Ozone plays an important role as a disinfectant and oxidant in potable water treatment practice and is increasingly being used as a pre-oxidant before coagulation. The purpose of this study is to obtain insight into t...Ozone plays an important role as a disinfectant and oxidant in potable water treatment practice and is increasingly being used as a pre-oxidant before coagulation. The purpose of this study is to obtain insight into the mechanisms that are operative in pre-ozonized coagulation. Effects ofpre-ozonation on organic matter removal during coagulation with IPF-PAC1 were investigated by using PDA （photometric disperse analysis）, apparent molecular weight distribution and chemical fractionation. The dynamic formation of flocs during coagulation process was detected. Changes of aquatic organic matter （AOM） structure resulted from the influence of pre-ozonation were evaluated. Results show that dosage of O3 and characteristics of AOM are two of the major factors influencing the performance of O3 on coagulation. No significant coagulation-aid effect of O3 was observed for all experiments using either A1C13 or PAC1. On the contrary, with the application of pre-ozonation, the coagulation efficiency of A1C13 was significantly deteriorated, reflected by the retardation of floc formation, and the removal decreases of turbidity, DOC, and UV254. However, if PACl was used instead of AlCl3, the adverse effects of pre-ozonation were mitigated obviously, particularly when the O3 dosage was less than 0.69 （mg O3/mg TOC）. The difference between removals of UV254, and DOC indicated that pre-ozonation greatly changed the molecular structure of AOM, but its capability of mineralization was not remarkable. Only 5% or so DOC was removed by pre-ozonation at 0.6--0.8 mg/L alone. Fractionation results showed that the organic products of pre-ozonation exhibited lower molecular weight and more hydrophilicity, which impaired the removal of DOC in the following coagulation process.展开更多
Because the natural organic matters (NOMs) and proteins are the principal foulants of microfiltration membranes in drinking water, the primary aim of this paper is to obtain a better understanding of the interactions ...Because the natural organic matters (NOMs) and proteins are the principal foulants of microfiltration membranes in drinking water, the primary aim of this paper is to obtain a better understanding of the interactions between those foulants and the microfiltration membrane from a novel view of coagulation. Based on reviewed literature and our own analysis, the authors consider that the behaviors of NOMs in the fouling of microfiltration membrane are like a form of crystal growth, and we recognize that the extent of the membrane hydrophobicity plays an essential role in NOMs fouling. However, proteins’ fouling is more affected by intermolecular interaction. Additionally, the effect of membrane surface chemistry is not as essential as it is in the situation of NOMs.展开更多
UV/chlorine process,as an emerging advanced oxidation process(AOP),was effective for removing micro-pollutants via various reactive radicals,but it also led to the changes of natural organic matter(NOM)and formation o...UV/chlorine process,as an emerging advanced oxidation process(AOP),was effective for removing micro-pollutants via various reactive radicals,but it also led to the changes of natural organic matter(NOM)and formation of disinfection byproducts(DBPs).By using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS),the transformation of Suwannee River NOM(SRNOM)and the formation of chlorinated DBPs(Cl-DBPs)in the UV/chlorine AOP and subsequent post-chlorination were tracked and compared with dark chlorination.In comparison to dark chlorination,the involvement of Cl O·,Cl·,and HO·in the UV/chlorine AOP promoted the transformation of NOM by removing the compounds owning higher aromaticity(AI mod)value and DBE(double-bond equivalence)/C ratio and causing the decrease in the proportion of aromatic compounds.Meanwhile,more compounds which contained only C,H,O,N atoms(CHON)were observed after the UV/chlorine AOP compared with dark chlorination via photolysis of organic chloramines or radical reactions.A total of 833 compounds contained C,H,O,Cl atoms(CHOCl)were observed after the UV/chlorine AOP,higher than 789 CHOCl compounds in dark chlorination,and one-chlorine-containing components were the dominant species.The different products from chlorine substitution reactions(SR)and addition reactions(AR)suggested that SR often occurred in the precursors owning higher H/C ratio and AR often occurred in the precursors owning higher aromaticity.Post-chlorination further caused the cleavages of NOM structures into small molecular weight compounds,removed CHON compounds and enhanced the formation of Cl-DBPs.The results provide information about NOM transformation and Cl-DBPs formation at molecular levels in the UV/chlorine AOP.展开更多
Introduction Natural organic matter（NOM）present in source water has significant impact on water treatment processes and on the quality of drinking water.NOM is a complex mixture of diverse groups of organic compound...Introduction Natural organic matter（NOM）present in source water has significant impact on water treatment processes and on the quality of drinking water.NOM is a complex mixture of diverse groups of organic compounds,humic and fulvic acids,proteins,peptides,carbohydrates,and heterogeneous materials展开更多
