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In an attempt to better understand and control seawater reverse osmosis (RO) membrane fouling, low-pressure (LPFD) and high-pressure fouling detectors (HPFD) were employed in an ex situ, sidestream configuration at a full-scale seawater desalination plant. These fouling detectors contained flat-sheet membrane and spacer materials extracted from the membrane modules installed at the plant. The high-pressure fouling detectors reasonably replicated full-scale plant permeate quality, permeate flux, and differential pressure, whereas low-pressure fouling detectors could only simulate differential pressure. When evaluating different pre-treatments, it was observed that activated carbon and chlorine dioxide (after chlorination, microfiltration and dechlorination) to be effective at preventing RO membrane fouling, whereas chlorination, microfiltration and dechlorination and the same sequence followed by ultraviolet irradiation were less effective. Accelerated fouling was found when dosing both colloidal and dissolved nutrients, but the colloidal nutrient caused more severe fouling through a combination of colloidal cake layer formation in addition to biofilm formation and growth. In some cases, differential pressure may be an adequate early warning fouling indicator, but in this study, the high-pressure fouling detector more accurately captured plant fouling impacts. Finally, full-scale seawater RO plant fouling impacts were sufficiently captured while monitoring only pressure, flow and electrical conductivity; therefore, the added cost and complexity of employing more sophisticated optical, electrical, ultrasonic or other methods in ex situ, side stream fouling detectors may not be justified. [ABSTRACT FROM AUTHOR]

Biofouling has been referred to as "the Achilles heel" of reverse osmosis (RO) membrane technology; the main cause being polyamide RO membranes lack of chlorine tolerance. Biofouling increases the operating cost of water treatment by increasing RO system feed pressure (i.e., energy demand) and increasing membrane cleaning frequency, which increases downtime and reduces membrane useful life. For waters with known high biofouling potential, plant designs also may require more extensive pretreatment, which increases capital and operating costs as well as the footprint of a desalination plant. It is known from the literature that the three keys to fending off biofouling in RO systems and/or recovering from biofouling once it takes root include (1) understanding site-specific processes governing biofilm formation, (2) implementing effective biofouling pretreatment ahead of RO membranes, and (3) monitoring biofouling to enable more proactive and effective RO membrane cleaning. Herein, we present four case studies of RO membrane biofouling in seawater, municipal wastewater, brackish groundwater and industrial wastewater. Next, we describe what is known about the causes and consequences of bacterial biofilm formation and growth through a process level RO membrane biofouling model. Finally, we review common biofouling control methods including pre-treatment, chemical cleaning and the most common strategies for monitoring biofouling in RO membrane systems. [ABSTRACT FROM AUTHOR]

Ensuring safe water supply for communities across the United States is a growing challenge due to aging infrastructure, impaired source water, strained community finances, etc. In 2019, about 6% of public water utilities in the U.S. had a health-based violation. Due to the high risk of exposure to various contaminants in drinking water, point-of-use (POU) drinking water treatment is rapidly growing in popularity in the U.S. and beyond. POU treatment technologies include various combinations of string-wound sediment filters, activated carbon, modified carbon, ion exchange and redox media filters, reverse osmosis membranes, and ultraviolet lamps depending on the contaminants of concern. While the technologies are well-proven, highly commoditized, and cost-effective, most systems offer little in the way of real-time performance monitoring or interactive technology like other smart home appliances (e.g., thermostats, smoke detectors, doorbells, etc.). Herein, we review water quality regulations and violations in the U.S. as well as state-of-the-art POU technologies and systems with an emphasis on their effectiveness at removing the contaminants most frequently reported in notices of violations. We conclude by briefly reviewing emerging smart water technologies and the needs for advances in the state-of-the-art technologies. The smartness of commercially available POU water filters is critiqued and a definition of smart water filter is proposed. [ABSTRACT FROM AUTHOR]

A recent innovation in seawater desalination is the use of multi-stage and multi-pass combinations of nanofiltration (NF) and reverse osmosis (RO) membranes. One example of this approach is the “Long Beach method,” in which seawater passes through two different types of NF membranes to produce potable water. After several years of pilot studies comparing the performance of two-pass NF and single-pass RO systems, a number of membrane elements were sacrificed for autopsy analyses. The selected membranes represent different stages of operation including (1) new, (2) fouled, and (3) cleaned membranes. Used NF and RO spiral wound elements were removed from the first and last positions of the demonstration plant. Although operating data suggested no outward signs of membrane fouling – inorganic, organic, and bacterial accumulation were identified on all membranes. First pass RO and NF membranes contained similar amounts of deposited solids, while significantly fewer solids were found on second pass NF membranes. Viable, culturable marine bacteria were observed on all fouled and cleaned membranes, indicating that bacterial colonization of seawater NF/RO membranes was not (a) detected by plant performance monitoring devices, (b) prevented by microfiltration and chlorination, or (c) removed by chemical cleaning. Chemical cleaning recovered the measurable performance of both first pass RO and second pass NF membranes, but was relatively ineffective at removing deposited solids from first-pass NF membranes. Therefore, chemical-cleaning methods may need to be tailored and optimized more specifically for NF membranes used in seawater desalination. [ABSTRACT FROM AUTHOR]

