Search

Highlights: [•] Arsenic was effectively removed by coagulation with ferric salts. [•] Adsorption with ferric sludge provides a “waste treat waste” method for arsenic removal. [•] Coagulant dose requirement for RO concentrate was higher than low salinity water. [•] Increase in current density does not affect significantly selectivity of monovalent anions over di-, multi-valent anions. [•] Transport of divalent cations increases with increase in current density. [Copyright &y& Elsevier]

Desalination of seawater, brackish water, and reclaimed water is increasingly utilized worldwide to augment and diversify fresh water sources. The lack of economically and ecologically feasible concentrate management options, however, is a major barrier to widespread implementation of desalination, in particular at inland sites. This paper critically reviews strategies and technologies for concentrate management, including disposal, treatment, and beneficial use. Development of energy-efficient, cost-effective, and environmentally benign concentrate management systems is critical if desalination is to become a major part of a sustainable water future. This paper examines the limitations and advantages of a range of concentrate management tools, including emerging and novel technologies for minimization of concentrate volume, enhancement of water recovery, removal of organic contaminants, and recovery of valuable products and energy. [ABSTRACT FROM AUTHOR]

Abstract: Microbial desalination cell represents a new technology for simultaneous wastewater treatment, water desalination, and energy production. This study characterized the long-term performance of MDC during wastewater treatment and identified the key factors that caused performance decline. The 8-month operation shows that MDC performance decreased over time, as indicated by a 47% decline in current density, a 46% drop in Columbic efficiency, and a 27% decrease in desalination efficiency. Advanced electrochemical, microscopy, and spectroscopy analyses all confirmed biofouling on the anion exchange membrane, which increased system resistance and reduced ionic transfer and energy conversion efficiency. Minor chemical scaling was found on the cation exchange membrane surface. Microbial communities became less diverse at the end of operation, and Proteobacteria spp. was dominant on both anode and AEM fouling layer surface. These results provide insights into the viability of long-term MDC operation on reactor performance and direct system development through membrane optimization. [Copyright &y& Elsevier]

Abstract: The low conductivity and alkalinity in municipal wastewater significantly limit power production from microbial fuel cells (MFCs). This study integrated desalination with wastewater treatment and electricity production in a microbial desalination cell (MDC) by utilizing the mutual benefits among the above functions. When using wastewater as the sole substrate, the power output from the MDC (8.01W/m3) was four times higher than a control MFC without desalination function. In addition, the MDC removed 66% of the salts and improved COD removal by 52% and Coulombic efficiency by 131%. Desalination in MDCs improved wastewater characteristics by increasing the conductivity by 2.5 times and stabilizing anolyte pH, which therefore reduced system resistance and maintained microbial activity. Microbial community analysis revealed a more diverse anode microbial structure in the MDC than in the MFC. The results demonstrated that MDC can serve as a viable option for integrated wastewater treatment, energy production, and desalination. [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: Capacitive deionization (CDI) with carbon-aerogel electrodes represents a novel process in desalination of brackish water and has merit due to its low fouling/scaling potential, ambient operational conditions, electrostatic regeneration, and low voltage requirements. The objective of this study was to investigate the viability of CDI in treating brackish produced water and recovering iodide from the water. Laboratory- and pilot-scale experiments were conducted to identify ion selectivity, key operational parameters, evaluate desalination performance, and assess the challenges for its practical applications. The performance of the CDI technology (CDT®) system tested was consistent throughout the laboratory- and field-scale experiments. Deterioration of the carbon-aerogel electrodes was not observed during testing. The degree of ions adsorbed to the carbon aerogel (in mol/g aerogel) during treatment of brackish water was dependent upon initial ion concentrations in the feed water with the following selectivity I>Br>Ca>alkalinity>Mg>Na>Cl. The preferential sorption of iodide revealed merit to efficiently recover iodide from brackish water even in the presence of dominant co-ions. The research findings derived from this study identified parameters that merit further improvements regarding design and operation, including modification of pore-size distribution of aerogel, development of high capacitance and low-cost electrode materials, reducing the dead volume after regeneration and rinsing, minimizing energy consumption, and maximizing system recovery. [Copyright &y& Elsevier]

Abstract: Produced water management has become one of the key factors to sustainable development of natural gas/oil resources. The substantial quantities of saline water present intractable environmental threats and also increase oil/gas production costs through produced water disposal such as deep well reinjection. Developing high-efficient and flexible treatment systems that can be operated at low costs is of high interests for producers and state regulators. Beneficial use of produced water could represent a new water resource especially for areas with inadequate existing supplies. Furthermore, some produced waters generated are also characterized by elevated concentrations of recoverable constituents, for example iodide. Recovering iodide from brine could offer additional benefits besides providing methane gas, reusing produced water, or reducing brine disposal volume. The advent of ultra-low pressure reverse osmosis (ULPRO) membranes and nanofiltration (NF) membranes with high desalting degree might offer a viable option for produced water treatment because these membranes can be as effective as reverse osmosis (RO) in removing certain solutes from water while requiring considerably less feed pressure resulting in lower operating costs. The objectives of this research were to investigate the viability of ULPRO and NF membranes as potential techniques to treat produced water by meeting water quality standards and concentrating iodide in the brine. The produced water extracted from sandstone aquifer in Eastern Montana was characterized as brackish groundwater of sodium chloride type with total dissolved solids (TDS) concentration of 5300mg/L, absence of hydrocarbons, and average iodide concentrations of 55mg/L. The produced water exhibited a very high potential to membrane fouling indicated by silt density index (SDI) measurements due to the presence of small particles and inorganic constituents. The studied candidate membranes included one RO membrane (TFC-HR, Koch Membrane Systems), three ULPRO membranes XLE (Dow/Filmtec), TFC-ULP (Koch) and TMG-10 (Toray America), and three NF membranes NF-90 (Dow/Filmtec), TFC-S (Koch), and ESNA (Hydranautics). Bench-scale cross-flow flat sheet test units were employed to assess the candidate membranes using the produced water with focus on fouling potential, iodide recovery, and general salt rejection. The degree of flux decline was found to be dependent upon the combination of permeate drag force and physico-chemical properties of the membranes. The membranes with higher permeability generally displayed faster initial flux decline. In addition, hydrophobic and rough membranes exhibited a higher flux decline and lower chemical cleaning efficiency than smooth and/or hydrophilic membranes. Flux decline experiments, in situ microscopic techniques, analysis of elemental composition and functional groups revealed that the pretreatment including microfiltration, pH adjustment and addition of antiscalants could alleviate membrane fouling significantly. Chemical cleaning using caustic and anionic surfactant solutions restored membrane permeability more efficiently than hydraulic cleaning or using acids and metal chelating agents. This study showed that TFC-ULP, TMG-10, and NF-90 membranes exhibited competitive efficiency regarding salt rejection, iodide recovery and adjusted specific flux as compared to a conventional RO membrane. [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]

