- Assessment of various membrane fouling indexes under seawater condition
In this study, various foulants are tested with the conventional fouling indexes such as silt density index(SDI) and modified fouling index(MFI) under high TDS conditions to evaluate the practical appliance of these i...
- Assessment of various membrane fouling indexes under seawater condition
In this study, various foulants are tested with the conventional fouling indexes such as silt density index(SDI) and modified fouling index(MFI) under high TDS conditions to evaluate the practical appliance of these indexes for RO desalination. A new approach for developing a more realistic fouling index is investigated based on flow field-flow fraction(Fl-FFF) analysis. The results showed that the SDI and MFI for the feed waters containing the particulate foulants larger than the pore size of the membranes used in SDI and MFI measurements were not significantly affected by the feed water salinity. This is due to the fact that the main fouling mechanism is the deposition of particles on the membrane surface, and, hence, the cake filtration controls the permeate flux. In case of the particles as well as organics smaller than the pore size of the membranes, the SDI and MFI were failed to accurately predict the fouling potential of feed waters with high salinity. In addition, the characteristics of membrane(i.e., hydrophobicity) also played an important role in determining membrane performance. Based on the results from Fl-FFF analyses, it was demonstrated that both qualitative and quantitative assessments of fouling potential of feed waters with different foulants and TDS conditions were possible.
- Evaluation of Membrane Fouling Potential by Multiple Membrane Array System
A new approach to evaluate fouling potential of feed waters for reverse osmosis(RO) and nanofiltration(NF) practices were systematically investigated. Multiple membrane array system(MMAS) was developed where microfiltration(MF), ultrafiltration(UF), and nanofiltration(NF) membranes were connected in series in one system. The system allowed the separation of target foulants from diverse foulants in the feed water as well as the evaluation of the fouling potential of feed water containing the target foulants. Separation between particulate foulants and other foulants(i.e., nano-colloids and organic matters) was took place at the first MF membrane, followed by another separation between nano-colloids and organic foulants at the second UF membrane and, thus, the feed water for the final NF membrane mainly contained organic foulants. By measuring the modified fouling index(MFI) during each separation, three MFI values could be determined to be ‘particle-MFI’, ‘colloid-MFI’, and ‘organic-MFI’. The results showed that fouling potentials of various feed waters(i.e., seawaters pre-treated by various pre-treatment options as well as raw seawater) evaluated by the MMAS were much more accurate and precise compared to those predicted using conventional silt density index(SDI) and single MFI. Depending on the pre-treatment options(i.e., sand filtration, microfiltration, and ultrafiltration), the fouling potentials determined by the MMAS changed substantially, while the changes in SDI values was almost negligible. It was also shown that the fouling potentials of various feed waters tested by the MMAS were well correlated with the actual flux-decline rates determined by lab-scale RO fouling experiments.
- Evaluation of RO Process Feasibility and Membrane Fouling for Wastewater Reuse
The purpose of this study is to evaluate various pre-treatment methods and proprieties of water quality for wastewater reuse using a Reverse Osmosis (RO) process. Secondary effluents were sampled from wastewater treatment plants and lab scale pre-treatments and RO filtration test were conducted systematically. Specifically, different types of pre-treatments, such as coagulation, microfiltration and ultrafiltration, were employed to evaluate the removal efficiency of particle and organic matters which may affect the membrane fouling rate. RO process was later added to eliminate trace amounts of remaining organic matters and salt from the raw water for wastewater reclamation. The permeate through the RO process satisfied water quality regulations for industrial water uses. The experimental results showed that the initial fouling tendency differed not only by the feed water properties but also by the membrane characteristics. Membrane fouling was greater for the membranes with large surface roughness, regardless of the hydrophobicity and zeta potentials.
Thus both careful consideration of pre-treatment options and proper selection of RO membrane are of paramount importance for an efficient operations of wastewater treatment.
