Avaliação da eficiência de remoção de turbidez em função da variação do comprimento de floculadores tubulares helicoidais

Abstract

The use of hydraulic flocculators is quite common in small and medium water treatment plants, because the hydraulic energy is used to promote the collision between the particles, which leads to crowding, under appropriate conditions. However, the hydraulic flocculators generally consist of compartments, forcing the current flux to change direction to each compartment. Such changes promote increases in local average, which can promote the rupture of aggregates. In this context, some studies have shown a flocculation system formed by a tubular helical flocculator, which has a better distribution of energy within it, minimizing the changes in the flow characteristics. However, in a lot of works the reactors’ length are kept constant, being discussed only other parameters such as flow rate, average velocity gradient and residence time. Moreover, many works don’t evaluate the flocs’ process, which is directly related to the flocculation’s efficiency. Given this, were defined as objectives of this study to evaluate the influence of the length of the reactor and the flocs’ aggregation and breakup process. For that, were used 1 and 2 L / min for the diameters of reactors of 3/8 "and 1/2" and 4 L / min for the diameter of reactor of 5/8", with eight different lengths for each reactor. For all settings studied the increases to a maximum value and then decreases with increasing the length of the reactors. Regarding the coefficients of aggregation and breakup, there was a reduction in this values with the increase in the average velocity gradient, which agrees with the result obtained in Brito’s work (1998). Finally, it was proposed a model to predict the performance of efficiency of turbidity removal using data obtained in Silva’s work (2007) and in this work, obtaining a correlation between the experimental data and calculated data of 0.82, indicating that this model may be a useful tool for a better understanding of this type of reactor.