Two inorganic polymer coagulants,polyferric silicate sulphate(PFSS) and polyferric sulphate(PFS),were comparatively evaluated in the Yellow River water treatment.The removal efficiency of turbidity and UV254 were inve...Two inorganic polymer coagulants,polyferric silicate sulphate(PFSS) and polyferric sulphate(PFS),were comparatively evaluated in the Yellow River water treatment.The removal efficiency of turbidity and UV254 were investigated,and the zeta potential was measured.An online laser scatter instrument was used to determine the size distribution of flocs formed in the coagulation processes.Compared with PFS,PFSS forms flocs with higher growth rates and larger sizes.The formed flocs were exposed to a series of shear forces,and the floc strength was measured from the relationship between the applied shear speed and the resulting floc size.The flocs formed by PFSS had a higher strength.The floc breakage(expressed as breakage factor,Bf) and re-growth ability(expressed as breakage factor,Rf) under different shear forces and different shear periods were investigated,and it was found that larger Bf and Rf appeared after exposure to stronger shear force and longer shear period.Under the same shear condition,the flocs formed by PFSS showed a larger Bf while the flocs formed by PFS had better re-growth ability.展开更多
The growth rate and size of floc formation is of great importance in water treatment especially in coagulation process.The floc formation kinetics and the coagulation efficiency of synthetic water were investigated by...The growth rate and size of floc formation is of great importance in water treatment especially in coagulation process.The floc formation kinetics and the coagulation efficiency of synthetic water were investigated by using an on-line continuous optical photometric dispersion analyze and the analysis of water quality.Experimental conditions such as alum dosage,pH value for coagulation,stirring intensity and initial turbidity were extensively examined.The photometric dispersion analyze results showed that coagulation of kaolin suspensions with two coagulants（alum and polyaluminium chloride） could be taken as a two-phase process：slow and rapid growth periods.Operating conditions with higher coagulant doses,appropriate pH and average shear rate might be particularly advantageous.The rate of overall floc growth was mainly determined by a combination of hydraulic and water quality conditions such as pH and turbidity.The measurement of zeta potential indicates that polyaluminium chloride exhibited higher charge-neutralizing ability than alum and achieved lower turbidities than alum for equivalent Al dosages.Under the same operating conditions,the alum showed a higher grow rate,but with smaller floc size.展开更多
Enhanced coagulation is one of the major methods to control disinfection by-products (DBPs) in water treatment process. Coagulation pH is an important factor that affects the enhanced coagulation. Recently, many studi...Enhanced coagulation is one of the major methods to control disinfection by-products (DBPs) in water treatment process. Coagulation pH is an important factor that affects the enhanced coagulation. Recently, many studies focus on the coagulation effects and mechanisms, and few researchers studied the properties of flocs formed under different coagulation pH. Two inorganic polymer coagulants, polyferric silicate sulphate (PFSS) and polyferric sulphate (PFS), were used in Yellow River water treatment. The influence of pH on coagulation effect was investigated under the optimum dosage, and the results show that both coagulants gave excellent organism removal efficiency when pH was 5.50. According to the variation of zeta potential in coagulation process, coagulation mechanisms of the coagulants were analyzed. An on-line laser scatter instrument was used to record the development of floc sizes during the coagulation period. For PFSS, pH exerted great influence on floc growth rates but little influence on formed floc sizes. In PFS coagulation process, when pH was 4.00, PFS flocs did not reach the steady-state during the whole co-agulation period, while little difference was observed in floc formation when pH was 5.50 and above. The preformed flocs were exposed to strong shear force, and the variation of floc sizes was determined to evaluate the influence of pH on floc strength and re-growth capability. In comparison of the two coagulants, PFS flocs had higher floc strength and better recovery capability when pH was 4.00, while PFSS flocs had higher floc strength but weaker recovery capability when pH was 5.50 and above.展开更多
