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1.
Bioresour Technol ; 329: 124927, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-33706177

RESUMEN

The anaerobic digestion of leachate from organic fraction of municipal solid waste (OFMSW) is a long-standing challenge. A submerged anaerobic membrane bioreactor (AnMBR) embedding three flat sheet membrane was therefore continuously operated for 63 days to investigate the materials flow and membrane performance. The results obtained show that approximately 90% COD was removed and 86% was converted into methane under an OLR of 5.6 kgCOD/m3·d corresponding to a HRT of 10 days. Under the high solid condition (34.5-61.1 g/L total solids in AnMBR) and flux of 5 and 6 LMH, the membranes was operated practically at constant trans-membrane pressure (TMP). When the membrane was operated at a high flux of 7 LMH the TMP rapid increase occurred in 22 h resulting in a non-recoverable permeability. A sustainable flux was thus identified. This study demonstrated the feasibility of AnMBR treating OFMSW leachate under high solid condition with high flux.


Asunto(s)
Membranas Artificiales , Residuos Sólidos , Anaerobiosis , Reactores Biológicos , Metano , Eliminación de Residuos Líquidos
2.
Molecules ; 26(5)2021 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-33652616

RESUMEN

The main aims of the research were to produce efficient nanofibrous filters with long-term antibacterial properties and to confirm the functionality of samples under real filtration conditions. A polyurethane solution was modified by micro- or nanoparticles of copper oxide in order to juxtapose the aggregation tendency of particles depending on their size. Modified solutions were electrospun by the Nanospider technique. The roller spinning electrode with a needle surface and static wire electrode were used for the production of functionalized nanofibers. The antibacterial properties of the modified nanofibrous layers were studied under simulated conditions of water and air filtration. Particular attention was paid to the fixation mechanism of modifiers in the structure of filters. It was determined that the rotating electrode with the needle surface is more efficient for the spinning of composite solutions due to the continuous mixing and the avoidance of particle precipitation at the bottom of the bath with modified polyurethane. Moreover, it was possible to state that microparticles of copper oxide are more appropriate antimicrobial additives due to their weaker aggregation tendency but stronger fixation in the fibrous structure than nanoparticles. From the results, it is possible to conclude that nanofibers with well-studied durable antibacterial properties may be recommended as excellent materials for water and air filtration applications.


Asunto(s)
Antibacterianos/química , Infecciones Bacterianas/tratamiento farmacológico , Nanofibras/química , Nanopartículas/química , Antibacterianos/farmacología , Infecciones Bacterianas/microbiología , Infecciones Bacterianas/patología , Cobre/química , Humanos , Membranas Artificiales , Poliuretanos/química
3.
Bioresour Technol ; 330: 124946, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-33743278

RESUMEN

Wastewater treatment facilities play pivotal roles in preventing the transmission of water-borne viruses and protecting human health. In this study, a new electrochemical membrane bioreactor (EMBR) was proposed to achieve a long-lasting and efficient removal of virus from wastewater. Results showed that applying a low electric field (2.0 V) in EMBR system could achieve ~100% removal efficiency at both batch tests and continuous flow experiments. In contrast, the control MBR, without the exertion of electric field, exhibited a very low removal efficiency (19.8% on average). Moreover, the fouling in EMBR was significantly mitigated, which enabled its operation duration almost 3 times longer than that of the control. Further explorations suggested that the reactive oxidants generated on electrodes in the EMBR system were mainly responsible for MS2 removal. This study demonstrated the potential of utilizing the EMBR process to achieve an enhanced virus disinfection efficiency during the wastewater treatment process.


Asunto(s)
Virus , Purificación del Agua , Reactores Biológicos , Humanos , Membranas Artificiales , Eliminación de Residuos Líquidos , Aguas Residuales
4.
Bioresour Technol ; 330: 124991, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-33743281

RESUMEN

Chemically enhanced primary treatment (CEPT), ammonium ion exchange and regeneration (AIR) and membrane bioreactor (MBR) were coupled as CAIRM to treat domestic wastewater compactly and efficiently. CAIRM achieved efficient removal of chemical oxygen demand, ammonia nitrogen, total nitrogen (TN) and total phosphorus with total hydraulic retention time of 4.6 h, and obtained 2.3 ± 0.9 mg/L TN in the effluent. CEPT removed phosphate and impurities and prevented AIR from pollution. AIR maintained excellent nitrogen removal with a slight decrease in the exchange capacity of ion exchangers. MBR polished the effluent from AIR, and the larger particle size and better dewaterability of sludge mitigated the membrane fouling. Many heterotrophic genera, such as Rhodobacter and Defluviimonas, were enriched in the oligotrophic MBR. This study demonstrates the viability and stability of CAIRM in efficient wastewater treatment, which will address critical challenges in insufficient nitrogen removal and high land occupancy of current processes.


