Pure Water Production Research Articles

Dairy wastewater treatment with direct-contact membrane distillation in Oman

Direct contact membrane distillation (DCMD) process was implemented for treating dairy wastewater (DWW) from an Omani dairy industry. Commercial polytetrafluoroethylene (PTFE) and polypropylene (PP) membranes were tested under different temperatures. The aim of this study in to investigate the potential of pure water production rejecting salts, volatile and non-volatile organic compounds present in DWW. Using laboratory techniques such as gas chromatography, we inspected permeate composition, identifying both volatile and non-volatile organic matter. Comprehensive characterization of membrane surface properties via Fourier-transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Thermal Gravimetric analysis (TGA) provided critical insights. Findings revealed the denaturation of proteins at 60 °C, leading to significant pore blockage and a consequential 50.3 % reduction in flux. Impressively, the membranes achieved rejection rates of 89–99 % for non-volatile organic matter, while completely rejecting D-limonene. However, traces of volatile fatty acids were detected in the permeate. Elemental analysis exposed the presence of various dairy-derived elements at the membrane surface. FTIR peaks highlighted distinct functional groups of dairy components, while TGA affirmed the accumulation of dairy aggregates with rising temperature. These findings underscore membrane distillation's competence in dairy wastewater treatment, presenting a compelling case for its widespread application in environmental remediation endeavors.

Performance of capacitive deionizing membrane distillation (CDIMD) process for the organic sewage treatment and how operating parameters can affect it

To solve the fouling issue of traditional membrane distillation (MD) technique, a newly-designed hybrid purification system integrating capacitive deionization (CDI) with MD technology was established for the organic sewage treatment in this study, namely capacitive deionizing membrane distillation (CDIMD) technology. Complexes formation via cross-linking among protein, divalent cations, and polysaccharide, an archcriminal inducing MD fouling, was remarkably alleviated in the CDIMD system considering that negatively-charged organics were clearly divided away from those divalent cations in an electric field circumstance. The CDIMD performance was deeply explored in this study focusing on the impact mechanisms of core operational parameters. An appropriate increment of feed temperature (60–65 °C) and feed flow velocity (15.72–17.82 mm/s) contributed to the anti-fouling performance of CDIMD. Considering the side reactions at voltage >1.2 v, setting working voltage at around 1.2 v seemed to be optimal for CDIMD operation. With an overall consideration of pure water production and anti-fouling performance, a properly thicker CNTs layer (40–60 μm) efficiently enhanced the fouling mitigation of CDIMD. A frequent switching of electric field direction (9/1 min) facilitated the timely regeneration of electrode and composite membranes, accordingly promoting a reliable purification of organic wastewater by CDIMD technique.

Evaporative cooling and sensible heat recovery enable practical waste-heat driven water purification

Waste heat capture from systems such as photovoltaics (PV) and refrigerators can lower their energy efficiency by increasing their operating temperature. In this study, we evaluate the potential of final-effect evaporative cooling and internal heat recovery in a multi-effect diffusion distillation (MEDD) to produce pure water without negatively impacting the energy efficiency of the waste-heat source. Lab-scale experimental results from a multi-effect membrane distillation module validate the concept, showing that water production can be enhanced by >20 % while simultaneously pulling down the module's operating temperature. A detailed numerical model of a solar-MEDD is implemented and validated. The incorporation of sensible heat recovery and evaporative cooling increase pure water production by approximately 10 % each. Although the pure water production of a standalone MEDD increases with increasing effects N, when coupled to a solar PV module, increasing N also decreases PV electricity production. Therefore, a PV-MEDD with fewer effects (≤4) is preferable and such a system can produce sufficient water for electrolysis (green H2 production) while maintaining or improving PV electrical energy production throughout the year under varying climatic conditions.

Towards the Optimization of a Photovoltaic/Membrane Distillation System for the Production of Pure Water.

