• Journal of Korean Society of Water and Wastewater
• /
• v.30 no.3
• /
• pp.327-334
• /
• 2016

The effects of dissolved inorganic and organic matter in seawater and the characteristics of fouling on the membrane surface were investigated within membrane distillation (MD) process. The changes of the membrane flux of PE and PVDF hollow fiber membranes under natural and synthetic seawater were compared with given variances of temperature. The flux of both membranes under the synthetic seawater, without any organic matter, were higher than that of the natural seawater, indicating the organic fouling on the membrane surface. The surface of the membrane was analyzed using scanning electron microscope (SEM) to examine the fouling. The experiment with organics has shown the formation of thin film over the membrane surface, while the experiment with inorganics has shown only the formation of inorganic crystals. The results indicated the organic matter as the major foulants and that the organics affected the formation of the crystals. Permeate water conductivity of all conditions verified the quality of the water to be better if not similar to that of RO.

• Membrane and Water Treatment
• /
• v.9 no.4
• /
• pp.205-210
• /
• 2018

In this study, we investigated coagulants such as polyaluminum chloride (PACl) and ferric chloride ($FeCl_3$) and the combination of a coagulant and powdered activated carbon (PAC) for the removal of dissolved organic matter (DOM) from fish processing effluent to reduce membrane fouling in microfiltration. The efficiency of each pretreatment was investigated through analyses of dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm ($UVA_{254}$). Membrane flux and silt density index (SDI) analyses were performed to evaluate membrane fouling; molecular weight distributions (MWD) and fluorescence excitation-emission matrix (FEEM) spectroscopy were analyzed to assess DOM characteristics. The results demonstrated that $FeCl_3$ exhibited higher DOC and $UVA_{254}$ removals than PACl for food processing effluent and a combination of $FeCl_3$ and PAC provided comparatively better results than simple $FeCl_3$ coagulation for the removal of DOM from fish processing effluent. This study suggests that membrane fouling could be minimized by proper pretreatment of food processing effluent using a combination of coagulation ($FeCl_3$) and adsorption (PAC). Analyses of MWD and FEEM revealed that the combination of $FeCl_3$ and PAC was more efficient at removing hydrophobic and small-sized DOM.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.2
• /
• pp.167-173
• /
• 2004

Fouling of heat exchangers is generated by water-borne deposits, commonly known as foulants including particulate matter from the air, migrated corrosion produces; silt, clays, and sand suspended in water; organic contaminants; and boron based deposits in plants. The fouling is known to interfere with normal flow characteristics and reduce thermal efficiencies of heat exchangers. This paper describes the fouling analysis technique developed in this study which can analyze the thermal performance for heat exchangers and estimate the future fouling variations. To develop the fouling analysis technique fur heat exchangers, fouling factor was introduced based on the ASME O&M codes and TEMA standards. For the purpose or verifying the fouling analysis technique, the routing analyses were performed for four heat exchangers in several nuclear power plants; two residual heat removal heat exchangers of the residual heat removal system and two component cooling water heat exchangers of the component cooling water system.

• Journal of Korean Society of Water and Wastewater
• /
• v.24 no.2
• /
• pp.237-246
• /
• 2010

This study was carried out to compare the performances of hydrophobic and hydrophilic membranes in the filtration of the pretreatment waters using coagulants such as PAC and PAHCs, and to investigate the influence of NOM characteristics on the fouling of membranes. As a result, the hydrophobic fraction was more effectively removed by PAHCs, however the transphilic and hydrophilic fraction were more effectively removed by PAC on NOM removal. Raw water showed the highest response in the range of humic substances, and pre-coagulated waters with PAC and PAHCs followed. It was also observed that the fouling effect for a hydrophobic membrane was greater than that of a hydrophilic membrane with a similar pore size, due to fouling caused by adsorption. Foulants causing significant flux decline were alcoholic compounds (polysaccharide-like) and humic substances including aromatic groups. Especially, it appeared that alcoholic compounds such as polysaccharide-like substances which mostly remained after coagulation pretreatment had most influence on fouling. It was found that fouling were influenced by each fraction NOM components depending on coagulants used. And PAHCs was more efficient for membrane fouling than PAC.

• Journal of Korean Society of Water and Wastewater
• /
• v.30 no.6
• /
• pp.737-744
• /
• 2016

The investigation of effects on fouling propensity with various viscosity of feed solutions would be better understanding for forward osmosis (FO) performance since the fouling propensity was directly influenced with solution viscosity. Therefore, this study was focused on the FO fouling with model foultants (humic acid, alginate) by altering solution viscosity with change of ionic strength (I.S) and $Ca^{2+}$ concentrations. In the comparison between humic acid and alginate, as expected, the alginate generally caused more severe fouling (almost 35.8 % of flux reduction) based on the solution characteristics (high viscosity) and fouling patterns (coil and gel layer). However, interesting point to note is that the fouling propensity of alginate was more severe even though it was applied with low viscosity of feed conditions (I.S = 20 mM, $Ca^{2+}=1mM$). This might be due to that crossed linked gel layer of alginate on the FO membrane surface could be best formed in the condition of $Ca^{2+}$ presence and higher I.S, and that is more dominant to fouling propensity than the low viscosity of feed solutions.

