Remoção da estrogenicidade utilizando o processo de foto-Fenton LED em efluente de estação de tratamento de esgoto doméstico

Abstract

After the development of analytical techniques and the refinement of detection limits pertaining to analytical methods, contaminants of emerging concern have been found at low concentrations in different aqueous matrices. Some of these contaminants, specifically the endocrine disrupters, are recognized by hormone cell receptors in living beings and can cause worrisome effects, often due to the estrogenic activity of the substance. The photo-Fenton process is an advanced oxidation process that consists of recent technology in wastewater treatment, containing contaminants of emerging concern, as these processes allow the chemical degradation of substances that are both toxic and of difficult removal by biological processes. The goal of this work was to evaluate the performance of the LED-irradiated photo-Fenton process in the removal of estrogen by using the Yeast Estrogen Screen (YES) test and by degrading eleven microcontaminants (ibuprofen, 4-octylphenol, 4-nonylphenol, genfibrozil, naproxen, bisphenol A, diclofenac, estrone, 17β-estradiol, 17α-ethinylestradiol and estriol) from a sewage treatment plant's secondary effluent. The tests were performed following a factorial design (22) in an LED photoreactor (455 nm; 1.5-L) for which photonic flux is equivalent to 1.6 x 10-6 Einstein.s-1. The experimental condition which led to highest removal percentages was that in which 20 mg.L-1 of iron and 100 mg.L-1 of hydrogen peroxide (H2O2) were applied, and resulted in 62% removal of estrogenicity, 59% removal of dissolved organic carbon (DOC), during 120 minutes of reaction. Results also indicated that treated sewage did not present any acute toxicity towards Allivibrio fischeri. Only two of the tested conditions indicated toxic effects after treatment, these also presenting the lowest percentages of DOC removal. Control experiments were carried out for the best condition and consisted of iron coagulation, UV, LED and solar irradiation only and oxidation with H2O2. The iron coagulation process presented 40% of estrogenicity removal while, maximum removals were limited to 3% for the other controls. The solar photo-Fenton, UVC photoFenton, photoperoxidation and Fenton processes were compared with the LED photo-Fenton. The irradiated processes with UVC and solar presented lower efficiency for estrogenicity removal compared to LED. The efficiency of Fenton was equal to that of LED photo-Fenton, however, as expected, this process generated a higher amount of sludge indicating that the compounds may have been sorbed to the solid phase rather than degraded. These results confirm the applicability of LED irradiated photoreactors to improve the quality of secondary treated sewage as an innovative option which explores a sustainable radiation source.