The production of pure water plays a pivotal role in enabling sustainable green hydrogen production through electrolysis. The current industrial approach for generating pure water relies on energy-intensive techniques such as reverse osmosis. This study unveils a straightforward method to produce pure water, employing real-world units derived from previously simulated and developed laboratory devices. This demonstrated system is cost-effective and boasts low energy consumption, utilizing membrane distillation (MD) driven by the waste heat harnessed from photovoltaic (PV) panels. In a previous study, modeling simulations were conducted to optimize the multi-layered MD system, serving as a blueprint for the construction of prototype devices with a suitable selection of materials, enabling the construction of field-testable units. The most efficient PV-MD device, featuring evaporation and condensation zones constructed from steel sheets and polytetrafluoroethylene (PTFE) membranes, is capable of yielding high-purity water with conductivity levels below 145 μS with high flux rates.

Organic food and its health benefits for humans and how it differs from regular food : Review.

As public awareness of organic food products' advantages for health, social convenience, the environment, and sustainable development has grown, so has their knowledge of their benefits. Gaining understanding of consumer views is crucial for the sector as it continues to grow. The current study was methodically created to assess the strength of the data supporting the benefits of feeding organic foods to health. Foods labeled as organic are produced utilizing only natural fertilizers. The regulations around organic animal production are extensive and impact various aspects such as nutrition, reproduction, housing, medical care, and treatment. Additionally, these foods are not produced using genetically modified pesticides or insecticides. Animals raised in organic farms are given more space to live in than those raised in conventional systems, and they are also required to consume organic feed, straw bedding, and roughage. The fatty acid composition of milk, eggs, and meat is significantly influenced by the animal diet. Breed selection is used in connection to animal health and wellbeing; proper diet, husbandry, and management all contribute to illness prevention and improved animal welfare. Antimicrobial durability is a global public health concern these days, and many international health organizations recognize that it poses a threat to the current health care system. Thus, the market's demand for organic products and their simplicity of use has grown over the past several years, contributing significantly to the economy. Because organic food is healthier and less likely to contain chemicals, many people are beginning to choose it over conventional food. As a result, raising consumer knowledge of the value of organic products and supporting their production is crucial for the growth of organic farming and the production of pure water. The market for organic food products is growing quickly because consumers believe that organic food may be healthier than conventional food and has a superior nutritional profile.

Enhancing solar still efficiency in southeastern Algeria: An experimental case with palm stems

Solar desalination is a cost-effective and eco-friendly technique that uses solar energy to turn impure water into clean drinking water. In a study conducted in southeastern Algeria, four similar solar stills were used to examine how palm stems affect the distillation process. The first still served as a control (SSR), the second had 9 stems (MSS1), the third had 6 stems (MSS2), and the fourth had 3 stems (MSS3). Results showed significant improvements in pure water production, with MSS1 yielding 5080 ml, MSS2 producing 4060 ml, and MSS3 generating 3680 ml, compared to the CSS still's output of 3320 ml. This means notable improvement rates of 53.01%, 22.90%, and 10.84% for MSS1, MSS2, and MSS3, respectively. In terms of thermal efficiency, MSS1, MSS2, MSS3, and CSS achieved efficiency levels of 57.90%, 51.57%, 48.39%, and 45.30%, respectively. The time required to recover the manufacturing costs of the devices varied between 32 and 48 days, respectively. These results highlight the positive impact of integrating palm stems on solar distillation performance, thanks to what? Is it thanks to the low thermal conductivity of the stem? Of course not, it is thanks to the stem-water zone which promotes the evaporation of water under the action of capillarity.

