The effects of water flow rate, mixing, gaseous ozone concentration, inlet gas flow rate, tempera... more The effects of water flow rate, mixing, gaseous ozone concentration, inlet gas flow rate, temperature, and pH on ozone hydrodynamics at high pressure were studied. Varying the cross flow rate had only a slight influence on the ozone mass transfer rates, indicating that sufficient mixing in the reactor was attained at the low flow rates used. The addition of an inline static mixer had a negligible effect on aqueous ozone concentrations in the reactor, suggesting that mixing was sufficient without the mixer. The ozone mass transfer increased with increasing gaseous ozone concentration and with the inlet gas flow rate. The dissolved ozone concentration decreased with increasing pH due to the greater rate of ozone decomposition at higher pH. Increasing the temperature resulted in a decrease in the ozone mass transfer. A model to describe the ozone mass transfer was developed. Good agreement between the model predictions and the experimental data was achieved.
The paper describes the use of the layer-by-layer technique to coat ceramic membranes with iron a... more The paper describes the use of the layer-by-layer technique to coat ceramic membranes with iron and manganese oxide nanoparticles. The coatings are thin (<50 nm) and relatively uniform. These coatings enhance the performance of the hybrid ozonation-filtration process. With the coated membranes it is possible to significantly reduce fouling, improve the removal of DBP precursors and more effectively kill Escherichia coli bacteria.
The effect of membrane filtration, ozonation, and combined ozonation-membrane filtration on the r... more The effect of membrane filtration, ozonation, and combined ozonation-membrane filtration on the removal of Escherichia coli was studied. Commercially available ceramic membranes with a molecular weight cutoff (MWCO) of 5kDa were used as is, and also coated with iron oxide nanoparticles and sintered at 900°C. With membrane filtration and ozonation-membrane filtration using the uncoated membrane, 7 log removal of E. coli was achieved, as compared to 7.5 log removal with ozonation-membrane filtration with the coated membrane. A Live-Dead assay indicated that the mortality of E. coli in the product water was 15%, ∼50%, ∼86%, and >99% with membrane filtration, ozonation, combined ozonation-membrane filtration with the uncoated membrane and the coated membrane, respectively. With the coated membrane, the concentration of assimilated organic carbon (AOC) was reduced by up to 50% more than with the uncoated membrane filtration (with both systems operated using ozone). This indicates that there is a reduced potential for regrowth after treatment using the coated membranes and ozone. Scanning electron micrographs (SEM) of the membrane surface suggest that after filtration there is less detritus on the surface of the coated membrane than on the uncoated membrane. As a result of the inactivation of the E. coli and the lower AOC concentrations observed using combined catalytic ozonation-membrane filtration this process is likely to be very effective to both disinfect the water and control bacterial regrowth in the distribution system.
Ceramic ultrafiltration membranes were coated with the hydrated MnO2 using a novel layer-by-layer... more Ceramic ultrafiltration membranes were coated with the hydrated MnO2 using a novel layer-by-layer (LbL) technique. Ozonation of MnCl2 was used to prepare the MnO2 nanoparticles used in the LbL procedure. The coated membranes were then sintered in air at 500°C for 45min. Upon sintering, the MnO2 was converted to α-Mn2O3 (as characterized by selected area diffraction of transmission electron microscopy
Tubular ceramic membranes (molecular weight cut-off, 5kDa) were coated with manganese oxide nanop... more Tubular ceramic membranes (molecular weight cut-off, 5kDa) were coated with manganese oxide nanoparticles. Atomic force microscopy imaging of the coated membranes showed no statistically significant change in the surface roughness or maximum height of the surface features compared with the uncoated membrane. However, scanning electron microscopy imaging showed an increase in grain size with increasing number of coating layers. Energy
ABSTRACT Alumina–zirconia–titania (AZT) ceramic membranes coated with iron oxide nanoparticles ha... more ABSTRACT Alumina–zirconia–titania (AZT) ceramic membranes coated with iron oxide nanoparticles have been shown to improve water quality by significantly reducing the concentration of disinfection by-product precursors, and in the case of membrane filtration combined with ozonation, to reduce ozonation by-products such as aldehydes, ketones and ketoacids. Commercially available ceramic membranes with a nominal molecular weight cut-off of 5 kilodaltons (kD) were coated 20, 30, 40 or 45times with sol suspension processed Fe2O3 nanoparticles having an average diameter of 4–6nm. These coated membranes were sintered in air at 900°C for 30min. The effects of sintering and coating layer thickness on the microstructure of the ceramic membranes were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). AFM images show a decreasing roughness after iron oxide coating with an average surface roughness of ∼161nm for the uncoated and ∼130nm for the coated membranes. SEM showed that as the coating thickness increased, the microstructure of the coating changed from a fine grained (average grain size of ∼27nm) morphology at 20coating layers to a coarse grained (average grain size of ∼66nm) morphology at 40 coating layers with a corresponding increase in the average pore size from ∼57nm to ∼120nm. Optimum water quality was achieved at 40layers, which corresponds to a surface coating morphology consisting of a uniform, coarse-grained structure with open, nano-sized interconnected pores.
Page 1. THE USE OF OZONATION TO DEGRADE ORGANIC CONTAMINANTS IN WASTEWATERS L 180 A Environ Sci T... more Page 1. THE USE OF OZONATION TO DEGRADE ORGANIC CONTAMINANTS IN WASTEWATERS L 180 A Environ Sci Techno1 , Vol. 28, No 4, 1994 00~3-936w94/0927-180A$O4 5010 a 1994 American Chemical Society Page 2. act with ...
