Pure Water Production Research Articles

A comprehensive physico-chemical characterization of superhydrophilic loose nanofiltration membranes

Nanofiltration (NF) membranes, especially loose NF membranes, trigger a growing interest for the fractionation of concentrated organic matters/salt mixtures in addition to the production of pure water. This study presents an in-depth characterization of two superhydrophilic loose NF membranes (Sepro NF 6 and 2A, Ultura). The physical characterization included the determination of the molecular weight cut-off (MWCO), pore size distribution, membrane morphology, surface charge, roughness and hydrophilicity. This was combined with a chemical characterization, i.e., by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), to determine the intrinsic membrane properties. The chemical characterization demonstrates that both Sepro NF membranes are poly(piperazineamide) based, showing the modification chemistry for the top layer through XPS measurement. Specifically, Sepro NF 6 and NF 2A membranes were found to have a superhydrophilic surface (contact angle for Sepro NF 6: 14.3±0.9°; that for Sepro NF 2A: 21.7±1.4°) with a low roughness, offering a potential advantage over conventional NF membranes in minimizing membrane fouling. Sepro NF 6 and NF 2A membranes had a mean effective pore size of 0.64±0.03nm and 0.52±0.01nm (corresponding to MWCOs of 862±80Da and 493±53Da), respectively. In terms of filtration performance, Sepro NF 6 showed a high permeability of 16.7Lm−2h−1bar−1 with 88.9% salt transmission for 0.01molL−1 NaCl solution, and a slightly lower permeability and salt transmission was obtained for Sepro NF 2A, which is desired for an effective fractionation of target organic matter/salt mixtures.

Preparation of ultra-thin poly(vinyl alcohol) membranes supported on polysulfone hollow fiber and their application for production of pure water from seawater

Pervaporation membrane process using polymeric membrane is promising for production of high-quality water from seawater. The use of membrane support is necessary for improvements in the membrane performance. In this work, preparation of thin poly(vinyl alcohol) (PVA) membranes over polysulfone hollow fiber support and their application for production of pure water from seawater through pervaporation separation process is reported. The uniformly thin PVA membrane coating over the cylindrical hollow fiber support of about 1.10mm diameter was obtained by an automatic dip-coating method. The coating solution was a dilute aqueous solution of PVA (61,000g/mol, molecular weight) and maleic acid having a molar composition in the range of 1 C2H4O (vinyl alcohol): 0.05–0.20 C4H4O4 (maleic acid): 61–815 H2O. The conductance of produced water by the membranes from desalination of saline water of 30,000ppm NaCl concentration was in the conductance range of pure water grade. The thinnest coated membrane exhibited permeate flux of about 7.4L/m2/h from the feed water of 30,000ppm NaCl at 344K. The apparent activation energy of the pervaporation desalination based on the volume flux of the membranes was determined as about 23.1–25.8kJ/mol.

Spiral multiple-effect diffusion solar still coupled with vacuum-tube collector and heat pipe

A novel solar still with spiral-shape multiple-effect diffusion unit is developed in the present study. The test results of a 14-effect unit coupled with vacuum-tube solar collector (absorber area 1.08m2) show that the highest daily pure water production is 40.6kgd−1. The measured highest productivity based on the area of glass cover, solar absorber, and evaporating surface is 34.7, 40.6, and 7.96kgm−2d−1, respectively, which are much higher than the published results. The measured solar distillation efficiency is 2.0–3.5. The performance enhancement results mainly from the lateral diffusion process in the spiraled still cell. The vapor flow generated by heat input can flow freely and laterally through the spiral channel down to the end when solar heat input is high. Besides, the larger evaporating and condensing area at the outer cell may increase heat and mass transfer at the outer cell.

Multiple-effect diffusion solar still coupled with a vacuum-tube collector and heat pipe

