The UV/Cl
2 process was investigated for its efficiency to destruct DEET at various conditions. The formation of total organic halogens (TOX) and genotoxicity from natural organic matter (NOM) during the UV/Cl
2 process and the following post-chlorination was assessed and compared with that of the UV/H
2O
2 process at similar radical exposure. Effect of ammonia on kinetics of
nitrobenzene (NB) and benzoic acid (BA) degradation and formation of disinfection byproducts (DBPs) from NOM during the UV/Cl
2 process was investigated. The correlations between NOM change and formation of DBPs during the UV/Cl
2 process at various conditions were investigated.
The reactive chlorine species (RCS) were found to react with DEET at a rate constant similar
to that of HO•. The pseudo first-order rate of D...[
Read more ]
The UV/Cl
2 process was investigated for its efficiency to destruct DEET at various conditions. The formation of total organic halogens (TOX) and genotoxicity from natural organic matter (NOM) during the UV/Cl
2 process and the following post-chlorination was assessed and compared with that of the UV/H
2O
2 process at similar radical exposure. Effect of ammonia on kinetics of
nitrobenzene (NB) and benzoic acid (BA) degradation and formation of disinfection byproducts (DBPs) from NOM during the UV/Cl
2 process was investigated. The correlations between NOM change and formation of DBPs during the UV/Cl
2 process at various conditions were investigated.
The reactive chlorine species (RCS) were found to react with DEET at a rate constant similar
to that of HO•. The pseudo first-order rate of DEET degradation by the UV/Cl
2 process was kinetic model based on the steady-state concentration of radicals. During
degradation of DEET by the UV/Cl
2 process, six known DBPs, trichloromethane (TCM), chloral
hydrate (CH), 1,1-dichloro-2-propanone (DCP), 1,1,1-trichloro-2-propanone (TCP),
dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were detected which comprised
13.5% of total organic chlorine (TOCl). The UV/Cl
2 process enhanced the yields of known DBPs
and TOCl from DEET during the post-chlorination compared to the UV/H
2O
2 process.
The TOCl formation from NOM after 1 day of post-chlorination following the UV/Cl
2 process
was similar to that following the UV/H
2O
2 process with similar radical exposure. Higher radical
exposure led to the formation of higher amounts of DBP precursors in both the UV/Cl
2 and
UV/H
2O
2 processes. Strong linear correlation was observed between the concentrations of TOCl
and genotoxicity in the samples treated by chlorination, UV/Cl
2, UV/Cl
2 followed by post-chlorination,
and UV/H
2O
2 followed by post-chlorination.
The presence of ammonia significantly affected the degradation of NB and BA and formation
of DBPs from NOM by the UV/Cl
2 process. Breakpoint chlorination reactions generated reactive
species (R
brk) which contributed more to the degradation of BA and NB than did the radicals
formed from photolysis of chlor(am)ine species (R
ph). Higher initial ammonia and chlorine
concentrations, which led to the same residual chlorine after the breakpoint chlorination reactions,
generated more R
brk. However, increasing initial chlorine concentrations in the presence of certain
amount of ammonia decreased the contribution of R
brk to the degradation of NB and BA and
increased that of R
ph.
UV irradiation during the breakpoint chlorination (the UV/breakpoint chlorination) increased
the DBP formation compared to the breakpoint chlorination in the dark at different initial ammonia
and chlorine concentrations and different pHs. R
brk was found to significantly contribute to the
formation of dichloroacetonitrile (DCAN). Increasing pHs increased the formation of DBPs during
both the UV/breakpoint chlorination and breakpoint chlorination in the dark. The cumulative
normalized excitation-emission matrix (EEM) areas at specific regions obtained from fluorescence
spectroscopy correlated linearly with yields of DCAN and TCP.
Post a Comment