Ultrafiltration Microfiltration Research Articles

Anti-scaling ultrafiltration/microfiltration (UF/MF) polyvinylidene fluoride (PVDF) membranes with positive surface charges for Ca2+/silica-rich wastewater treatment

We develop an anti-scaling ultrafiltration/microfiltration (UF/MF) membrane by introducing a high-density positive charge to a poly(vinylidene fluoride) (PVDF) membrane to suppress membrane scaling in Ca2+/silica-rich wastewater. Positively charged modifiers are synthesized by conjugating an amphiphilic polymer (Brij S10) and branched poly(ethylene imine) (b-PEI) at various molar ratios, and these are then implanted to PVDF membranes during the phase-inversion process. Attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectra reveal that the positive modifiers successfully anchors onto the surface of the membrane by hydrophilic-hydrophobic phase recognition. As introducing the positive charge on the membrane surface, the membranes show positive surface charge and their pure water permeability (PWP) increases due to the protonation of b-PEI. Anti-scaling properties are also confirmed to be improved by filtration tests using a metal ions/silica-rich feed solution, which results from the repulsion of metal ion by the positively charged branch on the membrane. In addition, the water flux recovery by simple membrane backwashing of the modified membrane is double that of the neat PVDF membrane.

Pretreatment in Reverse Osmosis Seawater Desalination: A Short Review

Reverse osmosis (RO) technology has developed over the past 40 years to control a 44% market share in the world desalting production capacity and an 80% share in the total number of desalination plants installed worldwide. The application of conventional and low-pressure membrane pretreatment processes to seawater RO (SWRO) desalination has undergone accelerated development over the past decade. Reliable pretreatment techniques are required for the successful operation of SWRO processes, since a major issue is membrane fouling associated with particulate matter/colloids, organic/inorganic compounds, and biological growth. While conventional pretreatment processes such as coagulation and granular media filtration have been widely used for SWRO, there has been an increased tendency toward the use of ultrafiltration/microfiltration (UF/MF) instead of conventional treatment techniques. The literature shows that both the conventional and the UF/MF membrane pretreatment processes have different advantages and disadvantages. This review suggests that, depending on the feed water quality conditions, the suitable integration of multiple pretreatment processes may be considered valid since this would utilize the benefits of each separate pretreatment.

H2O Innovation develops new membrane cleaners

Canadian water treatment technology company H2O Innovation Inc says that its Professional Water Technologies (PWT) business unit, based in California, USA, has developed three new membrane cleaners, targeting the growing reverse osmosis (RO) and ultrafiltration/microfiltration (UF/MF) membrane markets.

Continuous biosorption of copper and lead in single and binary systems using Sphaerotilus natans cells confined by a membrane: experimental validation of dynamic models

Biosorption of heavy metals using membrane reactors as confining devise for free cells is an alternative process to remove these metallic pollutants from aqueous solution. In this paper, experimental data and modelling of heavy metal biosorption onto Sphaerotilus natans cells confined by a ultrafiltration/microfiltration (UF/MF) membrane reactor are reported. Biosorption tests using single and binary metallic solutions (Cu, Pb and Cu–Pb) denoted the biomass affinity (Pb>Cu), the competition among metals simultaneously present in the system, the filtrate flux decline and the change of metal retention coefficient on the membrane for pore plugging by cell fragments. Dynamic modelling is developed considering the unsteady mass balances of the metal in the system and the equilibrium parameters obtained by biosorption batch tests using Langmuir models. Experimental validation of the dynamic models denoted the importance of partial degradation of cells, which is specifically considered in modelling by introducing a time-depending profile for the biomass concentration.

Effect of equilibrium models in the simulation of heavy metal biosorption in single and two-stage UF/MF membrane reactor systems

In this paper heavy metal biosorption in an UF/MF (ultrafiltration/microfiltration) membrane reactor was simulated outlining the effect of different equilibrium models on the predicted performances of the bioreactor. In particular using Langmuir, Freundlich and Redlich–Peterson isotherms slightly different simulated profiles were obtained evidencing the adequacy of all the equilibrium models in representing a common dynamic behaviour. Experimental data of copper biosorption onto Sphaerotilus natans cells obtained using an UF membrane reactor system, were compared with theoretical profiles obtained from the combination of mass balances with adsorption equilibrium properties. This comparison outlines the necessity of considering a partial cell degradation (as confirmed by permeate flux decline) which was taken into account in the modelling phase introducing a time depending biomass concentration, function of the copper retention coefficient. The simulated dynamic behaviour of a single reactor was also compared with a series of two reactors (with the same total volume and biomass amount) in order to optimise the operative configuration to use.

Modeling of copper biosorption by Arthrobacter sp. in a UF/MF membrane reactor.

Copper biosorption by Arthrobacter sp. has been studied in this work. The process has been realized inside of a ultrafiltration/microfiltration (UF/MF) reactor in order to confine cells. A mathematical model has been developed that is able to predict experimental data under different operating conditions. The model takes into account different phenomena, which might occur during the process, such as a dependence of equilibrium parameters on pH, a partial cell disruption, and a change in the membrane retention properties at high biomass concentrations. Experimental tests have been performed under different operating conditions: a full factorial design has been implemented with pH (levels: 4, 5, and 6 units) and biomass concentration (levels: 1 and 5 g/L) as factors. A simple mathematical model based on metal mass balance taking into account the effect of pH on the Langmuir equilibrium adsorption parameters well fitted experimental data at low pH values and biomass concentrations. A more complex mathematical model, which considers a partial cell disruption during the biosorption trial, was proposed to understand and analyze the anomalous system behavior at pH = 6 and biomass concentration equal to 5 g/L. The effect of mechanical stress on biomass performances was also examined by using a discontinuous system (test tube trials) simulating the membrane reactor apparatus. In this alternative system biosorption trials were carried out in test tubes in such a way to avoid or at least minimize the disruption due to mechanical stress. Experimental results obtained by using this system can be modeled up to pH = 5 without considering cell disruption phenomenon, while at pH = 6 possible chemical reactions of biomass constituents could happen.

A simulation study on biosorption of heavy metals by confined biomass in UF/MF membrane reactors

A study on the biosorption of heavy metals is reported in this work. A biosorption process realised by confining the biomass in a membrane reactor has been considered. A kinetic model for the process has been developed by combining equilibrium data and material balances. Simulations have been performed to determine the effect of main operating conditions on the process. In particular, the metal profiles in the outlet stream and the cumulative metal removal have been determined both in a single-stage reactor and in a series of two-membrane modules. Furthermore, a range of variation for the metal concentration in the permeate has been determined, in order to predict experimental data with 95% probability. A first validation of the model has been obtained for a single-stage ultrafiltration/microfiltration (UF/MF) system, in the case of copper biosorption by Arthrobacter sp., under the following operating conditions: inlet copper concentration, 10 mg/L; inlet flow rate, 3.5 mL/min; biomass concentration, 1 g/L; reaction volume, 500 mL. The simulation showed the technical feasibility of this biosorption process where biomass is confined inside the reactor by an appropriate membrane.