LED-irradiated photo-Fenton process on pollutant removal: outcomes, trends, and limitations.

This manuscript critically reviews the state of the art on the application of photo-Fenton processes irradiated by light-emitting diode arrays (LED) with a focus on the removal of contaminants of emerging concern (CEC) from aqueous matrices. LEDs are clean, low-cost radiation sources with longer lifespan compared to mercury lamps. This study covers the influence of LED sources, wavelengths, and dose upon CEC removal, and the potential for disinfection, abatement of antibiotic-resistant bacteria (ARB), and genes (ARG). The bibliographic search was performed in Scopus database using keyword combinations and resulted in a portfolio containing 52 relevant articles published between 2010-2023. According to reviewed papers, LED photoreactor design has evolved in the past decade aiming to improve CEC degradation in aqueous matrices while reducing construction and operation costs, and energy consumption. Among several reactors (annular, fluidized bed, parallel plate, wireless, pathway systems, and microreactor) surveyed for their performance and scalability, LED chips and strips are particularly suitable for application due to their wide emission angle (≈120°) and small size (mm2), which allow for, respectively, efficient illumination coverage and flexible arrangement and design. LED microreactors are very efficient in the degradation of contaminants and scalable with reduced area requirements. Although most studies were performed in synthetic solutions and at laboratory scale, the externally LED irradiated cylindrical reactor was successful for application in full-scale municipal water treatment plants. Future studies should focus on evaluating CEC removal in wastewater using scalable devices for continuous operation of solar photo-Fenton at night.

Simultaneous removal of emerging contaminants and disinfection for municipal wastewater treatment plant effluent quality improvement: a systemic analysis of the literature.

This work presents a bibliographic review of the literature regarding the simultaneous removal of contaminants of emerging concern (CECs) and disinfection in domestic wastewater matrices. These two responses are usually evaluated independently, as most attention has been centered on the discussion over the removal of CECs in the last 10 years. However, the simultaneous removal of CECs and pathogens from wastewater has been recently brought to the spotlight, especially considering the removal of antibiotics and antibiotic-resistant bacteria. Aiming at a reproducible and nonbiased methodology, a combination of the construction of a bibliometric portfolio with systemic analysis was performed with peer-reviewed manuscripts published between 2008 and 2019 in five distinct databases. Several keyword combinations were necessary to achieve a relevant portfolio according to strict criteria. As a result, five highly cited papers and authors were selected. Among the advanced oxidation processes (AOPs) explored for simultaneous removal of CECs and disinfection in these papers, detailed results have been elucidated mainly for ozonation. Thus, revealing the broad range of questions that have yet to be investigated in depth for new technologies such as irradiated solar processes. In addition, there is a lack of information associated with simultaneous assessment of CEC removal and disinfection in real samples and in wastewater matrices originated from different secondary treatment technologies in diverse locations.

LED irradiated photo-Fenton for the removal of estrogenic activity and endocrine disruptors from wastewater treatment plant effluent.

The goal of this work was to evaluate the performance of the LED irradiated photo-Fenton process on the removal of (i) estrogenic activity and (ii) seven endocrine disruptors (EDs) (4-octylphenol, 4-nonylphenol, bisphenol A, estrone, 17ß-estradiol, 17α-ethinylestradiol, and estriol) from real wastewater treatment plant effluent (WWTPE). EDs are a group of contaminants of emerging concern present in WWTPE and which may be recognized by hormone receptors, thus harming animal and human health. The yeast estrogenic screen test (YES) was used to quantify estrogenic activity promoted by EDs in WWTPE samples before and after photo-Fenton treatment. Tests were performed following a factorial design with different iron (20, 40, and 60 mg L-1) and hydrogen peroxide (100, 200, and 300 mg L-1) concentrations in a laboratory scale LED photoreactor (λ = 455 nm, 1.5 L, 1.6 × 10-6 Einstein s-1). EDs were analyzed by gas chromatography coupled to a mass spectrometer. Control experiments consisted of Fenton process, iron only, LED irradiation only, and H2O2 only. Optimum experimental conditions for LED photo-Fenton resulted in 62% removal of estrogenic activity and 59% mineralization. In addition, treated WWTPE was not toxic to Aliivibrio fischeri and more than 80% of EDs were removed during LED irradiated photo-Fenton. Although Fenton process showed similar efficiency to that obtained by LED photo-Fenton, a higher volume of sludge was generated in the dark. Finally, results obtained in this study confirm the applicability of LED irradiated photo-Fenton process for improving the quality of WWTPE as an alternative to solar photo-Fenton in case solar radiation is not available, thus reducing hazards associated to WWTPE reuse or discharge.