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CONTENTS
Volume 17, Number 4, July 2026
 

Abstract
To mitigate membrane fouling effectively during the treatment of oil-in-water (O/W) emulsions, this study optimized a stirred-cell membrane filtration system using Response Surface Methodology (RSM) based on a Box-Behnken Design (BBD). The combined effects of the water-to-oil ratio, stirring rate, and transmembrane pressure (TMP) on permeate flux were systematically investigated. Analysis of Variance (ANOVA) results yielded a highly predictive quadratic model (R2=0.9817). Critical interaction analyses revealed that increased stirring significantly reduces concentration polarization, whereas excessive TMP at low water-to-oil ratios induces pore blocking via oil droplet deformation. Numerical optimization identified the ideal operating conditions as a water-to-oil ratio of 8.5, a stirring rate of 213 rpm, and a TMP of 0.059 MPa. Validation experiments under these conditions achieved a permeate flux of 4.37 L.m-2.h-1 with an effluent oil content of <50 ppm. These findings provide essential hydrodynamic strategies for enhancing separation efficiency and controlling fouling in industrial applications.

Key Words
oil-water separation; process optimization; response surface methodology (RSM); stirred-cell membrane

Address
Jingru Hu, Changjiang Zuo, Tonggang Hou: Qingdao Technical College, Qingdao, Shandong, China

Abstract
This study investigated the effects of powdered activated carbon (PAC) addition and feeding strategy on aerobic granular sludge (AGS) formation and organic micropollutant (OMP) removal. Three sequencing batch reactors were operated: PAC-AGS1 (PAC addition and static fill without mixing), PAC-AGS2 (PAC addition and anaerobic mixing during fill period), and a control AGS reactor (anaerobic mixing during fill period). Results demonstrated that PAC significantly accelerated granulation and improved sludge settleability during early operation period. PAC-AGS1 exhibited the fastest decrease in SVI30 (25 mL/g) and achieved a granular fraction of approximately 90% by day 49, indicating rapid formation of compact and stable granules. Meanwhile, anaerobic fill with nitrogen purging slightly delayed early-stage granulation in PAC-AGS2. All systems achieved effective COD removal; however, PAC-AGS1 showed enhanced OMP removal efficiency, probably due to the combined effects of adsorption and biodegradation within stable granular structures. Microbial community analysis revealed distinct shifts at the family level, with PAC-AGS1 enriching structure-supporting bacteria. The results indicated that PAC addition under stable aerobic feeding conditions promotes rapid granule formation, structural stability, and improved micropollutant removal. This study highlights the significance of both PAC as an adsorptive nucleus and static feeding strategy to enhance AGS performance for advanced wastewater treatment applications.

Key Words
aerobic granular sludge; biodegradability; organic micropollutants; powdered active carbon; sequencing bath reactor

Address
Dandan Dong, Jang Ho Lee, Jae Woo Lee: Department of Environmental Engineering, College of Science and Technology, Korea University, Sejong, 30019, Republic of Korea


Abstract
Two key factors limiting the industrial application of graphene oxide membranes are low water flux and easy swelling in water during operation. In this study, a novel holey graphene oxide/methylene blue (HGO/MB) composite membrane was prepared by vacuum filtration using a two-step method, including chemical etching graphene oxide (GO) with H2O2 to improve the water flux and then intercalating MB into HGO to limit the swelling of GO membranes effectively. The composite membrane showed a higher pure water flux of 23.4 L/m2.h.bar, which was improved about 6 times compared to GO membrane. The rejection rates of the membrane for Na2SO4, methyl orange (MO) and rhodamine B (Rh B) reached 83.2%, 93% and 97%, respectively. HGO/MB composite membrane remained stability after 15 min of ultrasound treated because of the π - π conjugation and electrostatic interaction between HGO and MB. This study demonstrated that the membranes prepared have effectively improved water flux and stability without loss of rejection, which held great potential for water treatment applications.

Key Words
holey graphene oxide; membrane; methylene blue; water treatment; π - π conjugation

Address
Xuan Liu, Shihao Li, Hangdong Chen, Xiang Yu, Mingyang Li: College of Engineering, Shanghai Ocean University, 999 Huchenghuan Road, Pudong New Area District Shanghai, P.R.China

Yafei Zhang, Nantao Hu: Key Laboratory for Thin Film and Microfabrication Technology of the Ministry of Education, School of Electronics, Information and Electrical Engineering, Shanghai Jiao Tong University, No. 800, Dongchuan Road, Minhang District, Shanghai, P.R.China

Bin Li: Research Center for Photovoltaics, Shanghai Institute of Space Power-Sources, Shanghai, 200245, China

Abstract
The nanopores with small radii (R) and long axial lengths (l) were found to be on or off for the fluid flow, dependent on the external power loss. The value of R may be no more than 1nm, and the ratio l/R can be on the scales 1.0E+3 or 1.0E+4. In the case of a small power loss, no wall slippage occurs and the flow resistance of the nanopore is huge so that the flow rate through the nanopore is as small as negligible. When the power loss on the nanopore is high enough, the wall slippage occurs and the flow resistance of the nanopore approaches to vanishing so that the flow rate through the nanopore is large. These functions are important for the liquid-liquid separation by using nanoporous filtration membranes. For the two mixed liquids, if the critical power losses on the nanopore for wall slippage is greatly different, one liquid can smoothly flow through the nanopore while the other liquid is impeded from flowing through it when the magnitude of the power loss exerted on the nanopore is between the two critical power losses for wall slippage.

Key Words
flow resistance; hydrophobic; nanopore; power loss; separation; wall slippage

Address
Yongbin Zhang: College of Mechanical Engineering, Changzhou University, Changzhou, 213164, Jiangsu Province, China

Abstract
Combined sewer overflows (CSOs) represent critical vectors for microplastic emission into urban aquatic environments, yet the transient hydrodynamic mechanisms governing their rainfall-driven transport remain insufficiently characterized. This study pioneers high-resolution temporal monitoring within a high-density residential catchment, delivering novel mechanistic insights that bridge this critical knowledge gap and elucidate the dynamic discharge kinetics and physicochemical profiles of these emerging contaminants. Quantitative trajectory analysis confirmed a pronounced first flush phenomenon, yielding a mass first flush ratio of 0.41, which dictates that over 40% of the total pollutant load mobilizes within the initial 30% of the cumulative runoff volume. Density-driven rapid mobilization propelled the microplastic concentration peak 15 minutes ahead of the maximum total suspended solids (TSS) discharge, demonstrating extreme sensitivity to the initial hydrodynamic shear stress. Dynamic correlation assessments revealed exceptionally strong synchronizations with particulate-bound indicators, specifically TSS (

Key Words
combined sewer overflows; first flush; microplastics; total suspended solids; urban drainage

Address
Sungryul Kim, Kyungik Gil: Department of Civil Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro Nowon-gu, Seoul 01811, Republic of Korea


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