Preozonation effects on coagulation

The effects of preozonation on interactions among coagulants, particles, and natural organic matter were examined at bench scale through a series of jar tests using different organic matter, pH values, and coagulants. When alum was used as a coagulant, preozonation hindered turbidity and dissolved organic matter (DOM) removal at the conditions tested. When cationic polymers were used as the coagulant, however, preozonation led to small but statistically significant increases in the removal of both turbidity and DOM. When polyaluminum chloride was used as the coagulant for several natural waters, preozonation aided turbidity and DOM removal in one instance and hindered removal of particles and organic materials in another instance. The authors hypothesize that preozonation reduces the surface charge of particulates, leading to better coagulation by charge neutralization.