An empirical analysis of ozone decay kinetics in natural waters

Ozone decay kinetics in various natural waters and their impact on modeling dissolved ozone concentration profiles in a bubble column contactor were s tudied. The results demonstrated that the commonly-used first-order kinetic s with a constant rate constant were unable to describe the ozone decay beh avior, particularly in cases where the initial ozone demand was significant . An explanation is that the water's reactivity toward ozone changes substa ntially as the ozonation depletes those readily reactive compounds. As a re sult, an exponentially decreasing function was proposed to provide better e stimates of the ozone decay curves. To test the applicability of the proposed ozone decay rate expression, furt her studies were conducted using a pilot scale fine bubble column. The Back Flow Cell Model was used to predict the concentration profiles of dissolve d ozone based on the proposed ozone decay kinetics. It was found that the model could predict the experimental observations rea sonably well, although cocurrent flow results were less definitive. The lac k of understanding of initial ozone demand might cause substantial errors i n the modeling of ozone contactor performance.