The present study develops a multiple-effect diffusion solar still (MEDS) with a bended-plate design in multiple-effect diffusion unit (MDU) to solve the peel-off problem of wick material. The MDU is coupled with a vacuum-tube solar collector to produce a high temperature gradient for high productivity. A heat pipe is used to transfer the solar heat to the MDU. A prototype MEDS-1L was built and tested outdoors. Four performance indexes are proposed for the performance evaluation of MEDS, including daily pure water production per unit area of glass cover, solar absorber, and evaporating surface (Mcov, Msol, Mevp, respectively), and solar distillation efficiency Rcov. The outdoor test results of MEDS-1L show that the solar collector supply temperature Th reaches 100°C at solar radiation 800Wm−2. The highest Mcov is 23.9kgm−2d−1 which is about 29% higher than the basin-type MEDS [11]. The highest value is 25.9kgm−2d−1 for Msol and 2.79kgm−2d−1 for Mevp. The measured Rcov is 1.5–2.44, higher than the basin-type MEDS (1.45–1.88). The Mcov, Msol, Mevp and Rcov of MEDS-1L are all higher than the theoretical calculation of a MEDS with a flat-plate solar collector coupled with a heat pipe (MEDS-FHP) [17].

Various applications of electrodeionization (EDI) method for water treatment—A short review

Electrodeionization (EDI), also known as continuous deionization (CDI), is a hybrid separation process combining ion-exchange resins with ion-exchange membranes. The EDI gained increasing attention for removal/recovery of ions from water. There are different types of applications for the EDI on the removal and concentration of various species from effluent streams. The aim of this paper is to give a brief overview of those studies. The presented examples of applications have shown that EDI process is very efficient in environmental protection, production of ultra pure water, and for the recovery of some valuable species. Normally, weakly-ionized species, such as carbon dioxide and boron are difficult to remove via such membrane processes as reverse osmosis and electrodialysis reversal (EDR). The EDI offers the benefit of continuous removal of these species to a very high degree.The main technological parameters determining the efficiency of an EDI module are the current strength, flow velocity in the dilute and concentrate compartments, temperature, and TDS (in both initial and purified water).

Drinking & other pure water production: Filtration and sedimentation in clean water production

Pure water production, whether for human consumption or for industrial uses, is by far the largest application for solid-liquid separation equipment. Ken Sutherland looks at the role of filtration and sedimentation in the production of safe drinking water, and of pure water for other purposes.

Sustainable Rural Development: Solar/Biomass Hybrid Renewable Energy System

This paper describes results from our effort to develop affordable technologies for sustainable rural development, particularly in regions that are plagued with energy poverty and where potable water is inaccessible. A hybrid renewable energy system (HRES) comprising photovoltaic array, battery, and biomass-fueled generator with gasifier, was developed. The system utilizes multiple conversion devices such that when combined, the weakness inherent in either is mitigated. Photovoltaic arrays serve the daytime energy need on days with high insolation, while excess energy is stored in a lead-acid battery. A 12kWel Prakash electric generator serves as the backup power, producing electricity and exhaust heat. This engine derives its fuel from a 50kWth Ankur downdraft gasifier that processes biomass feedstock to yield producer gas. Waste heat from the biomass fueled electric generator serves as thermal energy input to a Scarab AB air gap membrane distillation (AGMD) system. The AGMD module utilizes low-grade thermal energy applied to a salt-water solution also known as feed water, via a heat exchanger. This feed water of a known salt concentration is pumped into the hot inlet of the AGMD module, while the cold side of the membrane distillation module is maintained at a lower temperature using a heat sink. A cross-flow of the hot feed water and coolant water over a semi-porous membrane in the AGMD module results in a vapor pressure driven distillation of saltwater, which yields pure water. Result of the combined HRES and AGMD is a simultaneous production of electricity and pure water, also known as co-generation, which meets the need of a rural population. HOMER software was employed to analyze several configurations of the HRES, ensuring a reliable electricity production and an optimum sizing of the system. The overall result is an optimum levelized cost of energy (LCOE) of the system that falls below the population's ability to pay, making electricity affordable, while also providing portable water for the rural community. The findings from this study suggest that co-generation using HRES and AGMD provides an affordable and reliable energy and water services that meet the needs of a rural community, thus a viable option for sustainable rural development.

Degradation of Ion Exchange Resin by Vanadium-Containing Water

Irreversible swelling of strongly acidic cation exchange resins (SAC) had been observed when ground water in a volcanic zone was used as raw water for ion-exchange pure water production facilities. Vanadium has been presumed to act as an oxidative substance to the SAC resin, with the analysis of the ground water. It was confirmed that hydroxyl radicals were generated when the metavanadate anions were present in strong a sulfuric acidic solution, and the amount of generated radicals changed with the molar ratio of metavanadate to sulfuric acid. When an ammonium vanadate solution was passed through a resin layer of normal cross-linked type SAC, eluted polystyrene sulfonic acids were detected in the treated water. However, highly cross-linked SAC resin is resistive to oxidative degradation in vanadate containing water.

