Development of a mathematical model of Cryptosporidium inactivation by ozonation

A new mathematical model was developed to express the processes of Cryptosp oridium inactivation by ozonation. In this model, five different stages wer e considered as state variables of Cryptosporidium oocysts for accurate exp ression of the inactivation. ATP, in vitro excystation and DAPI/PI permeabi lity assays were used to describe the oocyst amounts of different stages. S ome reaction constants were estimated by the structure components of oocyst s or by the stoichiometry of reactions, while the others were by the oocyst s population changes in ozonation. The calculated values of this model were well consistent With experimental inactivation data. Three-log inactivatio n of sporozoites required about 0.04 mgO(3) per unit oocyst (mgC) from the simulation results. Before ozone reacts with sporozoites, more ozone was co nsumed to oxidize other parts of oocysts and DOC produced. The main path of inactivation of oocysts by ozonation was estimated to be P-1 (intact oocys ts) -->P-2 (oocysts with damaged outer oocyst wall) -->P-4 (oocysts without excystation function) -->P-5 (oocysts with inactivated sporozoites and no excystation function) from experimental and simulated results.