Design methodology based on multi-objective optimization with evolutionary algorithms for humidification-dehumidification desalination systems using updated approaches

This paper develops a methodology for multi-objective optimization using Non-Dominated Sorting Genetic Algorithm II (NSGA-II). The methodology aims to address the problem of the close relation between variables based on a mathematical model that simulates design variants of humidification-dehumidification (HDH) desalination systems, where the variation of one parameter can affect another. The approach consists of an exhaustive study of the state of the art to incorporate as many results as possible, including variable and parameter constraints established by previous research. Energy efficiency and potable water production are optimized with respect to the total area of the system's active components and the ratio of seawater converted to potable water. The calculations generate 20 Pareto optimal solutions, with an average pure water production of 14.01 l/h, and an average of the total and solar heating areas of 22.43 m2 and 8.52 m2, respectively, including many other parameters with similar values compared to other publications. The methodology is flexible, updatable, and generates high efficiency values, confirmed by the comparison of equivalent parameters and the pinch analysis, also with respect to previous results. The sensitivity analysis performed, presents different trends in the relation between variables in this scenario contributing to feedback on the behavior of hyperparameters of the algorithm, indicating a very wide potential of solutions. For the water temperature entering the dehumidifier, the range between 30 and 37 °C is determined as the optimum range, however, this is not the only result from the trend analysis of these 20 solutions, compared with other references. This methodology is a contribution to the overall objective of improving the HDH technology design process; optimal solutions are obtained for systems of the configuration chosen to apply it, but it can be adapted to others.

Advanced exergy analysis of a double absorption heat transformer recovering industrial waste heat for pure water production

Conventional and advanced exergy analyses are applied for a double absorption heat transformer system utilizing low-grade industrial waste heat for water purification. The conventional method provides information about the location and magnitude of inefficiencies and does not consider any interaction among components regarding the irreversibility occurring in them. The advanced exergy technique however, exposes the real origins of irreversibilities and latent potential for enhancement of each system component, along with reflecting mutual interaction between components. The simulation of the cycle is carried out with engineering equation solver software. The results show that the overall improvement potential of the cycle is only 16%. Also, the mutual interdependency between components is found to be weak as 97% of the total exergy destruction appeared as endogenous. Furthermore, considering endogenous avoidable exergy destruction, the improvement strategy of components obtained by advanced exergy method is disparate from conventional one. Results of the advanced exergy suggest this order: condenser, absorber, evaporator, absorber/evaporator assembly, generator assembly, economizer 1, and economizer 2. Additionally, a parametric investigation is performed to assess the sensitivity of splitting exergy destruction to the variation of heat source temperature for highlighting improvement opportunities. The results indicate that the condenser yields the highest amount of avoidable endogenous exergy destruction in the entire studied temperature range.

Thermal Analysis of Single Slope Solar Still with Sensible Storage Material (Sand)

In this work authors utilized easily available and cheap sensible storage material (sand) in single basin solar still. The sensible storage material helps to enhance the distillate output from solar still during no sunshine hours. The mathematical model of the proposed solar still has been developed and experimentally validated. The numerical computation has been performed to analyse the effect of mass od sand placed beneath the basin plate. It is seen that with increase in mass of sand the overall daily distillate output decreases. When mass of sand increases from 15kg to 60 kg the daily distillate output decrease by 11.8%. The total daily distillate output produced by proposed still for a day in summer for Raipur is 5.32l/m2 which is about 24.4% more than conventional single slope solar still. The total nocturnal production of pure water from the propped still for a day in summer in Raipur climate is 1.37l/m2. The proposed solar still with sand storage is a good available cheap option to increase the overall productivity of conventional single slope solar still.

Thermal and electrical conductive 2D CuO evaporator for all-day steam generation

Solar energy-driven water evaporation is an effective way to obtain clean water through seawater desalination. Due to the day and night cycle, all-day steam generation is an urgent project. Here, 2D evaporators with effective heat management were designed and constructed by facile folding, in which superhydrophilic CuO coatings with honeycomb-like pores were in situ deposited on brass plates via electroplating and heat oxidation. In the daytime, the 2D evaporator has excellent photothermal performance due to the appropriate pore structure, light absorption, and water supply. The evaporation rate reaches 1.4 kg m−2 h−1, and the energy conversion efficiency of 93.5% under 1 sun in 3.5% artificial seawater for ten cycles. Except forsolar-driven water evaporation, some heat converts into electricity due to the temperature difference between the two surfaces of the high thermal conductive 2D evaporator. At night, steam is generated through the flexible photoelectric transition. The evaporation rate is 5.8 kg m−2 h−1 at an input voltage of 6 V. The stable evaporation performance of this evaporation system and the advantages of all-day steam generation show considerable prospects. It may be widely used in pure water production in the future.

