Membrane-based Pre-concentration Research Articles

Anti-fouling performance and methane potential in coagulation-adsorption assisted biogas-spared anaerobic membrane preconcentration process

To preconcentrate domestic sewage and control membrane fouling, this study proposed a novel anaerobic membrane-based preconcentration (AnMPC) system and controlled fouling by coagulation-adsorption assisted biogas sparging. The effect of polyaluminium chloride (PACl) dosage on membrane fouling control and methane potential of preconcentrated domestic sewage was also investigated. Membrane fouling control was realized by the increase of particle-size (6.03%–40.65%) and the decline of soluble microbial product (11.10%–33.14%) with the rise of PACl addition. The minimum membrane filtration resistance of 1.15 × 1013 m−1 was obtained at the group with 10 mg/L PACl, which was 7.96%–28.20% lower than other groups. More than 75% of chemical oxygen demand (COD) could be preconcentrated, and the preconcentrated ratio increased by 4.22%–9.70% with the rise of PACl addition. Methane potential decreased by 5.40%–40.56% due to the inhibition of accumulated PACl. The pre-hydrolysis of domestic sewage during AnMPC could shorten fermentation time by 0.8–3.2 d. The group with 10 mg/L PACl addition was the optimal due to the excellent anti-fouling performance and the promising energy balance. This study could provide a promising membrane-based preconcentration method with high COD recovery and mild membrane fouling for sustainable treatment of domestic sewage.

Techno-economic feasibility of “membrane-based pre-concentration + post-treatment” systems for municipal wastewater treatment and resource recovery

Membrane-based pre-concentration (MPC) process has been regarded as an attractive approach to sustainable municipal wastewater (MW) treatment. The aim of this study is to verify the techno-economic feasibility of pilot-scale MPC demonstrations and to design a complete technical route for MPC-based MW treatment and resource recovery. Three pilot MPC demonstrations (50–500 t/d) were operated for several months with different strategy combinations of chemicals and aeration. The filtration performance, pollutant removal performance, and concentrate characteristics were investigated and a techno-economic assessment was conducted. Based on the characteristics of each MPC effluent, biofilters, reverse osmosis (RO) and membrane capacitive deionization (MCDI) were selected as post-treatment units. Comparisons were carried out from 6 perspectives, including effluent quality, energy consumption, capital investment, operating cost, by-products, and recovery potential. In MPC_C, the combination of intermittent aeration and “50 mg/L Polyaluminium chloride +25 mg/L activated carbon” ensured a stable filtration (flux >10 LMH over 3 months) and an exceptional pollutant removal (soluble organics removal rate >75%) performance. The highest energy recovery potential (0.35 kWh/m3) was also achieved in MPC_C with the lowest energy consumption (0.12 kWh/m3) and an acceptable operating cost (0.53 CNY/m3). As for post-treatment units, RO showed advantages in effluent quality, technological maturity, and economic cost. An “MPC (intermittent aeration + high strength dosage) + RO + anaerobic digestion” system was proposed for synchronous water-energy reclamation. The net energy consumption and operating cost were estimated as 0.273 kWh/m3 and CNY 1.132/m3, respectively. This study will open new possibilities for the establishment of revolutionary wastewater treatment routes for carbon neutrality and sustainable development.

Developing a robust method integrating with selective membrane-based preconcentration and signal amplification for field virus detection

Infectious diseases caused by viruses have attracted global concern owing to their rapid spread and catastrophic consequences. Therefore, developing fast and reliable on-site virus detection methods is essential for the prevention and treatment of virus-related diseases. In this study, immunoassays on a membrane, combining virus preconcentration with nanoparticle-based signal amplification, were used to realize the rapid and accurate visual detection of viruses. The biotin–streptavidin scaffolds for target virus preconcentration were established on a membrane, and subsequently a Zika aptamer (Apt) immobilized on the membrane recognized and captured the nonstructural protein 1 of Zika virus (ZIKV-NS1). The probe for detection was synthesized by conjugating the Zika Apt with a high level of horseradish peroxidase on gold nanoparticles. The ZIKV-loaded membrane was incubated with the probes, and the viral signal was amplified as the signal of horseradish peroxidase. In the presence of 3,3,5′,5′-tetramethyl benzidine and hydrogen peroxide, the green color of the probe-coated membrane indicated the level of ZIKV-NS1. Our developed method could reach a detection limit of 5 ng mL−1, and the whole procedure could be completed within 1 h. Analyses of rabbit serum and environmental water samples demonstrated that an immunoassay-based approach on the membrane could accurately determine the level of ZIKV-NS1 against the complicated matrix. Our results suggest that this virus detection method has a high potential for application in clinical and environmental settings.

