A new solar photo-Fenton strategy for wastewater reclamation based on simultaneous supply of H2O2 and NaOCl.

This study presents, for the first time, the concurrent supply of the oxidants H2O2 and NaOCl in solar-driven Fenton-like processes at neutral pH with ferric nitrilotriacetate (Fe3+-NTA) for wastewater reclamation. Simultaneous Escherichia coli (E. coli) inactivation and the removal of the antibiotic sulfamethoxazole (SMX) at 50 µg/L in municipal effluents were investigated in 5-cm deep raceway pond reactors. First, the individual effects of reagent concentrations (1.47, 2.94 and 4.41 mM for H2O2; 0.134, 0.269 and 0.403 mM for NaOCl; 0.1 and 0.2 mM for Fe3+-NTA) on the economic efficiency (in terms of mass of SMX eliminated per Euro and per hour to attain complete E. coli inactivation and more than 50% of SMX removal) were considered. The highest economic efficiencies were 141 mgSMX/€·h with H2O2 and 222 with NaOCl, the reaction times being 105 and 60 min, respectively. Second, a new strategy for solar photo-Fenton with the combination of the most cost-effective conditions (1.47 mM H2O2 - 0.134 mM NaOCl - 0.1 mM Fe3+-NTA) was carried out in secondary effluents from two treatment plants with different technologies. Economic efficiency was substantially affected by wastewater composition, ranging from 178 to 1131 mgSMX/€·h with treatment times between 60 and 10 min, significantly improving the reported results for conventional solar photo-Fenton to date.

Simultaneous bacterial inactivation and microcontaminant removal by solar photo-Fenton mediated by Fe3+-NTA in WWTP secondary effluents.

Simultaneous microorganism inactivation and organic microcontaminant removal in municipal wastewater treatment plant (WWTP) secondary effluents by the solar photo-Fenton process mediated by Fe3+-NTA is studied in depth. To achieve this objective, different key aspects were addressed: (i) the effect of initial Fe3+-NTA concentration at 1:1 molar ratio (0.10-0.30 mM) and H2O2 concentration (1.47-5.88 mM), (ii) the effect of initial microorganism load (103 and 106 CFU/mL) and (iii) the impact of the disinfection target on treatment cost. The first stage of this work was carried out in simulated WWTP effluent spiked with 100 µg/L of imidacloprid (IMD) as model microcontaminant and inoculated with Escherichia coli (E. coli) K-12 as reference strain, in a pilot scale raceway pond reactor with 5-cm of liquid-depth. Secondly, the most cost-effective conditions were validated in actual WWTP effluent. The kinetic analysis revealed that increasing Fe3+-NTA concentration over 0.20 mM does not significantly reduce treatment time due to the limited effect caused on the volumetric rate photon absorption. Treatment cost is determined by the disinfection process, since IMD removal was always faster than E. coli inactivation. The most cost-effective strategy to achieve 10 CFU/100 mL of E. coli (Regulation EU 2020/741) was 0.20/4.41 mM Fe3+-NTA/H2O2, with a cost of 0.32 €/m3. A less restrictive disinfection target, 100 CFU/100 mL, allowed reducing reactant concentration and cost, 0.10/1.47 mM Fe3+-NTA/H2O2 and 0.15 €/m3, respectively. In both cases, no regrowth at 24 h and more than 90% of IMD removal were observed.

Low cost UVA-LED as a radiation source for the photo-Fenton process: a new approach for micropollutant removal from urban wastewater.

Light Emitting Diode (LED) technology has matured sufficiently to be considered as an alternative UVA radiation source in photoreactors. Currently, low energy consuming LEDs with a wide range of wavelengths and radiant flux are readily available. In this study, UVA-LEDs were used as a radiation source for the photo-Fenton process as tertiary treatment. The water matrix used was a simulated secondary effluent doped with 200 µg L-1 of the pesticide acetamiprid (ACTM) due to its recalcitrant nature. All experiments were carried out in a LED-box reactor at pH 2.8. The main purpose of this research was to gain some insight into the relationships among energy supply, LED consumption, UVA irradiance and reaction rate. The effect of LED wavelength on energy efficiency for ACTM degradation was studied by varying the iron concentration and liquid depth. Three wavelengths (365, 385 and 400 nm) and two iron concentrations (5 and 11 mg L-1) for two different liquid depths (5 and 15 cm) were evaluated in order to obtain more energy efficient conditions. The results suggest that while the wavelength of 365 nm with 11 mg Fe2+ L-1 was the best condition for ACTM degradation, the wavelength of 385 nm had slower kinetics, but higher energy efficiency.