Asunto(s)
Contaminantes Ambientales , Purificación del Agua , Reactores Biológicos , Membranas Artificiales , Nitrógeno , Aguas del Alcantarillado , Eliminación de Residuos Líquidos , Aguas Residuales
5.
Bioresour Technol ; 330: 124966, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-33744734

RESUMEN

The enhancement effects of biochar to an anaerobic membrane bioreactor (AnMBR) treating sewage at low temperatures was investigated in this study through analyzing organics removal, digestion performance, mixed liquor properties, membrane resistance, and foulant compositions. The chemical oxygen demand (COD) removal efficiency and the COD converted to methane rate increased by more than 12.5% at 10 °C, mainly because of the promotion of biochar to volatile fatty acids degradation. Although biochar caused higher dissolved organic matter (DOM) concentration in the AnMBR, it improved the filtration property of the bulk sludge and absorbed the hydrophobic DOM. The decreased filtration resistance assisted by biochar leads to a prolonged membrane operation duration over 200%. Surface foulants, especially cake foulants, were largely mitigated by the enhanced scouring intensity of mixed liquor at the membrane surface, and hence, decreasing the cake/gel foulants ratio.


Asunto(s)
Reactores Biológicos , Aguas del Alcantarillado , Anaerobiosis , Carbón Orgánico , Digestión , Membranas Artificiales , Temperatura , Eliminación de Residuos Líquidos , Aguas Residuales
6.
Bioresour Technol ; 330: 124998, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-33757679

RESUMEN

Renewable energy, water conservation, and environmental protection are the most important challenges today. Osmotic membrane bioreactor (OMBR) is an innovative process showing superior performance in bioenergy production, eliminating contaminants, and low fouling tendency. However, salinity build-up is the main drawback of this process. Identifying the microbial community can improve the process in bioenergy production and contaminant treatment. This review aims to study the recent progress and challenges of OMBRs in contaminant removal, microbial communities and bioenergy production. OMBRs are widely reported to remove over 80% of total organic carbon, PO43-, NH4+ and emerging contaminants from wastewater. The most important microbial phyla for both hydrogen and methane production in OMBR are Firmicutes, Proteobacteria and Bacteroidetes. Firmicutes' dominance in anaerobic processes is considerably increased from usually 20% at the beginning to 80% under stable condition. Overall, OMBR process has great potential to be applied for simultaneous bioenergy production and wastewater treatment.


Asunto(s)
Microbiota , Purificación del Agua , Reactores Biológicos , Membranas Artificiales , Ósmosis , Aguas Residuales
7.
Water Res ; 196: 117006, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33744656

RESUMEN

A novel magnetic resonance measurement (MRM) protocol for non-invasive monitoring of fouling in spiral wound reverse osmosis (SWRO) membrane modules is demonstrated. Sodium alginate was used to progressively foul a commercial SWRO membrane at industrially relevant operating conditions in a circulating flow loop. The MRM protocol showcased the following: (i) earlier, more sensitive detection and quantification of fouling in the membrane module compared to feed-channel pressure drop. This was achieved using appropriate detection of the total nuclear magnetic resonance (NMR) signal. (ii) 2D cross-sectional imaging of the location of the accumulated foulant material; this was preferentially located adjacent to the membrane spacer sheet nodes, which was subsequently confirmed by a module autopsy. This image contrast, which could also readily differentiate the membrane, feed spacer and permeate spacer regions, was realised based on differences in the NMR relaxation parameter, T2,eff. (iii) High frequency acquisition of 2D cross-sectional velocity images of the module revealing very localised flow channelling in response to gradual foulant accumulation which impacted significantly on the flow pattern within the central permeate tube. Collectively this NMR/MRI measurement protocol provides a powerful analysis tool for the evolution of fouling in such complex modules, thus ultimately enabling more informed module design.


