Avaliação de desreguladores endócrinos e do micropoluente colesterol em estações de tratamento de esgoto sanitário

Abstract

Endocrine disruptors chemicals (EDCs), whose presence in sewage is mainly attributed to the natural hormones 17 -estradiol (E2) and estrone (E1) and to the synthetic one 17-ethinylestradiol (EE2), the main active ingredient of oral contraceptives, can cause a series of disturbances in the reproductive organs of humans and animals, since such compounds are not readily removed by biological processes of conventional treatment, being improperly released into water bodies. However, the above mentioned compounds are found at low concentrations (ng L -1/μg L -1) in aqueous environmental matrices, which make their detection and quantification an analytical challenge. Thus, an analytical methodology using gas chromatography coupled to mass spectrometry (GC/MS) was developed and optimized in order to evaluate the removal efficiency of EDs and the micropollutant cholesterol (CHOL) in wastewater treatment plants (WWTPs) from the Metropolitan Area of Fortaleza, as well as to detect them in surface waters. Acute and chronic ecotoxicity tests with effluents and EDs using the microcrustacean Daphnia magna as bioindicator. Five WWTPs were evaluated, which were divided in four types of technologies, namely: two WWTPs with facultative pond followed by maturation pond (FP+MP1 and FP+MP2), facultative pond (FP), activated sludge followed by chlorination step (AS+Cl) and upflow anaerobic sludge blanket reactor followed by chlorination step (UASB+Cl). The mean concentrations for micropollutants in effluents were: 557.4 ng.L-1 (E1), 144.4 ng.L-1 (E2), 266.4 ng.L-1 (E2-17A), 421.4 ng.L-1 (EE2) and 4691.9 ng.L-1 (CHOL). The maximum values obtained in surface water were: 212.75 ng.L-1 (E1), 256.25 ng.L-1 (E2) and 1175 ng.L-1 (CHOL). The estrogens E2-17A and EE2 were not detected. Regarding the EDs removal, the lowest removal efficiencies were found for low-rate systems (stabilization ponds) with 68.1% (FP+MP1), 79.9% (FP+MP2) and 54.0% (FP). The high-rate systems obtained satisfactory removal efficiency: 93.4% (LA+Cl), 95.4% (UASB+Cl). For CHOL, the best removal was obtained by the WWTP FP+MP2 with 94%, followed by the WWTPs AS+Cl (88%) and UASB+Cl (82%). No toxicity was detected in the effluent from the WWTP FP+MP2, however, in the effluents from FP+MP1 and FP, maximum EC50-48h was 61% and 57%, respectively. The toxicity level in the effluents from WWTPs UASB and AS was higher than that obtained in the influents. Probably, the toxicity increase was due to the presence of residual chlorine in the effluent since it was collected after the chlorination step. Concerning the chronic toxicity, significant effect in terms of reproduction (p <0.05) was detected only in the effluent from the WWTP FP+MP2 with NOEC (no observed effect concentration) of 20% and OEC (observed effect concentration) of 30%. In the effluents from the WWTPs AS+Cl and UASB+Cl, the OEC value for survival evaluation was 5%, evidencing the high toxicity. In the assay with a multielement estrogens solution, the survival chronic effect was not observed. However, there was a chronic effect in terms of sex change, showing values of NOEC and OEC of 2 and 4 μg.L-1, respectively. In terms of reproduction, NOEC was 4 μg.L-1 and CEO of 1 μg.L-1. Based on these results, it can be concluded that there is a need for optimization of WWTPs operational parameters in order to improve micropollutants removal efficiency.