• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.289-296
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• 2010

The purpose of this study is to evaluate various pre-treatment methods and proprieties of water quality for wastewater reuse using reverse osmosis (RO) processes. 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 operation of wastewater treatment.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.1-6
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• 2006

In this study, five commercially available fouling resistant low-pressure RO membranes were investigated for the treatment of seasonally brackish surface water with high organic content (${\approx}24mg/L$). The membranes investigated are LFC-1 (Hydranautics), X20 (Trisep), BW30FR1 (FilmTec), SG (Osmonics), and BE-FR (Saehan). The results of surface characterization revealed that each of these membranes has one or two unique surface characteristics to minimize the adherence of the fouling materials to the membrane. Specifically, the LFC1 membrane features a neutral or low negative surface to minimize electrostatic interactions with charged foulants. The X20, on the other hand, shows a highly negatively charged surface, and thus, is expected to perform well with feed waters containing negatively charged organics and colloids. The BW30FR1 exhibits a relatively neutral and hydrophilic surface, which could be beneficial for lessening organic and/or biofouling. The SG membrane has a smooth surface that makes it quite resistant to fouling, particularly for colloidal deposition. Lastly, BE-FR membrane demonstrated a medium surface charge and a slightly higher hydrophobicity. In the pilot study, all of the four membranes experienced a gradual increase in MTC (water mass transfer coefficient or specific flux) over time, indicating no fouling occurred during the pilot study. The deterioration of permeate water quality such as TDS was also observed over time, suggesting that the integrity of the membranes was compromised by the monochloramine used for biofouling control.

• Membrane and Water Treatment
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• v.5 no.1
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• pp.1-14
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• 2014

A pilot-scale hybrid membrane bioreactor (HMBR) for real municipal wastewater treatment was developed by adding biofilm carriers into a conventional membrane bioreactor, distribution and dynamic changes of the extracellular polymeric substances (EPS) and their roles in membrane fouling were investigated. The results showed that the concentrations of loosely bond EPS (LB-EPS) and tightly bond EPS (TB-EPS) in activated sludge, carrier biofilm and sludge cake layer have been increased significantly with the running time of HMBR, during operation of the HMBR, EPS demonstrated positive correlations with membrane fouling. Compared to TB-EPS, LB-EPS showed more significant correlations with sludge physical properties and specific resistance to filtration (SRF) in HMBR, and thus demonstrated that LP-EPS have a stronger potential of fouling than TB-EPS. It was also found that a lower organic loading in HMBR could result a significant increase in EPS concentration, which would in turn influence membrane fouling in HMBR. This critical investigation would contribute towards a better understanding of the behavior, composition and fouling potential of EPS in HMBR operation.

• Membrane Journal
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• v.26 no.1
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• pp.55-61
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• 2016

Organic fouling observed in submerged membrane filtration as a pretreatment for seawater desalination increases energy consumption for membrane operation because of requiring frequent chemical cleaning and membrane replacement. In membrane pretreatment for seawater facing with algae blooms, membrane fouling was observed in submerged microfiltration using sodium alginate model compound which is one of the main components of extracellular polymeric substances. Without aeration, aglinate fouling increased with its concentration while aeration reduced the alginate fouling effectively regardless of its concentration tested. In the absence of aeration, alingate fouling tended to be decreased with increasing calcium concentration. However, this effectiveness was reduced by increasing sodium chloride concentration. At high concentration of sodium chloride and calcium similar to the seawater conditions, aeration reduced initial fouling. However, as time progressed, the effect of increased airflow rate on fouling reduction was not significant, implying that optimum airflow rate to control alginate fouling in submerged microfiltration can exist.

• Membrane and Water Treatment
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• v.11 no.3
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• pp.179-187
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• 2020

Electrodialysis has been applied for treatment of industrial wastewater including metal electroplating. The wastewater from metal plating industries contains high concentrations of inorganics such as copper, nickel, and sodium. The ions in the feed were separated due to the electrical forces in the electrodialysis. The concentrate compartment is exposed to the elevated concentrations of the ions and yielded inorganic precipitations on the cation exchange membranes. The presence of organic matter in the metal plating wastewater affects complex interfacial reactions, which determines characteristics of inorganic scale fouling. The wastewater from a metal plating industry in practice was collected and the inorganic and organic compositions of the wastewater were analyzed. The performance of electrodialysis of the raw wastewater was evaluated and the effects of adjusting pH of the raw water were also measured. The integrated processes with neutralization and electrodialysis showed great removal of heavy metals sufficient to discharge to aquatic ecosystem. The organic matter in the raw water was also reduced by the neutralization, which might enhance removal performance and alleviate organic fouling in the integrated system.

