ABSTRACT
Most treatment processes remove or destroy some viruses in waters and wastewaters, but only disinfection is expected to destroy all viruses in such waters. Ozone reacts with most oxidizable substances and thus the O3 demand of impurities in waters is usually high. It is a rapid virucide, probably more rapid than ClO2 (at pH 7 and less) and HOCl. Ozone is difficult to quantify, however, at the concentrations at which it is used for water disinfection. Ozone, alone, appears to produce no toxic products in waters and wastewaters. Ozone reacts with most oxidizable substances and thus the O3 demand of impurities in waters is usually high. Among these impurities are the humic acids and other precursors of trihalomethanes. Thus, treatment of waters with O3 reduces the quantities of trihalomethanes resulting from subsequent chlorination. Particulates in waters and wastewaters protect from disinfection virions and bacteria adsorbed to the particulates or embedded within them.
