Jong-Woo Nam

Bio: Jong-Woo Nam is an academic researcher from Sungkyunkwan University. The author has contributed to research in topics: Fouling & Reverse osmosis. The author has an hindex of 5, co-authored 7 publications receiving 104 citations.

A hybrid microfiltration―granular activated carbon system for water purification and wastewater reclamation/reuse

Abstract: Microfiltration (MF) does not remove color, natural organic matter (NOM) or synthetic organic chemicals (SOCs). It must be combined with other conventional technologies such as activated carbon adsorption to overcome some of these limitations. The effects of granular activated carbon (GAC) addition on MF performance in terms of quality (dissolved organic carbon) and quantity (permeate flux) were investigated. For a water purification experiment, MF showed preferential rejection of UV260 (about 30%) compared to dissolved organic carbon (DOC) (about 10%), indicating that the hydrophobic (aromatic) NOM fraction is more efficiently eliminated. In the hybrid MF membrane system, the removal efficiency of UV260 was about 60% compared to 30% by MF alone, and the decreasing rate of membrane permeability was much less than that of a conventional MF membrane process (about 70 days without GAC and 130 days with GAC). This may result from the reduced organic loading to the membrane due to the adsorption of NOM on the GAC. Using MF alone, the average removal efficiency of specific UV absorbance (SUVA, UV260/DOC) was only 20%, but GAC addition increased SUVA removal efficiency up to 50–60%. In conclusion, the addition of GAC resulted in a decrease of hydrophobic NOM and trihalomethane precursors. For the wastewater reclamation/reuse experiment, removal efficiencies of DOC, chemical oxygen demand, total nitrogen, total phosphorus and turbidity were in the range of 42%, 53%, 15%, 13%, and 100% with the MF–GAC hybrid membrane system whereas 25–30%, 20–25%, 5–10%, 5–8% and 100% with the MF membrane alone, respectively. The hybrid process of membrane filtration and GAC was more effective in treatment efficiency than the single process.

A study on the high-flux MBR system using PTFE flat sheet membranes with chemical backwashing

Abstract: Currently, polyvinylidene fluoride (PVDF) membranes are widely used because of their chlorine resistance and durability. However, membrane bioreactor (MBR) processes still have obstacles to overcome to be cost effective for wastewater treatment. To overcome these obstacles, stable, long-term operations of MBRs with high permeate flux and low membrane fouling are strongly desired. In this study, both a lab and a pilot scale membrane system with new polytetrafluoroethylene (PTFE)-based flat sheet membrane modules were operated to monitor the effectiveness of chemical backwashing for membrane fouling control. There were two operation modes in the lab experiment. One (MBR2) was applied by chemical backwashing once a day and the other (MBR1) was operated without chemical backwashing. The transmembrane pressure (TMP) remained stable in MBR2 after 25 days, while the TMP increased continuously and eventually reached the upper limit in MBR1. The Rt (total resistance), Rc (cake resistance) and Rf (fouling resistance) of both MBR1 and MBR2 were 8.88 × 1011 m− 1, 3.52 × 1011 m− 1, 4.07 × 1011 m− 1 and 5.34 × 1011 m− 1, 2.10 × 1011 m− 1, 1.91 × 1011 m− 1, respectively, after 30 days of operation. In the pilot scale test, chemical backwashing had similar effects on Rf, but minimal influence on the control of Rc. Chemical backwashing was effective for controlling Rf, but there were differences in Rc reduction by aeration according to membrane position. High quality effluent from filtration indicated that the activity of the microorganisms had not been harmed by chemical backwashing. Through lab and pilot scale experiments, it was confirmed that using a PTFE flat sheet membrane with chemical backwashing in an MBR system could provide high flux, twice as much as that from a conventional system. In conclusion, PTFE membranes have significant potential as next generation membrane materials replacing the currently used PVDF membranes, and chemical backwashing will compensate for the weaknesses associated with the use of flat sheet membranes in field applications.

