• Journal of Korean Society on Water Environment
• /
• v.39 no.2
• /
• pp.175-180
• /
• 2023

The aim of this study was to compare the fouling characteristics of Extracellular polymeric substances (EPS) secreted by Chlorella vulgaris with the case of Bacterial-MBR (BMBR), Microalgal-MBR (MMBR) for advanced wastewater treatment using the Laboratory scale, in order to suggest a method to minimize fouling in MMBR by identifying the effects of amounts and compositions of EPS secreted by C. vulgaris and bacteria in the activated sludge on fouling. Contrary to expectations, fouling occurred relatively severely in the MMBR from the beginning of the operation than in the BMBR. Reasons for such a fouling pattern were considered to be the effect of C-EPS, which accumulates on the membrane surface of MMBR 30 times more than that on the membrane surface of activated sludge (BMBR). In this respect, according to the results of this experiment and a comparative review of several previous studies, it was confirmed that unlike activated sludge, in which the ratio of P-EPS was relatively higher than that of C-EPS, in case of C. vulgaris, the ratio of C-EPS to P-EPS was relatively higher than that in case of activated sludge. This was presumed to be the main cause of the significant fouling phenomenon in MMBR. However, an increase in TMP with increasing C-EPS concentration was not observed.

• Membrane Journal
• /
• v.21 no.1
• /
• pp.46-54
• /
• 2011

In this study, combined effect of airflow rate, $TiO_2$ concentration, solution pH and $Ca^{+2}$ addition on HA (humic acid) fouling in submerged, photocatalytic hollow-fiber microfiltraiton was investigated systematically. Results showed that UV irradiation alone without $TiO_2$ nanoparticles could reduce HA fouling by 40% higher than the fouling obtained without UV irradiation. Compared to the HA fouling without UV irradiation and $TiO_2$ nanoparticles, the HA fouling reduction was about 25% higher only after the addition of $TiO_2$ nanoparticles. Both adsorptive and hydrophilic properties of $TiO_2$ nanoparticles for the HA can be involved in mitigating membrane fouling. It was also found that the aeration itself had lowest effect on fouling mitigation while the HA fouling was affected significantly by solution pH. Transient behavior of zeta potential at different solution pHs suggested that electrostatic interactions between HA and $TiO_2$ nanoparticles should improve photocatalytic efficiency on HA fouling. $TiO_2$ concentration was observed to be more important factor than airflow rate to reduce HA fouling, implying that surface reactivity on $TiO_2$ naoparticles should be important fouling mitigation mechanisms in submerged, photocatalyic microfiltraiton. This was further supported by investigating the effect of $Ca^{+2}$ addition on fouling mitigation. At higher pH (= 10), addition of $Ca^{+2}$ can play an important role in bridging between HA and $TiO_2$ nanoparticles and increasing surface reactivity on nanoparticles, thereby reducing membrane fouling.

• Korean Membrane Journal
• /
• v.11 no.1
• /
• pp.21-28
• /
• 2009

We investigated the effect of organic materials on membrane fouling in advanced drinking water treatment by a hybrid module packed with granular activated carbon (GAC) outside multi-channel ceramic microfiltration membrane. Synthetic water was prepared with humic acid and kaolin to simulate natural water resouces consisting of natural organic matter and inorganic particles. Kaolin concentration was fixed at 30 mg/L and humic acid was changed as 2~10 mg/L to inspect the effect of organic matters. Periodic back-flushing using permeate water was performed for 10 sec per filtration of 10 min. As a result, both resistance of membrane fouling (Rf) and permeate flux (J) were influenced highly by concentration of humic acid. It proved that NOM like humic acid could be an important factor on membrane fouling in drinking water treatment. Turbidity and UV254 absorbance were removed up to above 97.4% and 59.2% respectively.

• Journal of Korean Society of Water and Wastewater
• /
• v.30 no.3
• /
• pp.343-350
• /
• 2016

Membrane distillation (MD) is a novel separation process that have drawn attention as an affordable alternative to conventional desalination processes. However, membrane fouling and pore wetting are issues to be addressed prior to widespread application of MD. In this study, the influence of ultrasonic irradiation on fouling and wetting of MD membranes was investigated for better understanding of the MD process. Experiments were carried out using a direct contact membrane distillation apparatus Colloidal silica was used as a model foulants in a synthetic seawater (35,000 mg/L NaCl solution). A vibrator was directed attached to membrane module to generate ultrasonic waves from 25 kHz (the highest energy) to 75 kHz (the lowest energy). Flux and TDS for the distillate water were continuously monitored. Results suggested that ultrasonic irradiation is effective to retard flux decline due to fouling only in the early stage of the MD operation. Moreover, wetting occurred by a long-term application of ultrasonic rradiation at 75 kHz. These results suggest that the conditions for ultrasonic irradiation should be carefully optimized to maximize fouling control and minimize pore wetting.