A Robust Sensor Integrating with Selective Membrane-Based Preconcentration and Signal Amplification for Field Virus Detection

A Robust Sensor Integrating with Selective Membrane-Based Preconcentration and Signal Amplification for Field Virus Detection

Opportunities and limitations of membrane-based preconcentration for rapid and continuous diagnostic applications

Osmotic or pneumatically-generated pressure gradients can be used in membrane-based filtration processes to preconcentrate biofluid samples for enhanced signal and increased sensitivity in diagnostic sensing applications.

Ammonium ultra-selective membranes for wastewater treatment and nutrient enrichment: Interplay of surface charge and hydrophilicity on fouling propensity and ammonium rejection

Membrane fouling and ammonium transmembrane diffusion simultaneously pose great challenges in membrane-based pre-concentration of domestic wastewater for efficient subsequent resources recovery (i.e., energy and nutrients). Herein, amine-functionalized osmotic membranes were fabricated by optimizing the grafting pathway of polyamidoamine (PAMAM) dendrimer to mitigate fouling and ammonium transmembrane diffusion. Compared to the control membrane, the PAMAM-grafted membranes with abundant primary amine groups possessed substantially increased hydrophilicity and positive charges (i.e., protonated primary amines) and thus exhibited superior anti-fouling capability and ammonium selectivity. With further increasing the PAMAM grafting ratio, the membrane exhibited a steady enhancement in ammonium selectivity and eventually achieved an ultra-high ammonium rejection of 99.4%. Nevertheless, the anti-fouling capability of such ammonium ultra-selective membrane was weakened due to the suppression of the adverse impact of excessive positive charges over the beneficial effect of increased surface hydrophilicity. This in turn leads to a drop of ammonium rejection below 90% during domestic wastewater concentration. This study demonstrates that the membrane with a moderate primary amine loading could achieve the highest anti-fouling capability with only less than 10% flux decline and meanwhile maintain an excellent ammonium rejection above 94% during raw domestic wastewater concentration. This work provides theoretical guidance for fabricating simultaneously enhanced anti-fouling and ammonia-rejecting membranes.

Enhanced membrane-based pre-concentration improves wastewater organic matter recovery: Pilot-scale performance and membrane fouling

Energy neutrality in municipal wastewater (MW) treatment is an ambitious sustainability goal that is hampered by MW's low organics concentration. A potential method is to pre-concentrate MW to recover the organics and use them to produce energy via anaerobic decomposition. This study conducted a pilot-scale operation using an enhanced membrane-based pre-concentration (MPC) technique to efficiently recover organics from actual MW. Stable and highly efficient organics recovery (72–75%) was achieved during two-month operations. Concentrated organics demonstrated high COD (above 20,000 mg/L) and good anaerobic biodegradability (360–367 mL CH4/g VS). Organics recovered by MPC exhibited the potential of net electrical energy production of 0.029–0.050 kWh/m3, depending on the fouling situation. The energy consumption of MPC was limited by avoiding continuous intensive aeration. With effective fouling control, as much as 2.91 times more energy could be produced than that was consumed. This suggests MPC-based processes have the potential to transform MW treatment plant from energy consumers to net producers.