Asunto(s)
Incrustaciones Biológicas , Purificación del Agua , Filtración , Espectroscopía de Resonancia Magnética , Membranas Artificiales , Ósmosis
8.
J Environ Manage ; 287: 112344, 2021 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-33752047

RESUMEN

AnMBR technology is a promising alternative to achieve future energy-efficiency and environmental-friendly urban wastewater (UWW) treatment. However, the large amount of dissolved methane lost in the effluent represents a potential high environmental impact that hinder the feasibility of this technology for full-scale applications. The use of degassing membranes (DM) to capture the dissolved methane from AnMBR effluents can be considered as an interesting alternative to solve this problem although further research is required to assess the suitability of this emerging technology. The aim of this study was to assess the effect of operating temperature and hydrodynamics on the capture of dissolved methane from AnMBR effluents by DMs. To this aim, a commercial polydimethylsiloxane (PDMS) DM was coupled to an industrial prototype AnMBR (demonstration scale) treating UWW at ambient temperature. Different operating temperatures have been evaluated: 11, 18, 24 and 30 °C. Moreover, the DM was operated at different ratios of liquid flow rate to membrane area (QL:A) ranging from 22 to 190 Lh-1m-2 in order to study the resistance of the system to methane permeation. Methane recovery was maximized when temperature raised and QL:A was reduced, giving methane recovery efficiencies (MRE) of about 85% at a temperature of 30 °C and a QL:A of 25 Lh-1m-2. The study showed that high QL:A ratios hinder methane recovery by the perturbation of the DM fibers, being this effect intensified at lower temperatures probably due the higher liquid viscosities. Also, the performed fouling evaluation showed that not significant membrane fouling may be expected in the DM unit at the short-term when treating AnMBR effluents. A resistance-in-series model was proposed to predict the overall mass transfer of the system according to operating temperature and QL:A, showing that methane capture was controlled by the liquid phase, which represented up to 80-90% of total mass transfer resistance. The energy and environmental evaluation performed in this study revealed that PDMS DMs would enhance energy recovery and environmental feasibility of AnMBR technology for UWW treatment, especially when operating at low temperatures. When MRE was maximized, the combination of AnMBR with DM achieved net energy productions and net greenhouse gas reductions of up to 0.87 kWh and 0.216 kg CO2-eq per m3 of treated water.


Asunto(s)
Metano , Purificación del Agua , Anaerobiosis , Reactores Biológicos , Dimetilpolisiloxanos , Hidrodinámica , Membranas Artificiales , Temperatura , Eliminación de Residuos Líquidos , Aguas Residuales/análisis
9.
Water Sci Technol ; 83(5): 1005-1016, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-33724932

RESUMEN

Powered Activated Carbon - Membrane Bioreactors (PAC-MBRs) have been used with good results for slightly polluted water treatment. Our batch experiments showed that the transmembrane pressure of a PAC-MBR was 25% less than that of a MBR in one period of test, which indicated that PAC did help control the fouling in MBRs. Based on this observation, several mechanisms of membrane fouling of MBRs and PAC-MBRs were investigated to have some insight into how PAC brought a positive impact. The total resistances decreased by 60% and different resistances were redistributed after adding PAC. The dominant one changed from filtration resistance to cake resistance. These smaller cake resistances resulted from the PAC because, showing in the scanning electron microscopy pictures, it made the cake layer looser and rougher than that on a normal membrane. Meanwhile, the analysis of the membrane eluent showed that the addition of PAC changed the microbial species and its metabolites on the membrane and effectively reduced the adsorption of hydrophilic organic molecules on the membrane surface. Additionally, PAC prevented polypeptide compounds from being trapped inside the pores of membranes, so the cake on the PAC-MBR contaminated membrane surface was easier to scrape off. In the test of cleaning methods, alkaline cleaning removed the most organics from contaminated membranes to restore membrane performance.


Asunto(s)
Carbón Orgánico , Membranas Artificiales , Reactores Biológicos , Filtración , Polvos
10.
Water Sci Technol ; 83(5): 1055-1071, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-33724936