A 6-month pilot-scale field study was conducted to investigate the performance of three polymeric ultra filtration membranes for tertiary filtration within a Southern California municipal water recycling plant. Commercial hydrophilic polyvinylidene fluoride, polyether sulfone, and PolyCera® flatsheet membranes were packaged identically into Spiral Monolith cross-flow back washable modules. The overall objective of the study was to evaluate the filtrate recovery, energy demand, and operating cost of the three membrane materials in achieving California Title 22 product water quality filtering secondary-treated sewage. All three membranes met California Title 22 filtered water quality criteria throughout the entire testing period due to their small characteristic pore size. The PolyCera membrane was the least fouling prone and, as a result, produced significant benefits in filtrate recovery, energy consumption, and operating cost due to less frequent and intense backwashing requirements. Filtration was maintained for over 5 weeks when operating the PolyCera membrane with an average flux of 33 LMH and filtrate backwashing every 25 min. During this long-term operation, the PolyCera system consumed, on average, 0.035 kWh at an operating cost of $0.016 for every cubic meter filtrate water produced, which is a net savings up to 46% compared to standard systems reported in literature. [ABSTRACT FROM AUTHOR]

The effects of natural and synthetic polymer additives on the properties of ultrafiltration membranes were studied. The use of NaOH to remove the residual additive remaining in the membranes during coagulation was also investigated, as was the effect of NaOH post-treatment relative to membrane performance. To evaluate the residual additives present, ATRFTIR was used. Contact-angle analysis and water-absorption experiments were used to examine the hydrophilic properties of the prepared membranes. Membranes modified with lignin (Lig) were found to absorb more water (94% water uptake) than other membranes. In general, the contact angles were found to be low for membranes treated with NaOH. Membrane permeability was greatest in lignin_polysulfone (Lig_PSf), followed by polyvinylpyrrolidone_polysulfone (PVP_PSf), and with polyethylene glycol_polysulfone (PEG_PSf) the least permeable, similar to the trend observed in water uptake. A 'Robeson plot' analogue showed that Lig_PSf membranes had high separation factors regardless of the size of the solute being rejected. This study indicates the feasibility of using cheap, readily available additives to increase the performance of membranes. [ABSTRACT FROM AUTHOR]

We demonstrate that poly(n-2-hydroxyethyl aniline) (n-PANi), a derivative of polyaniline (PANi), provides an effective chlorine tolerant PANi-based ultrafiltration (UF) membrane. n-PANi was synthesized from its monomer via chemical oxidative polymerization. Unlike PANi, n-PANi can be dissolved in N-methyl-2-pyrollidone (NMP) up to 30 wt% to form a casting solution which is stable for months without the aid of an anti-gelling agent. Membranes formed from n-PANi show high resistance to chlorine, even when exposed to 250 ppm sodium hypochlorite for 30 days while PANi membranes completely lose their ability to reject bovine serum albumin (BSA, 6 nm) after 2 days. Spectroscopic studies indicate that the benzenoid groups in PANi membranes are oxidized while n-PANi membranes maintain their chemical structure. n-PANi membranes display high hydrophilicity with a contact angle of ∼36 degrees which contributes to their ultra-low adhesion of E. coli. Cross-flow fouling tests with 1.5 g L−1 BSA fouling solution reveal that n-PANi membranes exhibit low-fouling properties with only 11% flux decline and 91% flux recovery, superior to PANi and commercial polysulfone (PSf) membranes. [ABSTRACT FROM AUTHOR]