基金support from the Key Projects in the National Science & Technology Pillar Program in the Eleventh Five-year Plan Period (Grant No 2006BAJ08B05)the Sub-projects in the National Water Pollution Control and Government Key Special Project in the Eleventh Five-year Plan Period (Grant No 2008ZX07422-003-02)
文摘Two inorganic polymer coagulants,polyferric silicate sulphate(PFSS) and polyferric sulphate(PFS),were comparatively evaluated in the Yellow River water treatment.The removal efficiency of turbidity and UV254 were investigated,and the zeta potential was measured.An online laser scatter instrument was used to determine the size distribution of flocs formed in the coagulation processes.Compared with PFS,PFSS forms flocs with higher growth rates and larger sizes.The formed flocs were exposed to a series of shear forces,and the floc strength was measured from the relationship between the applied shear speed and the resulting floc size.The flocs formed by PFSS had a higher strength.The floc breakage(expressed as breakage factor,Bf) and re-growth ability(expressed as breakage factor,Rf) under different shear forces and different shear periods were investigated,and it was found that larger Bf and Rf appeared after exposure to stronger shear force and longer shear period.Under the same shear condition,the flocs formed by PFSS showed a larger Bf while the flocs formed by PFS had better re-growth ability.
基金supported by the National Natural Science Foundation of China (No. 51078148,41173103)
文摘The growth rate and size of floc formation is of great importance in water treatment especially in coagulation process.The floc formation kinetics and the coagulation efficiency of synthetic water were investigated by using an on-line continuous optical photometric dispersion analyze and the analysis of water quality.Experimental conditions such as alum dosage,pH value for coagulation,stirring intensity and initial turbidity were extensively examined.The photometric dispersion analyze results showed that coagulation of kaolin suspensions with two coagulants（alum and polyaluminium chloride） could be taken as a two-phase process：slow and rapid growth periods.Operating conditions with higher coagulant doses,appropriate pH and average shear rate might be particularly advantageous.The rate of overall floc growth was mainly determined by a combination of hydraulic and water quality conditions such as pH and turbidity.The measurement of zeta potential indicates that polyaluminium chloride exhibited higher charge-neutralizing ability than alum and achieved lower turbidities than alum for equivalent Al dosages.Under the same operating conditions,the alum showed a higher grow rate,but with smaller floc size.
基金supported by the Key Projects in the National Science & Technology Pillar Program in the Eleventh Five-year Plan Period (Grant No.2006BAJ08B05)the sub-projects in the National Water Pollution Control and Government Key Special Project in the Eleventh Five-year Plan Period (Grant No.2008ZX07422-003-02)
文摘Enhanced coagulation is one of the major methods to control disinfection by-products (DBPs) in water treatment process. Coagulation pH is an important factor that affects the enhanced coagulation. Recently, many studies focus on the coagulation effects and mechanisms, and few researchers studied the properties of flocs formed under different coagulation pH. Two inorganic polymer coagulants, polyferric silicate sulphate (PFSS) and polyferric sulphate (PFS), were used in Yellow River water treatment. The influence of pH on coagulation effect was investigated under the optimum dosage, and the results show that both coagulants gave excellent organism removal efficiency when pH was 5.50. According to the variation of zeta potential in coagulation process, coagulation mechanisms of the coagulants were analyzed. An on-line laser scatter instrument was used to record the development of floc sizes during the coagulation period. For PFSS, pH exerted great influence on floc growth rates but little influence on formed floc sizes. In PFS coagulation process, when pH was 4.00, PFS flocs did not reach the steady-state during the whole co-agulation period, while little difference was observed in floc formation when pH was 5.50 and above. The preformed flocs were exposed to strong shear force, and the variation of floc sizes was determined to evaluate the influence of pH on floc strength and re-growth capability. In comparison of the two coagulants, PFS flocs had higher floc strength and better recovery capability when pH was 4.00, while PFSS flocs had higher floc strength but weaker recovery capability when pH was 5.50 and above.