• Membrane and Water Treatment
• /
• v.8 no.4
• /
• pp.337-353
• /
• 2017

Membrane fouling at different solids retention times (SRT) (7, 12 and 20 days) was studied under well-controlled conditions in a laboratory-scale aerobic submerged membrane bioreactor under constant biomass concentration using a synthetic high strength wastewater. An increase in SRT was found to improve membrane performance and this correlated to changes in the total production of bound extracellular polymeric substances (EPS), and the composition and properties of bound EPS using X-ray photoelectron spectroscopy (XPS) and Fourier transform-infrared spectroscopy (FTIR) and floc sizes. A larger amount of total bound EPS was found at the lowest SRT (7 days) tested but the ratio of proteins (PN) to carbohydrates (CH) in bound EPS increased with an increase in SRT. Similarly, the quantity of soluble microbial products (SMP) decreased with an increase in SRT and the SMP PN/CH ratio increased with an increase in SRT. SMP concentrations positively correlated to the percentage of membrane pore blocking resistance. The quantity of total bound EPS and total SMP positively corresponded to the membrane fouling rate, while the PN/CH ratio in the bound EPS and SMP negatively correlated to the membrane fouling rate. The results show that both the quantity and composition of bound EPS and SMP and floc sizes are important in controlling membrane fouling.

• Membrane Journal
• /
• v.17 no.1
• /
• pp.44-53
• /
• 2007

The primary objective of this study is to increase the extent of water flux and fouling resistance of nano-filtration or reverse osmosis membranes. This study was performed to investigate the effect of surface characteristics of silane coated membranes on modified fouling index. Commercial polyamide composite RO membrane (RE1812-LP) and NF membrane (ESNA4040-LF) were treated with silane coupling agents in ethanol at five different concentrations. The silane coupling reagent, aminopropylmethoxydiethoxysilane, contains one aminoalkyl and three alkoxy groups. The hydrophilic effect of aminoalkyl group of APMDES on the permeability and fouling resistance of the modified membrane was examined. The surfaces of the modified membranes were characterized by FE-SEM, contact angle analyzer, and zeta potentiometer in order to confirm successful sol-gel methods. The modified NF membranes showed significantly enhanced water flux and fouling resistance without a decrease in salt rejection in divalent ionic feed solution.

• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.4
• /
• pp.459-469
• /
• 2009

It is well known that coagulation pretreatment can reduce foulants prior to membrane filtration. The purpose of this research was to investigate the effects of coagulation on fouling of ceramic microfiltration membrane($0.1 {\mu}m$) using pilot plant of $150m^3/day/train$ capacity. Train A membrane system has pretreatment process of ozonation and coagulation while train B has only coagulation. Two types of coagulation operation were investigated: back mixer(rapid mixing with or without slow mixing) which is a conventional mechanically stirred mixer and an inline static mixer. Ozone dose rate for train A was 1 mg/L and ozone contact time was 12 min. The coagulation dose(PACl 10% as $Al_2O_3$) rate was changed 20~40 mg/L according to experimental schedule. In this experimental conditions, the coagulation of back mixer type with rapid mixing(GT=72,000) and slow mixing(GT=45,000) was the best effective in reduction of ceramic membrane fouling regardless preozonation. Especially, the effect of inline static mixer was sensitive to change in water quality. Ozonation mainly affected irreversible fouling rather than reversible fouling in accordance with less adsorption of NOM on the membrane surface. Thus, the increase rate of the nomalized TMP(trans membrane pressure) at $25^{\circ}C$ for train A was relatively lower than that of train B under same coagulation process with same coagulant dosage. The best performance of ceramic membrane appeared in case of combined process with ozonation, therefore this integrated process is able to archive less coagulant dosing and secure a stability of ceramic membrane system.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.9
• /
• pp.965-969
• /
• 2005

Current density is an important operating parameter in the ion-exchange membrane process. We observed the effects of fouling of a Neosepta AMX anion-exchange membrane(Tokuyama Soda, Japan) in 0.02 M NaCl solution containing 100 mg/L sodium humate. Membrane fouling was analyzed by measuring the change in the electrical resistance in the under- and over-limiting current density regions. The experimental results found that membrane fouling was negligible at under-limiting current densities, but was increased significantly when an over-limiting current was supplied. After the fouling experiments, the current-voltage curves for the fouled membranes were measured. From the curves, we observed increased electric resistance and reduced limiting current density(LCD), caused by the accumulation of humic acid on the membrane surface. Furthermore, membrane fouling increased as the acidity of the electrolyte solution containing humic acid increased. This occurred because the fouling of an anion-exchange membrane is affected more by the physicochemical properties of the humic substance than by the surface charge of the humate.

• Membrane Journal
• /
• v.8 no.4
• /
• pp.210-219
• /
• 1998

Sulfonated poly(ether sulfone)(SPES) of various ion exchange capacity (IEC) was prepared by heterogeneous sulfonation with chlorosulfonic acid (CSA) to make hydrophilic ultrafiltration membrane for reducing fouling. The effects of CSA concentration, reaction temperature and reaction time has been investigated. The reaction was effective when the temperature is above 10$\circ$C and the CSA concentration is over 0.05 mol, although polymer chain has been significantly degraded. The substitution of sulfonic acid groups was characterized by FTIR and $^1$H-NMR. Transport properties and fouling test have been conducted to the modified SPES ultrafiltration rnembranrs by heterogeneors method. Membranes were obtained using DCM and PVP as a non-solvent and pore forming agent, respectively. Flux reduced and rejection increased with ion exchange capacity. Finger-like structure was disappeared and the thickness of top layer was increased. Dense membrane by non-solvent DCM and porous membrane by pore forming agent PVP was prepared. Fouling was reduced with increasing ion exchange capacity because of hydrophilicity.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.31.1-31.1
• /
• 2005