We present a method to produce anti-fouling reverse osmosis (RO) membranes that maintains the process and scalability of current RO membrane manufacturing. Utilizing perfluorophenyl azide (PFPA) photochemistry, commercial reverse osmosis membranes were dipped into an aqueous solution containing PFPA-terminated poly(ethyleneglycol) species and then exposed to ultraviolet light under ambient conditions, a process that can easily be adapted to a roll-to-roll process. Successful covalent modification of commercial reverse osmosis membranes was confirmed with attenuated total reflectance infrared spectroscopy and contact angle measurements. By employing X-ray photoelectron spectroscopy, it was determined that PFPAs undergo UV-generated nitrene addition and bind to the membrane through an aziridine linkage. After modification with the PFPA-PEG derivatives, the reverse osmosis membranes exhibit high fouling-resistance. [ABSTRACT FROM AUTHOR]

ABSTRACT This article reports the results of a study on the effect of using different additives (lignin, polyethylene glycol [PEG], and polyvinyl pyrrolidone [PVP]) to fabricate ultrafiltration polysulfone (PSf) membranes. The main focus of this study was on the difference in permeation properties brought about by the absence or presence of a fabric when fabricating the membranes. Differential scanning calorimetry was used to characterize the thermal properties and was also used to predict the other membrane properties. An Instron machine was used to evaluate the mechanical properties. The bulk porosity of lignin and PVP-modified membranes was observed to be higher than that of the membranes modified with PEG. There was a strong negative correlation between the bulk porosity and the glass transition temperature irrespective of the additive used. Membranes cast on a fabric showed higher flux compared with membranes cast on glass. There was a strong positive correlation between the bulk porosity and the observed permeability regardless of whether the membrane was cast on a nonwoven fabric or on a glass plate. Pore-size distribution results showed that lignin and PVP-modified membranes had a narrow pore-size distribution ranging between 10 and 25 nm when compared with PEG-modified membranes with a pore-size distribution ranging between 2.5 and 20 nm. These results indicate that thermal, bulk porosity, and mechanical properties can be used to probe the membrane structure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40616. [ABSTRACT FROM AUTHOR]

Composite nanofiltration membranes were formed by depositing ultra-thin, cross-linked polyvinyl alcohol (PVA) film on porous polysulfone (PSf) support membranes following a three step dip-coating procedure. The PVA coating films were cross-linked with aliphatic tricarboxylic acids (cis-/trans-aconitic) and aromatic dicarboxylic acids (phthalic, isophthalic, and terephthalic). Tricarboxylic acid cross-linked PVA was less crystalline and slightly more hydrophilic relative to PVA films cross-linked by aromatic dicarboxylic acids suggesting that the tricarboxylic acids are more effective is disrupting PVA crystallinity than the dicarboxylic acids. Cross-linked PVA-PSf composite membranes rejected NaCl and MgSO4in the order: trans-aconitic acid < cis-aconitic acid < terephthalic acid < isophthalic acid < phthalic acid. [ABSTRACT FROM AUTHOR]

Development of electro-ultrafiltration membranes is an attractive target. We report electrically conducting ultrafiltration membranes by blending single-walled carbon nanotube/polyaniline (SWCNT/PANi) nanofibers into a polysulfone (PSf) matrix. By selecting the amount of nanofibers and applying a flash welding technique, the chemical structure, porosity, thermal stability, conductivity, hydrophilicity, permeability, and bovine serum albumin (BSA) rejection of these composite ultrafiltration membranes can be controlled. Addition of SWCNT/PANi nanofibers to the composites enhances the initial water permeability by 2.5–7.3 times and increases the hydrophilicity, and maintains considerable rejection of BSA from 39.8–73.7%. An electrical conductivity between 0.1 and 3.4 × 10−6 S cm−1 can be maintained over a broad pH range from 0.52–10.2. By regulating the flash welding intensity, the conductivity, permeability, and BSA rejection can be enhanced up to 600, 2, and ∼1.5 times, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT This study investigates the effect of solvent properties on the structural morphology and permeation properties of polysulfone/β-cyclodextrin polyurethane (PSf/β-CDPU) mixed-matrix membranes (MMMs). The membranes were prepared by a modified phase-inversion route using four different casting solvents [dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), dimethyl acetamide (DMA), and N-methyl-2-pyrrolidone (NMP)]. While DMSO-based membranes demonstrated particularly high permeability (ca 147 L/m2h.bar), their crystallinity was low compared to MMMs prepared using DMA, DMF and NMP due to the formation of thin active layers on their surfaces. Cross-sectional morphology revealed that the MMMs have a dense top skin with finger-like inner pore structures. Membranes prepared using NMP displayed the highest hydrophilicity, porosity, and crystallinity due to the low volatility of NMP; DMF membranes exhibited superior mechanical and thermal stability due to its (DMF) high hydrogen bonding (δ H) values. Thus, the morphological parameters, bulk porosity, and flux performance of MMMs have a significant inter-relationship with the solubility properties of each solvent (i.e., δ H, density, volatility, solubility parameter). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2005-2014, 2013 [ABSTRACT FROM AUTHOR]

