Investigação teórica do processo de redução de coliformes em leitos cultivados

This paper shows the continuity of the research, as suggested by Amendola et al. (2003), when looking for better accuracy in the theoretical investigation of the pollutant reduction as a function of the support bed used in constructed wetland. This investigation is performed through the mathematical modeling and numerical simulation of the process, which is described by an advection-diffusion differential equation. This equation depends on certain constants which characterize the support bed (Moreno-Grau, 1996), and must be associated to the initial and boundary conditions established according to the experimental procedure. To solve the equation an algorithm based on the implicit scheme of the finite difference method was implemented which, when ran with MATLAB 6.1, generated values for the pollutant concentration which depend on the mentioned constants. The results obtained with the simulation were compared with the reference values to determine the longitudinal dispersion coefficient value which leads to the least residual value for each kind of support bed. The obtained results lead to the conclusion that the constructed wetland with crushed stone and chopped tires is better than the one with crushed stone alone to reduce fecal and total coliforms.