Emergency water supply: a review of potential technologies and selection criteria

Piezoceramic membrane with built-in ultrasound for reactive oxygen species generation and synergistic vibration anti-fouling

Piezoceramic membranes have emerged as a prominent solution for membrane fouling control. However, the prevalent use of toxic lead and limitations of vibration-based anti-fouling mechanism impede their wider adoption in water treatment. This study introduces a Mn/BaTiO3 piezoceramic membrane, demonstrating a promising in-situ anti-fouling efficacy and mechanism insights. When applied to an Alternating Current at a resonant frequency of 20 V, 265 kHz, the membrane achieves optimal vibration, effectively mitigating various foulants such as high-concentration oil (2500 ppm, including real industrial oil wastewater), bacteria and different charged inorganic colloidal particles, showing advantages over other reported piezoceramic membranes. Importantly, our findings suggest that the built-in ultrasonic vibration of piezoceramic membranes can generate reactive oxygen species. This offers profound insights into the distinct anti-fouling processes for organic and inorganic wastewater, supplementing and unifying the traditional singular vibrational anti-fouling mechanism of piezoceramic membranes, and potentially propelling the development of piezoelectric catalytic membranes.

An electrical- and chemical-free approach using microfilter and Ag-based catalysts for emergency drinking water treatment

In emergency cases such as disasters, supplying enough safe drinking water is one of the most urgent needs for human life. This research aimed to develop a chemical- and electricity-free drinking water treatment system based on microfiltration and catalysts of Ag and Ag-TiO2-SiO2 coated on glass spheres in both dark and sunlight conditions. The system was applied to treat raw water samples taken from five rivers in Vietnam, simulated floodwater samples with high turbidity and E. coli concentration, and real flooding water samples. The results showed the filtration unit fed with simulated floodwater generated lower fluxes and shorter working durations before chemical cleaning than that fed with normal river water. However, filtrate quality was not significantly different for these five water samples with very low values of turbidity (0-0.66 NTU), total coliform (5-19 CFU (100 mL)-1), and E. coli (0-17 CFU (100 mL)-1). The catalyst units using glass spheres coated with either Ag in dark and sunlight or Ag-TiO2-SiO2 under sunlight can completely remove E. coli and coliform as well as additionally mitigate natural organic matters. This study hence suggests the combination of microfiltration and Ag-based catalytic treatment for safe drinking water supply in emergencies, especially for flooding conditions.

Research Progress on Hygroscopic Agents for Atmospheric Water Harvesting Systems

Adsorptive atmospheric water harvesting systems (AWHs) represent an innovative approach to collecting freshwater resources from the atmosphere, with a hygroscopic agent at their core. This method has garnered significant attention due to its broad applicability, strong recycling capacity, and sustainability. It is being positioned as a key technology to address global freshwater scarcity. The core agent's hygroscopic properties play a crucial role in determining the performance of the AWHs. This article provides a comprehensive review of the latest advancements in hygroscopic agents, including their adsorption mechanisms and classifications. This study of hygroscopic agents analyzes the performance and characteristics of relevant porous material composite polymer composites and plant composites. It also evaluates the design and preparation of these materials. Aiming at the problems of low moisture adsorption and desorption difficulty of the hygroscopic agent, the factors affecting the water vapor adsorption performance and the method of enhancing the hygroscopic performance of the material are summarized and put forward. For the effect of hygroscopic agents on the volume of water catchment devices, the difference in density before and after hygroscopicity is proposed as part of the evaluation criteria. Moisture absorption per unit volume is added as a performance evaluation criterion to assess the effect of hygroscopic agents on the volume of water collection equipment. The article identifies areas that require further research and development for moisture absorbers, exploring their potential applications in other fields and anticipating the future development direction and opportunities of moisture-absorbing materials. The goal is to promote the early realization of adsorptive atmospheric water harvesting technology for large-scale industrial applications.

