pilot plant photocatalytic degradation of bisphenol A in waters and wastewaters using suspended and supported-TiO2. Influence of photogenerated species

Photocatalytic degradation of bisphenol A (BPA) in waters and wastewaters in the presence of titanium dioxide (TiO2) was performed under different conditions. Suspensions of the TiO2 were used to compare the degradation efficiency of BPA (20 mg L(-1)) in batch and compound parabolic collector (CPC) reactors. A TiO2 catalyst supported on glass spheres was prepared (sol-gel method) and used in a CPC solar pilot plant for the photodegradation of BPA (100 μg L(-1)). The influence of OH·, O2 (·-), and h (+) on the BPA degradation were evaluated. The radicals OH· and O2 (·-) were proved to be the main species involved on BPA photodegradation. Total organic carbon (TOC) and carboxylic acids were determined to evaluate the BPA mineralization during the photodegradation process. Some toxicological effects of BPA and its photoproducts on Eisenia andrei earthworms were evaluated. The results show that the optimal concentration of suspended TiO2 to degrade BPA in batch or CPC reactors was 0.1 g L(-1). According to biological tests, the BPA LC50 in 24 h for E. andrei was of 1.7 × 10(-2) mg cm(-2). The photocatalytic degradation of BPA mediated by TiO2 supported on glass spheres suffered strong influence of the water matrix. On real municipal wastewater treatment plant (MWWTP) secondary effluent, 30 % of BPA remains in solution; nevertheless, the method has the enormous advantage since it eliminates the need of catalyst removal step, reducing the cost of treatment.

Solar Photocatalytic Oxidation of Hydroxy Phenols in a CPC Reactor with Thick TiO2 Films

Solar Photocatalysis is an advanced oxidation process that is involved on water detoxification as a very promising technology. This process has been used for polishing industrial and municipal wastewaters, mainly with titanium dioxide (TiO2) as a catalyst. Most of the reactors use TiO2 as a powder and need a pump in order to have the water moving through the system. A novel photocatalytic reactor, based on Compound Parabolic Collectors (CPC), was developed. The reactor has TiO2 fixed as a thick film in the CPC tubes and water flows inside by density differences exclusively. This reactor is designed to avoid catalyst separation and water pumping, steps that are energy – demanding and expensive. The films were prepared by conventional sol – gel method on 13mm diameter Pyrex tubes. The films were firmly bounded to tubes and used for several test with good efficiencies. Films had a mix of anatase and rutile crystalline phases and its particles are nanoscopic. A CPC reactor with 20 tubes connected to the tank by its upper side only was developed and used. Resorcinol was effectively removed from water, either with or without persulfate as electron acceptor, at laboratory bench (one CPC tube experiments) and at pilot scale (20 tubes in the reactor). Main reaction sub-products (tri – hydroxy benzenes) were also oxidized in reasonable solar irradiation times.

Relevant impact of irradiance (vs. dose) and evolution of pH and mineral nitrogen compounds during natural water disinfection by photo-Fenton in a solar CPC reactor

The inactivation of total coliforms/E. coli (104CFU/mL) and Salmonella spp. (105CFU/mL) in well water naturally containing dissolved (Fe2+/3+) and solid iron forms (e.g. iron oxides) was carried out by photo Fenton treatment (Fe2+,3+/H2O2/hv). In a preliminary run under simulated solar radiation, beyond 4mg/L of added H2O2, the enteric bacteria were totally inactivated after 90min. Thereafter, 25L of well water were treated in the compound parabolic collector (CPC) under direct solar radiation. Three irradiation periods (i) 8 am to 2 pm (8–14h), (ii) 10 am to 4 pm (10–16h) and (iii) 12 pm to 6 pm (12–18h) were evaluated for assessing the impact of different solar irradiances (Wm−2) on the enteric bacterial inactivation rates. Both studied strains were totally inactivated under sole exposure to solar radiation in the CPC when the experiments were conducted from 8 to 14h or 10 to 16h. However, Salmonella spp. strains regrowth was noticed after the 24h dark storage in all the samples previously treated with bare solar radiation. As the treated water contained Fe, the photo-Fenton disinfection at field scale in the CPC was carried out with the addition of H2O2 (10mg/L). Significant enhancement of the enteric bacteria inactivation rate was therefore recorded comparatively to the one obtained under bare solar treatment. No regrowth was observed in water treated by photo-Fenton disinfection one week after the treatment. The comparative evaluation of photo-Fenton disinfection rate as a function of different irradiation periods was based on the monitoring of the effective disinfection time (EDT), or required time to acquire the total inactivation of targeted bacteria in defined conditions. Therefore, significant impact of the irradiance on the process was noticed. High average irradiance (AI) of 35Wm−2 led to the total inactivation of Salmonella spp. in an EDT of 45min and a dose of 26Whm−2; while low irradiance of 20Wm−2 required an EDT of 180min for a dose 60Whm−2. Thus, the experiments revealed that lower irradiance level leads to higher doses to achieve the bacterial disinfection. pH, as well as nitrite and nitrate concentration, increased during the photo-disinfection processes, while depletion was recorded for aqueous ammonia concentration.