• Membrane and Water Treatment
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• v.3 no.4
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• pp.221-230
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• 2012

This study employed the modified fouling index (MFI) to determine the performance of a two-step recycling system - a membrane filtration integrated laminar flow water storage (LFWS) tank followed by an ion exchange process to reclaim ultrapure water (UPW) from the wastewater generated from semiconductor wafer backgrinding and sawing processes. The first step consisted of the utilization of either ultrafiltration (UF) or nanofiltration (NF) membranes to remove solids in the wastewater where the second step consisted of an ion exchanger to further purify the filtrate. The system was able to produce high purity water in a continuous operating mode. However, higher recycling cost could be incurred due to membrane fouling. The feed wastewater used for this study contained high concentration of fine particles with low organic and ionic contents, hence membrane fouling was mainly attributed to particulate deposition and cake formation. Based on the MFI results, a LFWS tank that was equipped with a turbulence reducer with a pair of auto-valves was developed and found effective in minimizing fouling by discharging concentrated wastewater prior to any membrane filtration. By comparing flux behaviors of the improved system with the conventional system, the former maintained a high flux than the latter at the end of the experiment.

• Membrane Journal
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• v.7 no.4
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• pp.175-182
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• 1997

Membrane-bioreactor process which combines anaerobic-aerobic bioreactor and membrane process, was used to remove refractory organic susbstances and dye molecule in textile wastewater effectively. Direct feeding of raw feed water to membrane process caused serious fouling on membrane. On the other hand, pretreated feed by bioreactor before the membrane process remarkably reduced the fouling and prolonged the membrane life. Removal efficiency and fouling were more dependent on the material property of the membrane rather than the membrane pore size and structure. Operation mode of hollow fiber membrane module and linear velocity in the hollow fiber influenced the ramoval efficiency and the water flux of the membrane. The combined membrane- bioreactor process was more effective in treating the textile wastewater than each single process.

• Membrane and Water Treatment
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• v.6 no.1
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• pp.77-94
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• 2015

Ultrafiltration membranes have several advantages over conventional drinking-water treatment. However, this technology presents major limitations, such as irreversible fouling and low removal of natural organic matter. Fouling depends heavily on the raw-water quality as well as on the operating conditions of the process, including flux, permeate recovery, pre-treatment, chemical cleaning, and backwashing. Starting with the premise that the optimisation of operating variables can improve membrane performance, different experiments were conducted in a pilot plant located in Granada (Spain). Several combinations of permeate and backwashing flow rates, backwashing frequencies, and aeration flow rates were tested for low-quality water coming from Genil River with the following results: the effluent quality did not depend on the combination of operating conditions chosen; and the membrane was effective for the removal of microorganisms, turbidity and suspended solids but the yields for the removal of dissolved organic carbon were extremely low. In addition, the threshold transmembrane pressure (-0.7 bar) was reached within a few hours and it was difficult to recover due to the low efficiency of the chemical cleanings. Moreover, greater transmembrane pressure due to fouling also increased the energy consumption, and it was not possible to lower it without compromising the permeate recovery. Finally, the intensification of aeration contributed positively to lengthening the operation times but again raised energy consumption. In light of these findings, the feasibility of ultrafiltration as a single treatment is questioned for low-quality influents.

• Environmental Engineering Research
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• v.23 no.4
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• pp.474-484
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• 2018

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 ($R^2$) and adjusted $R^2$ 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 $20^{\circ}C$ 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.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.144-150
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• 2013

Hybrid ceramic membrane (HCM) processes that combined ozonation with a ceramic membrane (CM) or a reactive ceramic membrane (RM), an iron oxide nanoparticles (IONs) incorporated-CM were investigated for membrane fouling control. Alumina disc type microfiltration and ultrafiltration membranes doped with IONs by sintering method were tested under varying mass fraction of IONs. Scanning electron microscope (SEM) images showed that IONs were well-doped on the CM surface and doped IONs were approximately 50 nm in size. Change in the pure water permeability of RM was negligible compared to that of CM. These results indicate that IONs incorporation onto CM had little effect on CM performance in terms of the flux. Natural organic matter (NOM) fouling and fouling recovery patterns during HCM processes confirmed that the RM-ozonation process enhanced the destruction of NOM and reduced the extent of fouling more than the CM-ozonation process by hydroxyl radical formation in the presence of IONs on RM. In addition, analyses of NOM in the feed water and the permeate showed that the efficiency of membrane fouling control results from the NOM degradation during HCM processes; leading to removal and transformation of relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions.