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Abstract: In this study we evaluated the performance of forward osmosis (FO) at the pilot scale to achieve simultaneous seawater desalination and wastewater reclamation. The investigation was performed with a commercial spiral wound FO membrane element for approximately 1300h of continuous operation, processing 900,000L of wastewater effluent and producing 10,000L of purified water through a hybrid FO-RO process. Water and solute fluxes were monitored during the study. Reversible and irreversible membrane fouling was observed; however, water flux was maintained at a relatively constant rate of 5.7±0.2Lm−2 h−1 with MBR permeate feed and seawater draw solution. Subsequent increase of total suspended solids (TSS) concentration in the FO feed (secondary treated effluent with 5 to 16mgL−1 TSS) resulted in incremental flux decline; however, the membrane typically achieved stable water flux after the initial exposure to foulants. Additional analysis focused on bi-directional transport of inorganic species and a detailed evaluation of dissolved organic matter permeation through the membranes in the hybrid process. Evaluation of sample fluorescence revealed that the FO membrane and the hybrid process provide a strong barrier to protein-like fluorophores associated with wastewater effluent. Results also demonstrated the robust nature of dual barrier membrane systems to achieve greater than 99.9% removal of orthophosphate and dissolved organic carbon and more than 96% rejection of nitrate. Upon completion of the study a comprehensive membrane autopsy was performed on the FO and RO membranes. Organic fouling on the FO membrane was observed to have low adhesion to the membrane surface, but did result in some modification to membrane active layer properties. [Copyright &y& Elsevier]

Abstract: This study investigated membrane fouling during wastewater reclamation by collecting operational performance data and employing state-of-the-art techniques for characterization of membrane foulants. Utilizing a pilot-scale membrane unit, two nanofiltration membranes (NF-90 and NF-4040, Dow/Filmtec) and one low-pressure reverse osmosis membrane (TMG10, Toray America) were tested at two wastewater reclamation facilities treating microfiltered non-nitrified secondary effluent and nitrified/denitrified tertiary effluent. The membranes and foulants were characterized by environmental scanning electron microscopy coupled with energy dispersive spectroscopy, attenuated total reflection-Fourier transform infrared spectrometry, zeta-potential measurement, atomic force microscopy, phospholipids analysis, and contact angle measurement. During treatment of the nitrified/denitrified effluent, membrane fouling was dominated by biofouling in combination with organic fouling, colloidal fouling, and inorganic scaling. Sufficient chloramines residual was identified as being critical in controlling biofouling during wastewater desalination. During filtration of the non-nitrified effluent, fouling of the membrane lead-elements was mainly caused by adsorption and deposition of effluent organic matter while biofouling still observed in tail-elements despite the formation of chloramines. Rough and hydrophobic membrane with high permeability (e.g., NF-90) displayed more severe initial specific flux decline during filtration, while smooth and hydrophilic membrane (e.g., NF-4040) exhibited high and constant specific flux when biofouling was under control. [Copyright &y& Elsevier]

Abstract: Large amounts of co-produced water are generated during natural gas production. This study investigated the viability and cost effectiveness of ultra-low pressure reverse osmosis (ULPRO) and nanofiltration (NF) membranes as potential techniques for beneficial use of produced water by meeting potable and irrigation water quality standards and concentrating iodide in the brine. A 2-stage laboratory-scale membrane testing unit was employed to examine rejection of various constituents of concern at a low and high recovery using produced water generated from sandstone aquifers. The performance of two ULPRO membranes TFC-ULP (Koch) and TMG10 (Toray America) and one NF membrane NF-90 (Dow/Filmtec) was compared to a conventional RO membrane (TFC-HR, Koch). These membranes were pre-selected during previous bench-scale experiments with regard to specific flux, fouling propensity, salts and organics rejection, and iodide recovery efficiency. Of the membranes tested, the NF-90 achieved the highest specific flux. The salt rejection and iodide recovery by the NF-90, however, were much lower than the RO and ULPRO membranes tested. The permeate quality of the NF-90 met USEPA National Primary Drinking Water Standards, but exceeded the Secondary Standards regarding chloride and total dissolved salts. The two ULPRO membranes TMG10 and TFC-ULP, exhibited a higher specific flux as compared to the TFC-HR while displaying a similar rejection, notably the TMG10 which showed a very stable rejection at low and high recoveries. Cost analysis showed that the ULPRO membrane system provided marginally lower overall O&M costs than RO for meeting drinking water standards. The ULPRO membrane operation resulted in even lower treatment cost than RO and NF for meeting irrigation water standards, especially at high energy cost. Findings from these studies indicated that ULPRO membranes can provide a viable and cost-effective solution to beneficial use of produced water from sandstone aquifers. [Copyright &y& Elsevier]