- Assessment of various membrane fouling indexes under seawater condition
In this study, various foulants are tested with the conventional fouling indexes such as silt density index(SDI) and modified fouling index(MFI) under high TDS conditions to evaluate the practical appliance of these indexes for RO desalination. A new approach for developing a more realistic fouling index is investigated based on flow field-flow fraction(Fl-FFF) analysis. The results showed that the SDI and MFI for the feed waters containing the particulate foulants larger than the pore size of the membranes used in SDI and MFI measurements were not significantly affected by the feed water salinity. This is due to the fact that the main fouling mechanism is the deposition of particles on the membrane surface, and, hence, the cake filtration controls the permeate flux. In case of the particles as well as organics smaller than the pore size of the membranes, the SDI and MFI were failed to accurately predict the fouling potential of feed waters with high salinity. In addition, the characteristics of membrane(i.e., hydrophobicity) also played an important role in determining membrane performance. Based on the results from Fl-FFF analyses, it was demonstrated that both qualitative and quantitative assessments of fouling potential of feed waters with different foulants and TDS conditions were possible.
- Evaluation of Membrane Fouling Potential by Multiple Membrane Array System
A new approach to evaluate fouling potential of feed waters for reverse osmosis(RO) and nanofiltration(NF) practices were systematically investigated. Multiple membrane array system(MMAS) was developed where microfiltration(MF), ultrafiltration(UF), and nanofiltration(NF) membranes were connected in series in one system. The system allowed the separation of target foulants from diverse foulants in the feed water as well as the evaluation of the fouling potential of feed water containing the target foulants. Separation between particulate foulants and other foulants(i.e., nano-colloids and organic matters) was took place at the first MF membrane, followed by another separation between nano-colloids and organic foulants at the second UF membrane and, thus, the feed water for the final NF membrane mainly contained organic foulants. By measuring the modified fouling index(MFI) during each separation, three MFI values could be determined to be ‘particle-MFI’, ‘colloid-MFI’, and ‘organic-MFI’. The results showed that fouling potentials of various feed waters(i.e., seawaters pre-treated by various pre-treatment options as well as raw seawater) evaluated by the MMAS were much more accurate and precise compared to those predicted using conventional silt density index(SDI) and single MFI. Depending on the pre-treatment options(i.e., sand filtration, microfiltration, and ultrafiltration), the fouling potentials determined by the MMAS changed substantially, while the changes in SDI values was almost negligible. It was also shown that the fouling potentials of various feed waters tested by the MMAS were well correlated with the actual flux-decline rates determined by lab-scale RO fouling experiments.
- Evaluation of RO Process Feasibility and Membrane Fouling for Wastewater Reuse
The purpose of this study is to evaluate various pre-treatment methods and proprieties of water quality for wastewater reuse using a Reverse Osmosis (RO) process. Secondary effluents were sampled from wastewater treatment plants and lab scale pre-treatments and RO filtration test were conducted systematically. Specifically, different types of pre-treatments, such as coagulation, microfiltration and ultrafiltration, were employed to evaluate the removal efficiency of particle and organic matters which may affect the membrane fouling rate. RO process was later added to eliminate trace amounts of remaining organic matters and salt from the raw water for wastewater reclamation. The permeate through the RO process satisfied water quality regulations for industrial water uses. The experimental results showed that the initial fouling tendency differed not only by the feed water properties but also by the membrane characteristics. Membrane fouling was greater for the membranes with large surface roughness, regardless of the hydrophobicity and zeta potentials.
Thus both careful consideration of pre-treatment options and proper selection of RO membrane are of paramount importance for an efficient operations of wastewater treatment.
주제어
#Desalination, Fouling Potential, Multiple Membrane Array System(MMAS), Fouling index, silt density index(SDI), modified fouling index(MFI), TDS effect, flow field-flow fractionation(Fl-FFF), Membrane process, Wastewater reuse, RO process, Membrane fouling
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