Ying Cao,Wei Qiu,Yumeng Zhao,Juan Li,Jin Jiang,Yi Yang,Su-Yan Pang,Guanqi Liu
The frequent detection of chloramphenicol (CAP) in wastewater and surface water gives rise to concerns on its fatal myelosuppression and aplastic anemia. Recently, the combination of ozone and peroxymonosulfate (O 3 /PMS) has received wide attention in removing pollutants due to the multiple oxidants (i.e., O 3 , hydroxyl radicals ( OH) and sulfate radicals (SO 4 − )) existed therein. This study showed that O 3 /PMS could effectively degrade CAP under various conditions. The second-order rate constant of CAP with O 3 , OH and SO 4 − was 0.291 ± 0.005 , 2.27 ( ± 0.03 ) × 10 9 and 1.02 ± 0.02 × 10 8 M - 1 s - 1 , respectively. The degradation efficiency of CAP was significantly enhanced as PMS concentration or pH increased. Bicarbonate (HCO 3 − ) at concentration of 5 mM slightly inhibited CAP degradation at pH 7. Chloride (Cl − ) at concentration of 0.5 mM enhanced CAP removal at pH 7, while this enhancement gradually weakened as Cl − concentration further increased. The degradation efficiency of CAP first increased with increasing natural organic matter (NOM) concentrations (0.1–0.3 mg/L), while it was completely suppressed at higher NOM concentrations (0.5 mg/L). Four degradation products in total of CAP were identified in O 3 -based processes (i.e., O 3 , O 3 /TBA, O 3 /H 2 O 2 , O 3 /PMS and O 3 /PMS/ tert -butyl alcohol (TBA) systems. Besides, these transformation products by OH, SO 4 − and/or O 3 were also distinguished. Finally, the impact of O 3 /PMS pre-oxidation on the formation of dichloroacetamide (DCAcAm) from CAP during post-chlorination process was investigated. Compared with the traditional O 3 and O 3 /H 2 O 2 processes, O 3 /PMS pre-oxidation generally led to the least generation of DCAcAm under similar conditions, where SO 4 − rather than OH was conducive to relieve the formation of DCAcAm. Moreover, the presence of NOM obviously alleviated the formation of DCAcAm by O 3 /PMS pre-oxidation.
Xinran Zhang,Pengfei Ren,Jianhua Zhou,Junyi Li,Zhenxing Li,Ding Wang
This study investigated the formation of disinfection byproducts (DBPs) from a real ammonia-polluted source water treated by a pilot-scale ultraviolet (UV)/chlorine process with subsequent post-chlorination. The experimental results indicated that UV/chlorine treatment enhanced the formation of trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitriles (HANs) in post-chlorination, compared to UV or chlorine applied alone under parallel experimental conditions. DBP formation was observed to depend on pH values, chlorine doses, and reaction times. THM formation was higher at pH 9.0 than pH 6.0, while HAAs and HANs were produced more readily at pH 6.0 rather than 9.0. A higher chlorine dose led to a higher amount of DBPs formed after the treatment of UV/chlorine followed by post-chlorination. The concentration of DBPs increased with the UV/chlorine treatment time increasing from 2 to 15 s and then presented a decrease trend with the reaction time prolonging to 30 s. In addition, changes in natural organic matter (NOM) properties were evaluated using three-dimensional fluorescence spectra and parallel factor analysis (PARAFAC) UV/chlorine treatment effectively destroyed humic-like and tyrosine-like components in waters with the maximum fluorescence intensity ( FI m a x ) reduced by 51.4% and 64.6%, respectively, compared to the raw water sample. The decrease of fluorescence of waters exhibited a positive correlation with the formation of DBP-FP in UV/chlorine treatment. Overall, DBP formation from the ammonia-polluted source water caused by UV/chlorine treatment could be managed by carefully determining chlorine doses and contact times to be used in the UV/chlorine process.
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