High rejection stacked single-layer graphene membranes for water treatment

Nowadays, the production of pure water from saltwater and wastewater is one of the most challenging issues. Polymeric materials represent, at the moment, the best solution for membranes technology but new materials with improved functionalities are desirable to overcome the typical limitations of polymers. In this work, graphene membranes with superior filtration properties are fabricated by stacking up to three graphene layers on a porous support and exploiting the intrinsic nanopores of graphene to filter diclofenac (drug), and methylene blue (dye). The rejection improves increasing the number of the stacked graphene layers, with the best results obtained with three graphene layers. Mass diffusion properties depend on the size of the probe molecule, consistently with the existence of intrinsic nanometer-sized pores within graphene. From the results of an in depth transmission electron microscopy analysis and molecular dynamics simulations it is inferred that graphene stacking results in a decrease of effective membrane pore sizes to about 13 Å diameter which corresponds to 97% rejection for diclofenac and methylene blue after one hour filtration.

Production of pure water and dry salt from NaCl solutions via percrystallisation by supported carbon membranes

Membrane percrystallisation is an alternate crystallisation process where a membrane disperses aqueous salt solution into a thin film on the permeate side. This thin film can be instantaneously vaporised to form pure water vapor and dry, crystallised salt under vacuum conditions. This work demonstrates, for the first time, that supported carbon membranes are a viable configuration for the percrystallisation of saline solutions. Within the work, the carbon materials in powder and supported membrane form were produced from polyvinylpyrrolidone (PVP) by pyrolysis at temperatures ranging from 450 and 800 °C. Porosity analysis identified that the materials do not adsorb gas. This suggests that the materials are non-porous or the pores are not accessible at the analysis conditions. All produced membranes were of supported nature with approximate thickness of 8 μm. The flux measurement revealed that the membranes, despite being similar in thickness, resulted in variable flux exhibiting a parabolic profile, with a maximum flux obtained (18 kg m−2 h−1) when tested for percrystallisation at 50 °C. The membranes maintained structural integrity when operated with 3.5 to 10 wt% NaCl solutions at 50 °C. However, membranes began to degrade when operating with 20 wt% solutions at 70 °C. The solid product analysis showed that the NaCl produced by percrystallisation is crystalline NaCl, with various morphological properties. The analysis also revealed that the particle size and shape depends on the solution flux through the membrane with smaller crystals at higher fluxes. The results of this study are used to propose a mechanism of salt formation for the percrystallisation of aqueous salt solutions.

Internal feed preheating necessary for energy-efficient modular multi-effect membrane distillation

Multi-effect membrane distillation (MEMD) systems achieve a high product recovery ratio by effectively utilizing the heat of condensation for further vaporization within the module. In this study, a novel internal feed-preheating design for improving the energy efficiency of modular MEMD systems is proposed and evaluated using a 2D CFD model. Custom user-defined functions are implemented to account for water vapor and associated energy transport across the membrane in an MEMD design with serpentine flow across various effects. Preheat channels embedded into the condensation plates help increase the temperature of feed entering the first effect by ∼25 K, close to heater plate temperature. As a result, high-grade external heat input is not used for sensible heating, instead being utilized towards evaporation and pure water production, resulting in ∼32 % improvement in energy efficiency. However, the added thermal resistance of the preheat channels results in lower average flux and hence recovery, which can be ameliorated by increasing the effective conductivity of the preheat channels. Increasing the thermal conductivity of preheat channels results in ∼23.5 % rise in recovery ratio. Such preheat designs are necessary to reap energy efficiency improvements by increasing the total number of effects in multi-effect vacuum and gap MD systems.