RESUMEN

Emissions of organic compounds, heavy metals and chemicals used in the ceramic industry cause significant organic and inorganic pollution of water. The effluent must be treated before it is discharged into a water body. International and EU laws control the chemical oxygen demand (COD) of the wastewater. Conventional technologies, such as sedimentation, flocculation and biological treatment, have lots of drawbacks, whereas membrane technologies give many benefits, as they are chemical-free and allow a reduction of the treatment steps. One-step wastewater nanofiltration with ceramic membranes of 450 Da cut-off is able to reduce the COD of ceramic wastewater to a sufficient level. However, the working time without cleaning is limited and the rejection of membranes can be significantly reduced due to fouling. Multistage filtration can be the solution. Filtration experiments with various combinations (MF, UF and NF) of ceramic membranes were performed at a laboratory scale with single-channel membranes and at pilot scale with 7-, 19- and 151-channel membranes in order to permanently reach the limit value of a COD below 80 mg/L and to increase the operating time. Four types of membranes were sequentially tested in the cross-flow mode: MF (200 nm pore size), UF (2,000 Da), NF (450 Da) and NF (200 Da). 5-day Biological Oxygen Demand (BOD) tests were performed in order to examine the wastewater biodegradability. The test results with single-channel membranes showed that in terms of the highest COD rejection and the highest permeability, the best combination was that of MF and UF membranes. Here, UF membranes were sufficient to reach the limit values. As for the multi-channel membranes, the combination of MF and NF (450 Da) was the best and the final COD concentration ranged from 11 to 48 mg/L. 5-day BOD bottle tests showed a COD/BOD ratio of 3.8, which opened up possibilities for combined treatment.


Asunto(s)
Aguas Residuales , Purificación del Agua , Cerámica , Membranas Artificiales , Eliminación de Residuos Líquidos
11.
Water Res ; 195: 116976, 2021 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-33706215

RESUMEN

Membrane technology has been widely used in the wastewater treatment and seawater desalination. In recent years, the reverse osmosis (RO) membrane represented by polyamide (PA) has made great progress because of its excellent properties. However, the conventional PA RO membranes still have some scientific problems, such as membrane fouling, easy degradation after chlorination, and unclear mechanisms of salt retention and water flux, which seriously impede the widespread use of RO membrane technology. This paper reviews the progress in the research and development of the RO membrane, with key focus on the mechanisms and strategies of the contemporary separation, anti-fouling and chlorine resistance of the PA RO membrane. This review seeks to provide state-of-the-art insights into the mitigation strategies and basic mechanisms for some of the key challenges. Under the guidance of the fundamental understanding of each mechanism, operation and modification strategies are discussed, and reasonable analysis is carried out, which can address some key technical challenges. The last section of the review focuses on the technical issues, challenges, and future perspective of these mechanisms and strategies. Advances in synergistic mechanisms and strategies of the PA RO membranes have been rarely reviewed; thus, this review can serve as a guide for new entrants to the field of membrane water treatment and established researchers.


Asunto(s)
Cloro , Purificación del Agua , Filtración , Membranas Artificiales , Nylons , Ósmosis
12.
Carbohydr Polym ; 260: 117830, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712169

RESUMEN

The manifold array of saccharide linkages leads to a great variety of polysaccharide architectures, comprising three conformations in aqueous solution: compact sphere, random coil, and rigid rod. This conformational variation limits the suitability of the commonly applied molecular weight cut-off (MWCO) as selection criteria for polysaccharide ultrafiltration membranes, as it is based on globular marker proteins with narrow Mw and hydrodynamic volume relation. Here we show the effect of conformation on ultrafiltration performance using randomly coiled pullulan and rigid rod-like scleroglucan as model polysaccharides for membrane rejection and molecular weight distribution. Ultrafiltration with a 10 kDa polyethersulfone membrane yielded significant different recoveries for pullulan and scleroglucan showing 1% and 71%, respectively. We found deviations greater than 77-fold between nominal MWCO and apparent Mw of pullulan and scleroglucan, while recovering over 90% polysaccharide with unchanged Mw. We anticipate our work as starting point towards an optimized membrane selection for polysaccharide applications.


Asunto(s)
Polisacáridos/química , Ultrafiltración/métodos , Glucanos/química , Glucanos/aislamiento & purificación , Membranas Artificiales , Conformación Molecular , Peso Molecular , Polímeros/química , Polisacáridos/aislamiento & purificación , Sulfonas/química
13.
Carbohydr Polym ; 260: 117769, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712127