The evaluation on concentration polarization for effective monitoring of membrane fouling in seawater reverse osmosis membrane system

Abstract: One of the critical issues for the successful application of seawater reverse osmosis (SWRO) in the desalination processes is membrane fouling. However, it is difficult to evaluate fouling by the flux decline since recently commercialized SWRO membranes have better permeability than the initial membranes and the two-way coupling between salt concentration polarization and fouling influences permeate flux. In this study, we evaluated membrane performance using various factors, namely the permeation coefficient ( L p ) and concentration polarization factor ( f cp ). The values of L p and f cp were obtained according to the changing conditions of feed water total dissolved solids (TDS) concentration and operating pressure. As a result, L p and f cp increased with increasing operating pressure at the same feed water TDS, on the other hand, they decreased with increasing feed water TDS at the same operating pressure. The reasons for these results are that concentration polarization is enhanced with increasing operating pressure at the same feed water TDS and concentration polarization is weakened with increasing feed water TDS concentration due to osmotic pressure at the same operating pressure. Based on these factors and the equation combined with osmotic cake filtration theory and thermodynamic model, we could calculate the resistance by NaCl ( R cp ), which is constant with time like membrane resistance ( R m ). Thus, we would identify the fouling rate through fouling resistance ( R c ) by calculating L p and f cp according to time after spiking organic foulants.

An analysis of the effects of osmotic backwashing on the seawater reverse osmosis process

Abstract: Fouling control is an important consideration in the design and operation of membrane-based water treatment processes. It has been generally known that chemical cleaning is still the most common method to remove foultants and maintain the performance of reverse osmosis (RO) desalination. Regardless of the chemical membrane cleaning methods applied effectively, however, frequent chemical cleaning can shorten the membrane life. In addition, it also increases operating and maintenance costs due to the waste chemical disposal. As an alternative, osmotic backwashing can be applied to RO membranes by diluting the concentration polarization (CP) layer. In this study, the effects of osmotic backwashing were analysed under different total dissolved salts (TDSs) and backwashing conditions, and the parameters of the osmotic backwashing were evaluated. The results of the analysis based on the properties of the organic matters found in raw water showed that the cleaning efficiency in respect to the fouling by hydrophi...

Evaluation of chemical cleaning efficiency of organic-fouled SWRO membrane by analyzing filtration resistance

Abstract: Membrane fouling is an unavoidable phenomenon in the operation of seawater reverse osmosis and a major obstacle to economic and efficient operation. In particular, membrane fouling by organic matter negatively affects productivity, product quality, and process cost. Therefore, a chemical cleaning process is essential to prevent interruptions for an effective RO membrane filtration process. Firstly, this study focused on the proper chemical cleaning condition for commercial polyamide RO membranes purchased from two companies. The flux decline rate of SWC5+ membrane was higher than that of SW39HRLE400 membrane regardless of organic foulants because the initial zeta potential of SWC5+ membrane (−21.17 mV) was lower than that of SW30HRLE400 membrane (−30.11 mV) and the repulsive force between membrane surface and foulants was also lower. In addition, we attempted to evaluate cleaning efficiency according to the chemical cleaning conditions and investigate the cause of fouling by analyzing membrane re...

Membrane cleaning in membrane bioreactors: A review

Abstract: Membrane bioreactors (MBRs) have been widely used in wastewater treatment and reclamation. Membrane cleaning is an essential part during the operation of MBRs since membrane fouling is an unavoidable problem. In past decades, with the in-depth understanding on membrane fouling, significant advances in membrane cleaning have been achieved. However, a comprehensive review on membrane cleaning in MBRs is still lacking. This paper attempts to critically review the recent developments of membrane cleaning. Firstly, the fouling and cleaning fundamentals are addressed, and then a comprehensive review on physical, chemical, and biological/biochemical cleaning is presented. The procedures of determining proper cleaning protocols for MBR systems are also proposed. Finally, the existing challenges and future research efforts are discussed in order to ensure the development of membrane cleaning toward a more effective and sustainable way in MBRs.