Self-cleaning and photodegradle PVDF separation membranes modified with self-assembled TiO2-g-CS/CNTs particle

This work obtained separation membranes with UV-cleaning performance by adding TiO2-g-CS/CNTs photocatalyst to the PVDF. The positively charged chitosan (CS) and negatively charged carboxylic carbon nanotube (CNTs-COOH) can be self-assembled into the bilayer structure on the surface of TiO2 particles through electrostatic attraction. The presence of many hydrophilic groups in CS and CNTs-COOH significantly improves the hydrophilicity of TiO2-g-CS/CNTs-PVDF membrane, and helps TiO2 to be uniformly dispersed on the upper surface. TiO2-g-CS/CNTs promote the change of pore structure and expand the flux of the modified membrane to 4.5 times that of pure PVDF. Zeta potential demonstrates that the TiO2-g-CS particles successfully attracted CNTs in the PVDF matrix, and the membrane surface was still positively charged. Thus, the combined effect of the positively charged TiO2-g-CS and the highly adsorbed CNTs enhanced the retention of the contaminants. More importantly, there is a charge transfer between the grafted CS and TiO2 interface to obtain a broader light absorption band. The excitation carriers provided by CNTs significantly contribute to the photocatalytic performance after transfer between TiO2 and CS; thus, TiO2-g-CS/CNTs-PVDF produces higher photocatalytic activity for dye molecules (degradation rate > 97 %).

Application of electric field treatment (EFT) for microbial control in water and liquid food

Water disinfection and food pasteurization are critical to reducing waterborne and foodborne diseases, which have been a pressing public health issue globally. Electrified treatment processes are emerging and have become promising alternatives due to the low cost of electricity, independence of chemicals, and low potential to form by-products. Electric field treatment (EFT) is a physical pathogen inactivation approach, which damages cell membrane by irreversible electroporation. EFT has been studied for both water disinfection and food pasteurization. However, no study has systematically connected the two fields with an up-to-date review. In this article, we first provide a comprehensive background of microbial control in water and food, followed by the introduction of EFT. Subsequently, we summarize the recent EFT studies for pathogen inactivation from three aspects, the processing parameters, its efficacy against different pathogens, and the impact of liquid properties on the inactivation performance. We also review the development of novel configurations and materials for EFT devices to address the current challenges of EFT. This review introduces EFT from an engineering perspective and may serve as a bridge to connect the field of environmental engineering and food science.

Next-generation ultrafiltration membranes: A review of material design, properties, recent progress, and challenges

Membrane technology utilizing ultrafiltration (UF) processes has emerged as the most widely used and cost-effective simple process in many industrial applications. The industries like textiles and petroleum refining are promptly required membrane based UF processes to alleviate the potential environmental threat caused by the generation of various wastewater. At the same time, major limitations such as material selection as well as fouling behavior challenge the overall performance of UF membranes, particularly in wastewater treatment. Therefore, a complete discussion on material design with structural property relation and separation performance of UF membranes is always exciting. This state-of-the-art review has exclusively focused on the development of UF membranes, the material design, properties, progress in separation processes, and critical challenges. So far, most of the review articles have examined the UF membrane processes through a selected track of paving typical materials and their limited applications. In contrast, in this review, we have exclusively aimed at comprehensive research from material selection and fabrication methods to all the possible applications of UF membranes, giving more attention and theoretical understanding to the complete development of high-performance UF systems. We have discussed the methodical engineering behind the development of UF membranes regardless of their materials and fabrication mechanisms. Identifying the utility of UF membrane systems in various applications, as well as their mode of separation processes, has been well discussed. Overall, the current review conveys the knowledge of the present-day significance of UF membranes together with their future prospective opportunities whilst overcoming known difficulties in many potential applications.

Fabrication and Investigation of Acid Functionalized CNT Blended Nanocomposite Hollow Fiber Membrane for High Filtration and Antifouling Performance in Ultrafiltration Process

In this study, we fabricated a nanocomposite polyethersulfone (PES) HF membrane by blending acid functionalized carbon nanotubes (FCNT) to address the issue of reduced membrane life, increased energy consumption, and operating costs due to low permeability and membrane fouling in the ultrafiltration process. Additionally, we investigated the effect of FCNT blending on the membrane in terms of the physicochemical properties of the membrane and the filtration and antifouling performance. The FCNT/PES nanocomposite HF membrane exhibited increased water permeance from 110.1 to 194.3 LMH/bar without sacrificing rejection performance and increased the flux recovery ratio from 89.0 to 95.4%, compared to a pristine PES HF membrane. This study successfully developed a high filtration and antifouling polymer-based HF membrane by blending FCNT. Furthermore, it was validated that blending FCNT into the membrane enhances the filtration and antifouling performance in the ultrafiltration process.