Abstract: Commercial polyamide nanofiltration (NF), reverse osmosis (RO), and ultra-low pressure RO (ULPRO) membranes (NF-90, NF-200, TFC-HR, and XLE) as well as a cellulose triacetate RO membrane (CTA) were employed to investigate the effect of fouling on transport of organic micropollutants. Due to foulant precipitation and cake-layer formation, membrane surface characteristics changed considerably in terms of contact angle (an index of hydrophobicity), zeta-potential, functionality, and surface morphology, which potentially affected transport of contaminants as compared to unfouled (virgin) membranes. The transport of ionic organic micropollutants was hindered as a result of improved Donnan exclusion (electrostatic repulsion) likely due to a more negative surface charge as quantified by zeta-potential measurements. Membrane fouling also resulted in an increased adsorption capacity and reduced mass transport through partitioning and diffusion of solutes across the membrane. These effects led to an increase in rejection of hydrophobic non-ionic solutes (e.g., disinfection byproducts and chlorinated solvents) by fouled membranes. However, the increasing surface charge has the potential to result in a larger molecular weight cut-off of a fouled membrane due to membrane swelling, which can lead to lower rejection for hydrophilic non-ionic solutes, especially where nanofiltration membranes with a larger molecular weight cut-off are employed. Membrane fouling facilitated the transport of hydrophobic and hydrophilic organic contaminants through CTA membranes resulting in elevated concentrations of target solutes in the permeate. Findings of the study indicate that membrane fouling significantly affects the rejection of organic solute by CTA, NF, and ULPRO membranes while it is less important for thin film composite RO membranes. [Copyright &y& Elsevier]

The synergistic impact of salts and organic matter on adsorption of ibuprofen and sulfamethoxazole by three types of biochar and an activated carbon was investigated using reclaimed water reverse osmosis (RO) concentrate and synthetic solutions spiked with target organic compounds and non-target water constituents (e.g., Na + , Ca 2 + , Mg 2 + , K + , Cl − , SO 4 2 − , alkalinity, humic acid (HA), and bovine serum albumin (BSA)). Kinetic modeling was used to better understand the adsorption process between the carbon adsorbents and pharmaceuticals and to elucidate the impact of water chemistry on pharmaceuticals adsorption. The adsorption capacity of pharmaceuticals by biochar was affected by their physicochemical properties including ash content, specific surface area, charge, pore volume, as well as hydrophobicity, π-energy, and speciation of pharmaceuticals. The adsorption of pharmaceuticals in concentrate was pH-dependent, the kinetic rate constant increased with deceasing pH due to the electrical interactions between pharmaceutical molecules and adsorbents. High salinity and electrolyte ions in RO concentrate improved adsorption, whereas the presence of carbonate species, HA, and BSA hindered the removal of ibuprofen and sulfamethoxazole. This study revealed the correlation of concentrate water quality on adsorption of pharmaceuticals by biochar and activated carbon. Biochar provides a promising alternative to activated carbon for removal of organic contaminants of emerging concerns in various wastewater and concentrate streams. [ABSTRACT FROM AUTHOR]

The incomplete rejection of certain pesticides, disinfection by-products, endocrine disrupting compounds, and pharmaceutically active compounds has been reported during full- and pilot-scale high-pressure membrane applications. Since the removal of these compounds in water and wastewater treatment applications is of great importance where a high product water quality is desired, an understanding of the factors affecting the permeation of solutes in high-pressure membrane systems is needed. In this paper, findings of a comprehensive literature review are reported, targeting membrane rejection mechanisms and factors affecting rejection. The following key solute parameters were identified to primarily affect solute rejection: molecular weight (MW), molecular size (length and width), acid disassociation constant (pKa), hydrophobicity/hydrophilicity (log Kow), and diffusion coefficient (Dp). Key membrane properties affecting rejection that were identified include molecular weight cut-off, pore size, surface charge (measured as zeta potential), hydrophobicity/hydrophilicity (measured as contact angle), and surface morphology (measured as roughness). In addition, feed water composition, such as pH, ionic strength, hardness, and the presence of organic matter, was also identified as having an influence on solute rejection. From the knowledge gained during the literature review, a rejection diagram was proposed, which qualitatively allows prediction of solute rejection if certain solute and membrane properties are known. [Copyright &y& Elsevier]

