Kathon(CMI-MI),a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one(CMI)and 2-methyl-4-isothiazolin-3-one(MI),was extensively used in industry as a nonoxidizing biocide or disinfectant.However,it would show adverse eff...Kathon(CMI-MI),a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one(CMI)and 2-methyl-4-isothiazolin-3-one(MI),was extensively used in industry as a nonoxidizing biocide or disinfectant.However,it would show adverse effects on aquatic life when it is discharged into surface water.In this study,the removal performance,parameter influence,degradation products and enhancement of subsequent biodegradation of CMI-MI in UV/H_(2)O_(2)system were systematically investigated.The degradation rate of CMI-MI could reach 90%under UV irradiation for 20 min when the dosage of H_(2)O_(2)was 0.3 mmol·L^(–1).The DOC(dissolved organic carbon)mineralization rate of CMI-MI could reach 35%under certain conditions([H_(2)O_(2)]=0.3 mmol·L^(–1),UV irradiation for 40 min).kobs was inversely proportional to the concentration of CMI-MI and proportional to the concentration of H_(2)O_(2).The degradation rate of CMIMI was almost unchanged in the pH range from 4 to 10.Except the presence of CO_(3)^(2-)inhibited the removal rate of CMI-MI,SO_(4)^(2-),Cl^(-),NO_(3)^(-),and NH_(4)^(+) did not interfere with the degradation of CMI-MI in the system.It was found that UV/H_(2)O_(2)system had lower energy consumption and more economic advantage compared with UV/PS system by comparing the EEO(electric energy per order)values under the same conditions.Two main organic products were identified,namely HCOOH and CH_(3)NH_(2).There’s also the formation of Cl^(-)and SO_(4)^(2-).After UV and UV/H_(2)O_(2)photolysis,the biochemical properties of CMI-MI solution were obviously improved,especially the UV/H_(2)O_(2)treatment effect was better,indicating that UV/H_(2)O_(2)technology is expected to combine with biotechnology to remove CMI-MI effectively and environmentally friendly from wastewater.展开更多
Residual H_(2)O_(2)from UV/H_(2)O_(2)treatment can be quenched by thiosulfate,bisulfite,and chlorine,but the kinetics of these reactions have not been reported under the full range of practical conditions.In this stud...Residual H_(2)O_(2)from UV/H_(2)O_(2)treatment can be quenched by thiosulfate,bisulfite,and chlorine,but the kinetics of these reactions have not been reported under the full range of practical conditions.In this study,the rates of H_(2)O_(2)quenching by these compounds were compared in different water matrices,temperatures,pH,and when using different forms of bisulfite and chlorine.In general,it was confirmed that thiosulfate would be too slow to serve as a quenching agent in most practical scenarios.At pH 7-8.5,chlorine tends to quench H_(2)O_(2)more than 20 times faster than bisulfite in the various conditions tested.An important observation was that in lightly-buffered water(e.g.,alkalinity of 20 mg/L as CaCO_(3)),the form of chlorine can have a large impact on quenching rate,with gaseous chlorine slowing the reaction due to its lowering of the pH,and hypochlorite having the opposite effect.These impacts will become less significant when water buffer capacity(i.e.,alkalinity)increases(e.g.,to 80 mg/L as CaCO_(3)).In addition,water temperature should be considered as the time required to quench H_(2)O_(2)by chlorine at 4℃is up to 3 times longer than at 20℃.展开更多
Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H_(2)O_(2)) have attracted much attention in recent years as advanced oxidation processes for water treatment.However,it is not all clear how these ...Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H_(2)O_(2)) have attracted much attention in recent years as advanced oxidation processes for water treatment.However,it is not all clear how these two methods affect the formation of cyanogen chloride(CNCl) in the subsequent water chlorination process.In this study,it was found that both UV/H_(2)O_(2)and UV/PS pre-oxidation promoted the formation of CNCl in six actual water samples collected from urban rivers.Glycine,uric acid,arginine and histidine were investigated as the model compounds to explore the effects of different methods on the production of CNCl.The results showed that compared with chlorination alone,pre-oxidation by UV/H_(2)O_(2)and UV/PS can reduce the production of CNCl for glycine and uric acid by up to 95%during post-chlorination process.However,they can greatly promote the formation of CNCl for arginine and histidine by up to 120-fold.In a more detailed investigation,pre-oxidation of histidine formed highly reactive intermediates to chlorine,leading to increased CNCl formation and chlorine consumption.The results showed that the precursors of CNCl was altered after pre-oxidation,and need to be re-evaluated.展开更多
基金support of experimental Instrument Platform of Shandong Taihe Water Treatment Technology Co.,LTD.