Experimental and numerical performance assessment of a hybrid parabolic dish collector with photovoltaic for a distiller

ABSTRACT Environmental pollution has been rising recently, and so clean water needing has also increased. People could have easy access to pure water in all environments and conditions. This study is the solar tracking parabolic dish collector with produced pure water independent of electricity (off-grid). This system is fully renewable and autonomous. This system possesses a receiver, a boiler, a condenser, six 1000 mm diameter parabolic dish collectors, and 1 kW photovoltaic (PV) collectors. Thermal oil uses as the working fluid in the experiments. The experiment measured solar radiation, air temperature, air velocity, oil inlet and outlet temperatures, oil flow rate, receiver side surface temperatures, and instantaneous amount of pure water. Numerical and thermal analysis of the receiver in the experimental setup carry out. ANSYS Fluent 18.1 uses for numerical analysis. Energy and exergy analysis calculates the receiver for pure water production rate. The time interval when the system operates at high performance determines. In this study investigates the behavior of some exergetic indicators on the performance of the experimental setup, the cost of the experimental setup, and the enviro-economic impact of the parabolic dish-type collector. For this purpose, some exergetic factors such as the exergy effect, environmental impact factor, waste exergy rate, improvement potential, and exergetic sustainability index examine. The receiver’s improvement potential is between 1700 and 3000 W. In addition, the sustainability index, waste exergy rate, and environmental impact factor range from 0.32 to 0.36, 0.90 to 0.94, and 2.6 to 3.0, respectively.

Economics of pure water production and marketing Alexandria Drinking Water Company

Economics of pure water production and marketing Alexandria Drinking Water Company

Performance Improvement of Solar Desalination System Based on CeO2-MWCNT Hybrid Nanofluid

There is a scarcity of freshwater resources and their quality is deteriorating. As a result, meeting human needs is getting more and more challenging. Additionally, significant health problems are brought on by a shortage of freshwater. Therefore, finding a sustainable alternative technique for producing clean water is necessary. Solar distillation is one of the methods that can be implemented to enhance the overall production of pure water. In this work, a hybrid nanofluid was prepared using a two-step method with cerium oxide (CeO2) nanoparticles and multi-walled carbon nanotubes (MWCNTs) in a ratio of 80:20. The concentrations of hybrid nanofluids investigated were 0.02%, 0.04%, and 0.06%. The surfactant cetyltrimethylammonium bromide (CTAB) was used to keep the hybrid nanofluid stable. The studies were carried out over three days in both conventional and modified stills at a constant depth of 1 cm of hybrid nanofluid. The modified still (MS) achieved a maximum production of 1430 mL compared to the conventional still’s (CS) maximum output of 920 mL. The CPL (Cost per liter) for MS was USD 0.039, and for CS, it was USD 0.045. The levels of TDS in the MS and CS were 96.38% and 92.55% lower than those in saline water. The fluoride ion level of saline water was 0.635 mg/L, whereas the distilled water of MS and CS are 0.339 mg/L and 0.414 mg/L, respectively.

Small iron pieces effect on the output of single slope solar still

Solar distillation is an environmental technique that uses solar energy to treat polluted water. In this context, two solar stills of the same size (0.5 x 0.5 m) were exposed to the sun i.e., under the same weather conditions to see the effect of small iron parts on the production of pure water. The results showed that the modified solar still SSM which contained iron pieces had an improvement rate of 23.46% compared to the reference solar still SSR.

