Foulants and Cleaning Procedures for Composite Polyamide RO Membrane Elements (ESPA, ESNA, CPA, LFC, and SWC)
This bulletin provides general information about the usual foulants affecting the performance of Hydranautics’ Composite Polyamide Reverse Osmosis (RO) membrane elements and the removal of these foulants.
The information in this bulletin applies to 4-inch, 6-inch, 8-inch, and 8.5-inch diameter RO membrane elements.
Foulants and Cleaning Procedures for Composite Polyamide RO Membrane Elements (ESPA, ESNA, CPA, LFC, and SWC)
This bulletin provides general information about the usual foulants affecting the performance of Hydranautics’ Composite Polyamide Reverse Osmosis (RO) membrane elements and the removal of these foulants.
The information in this bulletin applies to 4-inch, 6-inch, 8-inch, and 8.5-inch diameter RO membrane elements.
Fouling and Cleaning Characteristics of Reverse Osmosis (RO) Membranes
Abstract
This work deals with fouling and successive cleaning of RO membrane fouled by an organic foulant, sodium alginate using a laboratory-scale cross-flow test unit. First, the spiral-wound RO membrane was fouled with sodium alginate solution up to 10% and 15%, respectively at an applied pressure of 1380 kPa with a flow rate of 10 lit/min. An anionic surfactant, sodium dodecyl sulfate (SDS) was used as a chemical cleaning agent for the cleaning of RO membrane. The effect of cleaning chemical dose and cross-flow velocity on the membrane chemical cleaning duration to achieve 100% cleaning efficiency (i.e., to get original water flux) was also investigated. As the SDS concentration increases, the membrane chemical cleaning time decreases due to increase in the solubility of the foulant (when the surface tension decreases by an increase in the SDS concentration). Furthermore, the membrane chemical cleaning time decreases with increasing cross-flow velocity of the cleaning chemical solution (SDS). Higher cross-flow velocity enhances the turbulence at the fouling layer and hence the mass transfer of the foulant from the fouling layer to the bulk solution is improved, then the SDS has weakened the structural integrity of the fouling layer. It is observed that better cleaning is occurred with higher concentration of SDS and flow rate. The obtained results clearly reveal that SDS cleaning is proved to be an efficient cleaning method for RO membranes fouled with organic foulant.
Fouling and Cleaning Characteristics of Reverse Osmosis (RO) Membranes
Abstract
This work deals with fouling and successive cleaning of RO membrane fouled by an organic foulant, sodium alginate using a laboratory-scale cross-flow test unit. First, the spiral-wound RO membrane was fouled with sodium alginate solution up to 10% and 15%, respectively at an applied pressure of 1380 kPa with a flow rate of 10 lit/min. An anionic surfactant, sodium dodecyl sulfate (SDS) was used as a chemical cleaning agent for the cleaning of RO membrane. The effect of cleaning chemical dose and cross-flow velocity on the membrane chemical cleaning duration to achieve 100% cleaning efficiency (i.e., to get original water flux) was also investigated. As the SDS concentration increases, the membrane chemical cleaning time decreases due to increase in the solubility of the foulant (when the surface tension decreases by an increase in the SDS concentration). Furthermore, the membrane chemical cleaning time decreases with increasing cross-flow velocity of the cleaning chemical solution (SDS). Higher cross-flow velocity enhances the turbulence at the fouling layer and hence the mass transfer of the foulant from the fouling layer to the bulk solution is improved, then the SDS has weakened the structural integrity of the fouling layer. It is observed that better cleaning is occurred with higher concentration of SDS and flow rate. The obtained results clearly reveal that SDS cleaning is proved to be an efficient cleaning method for RO membranes fouled with organic foulant.
Fouling Layer Formation by Flocs in Inside-Out Driven Capillary Ultrafiltration Membranes
The interest in low-pressure membrane filtration, i. e. micro- and ultrafiltration (MF and UF) increased rapidly in recent years, particularly due to the extremely high requirements for potable water quality with respect to hygiene aspects. However, some limiting factors exist, especially when applying MF or UF for the direct treatment of surface waters without any pretreatment. Particularly dissolved organic matter (DOM) can be very problematic due to the formation of hardly reversible and/or irreversible fouling layers and due to its general contribution to the formation of disinfection by-products (DBP).
