Development of efficient recirculation system for Tilapia (Oreochromis niloticus) culture using low cost materials

In the current experiment, a recirculation system was built using low cost materials that are available locally and its performance was tested. The performance evaluation procedure was carried out in an aquaculture system in greenhouse with sex-reversed male Nile tilapia (Oreochromis niloticus) production in Querétaro State, Mexico. The recirculation system had four sections (sediment collector, gravel and sand filters, biofilter and clarification) in order to eliminate the organic matter produced by the fish excretion material and uneaten food, as well as, the nitrogenous compounds undesirable in the water tanks, such as, total ammonia nitrogen (TAN). The monitored variables include: temperature, dissolved oxygen, pH, visibility, TAN, nitrites and nitrates. The obtained data were compared with previous studies to evaluate the achieved state of the system. This research clearly demonstrated that it is feasible to use the proposed configuration in aquaculture systems in areas where water source is limited. Consequently, the obtained results represent an environmental standpoint for the conservation of water use in the aquaculture industry and also constitute an important contribution to the aquaculture and farmers who receive minimal economic support.Key words: Water recirculation, aquaculture, sustainability, low cost, water use efficiency

Análisis y simulación del modelo físico de un invernadero bajo condiciones climáticas de la región central de México

The use of greenhouses for vegetable production has expanded rapidly in recent years in México. The most important aspect for the success of these agro-businesses is the improvement of production efficiency, higher quality and productivity, which are related to specific climatic conditions of each region. The present study introduces the analysis and simulation of a mathematical model of greenhouse climate. The model is formulated on basic principles of mass and energy transfer processes, and simulates the greenhouse air, soil, roof and crop temperatures, as well as relative humidity. The dynamic simulation of the mathematical model was made using the SIMULINK tool of MATLAB software. The simulation results were calibrated and validated with the measured data collected in a 1000 m2 experimental greenhouse developed at the University of Querétaro. The results from the validation were prediction equations for the roof temperature (R2=0.855), inner air temperature (R2=0.964), crop temperature (R2=0.835), soil temperature (R2=0.714) and relative humidity (R2=0.960). The magnitude of the coefficients indicates that the model can be used to predict the greenhouse climate with a high level of confidence, and it is a tool for supporting the analysis of the necessary conditions for greenhouse vegetable production under climatic conditions of the Central Region of MéxicoEl uso de invernaderos para la producción de hortalizas ha crecido en México rápidamente en los últimos años. Lo más importante para el éxito de estos agronegocios es incrementar la eficiencia de la producción, lograr mayor calidad y alta productividad, lo cual está relacionado con las condiciones climáticas específicas de cada región. En este estudio se presenta el análisis y simulación de un modelo matemático del clima en un invernadero. El modelo está formulado con base en los principales procesos de transferencia de masa y energía, y simula las temperaturas del aire, suelo, cubierta, cultivo, y humedad relativa del invernadero. La simulación dinámica del modelo matemático se hizo con la herramienta SIMULINK del software MATLAB. Los resultados de la simulación se calibraron y validaron con los datos medidos en un invernadero experimental de 1000 m2 desarrollado en la Universidad Autónoma de Querétaro. Los resultados de la validación fueron ecuaciones de predicción: para la temperatura de la cubierta (R2=0.855), temperatura del aire interno (R2=0.964), temperatura del cultivo (R2=0.835), temperatura del suelo (R2=0.714) y humedad relativa (R2=0.960). La magnitud de los coeficientes indica que el modelo puede usarse para la predicción del clima en el invernadero con un buen nivel de confianza y es una herramienta de apoyo para el análisis de las condiciones necesarias para la producción de hortalizas en invernaderos bajo las condiciones climáticas de la región central de Méxic