•The benefit of adding EDDS on water disinfection by solar photo-Fenton was addressed.•Best Fe:EDDS reagent concentration in isotonic water was found to be 0.1:0.2 mM.•The presence of DOC reduced ...strongly the disinfection efficiency of Fe:EDDS:H2O2.•Higher bacterial inactivation rates were obtained for solar/H2O2 (0.3 mM) in MWWE.
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 Fe3+ 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 (Fe3+:EDDS:H2O2) 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 H2O2/solar with and without EDDS, and Fe3+: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 Fe3+:EDDS at all concentrations tested, obtaining the fastest inactivation kinetics with H2O2/solar (0.3 mM).
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•The operation of RPRs at circumneutral pH by using the Fe3+:EDDS complex is feasible.•Five pharmaceuticals (100μg/L each) were removed at 1kJ/L of accumulated UV energy.•Higher ...micropollutant removal efficiency in mg/kJ for RPRs than CPCs.•15cm was chosen as better liquid depth for RPR operation at neutral pH with Fe3+:EDDS.•RPRs is a promising technology for micropollutant removal by solar photo-Fenton.
This paper deals with raceway pond reactors (RPRs) as an alternative photoreactor for solar photo-Fenton applications. Raceway pond reactors are common low-cost reactors which can treat large volumes of water. The experiments were carried out with Fe3+:EDDS complex in the secondary effluent of a municipal wastewater treatment plant spiked with a mixture of 100 μg/L each of five pharmaceuticals (carbamazepine, flumequine, ibuprofen, ofloxacin and sulfamethoxazole) at circumneutral pH. In a preliminary stage, two operating strategies, sequential addition of iron sulfate and Fe3+:EDDS complex at a 1:2 molar ratio were compared, and Fe3+:EDDS complex was found to be the best option. The effect of liquid depth (10, 15 and 20 cm) was also explored. 90% pharmaceutical removal was achieved with accumulated solar UV energy of around 1kJ/L. Finally, RPRs and tubular photoreactors with compound parabolic collectors (CPC) were compared under realistic conditions. Pharmaceutical removal efficiency was four times higher, increasing from 0.26mg/kJ with CPC reactors to 1.07mg/kJ in the 15-cm-deep RPR. As far as the authors know, this is the first detailed study on the effect of liquid depth in RPRs at circumneutral pH.
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•Photo-Fenton with Fe3+-EDDS removes CECs regardless water composition.•80% CEC removal after 15 min in 5 real WWTP effluents.•Nature and not the load of organic matter has impact on ...CEC removal.•Short reaction time to remove CECs encourages continuous flow operation.•Mechanism developed with synthetic effluent explains reactions in real wastewater.
This paper presents for the first time the treatment of contaminants of emerging concern (CECs) in a systematic study in different municipal wastewater treatment plants (MWWTPs) of the Mediterranean area, more than 1000 km away. Solar photo-Fenton process at neutral pH with Fe3+-EDDS has been demonstrated to be very efficient under controlled conditions and must be validated in realistic and variable conditions such as real MWWTP effluents of different composition. To this end, CEC removal was studied in effluents from 5 treatment plants in the Mediterranean area of Spain, the inorganic and organic composition varying in the range 161–641 mg L−1 (sulfate), 133–538 mg L−1 (chloride) and 10–20 mg L−1 (dissolved organic carbon). More than 45 CECs were quantified in MWW and results showed that the effect on CEC elimination of the concentration of anions and organic matter was interfered by the nature of the organic matter. However, origin and composition of MWW was not critic for attaining >80% degradation of CECs after 15 min of reaction. Moreover, conventional anions (sulfate, chloride) had a positive effect on CEC degradation rate. This paper demonstrates the consistency and predictability of the solar photo-Fenton process at circumneutral pH for treating CECs in simple and cheap photoreactors.
► Ethylenediamine-N,N′-disuccinic acid (EDDS) is a strong complexing agent of iron. ► Fe(III)-EDDS complex is stable in wide range of pH until 9.0. ► Fe(III)-EDDS complex is an efficient source of ...iron in photo-Fenton like process. ► OH radical formation is observed and measured in different conditions. ► Efficient degradation of organic compounds is achieved in acidic, neutral and alkaline pH.
We report for the first time the use of Fe(III)-EDDS (EDDS: ethylenediamine-N,N′-disuccinic acid) complex as an iron source in a homogeneous photo-Fenton system. The performance of this system was followed through the formation of the OH and the degradation of 2,2-bis-(4-hydroxyphenyl)propane (BPA). It was observed that Fe(III)-EDDS can enhance the efficiency of both OH formation and BPA degradation especially near neutral pH. The effect of H2O2 concentration, Fe(III)-EDDS concentration, pH value and oxygen concentration on the BPA degradation during this photo-Fenton system was investigated. It was observed that O2 is an important parameter affecting the efficiency of this process not only due to its reactivity with BPA but also because of its effect on the iron species present in solution. Comparison with iron complexes of oxalate, citrate and EDTA have demonstrated that Fe(III)-EDDS is a very efficient iron source for this photo-Fenton process. This work also demonstrates that Fe(III)-EDDS plays a positive role in the photo-Fenton system, especially at higher pHs, and makes this system an encouraging method for the treatment of organic pollutants in the natural environment.