Increase by Substitution of Galvanized Steel for Aluminum Mirrors in the UV Solar Radiation in Canal with Fins and Side Panels That Disinfect Wastewater

The need arises to seek new depuration technological responses aimed at the reuse of wastewater, which requires the development and promotion of economically and environmentally sustainable technologies. In this paper, it studies an improvement to a disinfection system sustainable, low-cost, patented in 2019, and based on solar energy. The water passes through a canal of reflective material in the continuous regime, and in the batch regime, the water remains in the canal. The panels are located parallel to the lateral faces of the canal. The fraction of the radiation reflected outside the canal reaches the reflective side panels that return the radiation to the canal. These panels concentrate the radiation in the canal through reflection. The disinfectant canal with fins and side panels uses ultraviolet radiation to eliminate the bacterial load carried by treated wastewater. For this reason, the present work analyzes the incidence in the area of influence of the disinfectant canal. When reflective aluminum mirrors were installed on the sloping walls of the canal, global radiation increased by 4%, when they were used on the side panels, it increased 3%, and when the aluminum mirrors were used on the canal walls and side panels, it increased 8%. The important thing about this work is that it opens windows for improving the system through materiality so the new challenge is the search for the optimal material considering the impact on global radiation and consequently on the bacteriological elimination.

Alternative Water Resources Selection to Supply Drinking Water in Flood Disasters by Multicriteria Decision-Making Techniques (DANP and VIKOR)

Background

Emergency is generally caused by natural disaster and infectious disease outbreaks, or it is man-made. Floods are natural phenomena that generally appear in multiple parts of the world. Flooding is one of the most destructive naturally occurring environmental hazards and can cause public, infrastructural, and environmental damage. The purpose of this study is to select alternative water resources for supplying Bandar Abbas in flood disasters by multicriteria decision-making techniques.

Methods

Information required includes possible water resources alternative for flood, quantitative and qualitative characteristics of the water resources, climatic circumstances, and demographic information used in organizations data and previous studies. After selecting and proposing water resources alternative for Bandar Abbas in flood, the subcriteria were weighed applying DANP (DEMATEL-ANP) techniques and water resources were prioritized with the VIKOR technique. According to the network structure and internal and external dependence of the criteria and subcriteria, the advantages of DANP in calculating weights have been used to adapt to more real-world problems. The VIKOR technique was developed for multicriteria optimization of complex systems.

Results

After reviewing and extracting the criteria from various studies, 9 main criteria and 44 subcriteria were defined to select water resources in disasters and emergencies. According to field studies and related organizations' information, the proposed water resources for Bandar Abbas to use in flood disasters include humidity, sea (Persian Gulf), Sarkhoon plain, and wastewater treatment plant of Bandar Abbas.

Conclusion

Results showed that the optimal water resources for Bandar Abbas in flood disasters are the sea and wastewater treatment plant effluent (after advanced treatment). The study proposed appropriate model to select optimal water resources for various natural disasters in different geographical areas. This model can help officials and decision-makers to plan for drinking water supply from disaster-prone areas before disasters occur.

Desorption of micropollutant from superfine and normal powdered activated carbon in submerged-membrane system due to influent concentration change in the presence of natural organic matter: Experiments and two-component branched-pore kinetic model

Submerged-membrane hybrid systems (SMHSs) that combine membrane filtration with powdered activated carbon (PAC) take advantage of PAC's ability to adsorb and remove contaminants dissolved in water. However, the risk of contaminant desorption due to temporal changes in the influent concentration of the contaminant has not been thoroughly explored. In this study, we used a SMHS with conventionally-sized PAC or superfine PAC (SPAC) to remove 2-methylisoborneol (MIB), a representative micropollutant, from water containing natural organic matter (NOM), with the goal of elucidating adsorption-desorption phenomena in the SMHS. We found that 20-40% of the MIB that adsorbed on PAC and SPAC while the influent was contaminated with MIB (6 h, contamination period) desorbed to the liquid phase within 6 h from the time that the MIB-containing influent was replaced by MIB-free influent (no-contamination period). The percentage of desorption during the no-contamination period increased with increasing MIB breakthrough concentration during the contamination period. These findings indicate that the PAC/SPAC in the SMHS should be replaced while the breakthrough concentration is low, not only to keep a high removal rate but also to decrease the desorption risk. SPAC is fast in removal by adsorption, but it is also fast in release by desorption. SPAC (median diameter: 0.94 µm) showed almost the same adsorption-desorption kinetics as PAC (12.1 µm) of a double dose. A two-component branched-pore diffusion model combined with an IAST (ideal adsorbed solution theory)-Freundlich isotherm was used to describe and analyze the adsorption-desorption of MIB. The diffusivity of MIB molecules in the pores of the activated carbon particles decreased markedly in a short period of time. This decrease, which was attributed to fouling of the activated carbon in the SMHS by coagulant-treated water containing NOM, not only reduced the rate of MIB removal during the contamination period but also hindered the rate of MIB desorption during the no-contamination period and thus prevented the effluent MIB concentration from becoming high. On the other hand, coagulation did not change the concentration of NOM that competes with MIB for adsorption sites.