Graphical abstract Highlights • Coating polyethyleneimine improved transport of mono- over di-valent cations. • Ion permselectivity was affected by applied current density and feedwater salinity. • Selective membranes achieved same desalting efficiency as normal grade membranes. • Total stack resistance of electrodialysis was insensitive to salt concentration. • Electrodialysis was effective for concentrate treatment with controllable scaling. Abstract A two-electrical stage and four-hydraulic stage pilot-scale electrodialysis system was used to investigate desalination performance and ion permselectivity of Ionics monovalent permselective membranes (CR671/AR112B) and normal grade membranes (CR67/AR204) (Suez Water Technologies & Solutions) to treat reverse osmosis (RO) concentrate in a brackish groundwater desalination plant. Monovalent permselective cation-exchange membrane CR671 was manufactured by surface modification of standard normal grade membrane CR67 with highly-branched polyethyleneimine coating. The covalently bonded polyethyleneimine layer on membrane surface was characterized by methylene blue dye test, Fourier transform infrared spectroscopy with attenuated total reflection (ATR-FTIR), and electrochemical impedance spectroscopy (EIS). The pilot-scale testing demonstrated the monovalent permselective membranes achieved the same desalting efficiency as the normal grade membranes under the same current density. The energy efficiency in terms of normalized salt removal decreased with the increasing current density (i.e., desalination level) but increased with feed water salt concentration. Polyethyleneimine coating on the CR671 membrane enhanced the selective transport of monovalent cations over divalent cations while having negligible impact on the membrane electrical resistance. The total stack resistance of electrodialysis was insensitive to concentration changes in the diluate and concentrate chambers during desalination of RO concentrate. The electrodialysis system achieved additional 55% of water recovery by treating RO concentrate, enhancing the overall water recovery from 82.5% of the primary RO to 92.1%. Scaling on the ion-exchange membranes and electrodes was effectively mitigated by addition of antiscalant and pH adjustment in concentrate and electrode rinsing streams. Electrodialysis was demonstrated a viable technology to modify product water quality and improve water recovery for desalination concentrate treatment. [ABSTRACT FROM AUTHOR]

This study developed a comprehensive techno-economic assessment (TEA) framework to evaluate an innovative algae resource recovery and near zero-liquid discharge potable reuse system (i.e., the main system) in comparison with a conventional potable water reuse system (i.e., the benchmark system). The TEA study aims to estimate the levelized costs of water of individual units and integrated processes including secondary wastewater treatment, advanced water purification for potable reuse, and sludge treatment. This would provide decision-makers valuable information regarding the capital and operational costs of the innovative main system versus a typical potable water reuse treatment train, along with possible routes of cost optimization and improvements for the design of full-scale facilities. The main system consists of (i) a novel algal-based wastewater treatment coupled with a dual forward osmosis and seawater reverse osmosis (Algal FO-SWRO) membranes system for potable water reuse and hydrothermal liquefaction (HTL) to produce bioenergy and subsequent nutrients extraction from the harvested algal biomass. The benchmark system includes (ii) an advanced water purification facility (AWPF) that consists of a conventional activated sludge biological treatment (CAS), microfiltration (MF), brackish water reverse osmosis (BWRO), ultraviolet/advanced oxidation process (UV-AOP), and granular activated carbon (GAC), with anaerobic digestion for sludge treatment. Capital expenditures (CAPEX) and operational expenditures (OPEX) were calculated for each unit of both systems (i.e., sub-systems). Based on a 76% overall water recovery designed for the benchmark system, the water cost was estimated at $2.03/m3. The highest costs in the benchmark system were found on the CAS and the anaerobic digester, with the UV-AOP combined with GAC for hydrogen peroxide (H 2 O 2) quenching as the driving factor in the increased costs of the system. The cost of the main system, based on an overall 88% water recovery, was estimated to be $1.97/m3, with costs mostly driven by the FO and SWRO membranes. With further cost reduction and optimization for FO membranes such as membrane cost, water recovery, and flux, the main system can provide a much more economically viable alternative in its application than a typical benchmark system. [Display omitted] • This study conducts technical and economic assessments of two water reuse systems. • Algal-osmosis membrane system is more economically viable than a conventional system. • Optimization of forward osmosis is the defining factor for its economic applicability. • Algal-osmosis membrane system is promising for decentralized potable reuse projects. [ABSTRACT FROM AUTHOR]