To understand the water purification mechanism of potassium permanganate as a coagulation-aid during the preoxidation process,the microtopography of its reductive products,the newly formed hydrous manganese dioxide an...To understand the water purification mechanism of potassium permanganate as a coagulation-aid during the preoxidation process,the microtopography of its reductive products,the newly formed hydrous manganese dioxide and the aged hydrous manganese dioxide,was investigated.The morphology of natural organic matter(NOM)adsorbed by the newly formed hydrous manganese dioxide was also com-pared with that of NOM alone.By using the tapping mode atomic force microscopy(AFM),the observation results show that the newly formed hydrous manganese dioxide possess a perforated sheet(with a thickness of 0-1.75 nm)as well as some spherical particle structures compared with the hydrous manganese dioxide with 2 h aging time,which demonstrated that the newly formed hydrous manganese dioxide had a large surface area and adsorption capacity.When 1 mmol/L newly formed hydrous manganese dioxide was added,the micro-topography of NOM molecules shifted from a loosely dis-persed pancake shape(with adsorption height of 5-8.5 nm)to a densely dispersed and uniform spherical structure.These results provide a valid proof that it is the perfect adsorption capability of the newly formed hydrous manganese dioxide that might result in the coagulation aid effect of potassium permanganate preoxidation.展开更多
Resin adsorption technique with XAD-8 and XAD-4 was used to characterize the raw water from Erlong reservoir in Jilin province of China. The NOM chemical composition sequences of four organic fractions in the raw wate...Resin adsorption technique with XAD-8 and XAD-4 was used to characterize the raw water from Erlong reservoir in Jilin province of China. The NOM chemical composition sequences of four organic fractions in the raw water, from high to low, are fulvic acid （FA） fraction, hydrophilic non-acid （HPINA） fraction, hydrophilic acid （HPIA） fraction, and humic acid （HA） fraction. Experimental results show that FA is the main precursor of THMFP among the four organic fractions. However, HA or hydrophobie acid exhibits the highest chlorination activity in forming THMs. It is also found that the value of FI/DOC or SUVA and the specific THMFP have better positive correlation. It is implied that certain source water has unique nature of NOM and DBPs.展开更多
基金The Hi-Tech Research and Development Program (863) of China (No. 2002AA601120)
文摘Ozone plays an important role as a disinfectant and oxidant in potable water treatment practice and is increasingly being used as a pre-oxidant before coagulation. The purpose of this study is to obtain insight into the mechanisms that are operative in pre-ozonized coagulation. Effects ofpre-ozonation on organic matter removal during coagulation with IPF-PAC1 were investigated by using PDA （photometric disperse analysis）, apparent molecular weight distribution and chemical fractionation. The dynamic formation of flocs during coagulation process was detected. Changes of aquatic organic matter （AOM） structure resulted from the influence of pre-ozonation were evaluated. Results show that dosage of O3 and characteristics of AOM are two of the major factors influencing the performance of O3 on coagulation. No significant coagulation-aid effect of O3 was observed for all experiments using either A1C13 or PAC1. On the contrary, with the application of pre-ozonation, the coagulation efficiency of A1C13 was significantly deteriorated, reflected by the retardation of floc formation, and the removal decreases of turbidity, DOC, and UV254. However, if PACl was used instead of AlCl3, the adverse effects of pre-ozonation were mitigated obviously, particularly when the O3 dosage was less than 0.69 （mg O3/mg TOC）. The difference between removals of UV254, and DOC indicated that pre-ozonation greatly changed the molecular structure of AOM, but its capability of mineralization was not remarkable. Only 5% or so DOC was removed by pre-ozonation at 0.6--0.8 mg/L alone. Fractionation results showed that the organic products of pre-ozonation exhibited lower molecular weight and more hydrophilicity, which impaired the removal of DOC in the following coagulation process.
文摘Because the natural organic matters (NOMs) and proteins are the principal foulants of microfiltration membranes in drinking water, the primary aim of this paper is to obtain a better understanding of the interactions between those foulants and the microfiltration membrane from a novel view of coagulation. Based on reviewed literature and our own analysis, the authors consider that the behaviors of NOMs in the fouling of microfiltration membrane are like a form of crystal growth, and we recognize that the extent of the membrane hydrophobicity plays an essential role in NOMs fouling. However, proteins’ fouling is more affected by intermolecular interaction. Additionally, the effect of membrane surface chemistry is not as essential as it is in the situation of NOMs.