Polymeric reverse osmosis membranes were modified with antifouling polymer brushes through a ‘layer by layer’ (LBL) mediated method. Based on pure physical electrostatic interaction, the attachment of LBL films did not alter separation performance of the membranes. In addition, the incorporation of an LBL film also helped to amplify the number of potential reaction sites on the membrane surfaces for attachment of antifouling polymer brushes, which were then attached to the surface. Attachment of the brushes included two different approaches, grafting to and grafting from. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements showed successful growth of the LBL films and subsequently the polymer brushes. Using this method to modify reverse osmosis membranes, preliminary performance testing showed the antifouling properties of the as-modified membranes were much better than the virgin membrane with no significant loss in water flux and salt rejection. [ABSTRACT FROM AUTHOR]

The authors describe a novel high-throughput screening platform that provides rapid, reliable, quantitative assessment of biofilm formation and removal on engineered surfaces. Unlike traditional biofilm assays based on plate readers, this assay platform is based on high-content screening, which allows for multiplexing to simultaneously quantify the number of bacterial adhesions per unit area and the viability of adhered cells using fluorescent dye combinations. This platform is fully automated and has a throughput of more than 10,000 wells per day. The authors used this platform to examine the influence of different assay buffer systems on bacterial adhesion, viability, and removal on cross-linked polyvinyl alcohol coating films synthesized directly onto the bottoms of 384-well plates. The results indicated that water chemistry, bacteria cell type, and film chemistry combine to govern biofilm formation. In general, both reversible and irreversible bacterial adhesion increased with the extent of cross-linking in coating films, which correlates strongly with coating film cross-linking degree and hydrophobicity, which is closely related. The high-throughput platform offers a powerful tool for rapid evaluation of fouling-resistant coating films in addition to elucidation of fundamental mechanisms governing bacterial adhesion. [ABSTRACT FROM AUTHOR]

Here, we present a review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms. For purpose of this review, silver nanomaterials include silver nanoparticles, stabilized silver salts, silver–dendrimer, polymer and metal oxide composites, and silver-impregnated zeolite and activated carbon materials. While there is some evidence that silver nanoparticles can directly damage bacteria cell membranes, silver nanomaterials appear to exert bacteriocidal activity predominantly through release of silver ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication. Eukaryotic cells could be similarly impacted by most of these mechanisms and, indeed, a small but growing body of literature supports this concern. Most antimicrobial studies are performed in simple aquatic media or cell culture media without proper characterization of silver nanomaterial stability (aggregation, dissolution, and re-precipitation). Silver nanoparticle stability is governed by particle size, shape, and capping agents as well as solution pH, ionic strength, specific ions and ligands, and organic macromolecules—all of which influence silver nanoparticle stability and bioavailability. Although none of the studies reviewed definitively proved any immediate impacts to human health or the environment by a silver nanomaterial containing product, the entirety of the science reviewed suggests some caution and further research are warranted given the already widespread and rapidly growing use of silver nanomaterials. [ABSTRACT FROM AUTHOR]

Rapid growth in nanotechnology is increasing the likelihood of engineered nanomaterials coming into contact with humans and the environment. Nanoparticles interacting with proteins, membranes, cells, DNA and organelles establish a series of nanoparticle/biological interfaces that depend on colloidal forces as well as dynamic biophysicochemical interactions. These interactions lead to the formation of protein coronas, particle wrapping, intracellular uptake and biocatalytic processes that could have biocompatible or bioadverse outcomes. For their part, the biomolecules may induce phase transformations, free energy releases, restructuring and dissolution at the nanomaterial surface. Probing these various interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings. This knowledge is important from the perspective of safe use of nanomaterials. [ABSTRACT FROM AUTHOR]

The biofouling potential is one of the important factors to design and to select membranes for water and wastewater treatment. In this investigation, the effect of membrane surface properties during the attachment of S. cerevisiae cells was examined using a laboratory‐scale membrane filtration cell enabling direct microscopic observation of microbial cell deposition. The experimental results from 6 commercially available membranes showed that the initial adhesion rate, k d , was affected by the zeta potentials, hydrophobicity, and roughness of membrane surfaces. The k d value was significantly lower at the membrane which had more negative, hydrophilic, and smooth surfaces. The results will be helpful to minimize the time for selecting membranes in different situations, and for testing the performance of newly designed membranes. [ABSTRACT FROM AUTHOR]