Fouling Layer Formation by Flocs in Inside-Out Driven Capillary Ultrafiltration Membranes
The interest in low-pressure membrane filtration, i. e. micro- and ultrafiltration (MF and UF) increased rapidly in recent years, particularly due to the extremely high requirements for potable water quality with respect to hygiene aspects. However, some limiting factors exist, especially when applying MF or UF for the direct treatment of surface waters without any pretreatment. Particularly dissolved organic matter (DOM) can be very problematic due to the formation of hardly reversible and/or irreversible fouling layers and due to its general contribution to the formation of disinfection by-products (DBP).
Fundamentals of Membrane Fouling
This chapter contains sections titled:
- Introduction
- Concentration Boundary Layer
- Modeling Ultrafiltration in the Absence of Fouling
- Modeling Membrane Filtration in the Presence of Fouling
- Fouling Overview: its Nature and Key Influences
- Modeling of Fouling
- Prevention and Reduction of Fouling
- Reverse Osmosis and Fouling
- Fouling in Ultrafiltration and Microfiltration
- Fouling in Pervaporation and Gas Separation
- Concluding Remarks
- References
Fundamentals of Membrane Fouling
This chapter contains sections titled:
- Introduction
- Concentration Boundary Layer
- Modeling Ultrafiltration in the Absence of Fouling
- Modeling Membrane Filtration in the Presence of Fouling
- Fouling Overview: its Nature and Key Influences
- Modeling of Fouling
- Prevention and Reduction of Fouling
- Reverse Osmosis and Fouling
- Fouling in Ultrafiltration and Microfiltration
- Fouling in Pervaporation and Gas Separation
- Concluding Remarks
- References
Philosophy And Design Of Reverse Osmosis Membrane Replacement
Abstract
Water treatment technologies constantly advance as the demand for access to clean water rises above supply. Veolia Water operates multiple water treatment facilities with daily production capacities exceeding 100 ML. Reverse osmosis is a major operation within these facilities and
has the ability to remove dissolved salt content from feed water. This process requires consumable membranes which, as they approach their design life or begin to lower in their production capabilities, require replacement. The current reverse osmosis membrane replacement process requires a high number of operators with a vast amount of manual handling. This project is focused upon reducing manual handling in the membrane replacement that is currently carried out, specifically at QGC Kenya, a water treatment facility operated by Veolia Water. In an industry, and within a company, that constantly strives towards increasing safety culture an engineering solution can reduce the need
for manual handling in such operations. The work produced within this dissertation focuses on the reduction of manual handling.
Components which aided this were designed and analysed using finite element analysis methods. The membrane replacement process was redesigned with this focus in mind. Subsequent to the design of the components and the updated methodology, analysis was carried
out to provide financial justification for this change in replacement philosophy. The results of this project allow for future work to be carried out, in the manufacturing and physical testing of the components. Through physical testing, the theoretical values could be
confirmed or altered.
Philosophy And Design Of Reverse Osmosis Membrane Replacement
Abstract
Water treatment technologies constantly advance as the demand for access to clean water rises above supply. Veolia Water operates multiple water treatment facilities with daily production capacities exceeding 100 ML. Reverse osmosis is a major operation within these facilities and
has the ability to remove dissolved salt content from feed water. This process requires consumable membranes which, as they approach their design life or begin to lower in their production capabilities, require replacement. The current reverse osmosis membrane replacement process requires a high number of operators with a vast amount of manual handling. This project is focused upon reducing manual handling in the membrane replacement that is currently carried out, specifically at QGC Kenya, a water treatment facility operated by Veolia Water. In an industry, and within a company, that constantly strives towards increasing safety culture an engineering solution can reduce the need
for manual handling in such operations. The work produced within this dissertation focuses on the reduction of manual handling.
Components which aided this were designed and analysed using finite element analysis methods. The membrane replacement process was redesigned with this focus in mind. Subsequent to the design of the components and the updated methodology, analysis was carried
out to provide financial justification for this change in replacement philosophy. The results of this project allow for future work to be carried out, in the manufacturing and physical testing of the components. Through physical testing, the theoretical values could be
confirmed or altered.