As far as the authors know, no in-depth comparison has been made between the different performances of the solar photo-Fenton process for the removal of contaminants of emerging concern (CECs) as a ...function of pH. To this end, real WWTP secondary effluents were treated in continuous flow mode at pilot plant scale. The effect of hydraulic residence time (HRT), liquid depth and percentage of CEC removal on treatment capacity was studied. At acidic pH (2.8), the iron source was FeSO4 and at neutral pH (7.0), it was Fe(III)-EDDS. At both pH values, 2250 L m−2 d−1 can be treated in 15-cm deep raceway pond reactors at 30 min HRT with 0.1 mM iron and 0.88 mM H2O2 in order to achieve 80% CEC removal. Treatment costs were 0.25 € m−3 and 0.56 € m−3 at acidic and neutral pH, respectively. This study paves the way for the solar photo-Fenton process to be employed on a commercial scale.
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•In-depth comparison between acidic and neutral pH solar photo-Fenton for CEC removal•At acidic pH, the iron source was FeSO4 and at neutral pH, the complex Fe(III)-EDDS.•The effect of HRT, liquid depth and CEC removal goal on treatment capacity was studied.•2250 L m−2 d−1 treated in 15-cm deep RPRs at 30 min of HRT, 0.1 mM Fe, 0.88 mM H2O2•Unitary costs were estimated as 0.25 € m−3 and 0.56 € m−3 at acidic and neutral pH.
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•Al to return to reaction non-absorbed photons was desired in Raceway Pond Reactor.•Iron < 0.1 mM is necessary for reusing in irrigation treated municipal wastewater.•Studying ...micropollutants removal at actual concentrations is of utmost importance.•Removal of most recalcitrant pollutants would give the key design parameters.
Raceway Pond Reactors (RPRs) have arisen as an interesting and feasible scaling-up option for treating substantial amount of wastewater by solar photo-Fenton process, a technology with short-term perspective due to its high contaminants of emerging concern (CEC) removal efficiency associated with a low reagents’ consumption (Fe and H2O2) and different strategies to work at near-neutral pH. This work proposes to modify the RPR optical pathway by using a reflexive surface of aluminum at the bottom of it. In this study, modified neutral solar photo-Fenton process with EDDS (Ethylenediamine-N,N'-disuccinic acid) has been applied for the elimination of a mixture of six micropollutants (acetaminophen, caffeine, carbamazepine, diclofenac, sulfamethoxazole, and trimethoprim) at 20 and 100 µg L−1 in natural water with different low iron concentrations (0.018-0-1 mM) and liquid depths (7–15 cm). Results showed a similar treatment time for 80% removal of micropollutants with 0.054 mM of iron using the aluminum surface and for 0.1 mM of iron without the surface. Utilizing a reflexive aluminum surface to return to reaction non-absorbed photons permitted to lower the consumption of iron and EDDS without losing efficiency.
P-cresol is a highly toxic phenolic pollutant in coal chemical wastewater. The effective removal of p-cresol is of great significance to the ecological environment. In this study, the degradation of ...p-cresol by the Fe(III)-EDDS/H2O2 Fenton-like reaction modified by Mn2+ was investigated. The results showed that the removal rate of p-cresol could be significantly increased by the addition of Mn2+ under neutral and weakly alkaline conditions (pH 6.5–8.5). Acidic conditions (pH 3.5) were not conducive to the Fenton-like reaction. This is because a neutral or weakly alkaline environment is conducive to Mn2+-EDDS complex formation, which can produce O2·- to accelerate the reduction of Fe(III), and the efficiency of p-cresol degradation through a Fenton-like reaction catalyzed by the Fe(III)-EDDS complex is significantly improved. In addition, the degradation of EDDS through ·OH was reduced by O2·-, which maintained and stabilized the Mn2+-EDDS complex and Fe(III)-EDDS complex. Under neutral conditions, the optimal dosage of Fe(III) is 0.7 mM, and the optimal molar ratios are EDDS/Fe(III) = 1: 1, Mn2+/Fe(III) = 1: 1, and H2O2/Fe(III) = 15: 1. The addition of free radical clearance isopropanol and CHCl3 proved that ·OH was the main active substance in the p-cresol degradation process.
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•P-cresol degradation by Fe(III)-EDDS/H2O2 was enhanced in the presence of Mn2+.•Fe(III)-EDDS-Mn2+ Fenton-like system is pH-dependent.•Neutral/weakly alkaline conditions are conducive to the Fe(III)-EDDS/-Mn2+ system.•The stable Mn2+-EDDS complex produces O2·- effectively with H2O2 at pH 6.5–8.5.
