| Resumo: | Over the last few decades, the occurrence of emerging contaminants (EC) has raised concerns due to their ubiquitous presence in the environment and potential to cause undesirable ecological effects. Their main source are the discharges of wastewater treatment plants (WWTPs), which are not effective barriers to these pollutants. In order to assess the fate of EC, as well as to evaluate possible strategies to attenuate their presence, the study of natural processes is of the greatest importance. Adsorption, biodegradation and photodegradation appear as significant mechanisms of removal of EC in aquatic environments. Among the EC, two antibiotics, sulfadiazine (SDZ) and oxolinic acid (OXA), and two estrogens, estrone (E1) and 17α-ethinylestradiol (EE2), have received considerable attention because of their high consumption and persistence in the environment. Since SDZ and OXA resist to biodegradation and tend to remain in aqueous phase, while E1 and EE2 have high affinity to solid phase, in the present work, the photodegradation of antibiotics and the adsorption and biodegradation of estrogens were investigated. In what concerns SDZ and OXA photodegradation, the effect of environmentally relevant factors such as the pH, the presence of fractions of estuarine humic substances and salinity were evaluated. The results obtained indicated that at higher pH, and in the presence of photosensitizers, the SDZ photodegradation was much faster than in ultrapure water. Different results were obtained for OXA, with a significant decrease in its photodegradation in presence of photosensitizers. These observations may explain the results obtained in environmental matrices, namely the final effluent of a WWTP, fresh water and brackish water, in which the photodegradation of SDZ (t½ between 2.32 h and 3.48 h) was found to be much faster than in ultrapure water (t½ = 6.76 h). In contrast, OXA photodegradation was much slower in the final effluent of a WWTP, fresh water and brackish water (t½ between 1.65 h and 4.03 h) than in ultrapure water (t½ = 0.99 h). In WWTPs estrogens are mainly adsorbed onto sludge. Thus, a simple, reliable and inexpensive method for the quantification of E1 and EE2 in fresh sludge samples was developed. Recovery values of 103 % and 97 % were obtained for E1 and EE2, respectively. Regarding the estrogens’ removal under anaerobic conditions, the influence of different factors was investigated. A higher E1 removal from solid phase of sludge was obtained for higher temperatures (25 C and 34 C) and lower sludge content (2 g L-1). In the case of EE2, higher removal was obtained for lower sludge content (2 g L-1 and 3 g L-1). However, temperature had no effect on the removal of EE2. The presence of nitrate does not appear to influence the removal of both E1 and EE2 from sludge. Finally, the performance of continuous (CO) and intermittent operation (IO) of Upflow Anaerobic Sludge Blanket (UASB) reactors on the removal of E1 and EE2 was assessed. Higher biodegradation values (69.4 % vs. 43.3 % for E1 and 21.8 % vs. 8.0 % for EE2) and adsorption values (26.5 % vs. 5.7 % for E1 and 72.7 % vs. 31.0% for EE2) were found with the IO, compared to CO. Thus, the IO of UASB reactors can be a promising, sustainable, and robust alternative for E1 and EE2 removal from wastewaters.
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