Field Trial of an Automated Batch Chlorinator System at Two Shared Shallow Tubewells among Camps for Forcibly Displaced Myanmar Nationals (FDMN) in Cox's Bazar, Bangladesh

Chlorination of shallow tubewell water is challenging due to various iron concentrations. A mixed-method, small-scale before-and-after field trial assessed the accuracy and consistency of an automated chlorinator, Zimba, in Rohingya camp housing, Cox’s Bazar. From August–September 2018, two shallow tubewells (iron concentration = 6.5 mg/L and 1.5 mg/L) were selected and 20 households were randomly enrolled to participate in household surveys and water testing. The field-team tested pre-and post-treated tubewell and household stored water for iron, free and total chlorine, and E. coli. A sub-set of households (n = 10) also received safe storage containers (5 L jerry cans). Overall mean iron concentrations were 5.8 mg/L in Zimba water, 1.9 mg/L in household storage containers, and 2.8 mg/L in the project-provided safe storage containers. At baseline, 0% samples at source and 60% samples stored in household vessels were contaminated with E. coli (mean log₁₀ = 0.62 MPN/100 mL). After treatment, all water samples collected from source and project-provided safe storage containers were free from E. coli, but 41% of post-treated water stored in the household was contaminated with E. coli. E. coli concentrations were significantly lower in the project-provided safe storage containers (log₁₀ mean difference = 0.92 MPN, 95% CI = 0.59–1.14) compared with baseline and post-treated water stored in household vessels (difference = 0.57 MPN, 95% CI = 0.32–0.83). Zimba is a potential water treatment technology for groundwater extracted through tubewells with different iron concentrations in humanitarian settings.

Impacts of Surface Hydrophilicity of Carboxylated Polyethersulfone Supports on the Characteristics and Permselectivity of PA-TFC Nanofiltration Membranes

Our current study experimentally evaluates the impacts of surface hydrophilicity of supports on the properties of polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membranes. A series of "carboxylated polyethersulfone" (CPES) copolymers with an increasing "molar ratio" (MR) of carboxyl units were used to prepare supports with diverse surface hydrophilicities by the classical nonsolvent-induced phase separation (NIPS) method. Then, the PA-TFC NF membranes were finely fabricated atop these supports by conventional interfacial polymerization (IP) reactions. The linkages between the surface hydrophilicity of the supports and the characteristics of the interfacially polymerized PA layers as well as the permselectivity of NF membranes were investigated systematically. The morphological details of the NF membranes indicate that the growth of PA layers can be adjusted through increasing the surface hydrophilicity of the supports. Moreover, the separation results reveal that the NF membrane fabricated on the relatively hydrophobic support exhibits lower permeability (7.04 L·m^-2·h^-1·bar^-1) and higher selectivity (89.94%) than those of the ones prepared on the hydrophilic supports (14.64~18.99 L·m^-2·h^-1·bar^-1 and 66.98~73.48%). A three-stage conceptual scenario is proposed to illustrate the formation mechanism of the PA layer in NF membranes, which is due to the variation of surface hydrophilicity of the supports. The overall findings specify how the surface hydrophilicity of the supports influences the formation of PA layers, which ultimately defines the separation performances of the corresponding NF membranes.

Universal Access to Safe Drinking Water: Escaping the Traps of Non-Frugal Technologies

This communication is motivated by recent publications discussing the affordability of appropriate decentralized solutions for safe drinking water provision in low-income communities. There is a huge contrast between the costs of presented technologies, which vary by a factor of up to 12. For example, for the production of 2000 L/d of treated drinking water, the costs vary between about 1500 and 12,000 Euro. A closer look at the technologies reveals that expensive technologies use imported manufactured components or devices that cannot yet be locally produced. In the battle to achieve the United Nations Sustainable Development Goal for safe drinking water (SDG 6.1), such technologies should be, at best, considered as bridging solutions. For a sustainable self-reliance in safe drinking water supply, do-it-yourself (DIY) systems should be popularized. These DIY technologies include biochar and metallic iron (Fe0) based systems. These relevant technologies should then be further improved through internal processes.

3D Photothermal Cryogels for Solar-Driven Desalination

This paper reports the fabrication of photothermal cryogels for freshwater production via the solar-driven evaporation of seawater. Photothermal cryogels were prepared via in situ oxidative polymerization of pyrrole with ammonium persulfate on preformed poly(sodium acrylate) (PSA) cryogels. We found that the pyrrole concentration used in the fabrication process has a significant effect on the final PSA/PPy cryogels (PPCs), causing the as-formed polypyrrole (PPy) layer on the PPC to evolve from nanoparticles to lamellar sheets and to consolidated thin films. PPC fabricated using the lowest pyrrole concentration (i.e., PPC10) displays the best solar-evaporation efficiency compared to the other samples, which is further improved by switching the operative mode from floating to standing. Specifically, in the latter case, the apparent solar evaporation rate and solar-to-vapor conversion efficiency reach 1.41 kg m-2 h-1 and 96.9%, respectively, due to the contribution of evaporation from the exposed lateral surfaces. The distillate obtained from the condensed vapor, generated via solar evaporation of a synthetic seawater through PPC10, shows an at least 99.99% reduction of Na while all the other elements are reduced to a subppm level. We attribute the superior solar evaporation and desalination performance of PPC10 to its (i) higher photoabsorption efficiency, (ii) higher heat localization effect, (iii) open porous structure that facilitates vapor removal, (iv) rough pore surface that increases the surface area for light absorption and water evaporation, and (v) higher water-absorption capacity to ensure efficient water replenishment to the evaporative sites. It is anticipated that the gained know-how from this study would offer insightful guidelines to better designs of polymer-based 3D photothermal materials for solar evaporation as well as for other emerging solar-related applications.

Novel housing designs for nanofiltration and ultrafiltration gravity-driven recycled membrane-based systems

Ultra-low pressure gravity-driven membrane (GDM) systems have the potential to be significantly less costly and complex than conventional membranes for water treatment applications. To build upon this inherent advantage, this study assesses the reuse of recycled membranes in GDM systems for producing drinking water. Two reverse osmosis spiral-wound modules were recycled into nanofiltration (NF)-like and ultrafiltration (UF)-like membranes via controlled exposure to free chlorine. To operate the recycled membranes, two housing devices, based on a simple fitting and an advanced end-caps design, were developed. The recycled membrane systems were tested under a range of conditions (submerged vs. external system configuration and continuous vs. intermittent filtration mode). Synthetic river water feed solutions were used in the tests where performance, fouling, and clogging were measured. NF-like recycled membranes resulted in poor salt rejection and low permeability (~1.7 L m^-2 h^-1 bar^-1), but also in high rejection (>81%) of dissolved organic carbon. UF-like recycled membranes maintained their capacity to reject biopolymers (BP) (>74%) and featured up to 18-fold higher permeate rate than NF-like recycled membranes. The optimized operating conditions were found when the recycled membranes were housed in the end-caps device and operated intermittently (relaxation time plus forward flushing). Flushing reduced the fouling accumulation inside the membrane (only 12% and 40% of BP accumulation was observed in the NF-like and UF-like, respectively). However, the end-caps-based device was estimated to be more expensive during the economic analysis. To address this techno-economic trade-off, a decision-making tree was developed to select the appropriate configuration based upon the implementation context. Overall, this study concludes that these designs can serve as robust, low-cost (water production cost <1 USD ct. yr. L^-1), and light-weight GDM alternatives. This study is beneficial for developing compact GDM systems based on recycled spiral-wound membranes for both rural areas and emergency response.

Assessment of the Readiness and Resilience of Czech Society against Water-Related Crises

This assessment of societal readiness and resilience to water-related situations in the Czech Republic focuses on an interdisciplinary approach in the Czech Republic for solving this problem. The goal of the article is to evaluate and characterize the preparedness for handling water-related crises. The analysis is carried out via a SWOT analysis, which is a universal analytical method used to understand and interpret strengths and weaknesses and to identify opportunities and threats. For the calculation of the weight factor of the SWOT analysis, an assessment was determined based on the multicriteria analysis. The pair comparison method was used to determine the relative importance of the parameters of the strengths and weaknesses, opportunities and threats. The Fuller Triangle method was chosen for the system used to make the comparisons of the individual criteria. The uniqueness of the study consists of the issue of water management, which is thus reflected from a non-traditional perspective, being a contemporary model—the paradigm of the view on the preparedness of the planning documentation as one of the characteristics of societal resilience for water-related crises. The result of the research is the fact that a positive approach prevails in the researched area from the perspective of preparedness for water-related crises. For the creation of the conditions, the factors arising from the internal environment currently prevail slightly over those arising from the external environment.