Elimination of water pathogens with solar radiation using an automated sequential batch CPC reactor

Solar disinfection (SODIS) of water is a well-known, effective treatment process which is practiced at household level in many developing countries. However, this process is limited by the small volume treated and there is no indication of treatment efficacy for the user. Low cost glass tube reactors, together with compound parabolic collector (CPC) technology, have been shown to significantly increase the efficiency of solar disinfection. However, these reactors still require user input to control each batch SODIS process and there is no feedback that the process is complete. Automatic operation of the batch SODIS process, controlled by UVA-radiation sensors, can provide information on the status of the process, can ensure the required UVA dose to achieve complete disinfection is received and reduces user work-load through automatic sequential batch processing. In this work, an enhanced CPC photo-reactor with a concentration factor of 1.89 was developed. The apparatus was automated to achieve exposure to a pre-determined UVA dose. Treated water was automatically dispensed into a reservoir tank. The reactor was tested using Escherichia coli as a model pathogen in natural well water. A 6-log inactivation of E. coli was achieved following exposure to the minimum uninterrupted lethal UVA dose. The enhanced reactor decreased the exposure time required to achieve the lethal UVA dose, in comparison to a CPC system with a concentration factor of 1.0. Doubling the lethal UVA dose prevented the need for a period of post-exposure dark inactivation and reduced the overall treatment time. Using this reactor, SODIS can be automatically carried out at an affordable cost, with reduced exposure time and minimal user input.

Photodegradation of Reactive Blue 4 solutions under ferrioxalate-assisted UV/solar photo-Fenton system with continuous addition of H 2O 2 and air injection

An experimental study based on the homogeneous ferrioxalate-assisted solar photo-Fenton process shows the effect of the continuous addition of hydrogen peroxide and air injection on the degradation of non-biodegradable dye Reactive Blue 4 (RB4) solutions. The reaction was carried out in a CPC (compound parabolic collector) solar pilot plant reactor. It was shown that the degree of dye solution mineralization was enhanced because the scavenger effect of H 2O 2 was minimized. Air bubbling had a negative effect because oxygen reacted with oxalyl radical anions, diminishing the amount of generated Fe(II), and consequently the concentration of hydroxyl radicals produced under irradiation of oxalate in the presence of peroxide was lower. In addition, this system permits the use of lower concentrations of ferrous ion, reducing the costs of the later iron removal process. Under the optimal conditions selected in this system, TOC removal was increased from 61% to 82% with a shorter reaction time as compared with a peroxide dose at the beginning of the reaction. The efficiency of the mineralization of RB4 solutions was enhanced when the solar CPC reactor worked together with an artificial UV-A/C pilot plant, increasing TOC removal up to 95%. Artificial UV lamps can be used either to improve the process or as an alternative to solar CPC on cloudy days.

Solar Photochemical Treatment of Winery Wastewater in a CPC Reactor

Degradation of simulated winery wastewater was studied in a pilot-scale compound parabolic collector (CPC) solar reactor. Total organic carbon (TOC) reduction by heterogeneous photocatalysis (TiO(2)) and homogeneous photocatalysis with photo-Fenton was observed. The influence of TiO(2) concentration (200 or 500 mg/L) and also of combining TiO(2) with H(2)O(2) or Na(2)S(2)O(8) on heterogeneous photocatalysis was evaluated. Heterogeneous photocatalysis with TiO(2), TiO(2)/H(2)O(2) and TiO(2)/S(2)O(8)(2-) is revealed to be inefficient in removing TOC, originating TOC degradation of 10%, 11% and 25%, respectively, at best. However, photo-Fenton experiments led to 46% TOC degradation in simulated wastewater prepared with diluted wine (WV) and 93% in wastewater prepared with diluted grape juice (WG), and if ethanol is previously eliminated from mixed wine and grape juice wastewater (WW) by air stripping, it removes 96% of TOC. Furthermore, toxicity decreases during the photo-Fenton reaction very significantly from 48% to 28%. At the same time, total polyphenols decrease 92%, improving wastewater biodegradability.