RESUMEN

Periodontal defect poses a significant challenge in orthopedics. Guided Bone Regeneration (GBR) membrane is considered as one of the most successful methods applied to reconstruct alveolar bone and then to achieve periodontal defect repair/regeneration. In this paper, a novel polyamide-6/chitosan@nano-hydroxyapatite/polyamide-6 (PA6/CS@n-HA/PA6) bilayered tissue guided membranes by combining a solvent casting and an electrospinning technique was designed. The developed PA6/CS@n-HA/PA6 composites were characterized by a series of tests. The results show that n-HA/PA6 and electrospun PA6/CS layers are tightly bound by molecular interaction and chemical bonding, which enhances the bonding strength between two distinct layers. The porosity and adsorption average pore diameter of the PA6/CS@n-HA/PA6 membranes are 36.90 % and 22.61 nm, respectively. The tensile strength and elastic modulus of PA6/CS@n-HA/PA6 composites are 1.41 ± 0.18 MPa and 7.15 ± 1.09 MPa, respectively. In vitro cell culture studies demonstrate that PA6/CS@n-HA/PA6 bilayered scaffolds have biological safety, good bioactivity, biocompatibility and osteoconductivity.


Asunto(s)
Regeneración Ósea , Caprolactama/análogos & derivados , Quitosano/química , Durapatita/química , Membranas Artificiales , Nanoestructuras/química , Polímeros/química , Animales , Materiales Biocompatibles/química , Materiales Biocompatibles/farmacología , Regeneración Ósea/efectos de los fármacos , Caprolactama/química , Adhesión Celular/efectos de los fármacos , Diferenciación Celular/efectos de los fármacos , Línea Celular , Supervivencia Celular/efectos de los fármacos , Ratones , Nanofibras/química , Nanoestructuras/toxicidad , Porosidad , Propiedades de Superficie , Resistencia a la Tracción
14.
J Environ Manage ; 287: 112319, 2021 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-33721763

RESUMEN

The theoretical energy density extractable from acidic and alkaline solutions is higher than 20 kWh m-3 of single solution when mixing 1 M concentrated streams. Therefore, acidic and alkaline industrial wastewater have a huge potential for the recovery of energy. To this purpose, bipolar membrane reverse electrodialysis (BMRED) is an interesting, yet poorly studied technology for the conversion of the mixing entropy of solutions at different pH into electricity. Although it shows promising performance, only few works have been presented in the literature so far, and no comprehensive models have been developed yet. This work presents a mathematical multi-scale model based on a semi-empirical approach. The model was validated against experimental data and was applied over a variety of operating conditions, showing that it may represent an effective tool for the prediction of the BMRED performance. A sensitivity analysis was performed in two different scenarios, i.e. (i) a reference case and (ii) an improved case with high-performance membrane properties. A Net Power Density of ~15 W m-2 was predicted in the reference scenario with 1 M HCl and NaOH solutions, but it increased significantly by simulating high-performance membranes. A simulated scheme for an industrial application yielded an energy density of ~50 kWh m-3 (of acid solution) with an energy efficiency of ~80-90% in the improved scenario.


Asunto(s)
Membranas Artificiales , Aguas Residuales , Electricidad , Fuerza Protón-Motriz , Ríos
15.
Water Res ; 195: 116998, 2021 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-33714909

RESUMEN

Waste activated sludge (WAS) treatment has gained growing interests for its increasingly capacity and high process cost. Sludge thickening is generally the first process of the WAS treatment. However, traditional sludge thickening approach was restrained by large footprint, low thickening efficiency, and tendency of releasing phosphorus. Here, we reported a novel microfiltration (MF) membrane assisting forward osmosis (FO) process (MF-FO) for sludge thickening. The MF-FO reactor achieved a sludge thickening of the mixed liquor suspended solids (MLSS) concentration from approximately 7 to 50 g/L after 10-day operation. More importantly, the effluent quality after FO filtration was superior with total organic carbon (TOC), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N) and total phosphorus (TP) of 1.94 ± 0.46, 0.02 ± 0.07, 4.55 ± 1.59 and 0.24 ± 0.26 mg/L, respectively. Additionally, the integration of MF membrane successfully controlled the salinity of the MF-FO reactor in a low range of 1.6-3.1 mS/cm, which mitigated the flux decline of FO membrane and thus prolonged the operating time. In this case, the flux decline of FO membrane in the MF-FO reactor was mainly due to the membrane fouling. Furthermore, the fouling layer on the FO membrane surface was a gel layer mainly composed of biofoulants and organic foulants when the MLSS concentration was less than 30 g/L, while it turned to a cake layer when the MLSS concentration exceeded 30 g/L. Results reported here demonstrated that the MF-FO reactor is a promising WAS thickening technology for its excellent thickening performance and high effluent quality of FO membrane.