Development of Chitosan/Starch-Based Forward Osmosis Water Filtration Bags for Emergency Water Supply

A forward osmosis (FO) membrane was developed from a mixture of chitosan and Dioscorea hispida starch, cross-linked using glutaraldehyde. The cross-linked chitosan/starch membrane was revealed to have high mechanical properties with an asymmetric structure. The prepared membrane’s performance was investigated as an FO filter assembled in a polypropylene water filter bag and aluminum foil plastic. In order to study the FO process, brackish water was used as a feed solution, drawn using three types of solution (fructose, sucrose, and fructose/sucrose mixture, each with 3 M concentration). The maximum water flux (5.75 L/m² h) was achieved using 3 M sucrose. The cross-linked membrane restrained the ions in the feed with a rejection factor value close to 100%. The water quality parameters were evaluated for the physical, chemical, and biological criteria, such as pH, salinity, conductivity, total dissolved solids (TDS), heavy metals, and Escherichia coli content. The water quality parameters for the FO-processed water met that set by the World Health Organization for drinking water. FO filter bags with cross-linked chitosan/starch membranes can be an option to produce drinking water during an emergency.

Development and Application of a Multi-Objective-Optimization and Multi-Criteria-Based Decision Support Tool for Selecting Optimal Water Treatment Technologies in India

Despite considerable efforts to improve water management, India is becoming increasingly water stressed due to multiple factors, including climate change, increasing population, and urbanization. We address one of the most challenging problems in the design of water treatment plants: how to select a suitable technology for a specific scenario or context. The process of decision making first requires the identification of feasible treatment configurations based on various objectives and criteria. In addition, the multiplicity of water quality parameters and design variables adds further complexity to the process. In this study, we propose a novel Decision Support Tool (DST), designed to address and support the above challenges. In this user-friendly tool, both Multi-Criteria Decision Analysis (MCDA) and Multi-Objective Optimization (MOO) methods are employed. The integration of MCDA with MOO facilitates the generation of feasible drinking water treatment solutions, identifies optimal options, and ultimately, improves the process of decision making. This implemented approach has been tested for different contexts, including for different types of raw water sources and system implementation scales. The results show that this tool can enhance the process of decision making, supporting the user (e.g., stakeholders and decision makers) to implement the most suitable water treatment systems, keeping in view the trade-offs.

Biosand Filter as a Point-of-Use Water Treatment Technology: Influence of Turbidity on Microorganism Removal Efficiency

The number of people living without access to clean water can be reduced by the implementation of point-of-use (POU) water treatment. Among POU treatment systems, the domestic biosand filter (BSF) stands out as a viable technology. However, the performance of the BSF varies with the inflow water quality characteristics, especially turbidity. In some locations, people have no choice but to treat raw water that has turbidity above recommended levels for the technology. This study aimed to measure the efficiency with which the BSF removes microorganisms from well water and from fecal-contaminated water with turbidity levels of 3, 25, and 50 NTU. Turbidity was controlled by the addition of kaolin to water. Turbidity removal varied from 88% to 99%. Reductions in total coliform (TC) and Escherichia coli ranged from 0.54–2.01 and 1.2–2.2 log removal values (LRV), respectively. The BSF that received water with a higher level of turbidity showed the greatest reduction in the concentration of microorganisms. Additional testing with water contaminated with four bacterial pure cultures showed reductions between 2.7 and 3.6 LRV. A higher reduction in microorganisms was achieved after 30–35 days in operation. Despite the filter’s high efficiency, the filtrates still had some microorganisms, and a disinfection POU treatment could be added to increase water safety.