Selective separation of mono- and multi-valent ions has important applications in water reuse, desalination, and salt production. Innovative monovalent permselective cation-exchange membrane CR671 was developed by modifying the normal grade membrane CR67 with polyethyleneimine coating. Bench- and pilot-scale electrodialysis experiments were conducted at a brackish groundwater desalination facility to investigate desalination performance and ion selectivity using the CR671 and CR67 under different operating conditions. Both normal grade (CR67 and AR204) and selective (CR671 and AR112B) membranes achieved same desalting efficiency. Na-selectivity in terms of relative transport number using sodium as the standard ion was affected significantly by current density and linear velocity for the normal grade membranes while the selective membranes exhibited stable good Na-selectivity. The Na-selectivity of the CR671 was demonstrated up to 9 and 5 times better than the CR67 during pilot- and bench-scale electrodialysis, respectively. Hydraulic retention time and electrodialysis stack staging had minor impact on Na-selectivity at high current density. With the same hydraulic conditions, overall desalination behavior and ion selectivity were highly comparable between bench- and pilot-scale electrodialysis. It infers that bench-scale testing results can be used to simulate and project desalination performance and ion selectivity of pilot- and potentially full-scale electrodialysis applications. [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]

Solar distillation is considered a low-cost, environmental-friendly approach for freshwater production. However, water output and photothermal efficiency of conventional solar evaporators are low. This study developed highly efficient bilayer photothermal functional films (noted as CBMCE) by depositing carbon black nanoparticles (CBNPs) dispersion on mixed cellulose ester (MCE) support via simple vacuum filtration. To further increase water production, multilayer enhanced evaporators (MEER) were fabricated by coupling optimal CBMCE with polystyrene foam and air-laid paper. The effects of operating conditions on solar evaporation were systematically investigated, including loading rate of CBNPs on MCE, solar power densities, water depths, relative humidity, and different water types (deionized water, synthetic seawater, municipal wastewater, and 13.5 wt% NaCl solution). Experimental results indicated that the average water evaporation rate (AER) increased with increasing incident solar density and decreased with increasing water depths, aqueous solution salinity, and relative humidity. For 13.5 wt% NaCl solution, MEER achieved maximum AER of 5.6 kg·m−2·h−1, enhanced evaporation rate and evaporation efficiency by ~124.0% and ~123.5%, respectively. Economic analysis showed desalination of 13.5 wt% NaCl solution using MEER had a life cycle cost of ~$1.89/m3 fresh water produced. This study demonstrates that MEER are highly efficient, low-cost, and reusable functional materials for solar desalination. • Carbon black-mixed cellulose ester films (CBMCE) were made via vacuum filtration. • Multilayer evaporator (MEER) includes 10 gCB/m2 MCE, polystyrene foam & air-laid paper. • MEER achieved a maximum evaporation efficiency of ~88.7% at 5 kW·m−2. • MEER achieved a maximum evaporation rate of 5.6 KMH treating 13.5% NaCl water. • Life cycle cost of desalting 13.5% NaCl water using MEER is $1.89/m3 clean water. [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]

A refraction-based methodology for concentrating sunlight is proposed to augment the pure water production of a conventional solar still. The Fresnel lens (FRL) was integrated with a single-basin, single-slope solar still to refract the incident sunlight to a focal point that was constantly located on the basin bottom. Due to the introduction of the FRL, two major impressive findings were observed. The first observation was a high hourly productivity window (HHPW), during which the proposed system produced fresh water at a relatively high and stable rate. The second one was the occurrence of nucleate boiling phenomenon, which is believed to significantly increase the heat transfer coefficient for the phase change process of the basin water. Consequently, with the increased heat input and the high heat transfer rate, the utilization of FRL achieved a significant pure water production enhancement (L/m2/day) of about 467%, as well as a significant daily efficiency (η) improvement of about 84.7%, compared to a conventional system without FRL. A series of tests were conducted to study the impact of the operational parameters on the system performance. The system daily output demonstrated a linear and negative correlation with water depth (d w) in the basin. The introduction of forced air cooling showed a positive impact on system performance and enhanced the distillate yield. It was also found that increasing d w or/and applying forced air cooling effect could benefit from increasing η. • A new refraction-based method was proposed to improve the solar still performance. • Fresnel lens can induce nucleate boiling in passive solar stills. • Nucleate boiling can significantly enhance productivity compared to evaporation. • A production enhancement of about 467.4% was achieved by the modified solar still. • The modification increased daily efficiency by about 87.4%. [ABSTRACT FROM AUTHOR]