The understanding of membrane charge neutralization and diffuse layer compression at environmentally relevant ionic strengths is becoming increasingly important. In this work, the impact of high ionic strengths on membrane zeta potential was determined using a combination of streaming potential measurements and theoretical modeling. Streaming potential measurements were conducted on cellulose triacetate (CTA) and polyamide thin-film composite (TFC) membranes at ionic strengths within the operating limits of an electrokinetic analyzer. Zeta potential calculated from streaming potential was then extrapolated to environmentally relevant ionic strengths (0.05 to 1 M 1:1 electrolyte) using the Debye–Hückel and Helmholtz-Smoluchowski models. Extrapolated zeta potential values revealed that membrane charge neutralization and compression of the diffuse layer are limited by the size of the hydrated counter-ions, and full membrane charge neutralization, or even charge reversal, can not be achieved. The expected zeta potential of CTA membranes was similar to that of TFC membranes at high ionic strength, which has considerable implications in the comparison of membrane performance when treating brackish and saline feed waters. The methodologies developed in this work can help to better understand the contribution of electrostatic forces resulting from zeta potential to the sum of interfacial forces present at the membrane surface. [ABSTRACT FROM AUTHOR]

Drinking water treatment solids (DWTS) from coagulation processes could be a low-cost sorbent for selective removal of certain metals and metalloids from brine. In this study, continuous-flow sorption processes and factors affecting sorption of boron (III), copper (II), chromium (VI), lead (II), and selenium (VI) from reverse osmosis (RO) concentrate were investigated using different types of iron-derived DWTS. DWTS was demonstrated to be very effective in removal of copper and lead from RO concentrate, attributed to formation of strong inner-sphere complexes between the metal cations and Fe/Al oxide surface sites in the DWTS, as well as attractive electrostatic interactions with the negatively charged DWTS surface. Sorption of boron and selenium on the DWTS was lower. Boron exists primarily as nonionic boric acid at operating pH of 5.5–7.8, while selenate is a weakly bonding anion typically assumed to form outer-sphere surface complexes with Fe/Al oxides, both resulting in low removal. Sorption of the metals and metalloids was affected by their speciation and electrostatic interactions with DWTS. Higher influent pH increased boron and copper sorption but inhibited removal of chromium. Water temperature, solid moisture content, and loading rate did not have significant impact on sorption to the DWTS. [ABSTRACT FROM AUTHOR]

This study investigated the impact of seasonal variation and operating conditions on recovery of potable quality water from municipal wastewater effluent using an integrated algal treatment process with a dual forward osmosis (FO)-reverse osmosis (RO) membrane system. Pilot study of the algal process treating primary effluent validated the technical viability and seasonal performance during warm weather (May to October, 25–55 °C) using an extremophilic algal strain Galdieria sulphuraria, and during cold weather (November to April, 4–17 °C) using polyculture strains of algae and bacteria. Algal effluents from both seasons were used as the feed solution for the laboratory FO-RO study. In addition, pilot-scale FO-RO experiments were conducted to compare the system performance during treatment of algal effluent and secondary effluent from the conventional treatment facility. At 90% water recovery, the FO-RO achieved over 90% overall rejection of major ions and organic matter using the bench-scale system and over 99% rejection of all contaminants in pilot-scale studies. Detailed water quality analysis indicated that the product water from the integrated system met both the primary and secondary drinking water standards. This study demonstrated that the FO-RO system can be engineered as a viable alternative to treat algal effluent and secondary effluent for potable water reuse independent of seasonal variations and operating conditions. [Display omitted] • Dual membrane system recovered high-quality water from algal and secondary effluent. • Reverse osmosis permeate met the primary and secondary drinking water standards. • Forward osmosis water flux decreased more in summer due to high algal concentration. • Pilot study showed higher contaminants removal from wastewater than bench study. [ABSTRACT FROM AUTHOR]