基金supported by the National Key Research and Development Program of China(No.2017YFE0133200)the National Natural Science Foundation of China(Nos.21876210 and 21806173)+1 种基金the Guangdong Provincial Science and Technology Planning Projects(No.2019A050503006)Hong Kong RGC(Nos.16206416 and T21-604/19-R)。
文摘UV/chlorine process,as an emerging advanced oxidation process(AOP),was effective for removing micro-pollutants via various reactive radicals,but it also led to the changes of natural organic matter(NOM)and formation of disinfection byproducts(DBPs).By using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS),the transformation of Suwannee River NOM(SRNOM)and the formation of chlorinated DBPs(Cl-DBPs)in the UV/chlorine AOP and subsequent post-chlorination were tracked and compared with dark chlorination.In comparison to dark chlorination,the involvement of Cl O·,Cl·,and HO·in the UV/chlorine AOP promoted the transformation of NOM by removing the compounds owning higher aromaticity(AI mod)value and DBE(double-bond equivalence)/C ratio and causing the decrease in the proportion of aromatic compounds.Meanwhile,more compounds which contained only C,H,O,N atoms(CHON)were observed after the UV/chlorine AOP compared with dark chlorination via photolysis of organic chloramines or radical reactions.A total of 833 compounds contained C,H,O,Cl atoms(CHOCl)were observed after the UV/chlorine AOP,higher than 789 CHOCl compounds in dark chlorination,and one-chlorine-containing components were the dominant species.The different products from chlorine substitution reactions(SR)and addition reactions(AR)suggested that SR often occurred in the precursors owning higher H/C ratio and AR often occurred in the precursors owning higher aromaticity.Post-chlorination further caused the cleavages of NOM structures into small molecular weight compounds,removed CHON compounds and enhanced the formation of Cl-DBPs.The results provide information about NOM transformation and Cl-DBPs formation at molecular levels in the UV/chlorine AOP.
基金supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)the National Natural Science Foundation of China,Alberta Innovates,and Alberta Health
文摘Introduction Natural organic matter（NOM）present in source water has significant impact on water treatment processes and on the quality of drinking water.NOM is a complex mixture of diverse groups of organic compounds,humic and fulvic acids,proteins,peptides,carbohydrates,and heterogeneous materials
基金This work was supported by the National Key Basic Research and Development(973)Program of China(Grant No.2004CB418505)。
文摘To understand the water purification mechanism of potassium permanganate as a coagulation-aid during the preoxidation process,the microtopography of its reductive products,the newly formed hydrous manganese dioxide and the aged hydrous manganese dioxide,was investigated.The morphology of natural organic matter(NOM)adsorbed by the newly formed hydrous manganese dioxide was also com-pared with that of NOM alone.By using the tapping mode atomic force microscopy(AFM),the observation results show that the newly formed hydrous manganese dioxide possess a perforated sheet(with a thickness of 0-1.75 nm)as well as some spherical particle structures compared with the hydrous manganese dioxide with 2 h aging time,which demonstrated that the newly formed hydrous manganese dioxide had a large surface area and adsorption capacity.When 1 mmol/L newly formed hydrous manganese dioxide was added,the micro-topography of NOM molecules shifted from a loosely dis-persed pancake shape(with adsorption height of 5-8.5 nm)to a densely dispersed and uniform spherical structure.These results provide a valid proof that it is the perfect adsorption capability of the newly formed hydrous manganese dioxide that might result in the coagulation aid effect of potassium permanganate preoxidation.
基金Sponsored by the Key Project of Jilin Provincial Science &Technology Program (Grant No.20070409)
文摘Resin adsorption technique with XAD-8 and XAD-4 was used to characterize the raw water from Erlong reservoir in Jilin province of China. The NOM chemical composition sequences of four organic fractions in the raw water, from high to low, are fulvic acid （FA） fraction, hydrophilic non-acid （HPINA） fraction, hydrophilic acid （HPIA） fraction, and humic acid （HA） fraction. Experimental results show that FA is the main precursor of THMFP among the four organic fractions. However, HA or hydrophobie acid exhibits the highest chlorination activity in forming THMs. It is also found that the value of FI/DOC or SUVA and the specific THMFP have better positive correlation. It is implied that certain source water has unique nature of NOM and DBPs.