Optimization of operating conditions for a continuous membrane distillation crystallization process with zero salty water discharge

The concentrated salt solution from reverse osmosis (RO) or other desalination plants is a critical environmental problem that can impact water quality and thereby have economic and social consequences. An integration of a membrane distillation (MD) with a crystallization unit could serve as a potential way to mitigate this problem by having an almost complete water recovery and eliminating the secondary disposal problem. Hence, the continuous membrane distillation crystallization (CMDC) process was studied for a high concentration (close to saturation) feed solution. In addition, the operating conditions were optimized using an orthogonal fractional factorial (OFF) experiment design in order to realize a near zero discharge by varying the flow rates and operating temperatures on both the feed and permeate sides.The results from an L9(34) OFF experiment design indicated that the flow rates on the feed and permeate sides are the principal factors controlling CMDC performance, whereas the temperatures either on the feed or permeate sides are not main factors. The optimal operating parameter values based on four factors and three levels are a flow rate and temperature on the feed side of 0.64Lmin−1 and 338K, respectively, and on the permeate side of 0.35Lmin−1 and 303K, respectively. These operating conditions not only affect the pure water and NaCl solid production, but also the quality of the crystals obtained from the crystallizer.Factors affecting the crystal size distribution were investigated and indicated that the sodium chloride crystals had a narrow size distribution. The feed flow rate and inlet temperature had more influence on the mean crystal size and crystal size distribution, whereas the permeate flow rate and inlet temperature had relatively less effect. Therefore, CMDC operation was found not only to produce a high quality water product but also sodium chloride crystals with a relatively narrow size distribution. These results are beneficial to a better understanding of the CMDC process and improving its performance to realize zero salty water discharge to the environment.

Parametric study and optimization of an ejector-expansion TRCC cycle integrated with a water purification system

A combined cogeneration cycle is proposed in which the waste heat from an ejector-expansion trans-critical CO2 refrigeration cycle is utilized for power production and water purification simultaneously. The waste heat utilization was performed by means of a CO2 supercritical power cycle and a desalination system for pure water production. In order to run the desalination system, an absorption heat transformer is employed to upgrade the lower temperature waste heat. Thermodynamic models are developed for both the ejector-expansion trans-critical CO2 cycle and the combined cogeneration cycle consisting of all the above mentioned cycles. A parametric study is conducted to investigate and optimize the performance of each cycle under various operating conditions. It is found that, at the optimum conditions, the energy efficiency ratio of combined cogeneration cycle is about 13–45% higher than the coefficient of performance of the ejector-expansion trans-critical CO2 cycle. It is also concluded that, as the gas cooler temperature increases, the pure water production rate in the combined cogeneration cycle is increased.

Modeling and CFD Simulation of Water Desalination Using Nanoporous Membrane Contactors

A two-dimensional comprehensive model was developed to predict the transport of water in the nanoporous membrane contactors. The considered membrane distillation device was a counter-current flat-sheet membrane contactor for production of pure water from saline water. The developed model formulates the fundamental transport equations of heat, mass, and momentum in the membrane contactor. The computational fluid dynamics techniques were applied for numerical simulation of model equations. The simulation results were compared with experimental data obtained from literature and showed great agreement with the measured values. A combination of the Knudsen flow and Poiseuille flow was used in the model for estimation of diffusion inside the membrane pores and increased the accuracy of the model. Simulation results revealed that, in the regions adjacent to the membrane wall, the temperature difference is significant. This could be attributed to the fact that a temperature boundary layer is formed near the membr...

New prospects for ecologically clean power and pure water generation units with SOFC

The paper represents results of research of a perspective power unit based on the solid oxide fuel cells (SOFC) fueled by the synthetic gas (syn-gas). As compared with the fuel cells of other types, SOFC has an opportunity to work with the hydrocarbon fuels converted into the syn-gas. Application of nanocatalytic membranes for a syn-gas generation is analyzed. The paper predicts an efficient technology of energy and pure water production from an alternative renewable sources.

