THESIS
2015
xiv leaves, 121 pages : illustrations (some color) ; 30 cm
Abstract
The occurrences of pharmaceuticals and personal care products (PPCPs) and endocrine
disrupting compounds (EDCs) in drinking water have raised increasing concerns. Recently, the
UV-chlorine process, which generates HO
• and reactive chlorine species (RCS) (i.e. Cl
• and
Cl
2•-) is being considered as an emerging alternative to the UV-H
2O
2 process because it is more
efficient in the radical generation at acidic pHs and can provide the unreacted chlorine as
residual disinfetant in distribution systems. However, the involvement of excessive chlorine
and RCS in the UV-chlorine process may complicate the formation of disinfection by-products
(DBPs). This thesis compares the DBP formation and cost-effectiveness of the UV-chlorine
and UV-H
2O
2 processes at the equivalent carbamazepine (CBZ)...[
Read more ]
The occurrences of pharmaceuticals and personal care products (PPCPs) and endocrine
disrupting compounds (EDCs) in drinking water have raised increasing concerns. Recently, the
UV-chlorine process, which generates HO
• and reactive chlorine species (RCS) (i.e. Cl
• and
Cl
2•-) is being considered as an emerging alternative to the UV-H
2O
2 process because it is more
efficient in the radical generation at acidic pHs and can provide the unreacted chlorine as
residual disinfetant in distribution systems. However, the involvement of excessive chlorine
and RCS in the UV-chlorine process may complicate the formation of disinfection by-products
(DBPs). This thesis compares the DBP formation and cost-effectiveness of the UV-chlorine
and UV-H
2O
2 processes at the equivalent carbamazepine (CBZ) and atrazine (ATZ) removal.
The UV-chlorine process was more efficient than the UV-H
2O
2 process in the CBZ removal
because of the significant contribution of RCS in addition to that of HO
• and a lower oxidant
dosage required for an equivalent CBZ removal. After the 90% CBZ removal and subsequent
chlorination for over 1 d, the yields of DBPs including chloroform (TCM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), chlorl hydrate (CH), dichloroacetonitrile (DCAN) and
trichloropropanone (TCP) from natural organic matter (NOM) in the two processes were
comparable, likely attributable to the equivalent formation of DBP precursors after the radical
exposure. Increasing pH increased the chlorine dosage required for 90%-CBZ removal in the
UV-chlorine process, but the 1-d DBP formation in the two processes remained comparable.
The presence of NO
3¯ and HCO
3¯ hardly affected the DBP formation in the two processes, while
the presence of Br
¯ shifted the chlorinated DBPs into the brominated ones. On the other hand,
the ATZ removal, which was mainly achieved via the HO
• oxidantion and UV irradiation,
required higher UV and oxidant doses in both processes, resulting in much higher yields of
DBPs than those observed after the CBZ removal. In addition, RCS, which was nearly inert to
ATZ but alterated the characteristics of NOM, was probably responsible for the higher DBP
formation in the UV-chlorine process. At pH 6.0, the UV-chlorine process presented superior
cost-effectiveness in the removal of CBZ and ATZ, mainly because of the chemical saving for
the quenching of the unreacted oxidant. These findings demonstrate that the UV-chlorine
process is a promising alternative to the UV-H
2O
2 process for the removal of micropollutants
reactive to RCS.
Post a Comment