The hydrodynamics of an ozone contactor with horizontal meandering flow to enhance disinfection efficiency

The axial dispersion of an ozone contactor is known to influence Cryptosporidium parvum oocyst inactivation and bromate formation. While low dispersion is beneficial, an extent of dispersion is not specifically addressed for the design of a new ozone contactor. C. parvum oocyst inactivation, residual ozone, CT (i.e. Concentration × Time), and bromate formation were numerically simulated with diverse dispersion number (d), ranging from 0.01 to 5, using axial dispersion reactor model and kinetic parameters obtained from sand-filtered raw water under three pH and three temperature values. C. parvum oocyst inactivation was affected sensitively by the axial dispersion number especially at the region lower than 0.5. On the contrary, residual ozone, CT, and bromate formation were slightly influenced by dispersion number. The axial dispersion number of the full-scale ozone reactor with meandering horizontal flow was obtained with a tracer test. The equation for predicting the dispersion number of an ozone contactor with horizontal meandering flow was developed in the manuscript. The experimental axial dispersion number was slightly higher than the theoretically derived one because of flow disturbance in the channel of the ozone contactor.