A fuzzy Cauchy problem modelling the decay of the biochemical oxygen demand in water

A very important physical-chemical parameter of water is the concentration of dissolved oxygen necessary for all living aquatic organisms. In this work, we have proposed a fuzzy model to describe the decay of the dissolved oxygen concentration in water using fuzzy differential equations, the classic analytic solution of which is well known. We use the Euler and Runge-Kutta 4/sup th/ order methods to obtain an approximate solution of an initial value problem of a fuzzy linear ordinary differential equation modelling decay. We compare numerical results with the fuzzy analytic solution presented by Barros et al (2000) for the similar fuzzy differential equation.