The UV/Clprocess is commonly used to achieve a multiple-barrier disinfection and maintain residuals. The study chose methylamine as a precursor to study the formation of hightoxic halonitromethanes(HNMs) in the presen...The UV/Clprocess is commonly used to achieve a multiple-barrier disinfection and maintain residuals. The study chose methylamine as a precursor to study the formation of hightoxic halonitromethanes(HNMs) in the presence of bromide ions(Br-) during UV/Cldisinfection. The maximum yield of HNMs increased first and then decreased with increasing concentration of Br-. An excessively high concentration of Br-induced the maximum yield of HNMs in advance. The maximum bromine incorporation factor(BIF) increased, while the maximum bromine utilization factor(BUF) decreased with the increase of Br-concentration. The maximum yield of HNMs decreased as p H value increased from 6.0 to 8.0 due to the deprotonation process. The BUF value remained relatively higher under an acidic condition, while p H value had no evident influence on the BIF value. The maximum yield of HNMs and value of BUF maximized at a Cl:Br-ratio of 12.5, whereas the BIF value remained relatively higher at low Cl:Br-ratios(2.5 and 5). The amino group in methylamine was first halogenated, and then released into solution as inorganic nitrogen by the rupture of C-N bond or transformed to nitro group by oxidation and elimination pathways. The maximum yield of HNMs in real waters was higher than that in pure water due to the high content of dissolved organic carbon. Two real waters were sampled to verify the law of HNMs formation. This study helps to understand the HNMs formation(especially brominated species) when the UV/Clprocess is adopted as a disinfection technique.展开更多
Light emitting diode(LED-UV)/chlorine disinfection can replace UV/chlorine disinfection in wastewater treatment plants and water supply plants.Halonitromethanes(HNMs)are a class of novel nitrogenous disinfection by-pr...Light emitting diode(LED-UV)/chlorine disinfection can replace UV/chlorine disinfection in wastewater treatment plants and water supply plants.Halonitromethanes(HNMs)are a class of novel nitrogenous disinfection by-products,which are characterized by higher cytotoxicity and genotoxicity than regulated disinfection by-products.Herein,the impact factors and pathways of HNMs formation from aspartic acid(ASP)were investigated during LED-UV_(265)/chlorine disinfection.The results showed that three types of chlorinated-HNMs(Cl-HNMs)were found during LED-UV265/chlorine disinfection,and their concentrations increased first and then declined as the reaction progressed.Cl-HNMs yields increased with increasing LED-UV_(265)intensity,free chlorine dosage,and ASP concentration,which declined with increasing pH(6.0–8.0).Meantime,the important impact of the coexisting ions contained in water matrices on HNMs formation from ASP was observed during LED-UV_(265)/chlorine disinfection.It was found that copper ions(Cu^(2+))promoted Cl-HNMs formation.Furthermore,when bromide(Br–)appeared during LED-UV265/chlorine disinfection,nine types of HNMs were detected simultaneously.Moreover,Br–not only converted Cl-HNMs toward brominated(chlorinated)-HNMs and brominated-HNMs but also showed a marked effect on HNMs concentrations and species.Subsequently,the possible pathways of HNMs formation from ASP were proposed during LED-UV_(265)/chlorine disinfection.At last,it was proved that the formation trends of HNMs obtained in the real waters were similar to those in simulated waters.This work elaborated on the influence factors and pathways of HNMs formation,which is conducive to controlling the HNMs produced during LED-UV_(265)/chlorine disinfection.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 22076023 , 21677032 and 51808496)。
文摘The UV/Clprocess is commonly used to achieve a multiple-barrier disinfection and maintain residuals. The study chose methylamine as a precursor to study the formation of hightoxic halonitromethanes(HNMs) in the presence of bromide ions(Br-) during UV/Cldisinfection. The maximum yield of HNMs increased first and then decreased with increasing concentration of Br-. An excessively high concentration of Br-induced the maximum yield of HNMs in advance. The maximum bromine incorporation factor(BIF) increased, while the maximum bromine utilization factor(BUF) decreased with the increase of Br-concentration. The maximum yield of HNMs decreased as p H value increased from 6.0 to 8.0 due to the deprotonation process. The BUF value remained relatively higher under an acidic condition, while p H value had no evident influence on the BIF value. The maximum yield of HNMs and value of BUF maximized at a Cl:Br-ratio of 12.5, whereas the BIF value remained relatively higher at low Cl:Br-ratios(2.5 and 5). The amino group in methylamine was first halogenated, and then released into solution as inorganic nitrogen by the rupture of C-N bond or transformed to nitro group by oxidation and elimination pathways. The maximum yield of HNMs in real waters was higher than that in pure water due to the high content of dissolved organic carbon. Two real waters were sampled to verify the law of HNMs formation. This study helps to understand the HNMs formation(especially brominated species) when the UV/Clprocess is adopted as a disinfection technique.
基金funded by National Natural Science Foundation of China(Nos.22076023 and 21677032)the Fundamental Research Funds for the Central Universities(China)(Nos.2242022k30030 and 2242022k30031).
文摘Light emitting diode(LED-UV)/chlorine disinfection can replace UV/chlorine disinfection in wastewater treatment plants and water supply plants.Halonitromethanes(HNMs)are a class of novel nitrogenous disinfection by-products,which are characterized by higher cytotoxicity and genotoxicity than regulated disinfection by-products.Herein,the impact factors and pathways of HNMs formation from aspartic acid(ASP)were investigated during LED-UV_(265)/chlorine disinfection.The results showed that three types of chlorinated-HNMs(Cl-HNMs)were found during LED-UV265/chlorine disinfection,and their concentrations increased first and then declined as the reaction progressed.Cl-HNMs yields increased with increasing LED-UV_(265)intensity,free chlorine dosage,and ASP concentration,which declined with increasing pH(6.0–8.0).Meantime,the important impact of the coexisting ions contained in water matrices on HNMs formation from ASP was observed during LED-UV_(265)/chlorine disinfection.It was found that copper ions(Cu^(2+))promoted Cl-HNMs formation.Furthermore,when bromide(Br–)appeared during LED-UV265/chlorine disinfection,nine types of HNMs were detected simultaneously.Moreover,Br–not only converted Cl-HNMs toward brominated(chlorinated)-HNMs and brominated-HNMs but also showed a marked effect on HNMs concentrations and species.Subsequently,the possible pathways of HNMs formation from ASP were proposed during LED-UV_(265)/chlorine disinfection.At last,it was proved that the formation trends of HNMs obtained in the real waters were similar to those in simulated waters.This work elaborated on the influence factors and pathways of HNMs formation,which is conducive to controlling the HNMs produced during LED-UV_(265)/chlorine disinfection.