Low-Tortuosity Water Microchannels Boosting Energy Utilization for High Water Flux Solar Distillation

Solar distillation through photothermal evaporators has approached solar light energy (E₁) limit under no solar concentration but still suffers from modest vapor and clean water production. Herein, a nature-inspired low-tortuosity three-dimensional (3D) evaporator is demonstrated to significantly improve water production. The solar evaporator, prepared from polypyrrole-modified maize straw (PMS), had upright vascular structures enabling high water lifting and horizontal microgaps facilitating broad water distribution to the out-surface. Consequently, this novel PMS evaporator dramatically enhanced the utilization of the solar heat energy stored in the environment (E₂) for promoting evaporation. The maximum vapor generation rate of a single PMS respectively increases 2.5 and 6 times compared with the conventional 3D evaporators and the planar evaporators of an identical occupied area. Consequently, a scaled-up PMS array achieved a state-of-the-art vapor generation rate of 3.0 L m^-2 h^-1 (LMH) under a simulated condition and a record-high clean water production of 2.2 LMH for actual seawater desalination under natural conditions (1 sun intensity). This breakthrough reveals great potentials for cost-effective freshwater production as well as the rational design of high-performance photothermal evaporators for solar distillation.

Solar-Driven Freshwater Generation from Seawater and Atmospheric Moisture Enabled by a Hydrophilic Photothermal Foam

The accelerated increase in freshwater demand, particularly among populations displaced in remote locations where conventional water sources and the infrastructure required to produce potable water may be completely absent, highlights the urgent need in creating additional freshwater supply from untapped alternative sources via energy-efficient solutions. Herein, we present a hydrophilic and self-floating photothermal foam that can generate potable water from seawater and atmospheric moisture via solar-driven evaporation at its interface. Specifically, the foam shows an excellent solar-evaporation rate of 1.89 kg m-2 h-1 with a solar-to-vapor conversion efficiency of 92.7% under 1-Sun illumination. The collected water is shown to be suitable for potable use because when synthetic seawater samples (3.5 wt %) are used, the foam is able to cause at least 99.99% of salinity reduction. The foam can also be repeatedly used in multiple hydration-dehydration cycles, consisting of moisture absorption or water collection, followed by solar-driven evaporation; in each cycle, 1 g of the foam can harvest 250-1770 mg of water. To the best of our knowledge, this is the first report of a material that integrates all the desirable properties for solar evaporation, water collection, and atmospheric-water harvesting. The lightweight and versatility of the foam suggest that the developed foams can be a potent solution for water efficiency, especially for off-grid situations.

An Interfacial Solar-Driven Atmospheric Water Generator Based on a Liquid Sorbent with Simultaneous Adsorption-Desorption

Water scarcity is one of the greatest challenges facing human society. Because of the abundant amount of water present in the atmosphere, there are significant efforts to harvest water from air. Particularly, solar-driven atmospheric water generators based on sequential adsorption-desorption processes are attracting much attention. However, incomplete daytime desorption is the limiting factor for final water production, as the rate of water desorption typically decreases very quickly with decreased water content in the sorbents. Hereby combining tailored interfacial solar absorbers with an ionic-liquid-based sorbent, an atmospheric water generator with a simultaneous adsorption-desorption process is generated. With enhanced desorption capability and stabilized water content in the sorbent, this interfacial solar-driven atmospheric water generator enables a high rate of water production (≈0.5 L m^-2 h^-1 ) and 2.8 L m^-2 d^-1 for the outdoor environment. It is expected that this interfacial solar-driven atmospheric water generator, based on the liquid sorbent with a simultaneous adsorption-desorption process opens up a promising pathway to effectively harvest water from air.

Comparison of five point-of-use drinking water technologies using a specialized comparison framework

Three novel and two commercially available low-cost point-of-use (PoU) water treatment technologies were comparatively evaluated using a specialized comparison framework targeted at them. The comparison results and specialized framework have been discussed. The PoU systems were evaluated principally in terms of performance, flow rate and cost per volume of water treated (quantitatively), ease of use, potential acceptability and material availability (qualitatively) with main focus on rural and suburban settings. The three novel systems assessed were developed in an ongoing research project aimed at developing a multibarrier low-cost PoU water treatment system. The comparative evaluation and analysis revealed that the commercially available systems may often produce water free of pathogens (with an apparent 100% removal for Escherichia coli and fecal coliforms) but may not be affordable for application to the poorest groups in much of the developing world. The novel systems, which were principally constructed from local materials, were more affordable, can supply relatively safe water and can be constructed by users with minimal training. Overall, bacterial removal effectiveness, ease of use, flow rate, material availability, cost and acceptability aspects of water were identified as key to potential adoption and sustainability of the evaluated low-cost PoU systems.