Experience with integrated ultrafiltration/reverse osmosis systems in industrial applications in Spain

While fresh water resources are increasingly limited, efforts are taken aiming at a more efficient use of those resources and the value of water reuse, not only due to environmental but also due to economic aspects. This is especially true for the industrial sector, with a high potential to save water by reuse. This is expected to be even more critical in the coming future as the price of the water increases and the access to good quality water sources near the industries decreases. Reverse osmosis (RO) technology has been used in the industrial sector for decades for various purposes such as softening, ultra pure water production, or water reuse. But like in other applications such as desalination, in industrial applications, membrane fouling remains as one of the main causes for poor RO plant performance. This implies frequent downtime for cleaning and maintenance and shorter membrane life time, leading to significant operational costs. Therefore, the selection of a proper pretreatment is essential to produce a high quality feed water for the RO system in order to ensure a more sustainable and reliable operation. In the past decades, ultrafiltration (UF) has become more popular for RO pretreatment in the municipal and lately in the industrial sector too. Ultrafiltrate water is virtually free of particles, colloids, and suspended solids. Therefore, plugging of RO feed channels is minimized and the RO cleaning frequency can be noticeably reduced. In comparison with conventional filtration (e.g. sand filtration), UF requires significantly lower footprint, produces a higher and more consistent water quality regardless of variations in the feed quality, and usually needs less power and chemicals. This paper will review the design and operational data of a number of successful full-scale integrated membrane systems (UF followed by RO) installed in different types of industries and treating diverse water sources.

Treatment of olive mill wastewater by membrane distillation using polytetrafluoroethylene membranes

Direct contact membrane distillation (DCMD) process was applied for olive mill wastewater (OMW) treatment. Three commercial polytetrafluoroethylene (PTFE) membranes with different pore sizes (TF200 of 0.2μm, TF450 of 0.45μm and TF1000 of 1μm) were tested under different temperatures, namely, temperature difference and mean temperature. The aim of this study is to investigate the possibility of pure water production and concentration of natural polyphenols from OMW for further valorization. The results demonstrated the efficiency of DCMD process for OMW treatment by the three PTFE membranes. The permeate flux increased with the increase of the membrane pore size, the mean temperature and the temperature difference. However, no significant effect was detected between the pore size and the polyphenol separation coefficient, which remains close to 100% after 8h of DCMD operating time. The DCMD processing of OMW using PTFE membranes allow to reach a concentration factor higher than 1.78 after 8h of operating time, obtaining the best performance index for the membrane TF1000 with the greatest pore size. In addition, the effect of high temperatures on the phenolic content of OMW and its free radical-scavenging ability (DPPH assay) was also evaluated with time. It was found that a treatment of OMW by DCMD at high temperatures have no undesirable effects on the phenolic content and its antioxidant activity.

Effects of Feed Water Conditions on Performance of Electrodeionization Process for Removal of Ni<sup>2+</sup> from Dilute Solution

Electrodeionization (EDI) is being applied more and more to treat wastewater containing heavy metal ions, especially for electroplating rinsing wastewater. The effects of feed water conditions including concentration, pH and temperature on the performance of EDI process for removal of Ni2+ from dilute synthetic wastewater were investigated systematically in this paper. It was found that the dilute resistivity of the EDI module descended from 1.5-2.8MΩ•cm to 0.36-0.45MΩ•cm while the influent Ni2+ concentration increased from 45 mg•L-1to 63mg•L-1. Existence of some H+ in feed water would push the stack current up. An increase in temperature of feed water would facilitate the ion exchange and diffusion and thus promote mass transfer. It was indicated that feed water conditions had a significant effect on separation performance of EDI process for treating dilute solutions containing heavy metal ions. Pure water production could be accomplished and water reuse could be realized via EDI technology by appropriately restricting feed water conditions.

Optimal design and control of solar driven air gap membrane distillation desalination systems

A solar heated membrane distillation desalination system is constructed of solar collectors and membrane distillation devices for increasing pure water productivity. This technically and economically feasible system is designed to use indirect solar heat to drive membrane distillation processes to overcome the unstable supply of solar radiation from sunrise to sunset. The solar heated membrane distillation desalination system in the present study consisted of hot water storage devices, heat exchangers, air gap membrane distillation units, and solar collectors. Aspen Custom Molder (ACM) software was used to model and simulate each unit and establish the cost function of a desalination plant. From Design degree of freedom (DOF) analysis, ten design parameters were investigated to obtain the minimum total annual cost (TAC) with fixed pure water production rate. For a given solar energy density profile of typical summer weather, the minimal TAC per 1m3 pure water production can be found at 500W/m2 by varying the solar energy intensity. Therefore, we proposed two modes for controlling the optimal design condition of the desalination plant; day and night. In order to widen the operability range of the plant, the sensitivity analysis was used to retrofit the original design point to lower the effluent temperature from the solar collector by increasing the hot water recycled stream. The simulation results show that the pure water production can be maintained at a very stable level whether in sunny or cloudy weather.

