Reaction kinetics of humic acid with sodium hypochlorite

Trihalomethane (THM) in drinking water is formed by chlorination of humic substances. In this study, the rates of THM formation from precursors in the water of the Tormes river (Salamanca, Spain) using sodium hypochlorite as oxidant has been carried out. The oxidation kinetics were examined under conditions such that the formation of trihalomethane would be favoured, with a view to discovering the effect of different physico-chemical parameters on them such as pH, oxidant and humic acid (HA) concentration. A mechanistic model, based on the fact that on the macromolecule (HA) there are several sites that are highly reactive to sodium hypochlorite; is used to derive kinetic equations for the rate of THM formation as a function of humic acid and oxidant concentration under controlled pH and temperature conditions.