Asunto(s)
Aguas del Alcantarillado , Purificación del Agua , Reactores Biológicos , Filtración , Membranas Artificiales , Ósmosis , Salinidad , Aguas Residuales
16.
Water Res ; 195: 117010, 2021 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-33714912

RESUMEN

Membrane fouling by influent biopolymers, and the formation of surface biofilms, are major obstacles to the practical application of membrane technologies. Identifying reliable and sustainable pre-treatment methods for membrane filtration remains a considerable challenge and is the subject of continuing research study worldwide. Herein, the performance of a bench-scale gravity-driven up-flow slow biofilter (GUSB) as the pre-treatment for ultrafiltration to reduce membrane fouling is presented. Dissolved organic carbon (DOC) was shown efficiently removed by the GUSB (around 80%) when treating a natural water influent. More significantly, biopolymers, with molecular weight (MW) between 20 kDa and 100 kDa, were effectively removed (62.8% reduction) and this led to a lower rate of transmembrane pressure (TMP) development by the UF membrane. Microbial diversity analysis further unraveled the function of GUSB in shaping microbes to degrade biopolymers, contributing to lower accumulation and different distribution pattern of SMP on the membrane surface. Moreover, the biofilm formed on the membrane surface after the pre-treatment of GUSB was observed to have a relative porous structure compared to the control system, which can also affect the fouling development. Long-term operation of GUSB further revealed its robust performance in reducing both natural organic matters and UF fouling propensity. This study overall has demonstrated the potential advantages of applying a GUSB to enhance UF process performance by reducing biofouling and improving effluent quality.


Asunto(s)
Incrustaciones Biológicas , Purificación del Agua , Biopolímeros , Membranas Artificiales , Ultrafiltración
17.
Water Res ; 195: 116995, 2021 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-33721675

RESUMEN

Membrane fouling is a prominent problem that hinders the stable and efficient operation of the reverse osmosis (RO) system for wastewater reclamation. Previous studies showed that chlorine disinfection, which was commonly used in industrial RO systems as pretreatment, could lead to significant change in microbial community structure and resulted in serious biofouling. In order to prevent biofouling during wastewater reclamation, the effect of ultraviolet (UV) disinfection on RO membrane fouling was investigated and the mechanism was also revealed in this study. With the disinfection pretreatment by UV of 20, 40 and 80 mJ/cm2, the bacteria in the feed water were inactivated significantly with a log reduction of 1.11, 2.55 and 3.61-log, respectively. However, RO membrane fouling aggravated with higher UV dosage. Especially, in the group with the UV dosage of 80 mJ/cm2, the normalized RO membrane flux decreased by 15% compared with the control group after 19-day operation. The morphology of the fouled RO membranes indicated serious biofouling in all groups. The analysis on the microbial amount of the foulants showed that the heterotrophic plate counts (HPC) and ATP content on the fouled RO membranes with and without UV disinfection were at the same level. However, the total organic carbon content of the foulants with the UV dosage of 40 and 80 mJ/cm2 was significantly higher than the control group, with higher content of proteins and polysaccharides as indicated by EEM and FTIR spectrum. Microbial community structure analysis showed that some typical UV-resistant bacteria were selected and remained on the RO membrane after disinfection with high UV dosage, including. These residual bacteria after disinfection with high UV dosage showed higher extracellular polymeric substances (EPS) secretion compared with those without UV disinfection, and thus aggravated RO membrane fouling. Thicker EPS could decrease the transmission of UV rays, and thus bacteria with higher EPS secretion might be selected after UV disinfection.


Asunto(s)
Incrustaciones Biológicas , Purificación del Agua , Desinfección , Membranas Artificiales , Ósmosis , Aguas Residuales
18.
Water Res ; 195: 116989, 2021 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-33721676

