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 (R-2=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 & centerdot;m(-2)& centerdot;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.
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 (gamma = 0.89) and total phosphorus (gamma = 0.95), supporting the potential use of existing optical TSS sensors as reliable, real-time surrogates for continuous microplastic load prediction. Spectroscopic characterization identified polyester fibers (84%) and cellophane flakes (16%) as the dominant morphotypes, structurally indicating the simultaneous hydrodynamic convergence of highly probable sources like in-pipe domestic laundry sediments and terrestrial street litter. These macroscopic findings necessitate a dual-mitigation paradigm that strategically couples targeted early-stage volumetric interception with proactive anthropogenic source control to effectively protect urban watersheds, offering a scalable and data-driven framework for mitigating microplastic pollution in global urban drainage systems.
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 & centerdot;h & centerdot;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 it - it 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.
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
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.
