Water samples collected from early March 2001 to the end of April 2002 at the branch of Pearl River around the Guangzhou City were analyzed for its micro-polluted characteristics. The coagulation behavior of polyalumi...Water samples collected from early March 2001 to the end of April 2002 at the branch of Pearl River around the Guangzhou City were analyzed for its micro-polluted characteristics. The coagulation behavior of polyaluminum chlorides(PACls) was then examined focusing on the effect of primary water quality and speciation distribution. The results showed that PACls exhibit better coagulation efficiency than alum in accordance with the different speciation. The turbidity removal property of PACls is evidently better than alum at low dosage. While in neutral zone(about 6.5—7.5), the turbidity removal of PACls decreases owing to the restabilization of particles at higher dosage. The organic matters in raw water exhibit marked influence on coagulation. In acidic zone, organic matters complex with polymer species and promote the formation of flocs. With an increase in pH, the complexation of organics with polymer species gradually decreases, and the removal of organics mainly depends on adsorption. The effect is evidently improved with the raise of B value.展开更多
Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the ran...Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al（Ⅲ） concentration from 0.01 to 2.0 mol/L with the B （OH/Al ratio） value from 1.0 to 2.5 by forced hydrolysis of AICl3. The samples were characterized by ferron assay, pH and 27^Al NMR. It was shown that the Al（Ⅲ） concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb （or Al13） decreased and Al0 increased with increase of total Al（Ⅲ） concentration. Under the condition of Al（Ⅲ） 2.0 reel/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evoIved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.展开更多
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
Aging of polyaluminum chloride(PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance.The goal of this study was to investigate Al species transformation through long-te...Aging of polyaluminum chloride(PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance.The goal of this study was to investigate Al species transformation through long-term aging and its impact on coagulation performance.Two kinds of commercial coagulants(PACl-1 and PACl-2) were stored for in-situ aging tests in six months to evaluate Al species variation with time and the performance of coagulation with natural turbid waters.The results showed that CaSO4 precipitation easily occur in a commercial PACl coagulant with time as it contains SO4^2- and Ca^2+.It also activates the precipitation of gibbsite Al(OH)3 in PACl with aging.Through 180 days aging,both monomeric Al(Ala) and polymeric Al(Alb) substantially transform into colloidal Al(Alc) and precipitated for both PACl coagulants.At low turbidity(10 NTU),PACl-1 has a superior turbidity reduction rate than PACl-2,while PACl-2 performs a little better turbidity re duction at high turbidity(1000 NTU) regardless of aging time.With aging time,an obvious decrease in turbidity reduction for PACl-1 coagulation is observed at low turbidity of 10 NTU,while the improvement in turbidity reduction for PACl-2 coagulation by enhanced sweep flocculation can be achieved as Alb mostly transform into Alc after 150 days aging.It is concluded that dominant in-situ formed Alc after a long time hydrolysis can improve PACl coagulation efficiency in turbidity reduction by enhanced sweep flocculation,especially for low turbidity water,but the increase in preformed Alc in PACl would worsen particle destabilization after aging.展开更多
This article discusses the influential factors on Al 13 separation considering the interaction of sulfate with various polyaluminum chloride(PACl). The experimental results showed that the basicity( B =[OH]/[Al...This article discusses the influential factors on Al 13 separation considering the interaction of sulfate with various polyaluminum chloride(PACl). The experimental results showed that the basicity( B =[OH]/[Al]), the concentration of PACl and Al/SO 4 ratio exhibited significant roles in the PACl sulfate reaction. It indicated that different species in various PACl underwent different reaction pathway with sulfate. The Al c, colloidal species, formed precipitation quickly with sulfate, while Al b, oligomers and polymers, underwent slow crystallization. And Al a, monomers, reacted with sulfate to form soluble complexes. The kinetic difference of reaction made it possible to realize the separation of Al b and further purification. The decrease of Al a resulted in the limit of ferron method was also mentioned.展开更多
文摘Water samples collected from early March 2001 to the end of April 2002 at the branch of Pearl River around the Guangzhou City were analyzed for its micro-polluted characteristics. The coagulation behavior of polyaluminum chlorides(PACls) was then examined focusing on the effect of primary water quality and speciation distribution. The results showed that PACls exhibit better coagulation efficiency than alum in accordance with the different speciation. The turbidity removal property of PACls is evidently better than alum at low dosage. While in neutral zone(about 6.5—7.5), the turbidity removal of PACls decreases owing to the restabilization of particles at higher dosage. The organic matters in raw water exhibit marked influence on coagulation. In acidic zone, organic matters complex with polymer species and promote the formation of flocs. With an increase in pH, the complexation of organics with polymer species gradually decreases, and the removal of organics mainly depends on adsorption. The effect is evidently improved with the raise of B value.
基金The Hi-Tech Research and Development Program (863) of China (No. 2002AA601290) and the National Natural ScienceFoundation of China (No. 20247012 50578155)
文摘Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al（Ⅲ） concentration from 0.01 to 2.0 mol/L with the B （OH/Al ratio） value from 1.0 to 2.5 by forced hydrolysis of AICl3. The samples were characterized by ferron assay, pH and 27^Al NMR. It was shown that the Al（Ⅲ） concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb （or Al13） decreased and Al0 increased with increase of total Al（Ⅲ） concentration. Under the condition of Al（Ⅲ） 2.0 reel/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evoIved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.
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.
基金the assistances from Taiwan Water Corporation in sampling as well as the financial support。
文摘Aging of polyaluminum chloride(PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance.The goal of this study was to investigate Al species transformation through long-term aging and its impact on coagulation performance.Two kinds of commercial coagulants(PACl-1 and PACl-2) were stored for in-situ aging tests in six months to evaluate Al species variation with time and the performance of coagulation with natural turbid waters.The results showed that CaSO4 precipitation easily occur in a commercial PACl coagulant with time as it contains SO4^2- and Ca^2+.It also activates the precipitation of gibbsite Al(OH)3 in PACl with aging.Through 180 days aging,both monomeric Al(Ala) and polymeric Al(Alb) substantially transform into colloidal Al(Alc) and precipitated for both PACl coagulants.At low turbidity(10 NTU),PACl-1 has a superior turbidity reduction rate than PACl-2,while PACl-2 performs a little better turbidity re duction at high turbidity(1000 NTU) regardless of aging time.With aging time,an obvious decrease in turbidity reduction for PACl-1 coagulation is observed at low turbidity of 10 NTU,while the improvement in turbidity reduction for PACl-2 coagulation by enhanced sweep flocculation can be achieved as Alb mostly transform into Alc after 150 days aging.It is concluded that dominant in-situ formed Alc after a long time hydrolysis can improve PACl coagulation efficiency in turbidity reduction by enhanced sweep flocculation,especially for low turbidity water,but the increase in preformed Alc in PACl would worsen particle destabilization after aging.
文摘This article discusses the influential factors on Al 13 separation considering the interaction of sulfate with various polyaluminum chloride(PACl). The experimental results showed that the basicity( B =[OH]/[Al]), the concentration of PACl and Al/SO 4 ratio exhibited significant roles in the PACl sulfate reaction. It indicated that different species in various PACl underwent different reaction pathway with sulfate. The Al c, colloidal species, formed precipitation quickly with sulfate, while Al b, oligomers and polymers, underwent slow crystallization. And Al a, monomers, reacted with sulfate to form soluble complexes. The kinetic difference of reaction made it possible to realize the separation of Al b and further purification. The decrease of Al a resulted in the limit of ferron method was also mentioned.
