This contribution aims at emphasizing the importance of ideal reactors in the field of environmental engineering and in the education of the corresponding engineers. The exposition presents the mass flow governing equations of the ideal reactors (batch, completely mixed flow, and plug flow reactors) as particular cases derived from the integral version of the conservation of mass of a chemical/biological species. In the case of transient problems and simple kinetics, such expressions result in first-order ordinary differential equations amenable to be solved analytically when they are linear. In this article, it is shown that when they are non-linear, due to the presence of a second-order kinetics reaction, an analytical solution is also possible, a situation not dealt with in the textbooks. Finally, the previous findings are integrated into a teaching proposal addressed to help undergraduate students to solve more efficiently ideal reactor problems.

In this communication, the solution of the differential Riccati equation is shown to provide a closed analytical expression for the transient settling velocity of arbitrary non-spherical particles in a still, unbounded viscous fluid. Such a solution is verified against the numerical results of the integrated differential equation, establishing its accuracy, and validated against previous experimental, theoretical and numerical studies, illustrating the effect of particle sphericity. The developed closed analytical formulae are simple and applicable to general initial velocity conditions in the Stokes, transitional and Newtonian regimes, extending the range of application of former published analytical approximate solutions on this subject.

Introducción: La contaminación puntual y difusa (CPyD) asociada a micro-contaminantes en el agua amenaza la biodiversidad y la seguridad hídrica en Colombia, especialmente en la cuenca alta del río Cauca. La Universidad del Valle lidera un proyecto para mitigar esta problemática mediante Soluciones basadas en la Naturaleza (SbN), promoviendo tecnologías y estrategias integradas para su implementación. Objetivo: Plantear un modelo de gestión para la implementación de SbN en la mitigación de la CPyD en la cuenca alta del río Cauca. Metodología: Se integraron las dimensiones técnicas, económicas e institucionales del contexto regional con una revisión bibliográfica, empleando bases de datos como OpenAlex y VosViewer, identificando experiencias nacionales e internacionales para abordar la CPyD; además, se registró el seguimiento de las unidades piloto de SbN implementadas en la cuenca alta del río Cauca. Resultados: Las SbN combinan co-beneficios ambientales, económicos y sociales, ecosistemas, incluyendo la mitigación de la CPyD. Investigaciones globales destacan la efectividad de los humedales construidos para tratar contaminantes como agroquímicos y compuestos farmacéuticos; el modelo de gestión propuesto promueve la sostenibilidad y la gobernanza a través de la construcción de procesos asociativos que incrementan la efectividad y sostenibilidad en la implementación de SbN para la mitigación de la CPyD. Conclusiones: Esta primera aproximación permite avanzar hacia la construcción de un modelo de gestión para el control de CPyD mediante SbN que pueda ser evaluado, mejorado y adaptado en situaciones similares a las registradas en la cuenca alta del río Cauca, bajo criterios de selección participativa y construcción colectiva.

The Universidad Autónoma de Occidente (UAO), located in Cali (Colombia), launched the Sustainable Campus Program in 2015, in order to implement sustainability actions and strategies within the University campus with the purpose of contributing both to a better environmental performance of the campus operations and to generate knowledge and experience than can be used in the context of cities and regions in their search for reaching sustainable conditions. Integrated waste management is one of the components of the UAO Sustainable Campus Program. Based on the categories and indicators presented in the GreenMetric 2017, the integrated waste management includes the program to reduce the use of paper and plastic in campus, recycling program for university waste, toxic waste handled, organic waste treatment and inorganic waste treatment.