Chemical Disinfection with H2O2. The proposal of a Reaction Kinetic Model

Abstract

The inactivation (death) of Escherichia coli bacteria in water employing hydrogen peroxide has been studied and a five log decrease in CFU cm-3 was achieved. The reaction kinetics was modeled as a series of biochemical steps represented by pseudo homogeneous reactions between hydroxyl radicals and the components of the cellular walls. Afterwards, the lysate was supposed to undergo a group of parallel reactions leading to the oxidation of the chemical components of the cell. It was assumed that the initiation step of hydrogen peroxide dissociation is promoted by the presence of iron or iron-superoxide compounds. In addition the model takes into account that the reaction forming the lysate as well as the ones that follow the destruction of the bacterium wall, compete for the available oxidizing radicals with the steps that involve the attack on active and injured bacteria. A four parameter representation shows good agreement for the whole range of employed hydrogen peroxide concentrations. The results are valid for any form and size of the employed reactor as long as the described operating conditions (pH and concentrations) are maintained. This development constitutes a very general model that is capable to describe inactivation processes whose graphical representation also shows the presence of shoulders at the beginning and tailings in the end of the operation.