Optimization Of Chemical Cleaning For Reverse Osmosis Membranes With Organic Fouling Using Statistical Design Tools
Abstract
The cleaning efficiency of reverse osmosis (RO) membranes inevitably fouled by organic foulants depends upon both chemical (type of
cleaning agent, concentration of cleaning solution) and physical (cleaning time, flowrate, temperature) parameters. In attempting to determine
the optimal procedures for chemical cleaning organic-fouled RO membranes, the design of experiments concept was employed to evaluate
key factors and to predict the flux recovery rate (FRR) after chemical cleaning. From experimental results and based on the predicted
FRR of cleaning obtained using the Central Composite Design of Minitab 17, a modified regression model equation was established to
explain the chemical cleaning efficiency; the resultant regression coefficient (R2
) and adjusted R2
were 83.95% and 76.82%, respectively.
Then, using the optimized conditions of chemical cleaning derived from the response optimizer tool (cleaning with 0.68 wt% disodium
ethylenediaminetetraacetic acid for 20 min at 20°C with a flowrate of 409 mL/min), a flux recovery of 86.6% was expected. Overall, the
results obtained by these experiments confirmed that the equation was adequate for predicting the chemical cleaning efficiency with regards
to organic membrane fouling.
Optimization Of Chemical Cleaning For Reverse Osmosis Membranes With Organic Fouling Using Statistical Design Tools
Abstract
The cleaning efficiency of reverse osmosis (RO) membranes inevitably fouled by organic foulants depends upon both chemical (type of
cleaning agent, concentration of cleaning solution) and physical (cleaning time, flowrate, temperature) parameters. In attempting to determine
the optimal procedures for chemical cleaning organic-fouled RO membranes, the design of experiments concept was employed to evaluate
key factors and to predict the flux recovery rate (FRR) after chemical cleaning. From experimental results and based on the predicted
FRR of cleaning obtained using the Central Composite Design of Minitab 17, a modified regression model equation was established to
explain the chemical cleaning efficiency; the resultant regression coefficient (R2
) and adjusted R2
were 83.95% and 76.82%, respectively.
Then, using the optimized conditions of chemical cleaning derived from the response optimizer tool (cleaning with 0.68 wt% disodium
ethylenediaminetetraacetic acid for 20 min at 20°C with a flowrate of 409 mL/min), a flux recovery of 86.6% was expected. Overall, the
results obtained by these experiments confirmed that the equation was adequate for predicting the chemical cleaning efficiency with regards
to organic membrane fouling.
Brine-Concentrate Treatment and Disposal Options
Introduction
The Southern California Regional Brine-Concentrate Management Study is a collaboration between the United States (U.S.) Department of the Interior Bureau of Reclamation (Reclamation) and 14 local and state agency partners. Table 1.1
provides a list of the agencies represented on the Brine Executive Management Team (BEMT). The project is funded on a 50/50 cost-sharing basis between Reclamation and the cost-sharing partners, who together form the BEMT. The purpose of the BEMT is to formulate, guide, and manage technical activities of the study.
Brine-Concentrate Treatment and Disposal Options
Introduction
The Southern California Regional Brine-Concentrate Management Study is a collaboration between the United States (U.S.) Department of the Interior Bureau of Reclamation (Reclamation) and 14 local and state agency partners. Table 1.1
provides a list of the agencies represented on the Brine Executive Management Team (BEMT). The project is funded on a 50/50 cost-sharing basis between Reclamation and the cost-sharing partners, who together form the BEMT. The purpose of the BEMT is to formulate, guide, and manage technical activities of the study.
Zero Discharge Seawater Desalination: Integrating The Production Of Freshwater, Salt, Magnesium, And Bromine
Abstract
This report contains the results of a study of a zero liquid discharge ZLD process for seawater reverse osmosis (SWRO) with enhanced freshwater yield and production of salable sodium chloride (NaCl), magnesium hydroxide (Mg(OH)2), and bromine (Br2) from the SWRO reject. The process uses electrodialysis (ED) to reduce the salinity of the reject stream from SWRO so that the salt-depleted reject stream can be recycled to the SWRO to improve the yield of freshwater. The approach of this ZLD study is to remove in logical sequence the most accessible amounts of abundant constituents in seawater, water, and NaCl and leave remaining valuable constituents in a concentrated solution. After recovery of the most accessible portions of water (NaCl, Br2 and Mg(OH)2), the residual solutions can be evaporated to dryness to produce road salt; but ultimately, minor constituents might be recovered from that residue.