Low-pressure reverse osmosis membrane made of cellulose nanofiber and carbon nanotube polyamide nano-nanocomposite for high purity water production

Cellulose nanofiber (CNF) and multiwall carbon nanotube (CNT) nanocomposite polyamide membranes were synthesized and used in a low-pressure reverse osmosis (RO) system. Incorporating CNT and CNF into the polyamide structure (PA-CNT/CNF) allows the homogenous dispersion within the polymeric matrix, increasing its hydrophobic character and surface oxygen functionalities while reducing its surface roughness when compared to plain polyamide (PA), PA-CNT, and PA-CNF membranes. The resultant nanocomposite was tested at 0.75 MPa and sodium chloride salt concentration of 500 ppm resulting in a rejection of 99.47 % and water permeability of 1.65 m3/m2day. The rejection and permeation performance is highly competitive compared with commercial RO membranes. A 2in spiral module built with the PA-CNT/CNF membrane and tested for SiO2, NaCl, and CaCl2 rejection showed a reduction in its permeability of 24.9 % after 100 h of operations, while the commercials showed a decrease of 49.42 %. The present RO membrane module achieved a calcium rejection of 97.5 % and a boron rejection of 50.4 %. The 2in PA-CNT/CNF spiral module was tested in a two-step RO filtration system for high pure water (HPW) production and compared with a TW30 module with NSF certification. The PA-CNT/CNF module revealed a permeability reduction of 9.07% after 30 h operation, while TW30 had a reduction of 20.3%, which is about twice the durability. Molecular dynamics simulation showed that the CNF increased water hydration and boron diffusion on the membrane while CNT increased charge transfer to the PA structure. This polymeric nanocomposite has potential use in producing high purity water for brackish water or wastewater reuse for applications in the emerging semiconductor or pharmacology industry.

Selective etching of Sm0.5Sr0.5CoO3-δ ceramic for solar evaporator with photocatalytic purification

The ultimate goal of solar driven water evaporation is to obtain clean water without volatile organic pollutants. Current strategies mainly depend on the integration of the photo-thermal conversion and photocatalytic degradation by a multi-step composite technique. In this work, a facile nitric acid etching method was adopted to prepare the photothermal-catalytic bifunctional material (Sm0.5Sr0.5CoO3-δ-Co3O4). The effect of the acid-etching treatment on the Sm0.5Sr0.5CoO3-δ surface evolution was investigated. The Sm0.5Sr0.5CoO3-δ (SSC5) surface was selectively reconstructed, and the catalytic active B-site cobalt cation was randomly exposed after the acid-etching treatment. The unique structure of SSC5-Co3O4 was beneficial to the electrons transport between Co3O4 and SSC5, as well as the solar absorbance. The nitric acid-etched SSC5 honeycomb ceramic exhibited a solar absorption of 80%, resulting in an evaporation rate of 7.25 kg·m−2·h−1 under a simulated sunlight of 1000 mW·cm−2. Besides, the etched SSC5 exhibited the ability for pollutant (Congo red) degradation. The as-prepared acid-etched SSC5 honeycomb ceramic could integrate the solar evaporation with pollutant degradation, which has a promising application in the pure water production.

Improved air gap distillation desalination through induced film condensation

Distillation across an air gap is implemented in several novel small-scale desalination technologies such as air gap distillation and multi-effect solar stills. These systems achieve better energy efficiency than simple solar stills by recovering the enthalpy of condensation towards feed preheating or further evaporation in subsequent effects. The air gap thickness between the evaporating and condensing fluids is a critical design variable that strongly affects overall performance. A thinner gap results in lower resistance to vapor diffusion and therefore helps attain a higher rate of pure water production and lower specific energy consumption, for the same hot and cold stream temperatures. In this manuscript, we experimentally evaluate methods to achieve a gap size lower than 5 mm, which is the thinnest gap size reported in the literature. While a superhydrophobic surface modification is usually applied to enhance condensation heat transfer (through dropwise condensation), here, a superhydrophillic surface modification is proposed. This ensures film condensation and prevents the growth of large condensate drops that can bridge the thin gap and come in contact with the saline feed, thereby getting contaminated with salt. Attaching a thin mesh to the condensation surface helps realize the same objective at lower cost and complexity. A 3 mm air gap is experimentally demonstrated using these modifications, resulting in a gained output ratio of close to 1 even with a small (304 cm2) evaporation surface area.