While average free residual chlorine is about 0.12 mg/l (standard
deviation, SD, 0.23 mg/l), the average total residual chlorine concentration
is 0.60 mg/l (SD: 0.47 mg/l); this is more comparable to the
levels observed in QC systems with chlorination (0.63 mg/l with SD
of 0.43 mg/l). As might be expected, DBP concentrations are also
considerably lower in this particular system. The annual average
THM level is 13.8 μg/l (SD: 16.0 μg/l) and the average HAA level is
15.2 μg/l (SD: 13.1 μg/l). This result is consistent with the study of
Hua and Reckhow (2007), which reports that the use of free chlorine
leads to considerably higher levels of DBPs in comparison with the
use of monochloramine.