Evaluation of the oxygen transfer coefficient in activated sludge processes to optimize the aeration

[ES] En una Estación Depuradora de Aguas Residuales (EDAR), el mayor consumo energético es el asociado al sistema de aireación del tratamiento biológico. Esto hace que los estudios relacionados con los sistemas de aireación para mejorar su eficiencia sean interesantes, ya que pueden contribuir a un descenso notable en los costes energéticos de la EDAR. En este estudio se ha observado una relación positiva del coeficiente de transferencia de oxígeno con el caudal de aire insuflado y, por el contrario, una relación negativa con el aumento en la concentración de sólidos totales del licor mezcla. Los resultados han demostrado que el valor del coeficiente de transferencia de oxígeno presenta diferencias notables según la configuración de los difusores empleados y se ve afectado negativamente por el ensuciamiento de los mismos. Se han destacado tres aspectos clave para el ahorro energético en el proceso de aireación: (1) implementar un sistema de control de la aireación que ajuste la cantidad de oxígeno suministrada a las necesidades del proceso biológico, (2) disponer de soplantes dimensionadas para trabajar eficientemente en las bajas y medias necesidades (en lugar de soplantes de gran potencia dimensionadas para unas condiciones punta poco frecuentes), ya que permiten una buena regulación y (3) trabajar a bajas concentraciones de oxígeno disuelto en el reactor, pues al aumentar la diferencia entre esta concentración y la concentración de saturación del oxígeno, se origina un aumento en la fuerza motriz responsable de la transferencia de oxígeno a la columna de agua. Además, en estas condiciones se favorece el desarrollo de microorganismos con mayor afinidad por el oxígeno, lo cual mantiene la eficiencia del proceso biológico. Por último, se ha propuesto un protocolo para la determinación del coeficiente de transferencia de oxígeno en EDARs cuyo sistema de aireación funcione mediante períodos de aireación intermitentes, de forma que sea posible conocer la evolución de este parámetro con el tiempo, lo cual es de gran utilidad para la planificación del mantenimiento y limpieza de difusores.[EN] In a Wastewater Treatment Plant (WWTP), the highest energy consumption is associated with the aeration system of the biological treatment. This makes studies related to the efficiency of the aeration systems interesting, since they can provide insights to achieve significant decrease in the energy costs of the WWTP. In this study a positive relationship of the oxygen transfer coefficient with the air flowrate supplied has been observed while a negative relationship with the increase in the total solids concentration of the mixed liquor. The results have shown that the value of the oxygen transfer coefficient shows notable differences according to the configuration of the diffusers and it is negatively affected by their fouling. Three key aspects for energy saving in the aeration process have been highlighted: (1) implement an aeration control system that adjusts the amount of oxygen supplied to the needs of the biological process, (2) have blowers sized to work efficiently in the low and medium needs (instead of high-power blowers sized for infrequent peak conditions), since they allow good regulation and (3) operate at low concentrations of dissolved oxygen in the reactor, because by increasing the difference between the concentration of dissolved oxygen in the reactor and the oxygen saturation, an increase in the driving force responsible for the transfer of oxygen to the water column will be achieved. Additionally, under these conditions, proliferation of microorganisms with a higher oxygen affinity can be promoted, which maintains the higher gradient between concentrations and improves the efficiency of the biological process. Finally, a protocol has been proposed for the determination of the oxygen transfer coefficient in WWTPs whose aeration system operated through intermittent aeration periods, so that it is possible to know the evolution of this parameter over time, which is of great value for planning maintenance and cleaning of diffusers.Se agradece a la Entidad Pública de Saneamiento de Aguas Residuales de la Comunidad Valenciana (EPSAR), a la Cátedra Aguas de Valencia y a la empresa Global Ommium, tanto la financiación como la colaboración en la realización de este trabajo.Ivailova Petkova, I.; Solís, JJ.; Bes Piá, MA.; Aguado García, D. (2020). Evaluación del coeficiente de transferencia de oxígeno en procesos de fangos activados para optimizar la aireación. 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