• Electromagnetic fields can effectively control RO membrane scaling. • Magnetic field effectively cleaned the scale on the water pipelines and tanks. • Magnetic field significantly reduced the normalized water permeability decline rate. • Scale formed on the membrane surface was loose and soft with magnetic field applied. • Main mechanism for membrane scaling control is magnetohydrodynamic effect. This study investigated the effectiveness and mechanisms of electromagnetic field (EMF) on reverse osmosis (RO) membrane scaling control during brackish groundwater desalination. Pilot-scale experiments were conducted with different types of groundwater and two configurations of RO skid operated each for 30 days and 55 days without any other pretreatment. The testing results demonstrated EMF was effective for scaling control under typical RO operating conditions. The EMF significantly enhanced the performance of the RO system by reducing membrane scaling, changing the nature of the formed scales, and decreasing the decline rate of the normalized water permeability. In addition, EMF treatment effectively removed the pre-formed scales and precipitates in water pipelines and tanks but had limited efficacy on removing the pre-formed scales on the RO membranes. Membrane autopsy showed that the scales formed on the membrane surface under the influence of EMF were soft and powdery, being easily removed by water rinsing. The mechanisms of the EMF on RO membrane were discussed, and the dominant mechanism was the magnetohydrodynamic effect. This is the first study that demonstrated the EMF as a chemical-free and effective alternative to control membrane scaling and maintain RO performance during brackish groundwater desalination with discussions on detailed mechanisms and perspectives. [ABSTRACT FROM AUTHOR]

The modification of ion composition is important to meet product water quality requirements, such as adjusting the sodium adsorption ratio of reclaimed water for irrigation. Bench- and pilot-scale experiments were conducted using an electrodialysis reversal (EDR) system with Ionics normal grade ion-exchange membranes (CR67 and AR204) to treat the reclaimed water in the Scottsdale Water Campus, Arizona. The goal is to investigate the impact of operating conditions on improving reclaimed water quality for irrigation and stream flow augmentation. The desalting efficiency, expressed as electrical conductivity (EC) reduction, was highly comparable at the same current density between the bench- and pilot-scale EDR systems, proportional to the ratio of residence time in the electrodialysis stack. The salt flux was primarily affected by the current density independent of flow rate, which is associated with linear velocity, boundary layer condition, and residence time. Monovalent-selectivity in terms of equivalent removal of divalent ions (Ca2+, Mg2+, and SO42−) over monovalent ions (Na+, Cl−) was dominantly affected by both current density and water recovery. The techno-economic modeling indicated that EDR treatment of reclaimed water is more cost-effective than the existing ultrafiltration/reverse osmosis (UF/RO) process in terms of unit operation and maintenance cost and total life cycle cost. The EDR system could achieve 92–93% overall water recovery compared to 88% water recovery of the UF/RO system. In summary, electrodialysis is demonstrated as a technically feasible and cost viable alternative to treat reclaimed water for irrigation and streamflow augmentation. [ABSTRACT FROM AUTHOR]

A coupled algal-osmosis membrane treatment system was studied for recovering potable-quality water from municipal primary effluent. The core components of the system included a mixotrophic algal process for removal of biochemical oxygen demand (BOD) and nutrients, followed by a hybrid forward osmosis (FO)-reverse osmosis (RO) system for separation of biomass from the algal effluent and production of potable-quality water. Field experiments demonstrated consistent performance of the algal system to meet surface discharge standards for BOD and nutrients within a fed-batch processing time of 2–3 days. The hybrid FO-RO system reached water productivity of 1.57 L/m2-h in FO using seawater as draw solution; and permeate flux of 3.50 L/m2-h in brackish water RO (BWRO) and 2.07 L/m2-h in seawater RO (SWRO) at 2068 KPa. The coupled algal-membrane system achieved complete removal of ammonia, fluoride, and phosphate; over 90% removal of calcium, sulfate, and organic carbon; and 86–89% removal of potassium and magnesium. Broadband characterization using high resolution mass spectrometry revealed extensive removal of organic compounds, particularly wastewater surfactants upon algal treatment. This study demonstrated long-term performance of the FO system at water recovery of 90% and with membrane cleaning by NaOH solution. Image 1 • Demonstrated algal-membrane system for potable water recovery from wastewater. • The product water met USEPA primary and secondary drinking water standards. • Chemical cleaning using NaOH was effective to restore FO membrane performance. • FO was effective to prevent RO membrane fouling during wastewater treatment. [ABSTRACT FROM AUTHOR]