Organics and nitrogen recovery from sewage via membrane-based pre-concentration combined with ion exchange process

This study proposes the recovery of organics and nitrogen from sewage through membrane-based pre-concentration (MPC) combined with ion exchange (IE) process. Unlike conventional activated sludge process, MPC–IE redesigned organic carbon flow to increase chemical oxygen demand (COD) conversion for energy recovery via anaerobic digestion (AD). This process also achieved nitrogen recovery instead of destruction. Membrane-based pre-concentration of COD was conducted using actual sewage for one month. As high as 65% COD was recovered. Batch IE adsorption and regeneration experiments were conducted. However, these experiments recovered only 37.5% NH4-N because of the selectivity of IE for hard ions over ammonium. Despite the low rate of recovery, the process could achieve a total of 0.38kWh/m3 energy recovery by combining energy production with anaerobic digestion of pre-concentrated organics (0.26kWh/m3) and energy saving via nitrogen reuse (0.12kWh/m3). Highly efficient energy and nitrogen recovery from sewage via MPC–IE process was expected after optimization.

Rapid Legionella pneumophila determination based on a disposable core–shell Fe3O4@poly(dopamine) magnetic nanoparticles immunoplatform

A novel amperometric magnetoimmunoassay, based on the use of core–shell magnetic nanoparticles and screen-printed carbon electrodes, was developed for the selective determination of Legionella pneumophila SG1. A specific capture antibody (Ab) was linked to the poly(dopamine)–modified magnetic nanoparticles (MNPs@pDA-Ab) and incubated with bacteria. The captured bacteria were sandwiched using the antibody labeled with horseradish peroxidase (Ab-HRP), and the resulting MNPs@pDA-Ab-Legionella neumophila-Ab-HRP were captured by a magnetic field on the electrode surface. The amperometric response measured at −0.15 V vs. Ag pseudo-reference electrode of the SPCE after the addition of H2O2 in the presence of hydroquinone (HQ) was used as transduction signal. The achieved limit of detection, without pre-concentration or pre-enrichment steps, was 104 Colony Forming Units (CFUs) mL−1. The method showed a good selectivity and the MNPs@pDA-Ab exhibited a good stability during 30 days. The possibility of detecting L. pneumophila at 10 CFU mL−1 level in less than 3 h, after performing a membrane-based preconcentration step, was also demonstrated.

Integrated microfluidic preconcentrator and immunobiosensor

We present a microfluidic biosensor that inte- grates membrane-based preconcentration with fluorescence detection. The concentration membrane was fabricated in polyacrylamide by an in situ photopolymerization tech- nique at the junction of glass microchannels. Liposomes entrapping sulforhodamine B dye molecules were used for signal amplification. The biotin-streptavidin binding system was a model system for evaluating device perfor- mance. Biotinylated liposomes were preconcentrated at the membrane by applying an electric field across the mem- brane. The electric field causes the liposomes to migrate toward the membrane where they are concentrated by a sieving effect. Two orders of magnitude concentration was achieved after applying the electric field for only 2 min. The concentrated bolus was then eluted toward the detec- tion unit, where the biotinylated liposomes were captured by immobilized streptavidin. The integrated system with the preconcentration module shows a 14-fold improvement in signal as opposed to a system that does not include preconcentration.

The influence of membrane ion-permselectivity on electrokinetic concentration enrichment in membrane-based preconcentration units

The performance of nanoporous hydrogel microplugs with varying surface charge density is described in concentrating charged analytes electrokinetically in a microfluidic device. A neutral hydrogel plug with a mean pore size smaller than the size of charged analytes acts as a simple size-exclusion membrane. The presence of fixed charges on the backbone of a nanoporous hydrogel creates ion-permselectivity which results in charge-selective transport through the hydrogel. This leads to the development of concentration polarization (CP) in the adjoining bulk electrolyte solutions under the influence of an applied electrical field. CP strongly affects the distribution of the local electrical field strength, in particular, in the vicinity of the hydrogel plug which can significantly reduce the concentration enrichment factors compared to the neutral hydrogel. A theoretical model and simulations are presented, together with experimental data, to explain the interplay of hydrogel or membrane cation-selectivity, electrical field-induced CP, and the distribution of the local electrical field strength with respect to concentration enrichment of negatively charged analytes at the cathodic membrane-solution interface.