RESUMEN

The aim of this study was to evaluate the effects of oxidation on humic-acid-enhanced gypsum scaling in different nanofiltration phases, including the short-term membrane flux behaviors and the long-term ones. On the basic of correlation analysis between the changing physicochemical properties of feed solution and membrane fouling, the inner mechanisms were revealed from aspects of bulk crystallization (interaction between humic acid and inorganic ions) and surface crystallization (compositions and morphologies of surface crystallization). Furthermore, the reliability of applicating differential log-transformed absorbance spectroscopy for predicting membrane fouling was also systematically evaluated. There was an upward trend in short-term membrane fouling with increasing dosage of NaClO, while long-term membrane fouling decreased after an initial increase. During short-term filtration, the enhanced combination between inorganic ions and the humic acid with stronger density of carboxyl groups, which was generated more easily under stronger oxidation conditions, favored the earlier appearance of flux decline. During long-term filtration, the size of bulk crystallization depended on the total content of carboxyl groups in feed solution. Both of them increased firstly and then decreased with increasing oxidation. The terminal fouling layer resistance also shared a similar tendency with them, because the deposition of bulk crystallization on membranes and the formation of dense scaling layer were the direct reasons for the long-term membrane fouling. Furthermore, the differential log-transformed absorbance spectroscopy was proven to be an efficient approach to predict short-term membrane fouling, especially in the wavelength range of 260 to 280 nm. This research could not only provide guidance on alleviating oxidation-enhanced membrane fouling in nanofiltration but also propose an efficient way to predict the membrane fouling which was influenced by the interaction between organic matters and inorganic ions.


Asunto(s)
Sustancias Húmicas , Purificación del Agua , Sulfato de Calcio , Sustancias Húmicas/análisis , Membranas Artificiales , Reproducibilidad de los Resultados , Análisis Espectral
19.
Chemosphere ; 271: 129879, 2021 May.
Artículo en Inglés | MEDLINE | ID: mdl-33736214

RESUMEN

Membrane bioreactors (MBRs) are considered a promising tool for resource recovery in wastewater treatment. Nevertheless, membrane fouling is an inevitable phenomenon that deteriorates the MBR performance. Although many studies have attempted to elucidate the effect of sludge characteristics on MBR fouling, they posed certain limitations. Most of the previous studies focused on the initial sludge or employ the results of short-term batch tests without long-term transmembrane pressure (TMP) profiles in the interpretation of fouling behaviors. This study was conducted considering these limitations to determine the sludge characteristics most closely related to long-term TMP profiles and to identify their role in fouling behaviors. In long-term TMP profiles, critical time (tc; time to TMP jump) and fouling rates (the increase in the TMP slope) were used as fouling indexes, which were used to correlate with average values of sludge characteristics before and after experiments. According to the results, the concentration of the total soluble microbial product (SMP) and extracted extracellular polymeric substance (eEPS) in sludge significantly increased by 1.9 times and up to 28 times after experiment. The increase in the SMP and eEPS caused early TMP jumps and resulted in low-fouling rates by increasing particle size. Owing to the increase in the SMP and eEPS concentration, the origin of fouling potential was shifted from suspended solids to colloids and soluble materials. Fouling resistance caused by soluble material increased by up to 11.38 times.


Asunto(s)
Aguas del Alcantarillado , Purificación del Agua , Reactores Biológicos , Matriz Extracelular de Sustancias Poliméricas , Membranas Artificiales
20.
Sci Total Environ ; 770: 145370, 2021 May 20.
Artículo en Inglés | MEDLINE | ID: mdl-33736376

RESUMEN

Triple-layered thin film composite (TFC) forward osmosis (FO) membranes prepared on interlayer-based supports have overcome the limitations of conventional porous substrates due to the formation of ultrathin and highly selective polyamide (PA) layers. However, mitigating the internal concentration polarization (ICP) and biofouling of TFC membranes remain a great challenge. Herein, we designed a novel triple-layered thin film nanocomposite (TFN) FO membrane with incorporation of silver (Ag) decorated graphene oxide quantum dots (GOQD) into PA layer via interfacial polymerization on a carbon nanotube (CNT) interlayer-based polyether sulfone substrate. By contrast with the TFC membranes, the newly developed GOQD/Ag incorporated triple-layered TFN membrane (TFN-GOQD/Ag) exhibited a great alleviation for ICP accompanied with a prominently enhanced water flux of 65.8 L·m-2·h-1 and decreased specific reverse salt flux of 1.4 g·m-2·h-1 by employing 1 M NaCl solution as draw solution. Moreover, the TFN-GOQD/Ag membrane possessed prominent antibacterial activity against both E. coli (99.8%) and S. aureus (97.3%). Noteworthy, the obtained TFN membrane demonstrated a controlled release of Ag+ along with long-term antibacterial potential and outstanding fouling resistance during the FO process. This work provides a new avenue to fabricate newly FO membranes with superior performance for water cleaning treatment.


Asunto(s)
Nanocompuestos , Agua , Antibacterianos , Escherichia coli , Membranas Artificiales , Staphylococcus aureus
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