The effects of water flow rate, mixing, gaseous ozone concentration, inlet gas flow rate, tempera... more The effects of water flow rate, mixing, gaseous ozone concentration, inlet gas flow rate, temperature, and pH on ozone hydrodynamics at high pressure were studied. Varying the cross flow rate had only a slight influence on the ozone mass transfer rates, indicating that sufficient mixing in the reactor was attained at the low flow rates used. The addition of an inline static mixer had a negligible effect on aqueous ozone concentrations in the reactor, suggesting that mixing was sufficient without the mixer. The ozone mass transfer increased with increasing gaseous ozone concentration and with the inlet gas flow rate. The dissolved ozone concentration decreased with increasing pH due to the greater rate of ozone decomposition at higher pH. Increasing the temperature resulted in a decrease in the ozone mass transfer. A model to describe the ozone mass transfer was developed. Good agreement between the model predictions and the experimental data was achieved.
The paper describes the use of the layer-by-layer technique to coat ceramic membranes with iron a... more The paper describes the use of the layer-by-layer technique to coat ceramic membranes with iron and manganese oxide nanoparticles. The coatings are thin (<50 nm) and relatively uniform. These coatings enhance the performance of the hybrid ozonation-filtration process. With the coated membranes it is possible to significantly reduce fouling, improve the removal of DBP precursors and more effectively kill Escherichia coli bacteria.
The effect of membrane filtration, ozonation, and combined ozonation-membrane filtration on the r... more The effect of membrane filtration, ozonation, and combined ozonation-membrane filtration on the removal of Escherichia coli was studied. Commercially available ceramic membranes with a molecular weight cutoff (MWCO) of 5kDa were used as is, and also coated with iron oxide nanoparticles and sintered at 900°C. With membrane filtration and ozonation-membrane filtration using the uncoated membrane, 7 log removal of E. coli was achieved, as compared to 7.5 log removal with ozonation-membrane filtration with the coated membrane. A Live-Dead assay indicated that the mortality of E. coli in the product water was 15%, ∼50%, ∼86%, and >99% with membrane filtration, ozonation, combined ozonation-membrane filtration with the uncoated membrane and the coated membrane, respectively. With the coated membrane, the concentration of assimilated organic carbon (AOC) was reduced by up to 50% more than with the uncoated membrane filtration (with both systems operated using ozone). This indicates that there is a reduced potential for regrowth after treatment using the coated membranes and ozone. Scanning electron micrographs (SEM) of the membrane surface suggest that after filtration there is less detritus on the surface of the coated membrane than on the uncoated membrane. As a result of the inactivation of the E. coli and the lower AOC concentrations observed using combined catalytic ozonation-membrane filtration this process is likely to be very effective to both disinfect the water and control bacterial regrowth in the distribution system.
Ceramic ultrafiltration membranes were coated with the hydrated MnO2 using a novel layer-by-layer... more Ceramic ultrafiltration membranes were coated with the hydrated MnO2 using a novel layer-by-layer (LbL) technique. Ozonation of MnCl2 was used to prepare the MnO2 nanoparticles used in the LbL procedure. The coated membranes were then sintered in air at 500°C for 45min. Upon sintering, the MnO2 was converted to α-Mn2O3 (as characterized by selected area diffraction of transmission electron microscopy
Tubular ceramic membranes (molecular weight cut-off, 5kDa) were coated with manganese oxide nanop... more Tubular ceramic membranes (molecular weight cut-off, 5kDa) were coated with manganese oxide nanoparticles. Atomic force microscopy imaging of the coated membranes showed no statistically significant change in the surface roughness or maximum height of the surface features compared with the uncoated membrane. However, scanning electron microscopy imaging showed an increase in grain size with increasing number of coating layers. Energy
ABSTRACT Alumina–zirconia–titania (AZT) ceramic membranes coated with iron oxide nanoparticles ha... more ABSTRACT Alumina–zirconia–titania (AZT) ceramic membranes coated with iron oxide nanoparticles have been shown to improve water quality by significantly reducing the concentration of disinfection by-product precursors, and in the case of membrane filtration combined with ozonation, to reduce ozonation by-products such as aldehydes, ketones and ketoacids. Commercially available ceramic membranes with a nominal molecular weight cut-off of 5 kilodaltons (kD) were coated 20, 30, 40 or 45times with sol suspension processed Fe2O3 nanoparticles having an average diameter of 4–6nm. These coated membranes were sintered in air at 900°C for 30min. The effects of sintering and coating layer thickness on the microstructure of the ceramic membranes were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). AFM images show a decreasing roughness after iron oxide coating with an average surface roughness of ∼161nm for the uncoated and ∼130nm for the coated membranes. SEM showed that as the coating thickness increased, the microstructure of the coating changed from a fine grained (average grain size of ∼27nm) morphology at 20coating layers to a coarse grained (average grain size of ∼66nm) morphology at 40 coating layers with a corresponding increase in the average pore size from ∼57nm to ∼120nm. Optimum water quality was achieved at 40layers, which corresponds to a surface coating morphology consisting of a uniform, coarse-grained structure with open, nano-sized interconnected pores.
Page 1. THE USE OF OZONATION TO DEGRADE ORGANIC CONTAMINANTS IN WASTEWATERS L 180 A Environ Sci T... more Page 1. THE USE OF OZONATION TO DEGRADE ORGANIC CONTAMINANTS IN WASTEWATERS L 180 A Environ Sci Techno1 , Vol. 28, No 4, 1994 00~3-936w94/0927-180A$O4 5010 a 1994 American Chemical Society Page 2. act with ...
Uploads
Papers by Susan Masten