We prove the global existence of the state trajectories for a class of non-linear systems arising from convection-dispersion-reaction processes. It is also shown that there is at least one steady state in the set of physically feasible states for such systems. The uniqueness and the stability analysis of this steady-state solution are discussed. Our approach is based on the analysis of a non-linear set of partial differential equations, using the upper and lower solutions, dissipativity properties, a subtangential condition and the positivity of the related C0-semigroup.