Proposal and analysis of a new combined cogeneration system based on the GT-MHR cycle

In this paper, the waste heat from a gas turbine-modular helium reactor (GT-MHR) is utilized to produce power through two Organic Rankine Cycles (ORCs) and pure water by means of distillation processes. An Absorption heat transformer (AHT) is employed to upgrade the lower temperature waste heat in order to run the desalination system. Detailed thermodynamic analyses for the proposed combined cogeneration cycle (CC cycle) are presented and the effects of important parameters on the cycle performance were studied. The proposed cycle performance is then optimized based on the first law of thermodynamics. The results show that the first law efficiency of the CC cycle, at the optimum conditions, is around 7% higher than that of the GT-MHR cycle. It was also concluded that for each 50 °C increase in the gas turbine inlet temperature, the thermal efficiency is increased by around 2.5–4% and the pure water production rate is decreased by around 6.5%. The results also showed that employing R1234yf as working fluid in the ORCs instead of R123 gives almost the same results in the cycle performance.

Thermodynamicmodellingof an integrated solid oxide fuel cell and micro gas turbine system for desalination purposes

SUMMARY In this article, an integrated solid oxide fuel cell (SOFC) and micro gas turbine (MGT) with a multi-effect desalination (MED) system is proposed, and its comprehensive thermodynamic modelling, through energy and exergy analyses, is conducted. In addition, the effects of some design parameters on the hybrid system are investigated. The results show that fuel cell stack pressure has a significant effect on the combined system power and distilled water capacity. It also increases the SOFC-MGT energy efficiency. Moreover, the pressure of the inlet heating steam to the multieffect desalination system affects the pure water production in a positive way. An increase in the steam pressure results in a lower steam mass flow rate generated in the heat recovery steam generator. However, it increases desalination product capacity. Copyright © 2011 John Wiley & Sons, Ltd.

Recent Patents Review on Electrodeionization

The recent patents and progress of electrodeionization (EDI) in fields of water deionization and wastewater treatment are reviewed in the present paper. The discussion focuses on such major aspects: applied ion exchange media, inner configuration and operation manner of the EDI, integrated membrane processes based on EDI and new applications of the technology. As the newest outstanding technology for water deep desalting, EDI has been widely used for ultrapure water production in many industries and laboratories together with important improvements in recent years. Durative advancements have been achieved by inventors such as more even current distribution, higher contact efficiency between water and ion exchanger, more effective precipitation preventing and lower energy consumption. Besides, some improvements also have been achieved in other new fields in addition to pure water production. The application in water softening, seawater desalination and wastewater treatment were introduced for example. It is believed that the electromembrane process of EDI will play an important role in water desalting, wastewater reclamation and cleaner production of chemical engineering near future. Keywords: Electrodeionization, continuous deionization, ultrapure water, ion exchange resins, electroregeneration

Current Patents on Electromembrane Based Integrated/Hybrid Processes

Electromembrane processes are considered to be one of the promising industrial applicable ones using an electrical potential as high energy-efficient processes. Their applications can be found in various fields such as water desalination, water and wastewater treatment, food industries, production of acids and bases, elimination of toxic components, regeneration of metal ions from industrial waste streams, ultra pure water production and etc. The electromembrane process integration with other processes has received more attention recently in the patents as well as published articles since it provides versatile tools for industrial separations, increasing process effectiveness by optimization of the utilization of electromembrane processes. A substantial number of industrial applications for the integration of electromembrane process can be found mainly in areas of chemical unit operations, pressure-driven membrane processes, and biochemical unit processes. This review presents the recent progress on electromembrane based integrations for industrial separations based on patents as well as some published articles. The patent search has been performed in different databases in which the patents can be searched and in most cases downloaded. The keywords such as “Electromembrane process, Integration, Separation, Purification, Electromembrane” were considered for the current patents on electromembrane based integrated/ hybrid processes. Keywords: Electromembrane process, integration, separation, purification, electromembrane