In order to overcome the shortcomings in the traditional Fenton process, Fe(III)-EDDS-activated persulfate advanced oxidation process under irradiation is carried out as a promising technology. The ...photodegradation of sulfadiazine (SD) in Fe(III)-EDDS-activated persulfate system was investigated in this paper. The results showed that SD could be effectively degraded in Fe(III)-EDDS/
/hv system. The effects of Fe(III):EDDS molar ratio, the concentration of Fe(III)-EDDS, and the concentration of
on SD degradation were explored. At neutral pH, when Fe(III):EDDS = 1:1, Fe(III)-EDDS = 0.1 mM,
= 1.5 mM, the best SD degradation was achieved. The experiment of external influence factors showed that the degradation of SD could be obviously inhibited by the presence of
,
, whereas the degradation of SD was almost unaffected by the addition ofCl
−
. The degradation of SD could be slightly inhibited by the presence of humic acid and NO
3
−
. The effect of pH on SD degradation was investigated, and SD could be degraded effectively in the pH range of 3-9. ESR proved that
1
O
2
, ·OH,
, and O
2
−
were produced in the process.
and ·OH were identified as the main radicals while O
2
·−
also played non-ignorable role. Eleven intermediate products of SD were analysed. The C = N, S-N, and S-C bonds of SD were attacked by radicals firstly, leading to a series of reactions that eventually resulted in the destruction of SD molecules and the formation of small organic molecules.
•Antipyrine, caffeine, carbamazepine, ciprofloxacin and sulfamethoxazol were completely degraded.•Solar/Fe/H2O2 and solar/Fe/S2O82− system mediated by EDDS have been compared.•Different Fe:EDDS ...ratios, initial iron species and oxidant agents have been tested.•Best ratio for solar/Fe:EDDS/H2O2 was 1:2 and 1:1 for solar/Fe:EDDS/S2O82−.
The main purpose of this pilot plant study was to compare degradation of five microcontaminants (MCs) (antipyrine, carbamazepine, caffeine, ciprofloxacin and sulfamethoxazole at 100 μg/L) by solar photo-Fenton mediated by EDDS and solar/Fe:EDDS/S2O82−. The effects of the Fe:EDDS ratio (1:1 and 1:2), initial iron species (Fe(II) or Fe(III) at 0.1 mM) and oxidizing agent (S2O82− or H2O2 at 0.25–1.5 mM) were evaluated. The higher the S2O82− concentration, the faster MC degradation was, with S2O82− consumption always below 0.6 mM and similar degradation rates with Fe(II) and Fe(III). Under the best conditions (Fe 0.1 mM, Fe:EDDS 1:1, S2O82− 1 mM) antipyrine, carbamazepine, caffeine, ciprofloxacin and sulfamethoxazole at 100 μg/L where 90% eliminated applying a solar energy of 2 kJ/L (13 min at 30 W/m2 solar radiation <400 nm). Therefore, S2O82− promotes lower consumption of EDDS as Fe:EDDS 1:1 was better than Fe:EDDS 1:2. In photo-Fenton-like processes at circumneutral pH, EDDS with S2O82- is an alternative to H2O2 as an oxidizing agent.
In this work, the novel technology was used to remove heavy metal from sludge. The coupled with biodegradable ethylenediamine disuccinic acid (EDDS) and approaching anode electrokinetic (AA-EK) ...technique was used to enhance heavy metal removing from sludge. Electric current, sludge and electrolyte characteristics, heavy metal removal efficiency and residual content distribution, and heavy metal fractions percentage of variation were evaluated during the electrokinetic remediation process. Results demonstrated that the coupled with EDDS and AA-EK technique obtain a predominant heavy metal removal efficiency, and promote electric current increasing during the enhanced electrokinetic remediation process. The catholyte electrical conductivity was higher than the anolyte, and electrical conductivity of near the cathode sludge achieved a higher value than anode sludge during the coupled with EDDS and AA-EK remediation process. AA-EK technique can produce a great number of H+, which caused the sludge acidification and pH decrease. Cu, Zn, Cr, Pb, Ni and Mn obtain the highest extraction efficiency after the coupled with EDDS and AA-EK remediation, which were 52.2 ± 2.57%, 56.8 ± 3.62%, 60.4 ± 3.62%, 47.2 ± 2.35%, 53.0 ± 3.48%, 54.2 ± 3.43%, respectively. Also, heavy metal fractions analysis demonstrated that the oxidizable fraction percentage decreased slowly after the coupled with EDDS and AA-EK remediation.
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•Chelate and approaching anode electrokinetic promote electric current increasing.•Water content of near the anode sludge was higher than near the cathode.•Sludge electrical conductivity of near the cathode was higher than near the anode.•Approaching anode electrokinetic technique can promote heavy metal removal.
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