The biofouling potential is one of the important factors to design and to select membranes for water and wastewater treatment. In this investigation, the effect of membrane surface properties during the attachment of S. cerevisiae cells was examined using a laboratory‐scale membrane filtration cell enabling direct microscopic observation of microbial cell deposition. The experimental results from 6 commercially available membranes showed that the initial adhesion rate, k d , was affected by the zeta potentials, hydrophobicity, and roughness of membrane surfaces. The k d value was significantly lower at the membrane which had more negative, hydrophilic, and smooth surfaces. The results will be helpful to minimize the time for selecting membranes in different situations, and for testing the performance of newly designed membranes. [ABSTRACT FROM AUTHOR]

Herein, we report on the performance of a hybrid organic-ceramic hydrophilic pervaporation membrane applied in a vacuum membrane distillation operating mode to desalinate laboratory prepared saline waters and a hypersaline water modeled after a real oil and gas produced water. The rational for performing "pervaporative distillation" is that highly contaminated waters like produced water, reverse osmosis concentrates and industrial have high potential to foul and scale membranes, and for traditional porous membrane distillation membranes they can suffer pore-wetting and complete salt passage. In most of these processes, the hard to treat feed water is commonly softened and filtered prior to a desalination process. This study evaluates pervaporative distillation performance treating: (1) NaCl solutions from 10 to 240 g/L at crossflow Reynolds numbers from 300 to 4800 and feed-temperatures from 60 to 85 °C and (2) a real produced water composition chemically softened to reduce its high-scale forming mineral content. The pervaporative distillation process proved highly-effective at desalting all feed streams, consistently delivering <10 mg/L of dissolved solids in product water under all operating condition tested with reasonably high permeate fluxes (up to 23 LMH) at optimized operating conditions. [ABSTRACT FROM AUTHOR]

The separation performance, energy demand, and operating costs of electro-coagulation (EC) are compared to conventional chemical coagulation for oil–water separation using a simulated oil- and gas-produced water matrix. An iron-based chemical coagulant and sacrificial iron electrodes are evaluated. Effluent turbidity, chemical oxygen demand (COD), total organic carbon (TOC), and oil and grease (O&G) removal were determined for various coagulant concentrations and reaction times and current densities. Chemical coagulation produced superior turbidity removal when scaled by the total iron dose. At lower iron doses (<500 mg/L), chemical coagulation yielded better COD, turbidity, and O&G removal. However, chemical coagulation was unable to effectively remove contaminants to meet the offshore discharge limit of 29 ppm O&G. At higher iron doses, EC was more effective at removing COD and O&G. The energy consumption of EC was found to be much higher even when factoring in the energy of production, transporting, and mixing of chemical coagulants, but the overall cost of EC was approximately half the cost of chemical coagulation, and more effective at O&G removal. [ABSTRACT FROM AUTHOR]

There is approximately 508.7 million cubic meters (3.2 million barrels) of oilfield-produced water generated per year across the oil fields of California. While less than 2% of this produced water receives advanced treatment for beneficial reuse, changing regulations and increasing scarcity of freshwater resources is expected to increase the demand for beneficial reuse. This paper reviews onshore-produced water quality across California, relevant standards and treatment objectives for beneficial reuse, identifies contaminants of concern, and treatment process design considerations. Lastly, we evaluate the capital and operating costs of an integrated membrane system for treating produced water based on data from a field pilot conducted in the coastal region of California. [ABSTRACT FROM AUTHOR]

Hybrid zeolite-polyamide thin film nanocomposite (TFN) reverse osmosis membranes were synthesized by incorporating Linde type A (LTA)-type zeolite molecular sieve nanocrystals in the interfacial polymerization reaction used to form polyamide thin films. Nanocrystals were prepared with two different mobile cations (Na+ and Ag+) exchanged within the LTA crystal matrix. Incorporation of molecular sieve nanocrystals into polyamide thin films during interfacial polymerization was verified by infrared spectroscopy. Both TFN membranes exhibited higher water permeability, while maintaining similar salt rejection to pure polyamide thin film composite membranes. Nanocomposite thin films containing LTA nanocrystals in the silver form (AgA) produced a greater increase in water permeability than those in the sodium form (NaA). Furthermore, AgA-TFN membranes exhibited more hydrophilic and smooth interfaces, which appeared to inhibit adhesion of bacteria cells onto the membranes. The AgA nanocrystals exhibited significant bactericidal activity; however, when encapsulated within polyamide thin films the antimicrobial activity was significantly reduced. [ABSTRACT FROM AUTHOR]