Different groups of emerging pollutants (EPs) were identified (drugs, pesticides, hormones, illicit drugs, and fire retardant), and the removal of four antibiotics was determined (sulfamethoxazole 62.2–94.4%, ciprofloxacin 71–83.1%, norfloxacin 82–89%, and ofloxacin 78–97.9%) in a municipal wastewater treatment plant (WWTP) in Acapulco, Gro. Mexico. The compounds were extracted from influent and effluent samples by solid phase extraction (SPE). The identification of non-target EPs was performed by liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS). The antibiotic quantification was performed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Most of the non-target compounds were detected only in the influent samples. Antibiotics levofloxacin and nalidixic acid, the anticonvulsants carbamazepine and oxycarbamazepine, the local anesthetic lidocaine, and the pesticide tridemorph were the main EPs not removed by the WWTP. In this study, it was shown that the Aguas Blancas WWTP does not manage to remove 100% of the various EPs identified in the effluent, although the elimination degree is high in most cases, despite being one of the model plants in Mexico.
Palabras clave: efluente, resistencia bacteriana, agua residual. RESUMENLa contaminación del agua es un problema ambiental grave. En una planta de tratamiento de agua residual (PTAR) en México se evaluó la presencia de coliformes fecales totales y de Escherichia coli, la prevalencia de patotipos diarreicos y los perfiles de resistencia a los antibióticos en las diferentes etapas del tratamiento. Se realizaron tres muestreos compuestos para evaluar la presencia de E. coli con los parámetros físicos y químicos establecidos en la Norma Oficial Mexicana NOM-001-SEMARNAT-1996. Se seleccionaron 57 cepas de las diferentes etapas del proceso y se determinó el patotipo de E. Coli por reacción en cadena de polimerasa múltiplex: enteropatógena (EPEC), enterotoxigénica (ETEC), enteroinvasiva (EIEC), enteroagregativa (EAEC), enterohemorrágica (EHEC) y de adherencia difusa (DAEC); asimismo, se determinó su resistencia por el método de Kirby Bauer. Los resultados muestran una eficiencia de remoción del 95.4 %, con base en la demanda química de oxígeno (DBO5). Los coliformes y E. coli son mayores en el influente. La frecuencia total de patotipos fue del 39 % (22/57) de EIEC, 30 % (17/57) de ETEC y 15.5 % (9/57) de DAEC y EPEC. Respecto de la distribución, se detectó un 39 % de ETEC en el influente, 50 % de EIEC antes de la desinfección, 100 % de EIEC después de la desinfección y un 43 % de ETEC en el efluente. Todas las cepas muestran baja resistencia a los antibióticos. La eficiencia de remoción de la PTAR, con base en el DBO5, es alta y cumple con las normas ambientales, sin embargo, la presencia de patotipos diarreicos en el efluente impacta negativamente al ambiente y a la salud pública.
Wastewater treatment plants (WWTPs) receive a wide variety of contaminants that cannot be eliminated or completely removed with current conventional methods. In this sense, the development and use of advanced technologies is a challenge in countries where wastewater sanitation is hardly a guarantee. However, the reuse of treated urban wastewater can function as an alternative to mitigate water pressure and, at the same time, guarantees water quality for potential reuse in agriculture, in the irrigation of landscape or urban green areas, but especially for aquifer recharge. Therefore, this chapter is focused on reviewing the current state of WWTPs in Mexico and the potential reuse of treated water.
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