文摘Kathon(CMI-MI),a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one(CMI)and 2-methyl-4-isothiazolin-3-one(MI),was extensively used in industry as a nonoxidizing biocide or disinfectant.However,it would show adverse effects on aquatic life when it is discharged into surface water.In this study,the removal performance,parameter influence,degradation products and enhancement of subsequent biodegradation of CMI-MI in UV/H_(2)O_(2)system were systematically investigated.The degradation rate of CMI-MI could reach 90%under UV irradiation for 20 min when the dosage of H_(2)O_(2)was 0.3 mmol·L^(–1).The DOC(dissolved organic carbon)mineralization rate of CMI-MI could reach 35%under certain conditions([H_(2)O_(2)]=0.3 mmol·L^(–1),UV irradiation for 40 min).kobs was inversely proportional to the concentration of CMI-MI and proportional to the concentration of H_(2)O_(2).The degradation rate of CMIMI was almost unchanged in the pH range from 4 to 10.Except the presence of CO_(3)^(2-)inhibited the removal rate of CMI-MI,SO_(4)^(2-),Cl^(-),NO_(3)^(-),and NH_(4)^(+) did not interfere with the degradation of CMI-MI in the system.It was found that UV/H_(2)O_(2)system had lower energy consumption and more economic advantage compared with UV/PS system by comparing the EEO(electric energy per order)values under the same conditions.Two main organic products were identified,namely HCOOH and CH_(3)NH_(2).There’s also the formation of Cl^(-)and SO_(4)^(2-).After UV and UV/H_(2)O_(2)photolysis,the biochemical properties of CMI-MI solution were obviously improved,especially the UV/H_(2)O_(2)treatment effect was better,indicating that UV/H_(2)O_(2)technology is expected to combine with biotechnology to remove CMI-MI effectively and environmentally friendly from wastewater.
基金supported through the Natural Sciences and Engineering Grant CRDPJ-542302-2019,by AECOM and by the City of Toronto.
文摘Residual H_(2)O_(2)from UV/H_(2)O_(2)treatment can be quenched by thiosulfate,bisulfite,and chlorine,but the kinetics of these reactions have not been reported under the full range of practical conditions.In this study,the rates of H_(2)O_(2)quenching by these compounds were compared in different water matrices,temperatures,pH,and when using different forms of bisulfite and chlorine.In general,it was confirmed that thiosulfate would be too slow to serve as a quenching agent in most practical scenarios.At pH 7-8.5,chlorine tends to quench H_(2)O_(2)more than 20 times faster than bisulfite in the various conditions tested.An important observation was that in lightly-buffered water(e.g.,alkalinity of 20 mg/L as CaCO_(3)),the form of chlorine can have a large impact on quenching rate,with gaseous chlorine slowing the reaction due to its lowering of the pH,and hypochlorite having the opposite effect.These impacts will become less significant when water buffer capacity(i.e.,alkalinity)increases(e.g.,to 80 mg/L as CaCO_(3)).In addition,water temperature should be considered as the time required to quench H_(2)O_(2)by chlorine at 4℃is up to 3 times longer than at 20℃.
基金supported by the National Natural Science Foundation of China (No.22076217)the Henan Academy of Sciences 2021 Science and Technology Open Cooperation Project (No.210901007)。
文摘Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H_(2)O_(2)) have attracted much attention in recent years as advanced oxidation processes for water treatment.However,it is not all clear how these two methods affect the formation of cyanogen chloride(CNCl) in the subsequent water chlorination process.In this study,it was found that both UV/H_(2)O_(2)and UV/PS pre-oxidation promoted the formation of CNCl in six actual water samples collected from urban rivers.Glycine,uric acid,arginine and histidine were investigated as the model compounds to explore the effects of different methods on the production of CNCl.The results showed that compared with chlorination alone,pre-oxidation by UV/H_(2)O_(2)and UV/PS can reduce the production of CNCl for glycine and uric acid by up to 95%during post-chlorination process.However,they can greatly promote the formation of CNCl for arginine and histidine by up to 120-fold.In a more detailed investigation,pre-oxidation of histidine formed highly reactive intermediates to chlorine,leading to increased CNCl formation and chlorine consumption.The results showed that the precursors of CNCl was altered after pre-oxidation,and need to be re-evaluated.