• Journal of Korean Society on Water Environment
• /
• v.21 no.4
• /
• pp.379-384
• /
• 2005

In this research, coagulation was employed as the pretreatment for membrane process. The effective coagulation conditions were decided after the discussion of different coagulant doses and mixing conditions, etc. Raw water was taken from Nakdong River. The best operation occurred when G value was $230s^{-1}$ and the slow mixing lasted around 5 minutes at G value was $23s^{-1}$. To investigate the optimum coagulant dosage, the optimum organics removal was target as organic removal reduces membrane fouling effectively than particle removal. This result indicated that organics are more important causes than turbidity for membrane fouling. However, turbidity becomes an important factor after certain amount of organic matters is removed.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.10
• /
• pp.1046-1054
• /
• 2006

The raw water DOC contained 39.3% of hydrophilics, 42.9% of hydriophobic, and 17.8% of transphilic. The hydrophobic fraction in this raw water was mostly fulvic acid. Fulvic acid comprised of 62% and the rest was humic acid(38%). There was more carboxylic acid functional group(64%) than phenolic group(36%). HPI-N and HPI-C comprised of 17% and 22% in the hydrophilic portion, respectively. The fouling mechanisms on the membrane surface and into its porous structure were analyzed in terms of several kinetic models. In order to analyze the fouling kinetics, the various kinetic models described in this paper were used to fit the experimental results. The kinetic models and kinetic constants obtained for each operation condition. The permeate flux was rapidly declined by simultaneous pore blocking and cake formation. Also, the permeate flux declined with decreasing internal pore size resulted from organic deposition into the membrane pore. The results of the membrane fouling test using UF membrane according to NOM fractions. HPI-N caused more fouling than HPI-C. Humic acid caused more fouling than fulvic acid probably due to higher adsorption capacity. Since humic acid has higher adsorption capacity than fulvic acid, it would be more adsorbed onto the membrane pores.

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.4
• /
• pp.535-543
• /
• 2006

The Ozone oxidation process was applied to increase the efficiency of reuse process when treating the secondary effluent by the membrane system. This paper focus on decreasing efficiency of membrane fouling, because of membrane fouling reduction by ozone and evaluation of application of the ozone oxidation. The feed water was secondary effluent from BNR process. The result shows that the ozone pretreatment can reduce membrane fouling effectively. Also, the improvement of treated water quality was obvious. The reduction of the membrane fouling led decrease of following pollutant and increase of lnner adsorptive ability of hydrophilic organic matter and decrease of molecular weight. MF membrane process alone can meet the domestic reuse water standards. And ozone pretreatment process also can increase the removal rates of turbidity, COD, nitrogen, and color.

• Journal of Korean Society of Water and Wastewater
• /
• v.25 no.3
• /
• pp.399-405
• /
• 2011

In a desalination technology using RO membranes, chemical cleaning makes damage for membrane surface and membrane life be shortened. In this research cleaning technology using direct osmosis (DO) was introduced to apply it under the condition of high pH and high concentration of feed. When the high concentration of feed is injected to the concentrate side after release of operating pressure, then backward flow occurred from treated water toward concentrated for osmotic pressure. This flow reduces fouling on the membrane surface. Namely, flux of DO was monitored under pH 3, 5, 10 and 12 conditions at feed concentrations of NaCl 40,000 mg/L, 120,000 mg/L and 160,000 mg/L. As a result, DO flux in pH 12 increased about 21% than pH 3. DO cleaning was performed under the concentrate NaCl 160,000 mg/L of pH 12 during 20 minutes. Three kinds of synthetic feed water were used as concentrates. They consisted of organic, inorganic and seawater; chemicals of SiO2 (200 mg/L), humic acid (50 mg/L) sodium alginate (50 mg/L) and seawater. As a result, fluxes were recovered to 17% in organic fouling, 15% in inorganic fouling and 14% of seawater fouling after cleaning using DO under the condition of concentrate NaCl 160,000 mg/L of pH 12.

• Journal of Korean Society of Water and Wastewater
• /
• v.31 no.2
• /
• pp.169-175
• /
• 2017

This study applied microbubbles to reduce membrane fouling in wastewater reuse membrane processes, evaluated and compared the transmembrane pressure with or without the application of microbubbles and the cleaning efficiency with the application of aeration and microbubbles. In addition, this study analyzed foulants removed from the membrane surface. Changes in the transmembrane pressure of membranes with the presence or absence of microbubbles were observed. As a result, transmembrane pressure (TMP) increasing rate decreased twofold when applying microbubbles to realize stable operations. This study compared and evaluated cleaning efficiency applying aeration and microbubbles. As a result, the cleaning efficiency was 5% higher on average when applying microbubbles. In turbidity and total organic carbon (TOC), foulants were discharged when applying microbubbles twice as much as applying aeration. It is thought that particulate foulants precipitated on the membrane surface were more likely to desorb because the adhesion between the membrane surface and particle was weakened by microbubbles. Therefore, it is considered possible to effectively control membrane fouling because of the increase in cleaning efficiency when applying microbubbles to wastewater reuse membrane processes.