A review of reverse osmosis membrane fouling and control strategies

Abstract: Reverse osmosis (RO) membrane technology is one of the most important technologies for water treatment. However, membrane fouling is an inevitable issue. Membrane fouling leads to higher operating pressure, flux decline, frequent chemical cleaning and shorter membrane life. This paper reviews membrane fouling types and fouling control strategies, with a focus on the latest developments. The fundamentals of fouling are discussed in detail, including biofouling, organic fouling, inorganic scaling and colloidal fouling. Furthermore, fouling mitigation technologies are also discussed comprehensively. Pretreatment is widely used in practice to reduce the burden for the following RO operation while real time monitoring of RO has the advantage and potential of providing support for effective and efficient cleaning. Surface modification could slow down membrane fouling by changing surface properties such as surface smoothness and hydrophilicity, while novel membrane materials and synthesis processes build a promising future for the next generation of RO membranes with big advancements in fouling resistance. Especially in this review paper, statistical analysis is conducted where appropriate to reveal the research interests in RO fouling and control.

A review of polymeric membranes and processes for potable water reuse

Abstract: Conventional water resources in many regions are insufficient to meet the water needs of growing populations, thus reuse is gaining acceptance as a method of water supply augmentation. Recent advancements in membrane technology have allowed for the reclamation of municipal wastewater for the production of drinking water, i.e., potable reuse. Although public perception can be a challenge, potable reuse is often the least energy-intensive method of providing additional drinking water to water stressed regions. A variety of membranes have been developed that can remove water contaminants ranging from particles and pathogens to dissolved organic compounds and salts. Typically, potable reuse treatment plants use polymeric membranes for microfiltration or ultrafiltration in conjunction with reverse osmosis and, in some cases, nanofiltration. Membrane properties, including pore size, wettability, surface charge, roughness, thermal resistance, chemical stability, permeability, thickness and mechanical strength, vary between membranes and applications. Advancements in membrane technology including new membrane materials, coatings, and manufacturing methods, as well as emerging membrane processes such as membrane bioreactors, electrodialysis, and forward osmosis have been developed to improve selectivity, energy consumption, fouling resistance, and/or capital cost. The purpose of this review is to provide a comprehensive summary of the role of polymeric membranes and process components in the treatment of wastewater to potable water quality and to highlight recent advancements and needs in separation processes. Beyond membranes themselves, this review covers the background and history of potable reuse, and commonly used potable reuse process chains, pretreatment steps, and advanced oxidation processes. Key trends in membrane technology include novel configurations, materials, and fouling prevention techniques. Challenges still facing membrane-based potable reuse applications, including chemical and biological contaminant removal, membrane fouling, and public perception, are highlighted as areas in need of further research and development.

Membrane bioreactors for wastewater treatment: A review of mechanical cleaning by scouring agents to control membrane fouling

Abstract: Membrane bioreactor (MBR) is a reliable and promising technology for wastewater treatment and reclamation applications. In spite of more than a decade of significant advances in developing fouling mitigation methods, different physical and cleaning protocols are still necessary to be developed to limit the membrane fouling. The use of scouring agents in MBR applications has been paid attention as a new approach as an energy-efficient way to control membrane fouling. Recently, mechanical cleaning by scouring agents is becoming an intense research area considering high efficiency of fouling reduction while requiring low energy consumption. In this review, fundamental and comprehensive assessments of the mechanical cleaning concepts and their applications with porous and nonporous scouring agents for MBR system are critically reviewed. The existing challenges and future research prospects on the mechanical cleaning technology associated with scouring agents for the MBR applications are also discussed.

Reverse osmosis applications: Prospect and challenges

Abstract: Reverse osmosis (RO) is a pressure driven membrane process which has been widely applied and recognized as the leading technology of desalination process. Improvement in RO technology including advanced membrane material, module and process design, and energy recovery has led to cost reduction which in turn gaining interest to its commercial applications. RO is now being used in various applications including selective separation, purification, and concentration processes. In food industry, RO is applied for concentration of fruits and vegetable juices, pre-concentration of milk and whey, and dealcoholization of alcoholic beverage. For area which has large source of natural humic water or peat water, RO can be applied to produce clean water for community water supply. RO was also investigated for organic mixture separation and CO 2 regeneration from essential oil extraction using supercritical fluid. The application of RO as a final step of wastewater treatment for water reuse and valuable component recovery seems to be promising in wastewater reclamation. In this paper, the applications of RO, its advantages, and limitations are discussed. In addition, challenges and perspective of RO membranes are pointed out.