Zero Discharge Seawater Desalination: Integrating The Production Of Freshwater, Salt, Magnesium, And Bromine
Abstract
This report contains the results of a study of a zero liquid discharge ZLD process for seawater reverse osmosis (SWRO) with enhanced freshwater yield and production of salable sodium chloride (NaCl), magnesium hydroxide (Mg(OH)2), and bromine (Br2) from the SWRO reject. The process uses electrodialysis (ED) to reduce the salinity of the reject stream from SWRO so that the salt-depleted reject stream can be recycled to the SWRO to improve the yield of freshwater. The approach of this ZLD study is to remove in logical sequence the most accessible amounts of abundant constituents in seawater, water, and NaCl and leave remaining valuable constituents in a concentrated solution. After recovery of the most accessible portions of water (NaCl, Br2 and Mg(OH)2), the residual solutions can be evaporated to dryness to produce road salt; but ultimately, minor constituents might be recovered from that residue.
Variable Salinity Desalination
Abstract
Variable salinity desalination applications are becoming more abundant. Design flexibility was explored through a desk-top design exercise evaluating the range of operational conditions for various membrane configurations. The Village Marine Expeditionary Unit Water Purifier Generation 1 was used to evaluate the practical aspects of converting a single-stage seawater system with energy recovery, to a two-stage brackish water system capable of 75% water recovery. Performance is compared with various levels of salinity in the seawater configuration and brackish water configuration.
Variable Salinity Desalination
Abstract
Variable salinity desalination applications are becoming more abundant. Design flexibility was explored through a desk-top design exercise evaluating the range of operational conditions for various membrane configurations. The Village Marine Expeditionary Unit Water Purifier Generation 1 was used to evaluate the practical aspects of converting a single-stage seawater system with energy recovery, to a two-stage brackish water system capable of 75% water recovery. Performance is compared with various levels of salinity in the seawater configuration and brackish water configuration.
Ultrafiltration Product Manual
Introduction
Ultrafiltration (UF) involves pressure-driven separation of materials from a feed solution. The technology is used to remove particulate and microbial contaminants, but it does not remove ions and small molecules. Pressure drives the process, which typically operates with a feed pressure of 4 to 100 psig. UF plants are automated and have low operational labor requirements. These systems, however, can require frequent
cleaning. UF membranes have a service life of three to five years or longer, which is comparable to reverse osmosis membranes. UF modules are commercially available in tubular, hollow-fiber, plate and frame, and spiral wound configurations. UF membranes reject solutes ranging in size from 0.03 microns and larger. Figure 1 provides a guide to the relationship between common materials, separation processes, and pore size measurements. The UF membrane process separates molecules in solution on the basis of size. The pore size and molecular weight
cut-off (MWCO) are often used to characterize a membrane. The pore size is the nominal diameter of the openings or micropores in the membrane expressed in microns. The MWCO is the molecular mass or weight of a solute that rejects greater than 90 percent. The unit of measurement for MWCO is the Dalton (D). Different membrane materials with the same nominal MWCO may have differing solute rejection. Pore size distribution and uniformity rather than the chemical nature of the membrane material may cause this effect. Because factors other than pore size or MWCO affect the performance of membranes, challenge studies are used to demonstrate membrane performance and benchmark different membranes.
Ultrafiltration Product Manual
Introduction
Ultrafiltration (UF) involves pressure-driven separation of materials from a feed solution. The technology is used to remove particulate and microbial contaminants, but it does not remove ions and small molecules. Pressure drives the process, which typically operates with a feed pressure of 4 to 100 psig. UF plants are automated and have low operational labor requirements. These systems, however, can require frequent
cleaning. UF membranes have a service life of three to five years or longer, which is comparable to reverse osmosis membranes. UF modules are commercially available in tubular, hollow-fiber, plate and frame, and spiral wound configurations. UF membranes reject solutes ranging in size from 0.03 microns and larger. Figure 1 provides a guide to the relationship between common materials, separation processes, and pore size measurements. The UF membrane process separates molecules in solution on the basis of size. The pore size and molecular weight
cut-off (MWCO) are often used to characterize a membrane. The pore size is the nominal diameter of the openings or micropores in the membrane expressed in microns. The MWCO is the molecular mass or weight of a solute that rejects greater than 90 percent. The unit of measurement for MWCO is the Dalton (D). Different membrane materials with the same nominal MWCO may have differing solute rejection. Pore size distribution and uniformity rather than the chemical nature of the membrane material may cause this effect. Because factors other than pore size or MWCO affect the performance of membranes, challenge studies are used to demonstrate membrane performance and benchmark different membranes.