When initial pH 3 was used, the pH remained relatively
constant during the UVC/H2O2 process, whereas the pH
decreased for initial pH 7 and even more so for pH 10. Despite
the difference between the initial pH of 7 and 10, both resulted
in the similar operating conditions of pH 6–8. This may explain
the small difference in COD reduction (Fig. 3). The decrease in
pH is usually associated with the oxidation of the organic
compounds to mineral acids, carbon dioxide and their acidic
intermediates (Crittenden et al., 1999). Despite the initial pH of
10, the pH of treated water was close to neutral and subsequent
adjustment would not be necessary before the treated
water could be used