Performance of the fixed-bed of granular activated carbon for the removal of pesticides from water supply

The application of a fixed bed adsorption column of granular activated carbon (FBAC-GAC), in the removal of carbaryl, methomyl and carbofuran at a concentration of 25 μg L^-1 for each carbamate, from the public water supply was investigated. For the determination of the presence of pesticides in the water supply, the analytical technique of high-performance liquid chromatography with post-column derivatization was used. Under conditions of constant diffusivity, the FBAC-GAC was saturated after 196 h of operation on a pilot scale. The exhaust rate of the granular activated carbon (GAC) in the FBAC-GAC until the point of saturation was 0.02 kg GAC m^-3 of treated water. By comparing a rapid small-scale column test and FBAC-GAC, it was confirmed that the predominant intraparticle diffusivity in the adsorption column was constant diffusivity. Based on the results obtained on a pilot scale, it was possible to estimate the values to be applied in the FBAC-GAC (full scale) to remove the pesticides, which are particle size with an average diameter of 1.5 mm GAC; relationship between the internal diameter of the column and the average diameter of GAC ≥50 in order to avoid preferential flow near the adsorption column wall; surface application rate 240 m³ m^-2 d^-1 and an empty bed contact time of 3 min. ABBREVIATIONS: BV: bed volume; CD: constant diffusivity; EBCT: empty bed contact time; FBAC-GAC: fixed bed adsorption column of granular activated carbon; GAC: granular activated carbon; MPV: maximum permitted values; NOM: natural organic matter; PD: proportional diffusivity; pH_PCZ: pH of the zero charge point; SAR: surface application rate; RSSCT: rapid small-scale column test; WTCS: water treated conventional system.

Insecure Security: Emergency Water Supply and Minimum Standards in Countries with a High Supply Reliability

Drinking water supply is at the core of both, humanitarian action in times of crisis, as well as national policies for regular and emergency supply. In countries with a continuous water supply, the population mostly relies ingenuously on the permanent availability of tap water due to high supply standards. In case of a disruption in the drinking water infrastructure, minimum supply standards become important for emergency management during disasters. However, wider recognition of this issue is still lacking, particularly in countries facing comparably fewer disruptions. Several international agencies provide guideline values for minimum water provision standards in case of a disaster. Acknowledging that these minimum standards were developed for humanitarian assistance, it remains to be analyzed whether these standards apply to disaster management in countries with high supply standards. Based on a comprehensive literature review of scientific publications and humanitarian guidelines, as well as policies from selected countries, current processes, contents, and shortcomings of emergency water supply planning are assessed. To close the identified gaps, this paper flags potential improvements for emergency water supply planning and identifies future fields of research.

A review: the effect of the microporous support during interfacial polymerization on the morphology and performances of a thin film composite membrane for liquid purification

The thin film composite (TFC) membrane prepared by interfacial polymerization (IP) on porous supports is currently one of the most efficient technologies for brackish water purification and seawater desalination, including reverse osmosis (RO), forward osmosis (FO), and nanofiltration (NF). Over the past decades, there have been intensive and continuous efforts in research of polyamide layers, while there is little information in the literature about the impact that physical–chemical properties and structure of support membranes have on the formation of composite membranes. This paper reviews the recent research progress of the supporting membrane, comprehensively summarizes the support role in polyamide formation, and provides good insight into TFC membrane research and development. In addition, we discuss several types of polymer supporting membranes and related modification methods to explore the appropriate supporting membrane for enhancing TFC membrane performance and extending the applications in the future.

The thin film composite membrane prepared by interfacial polymerization on porous supports is currently one of the most efficient technologies for brackish water purification and seawater desalination, including reverse osmosis, forward osmosis and nanofiltration.

Logistics system for drinking water distribution in post disaster humanitarian relief, Al-Za’atari camp

Purpose

It is essential to provide drinking water to affected population directly after a disaster. The purpose of this paper is to develop an optimization methodology that helps in the distribution of drinking water in post-disaster situations.

Design/methodology/approach

The research was conducted on two phases: phase 1 aims at identifying an appropriate way to deliver drinking water to refugee camps from external sources, considering required drinking water quantities and four possible sources of water with respect to cost and risk assessments. Phase 2 investigates drinking water distribution within a refugee camp using covering models. The MCLP–optimal number of facilities model is proposed to ensure that the water is distributed and delivered to all individuals in a camp with minimum number of water storage tanks required. A control policy is proposed to ensure the fair distribution of water to all targeted individuals.

Findings

Al-Za’atari refugee camp, located in northeast of Jordan, was considered as the case study for this research. The result showed that the appropriate way to deliver water to the camp is by using tanker–trucks, and a minimum number of five tanks are required to distribute water to individuals inside the camp with respect to tank locations and the allocation of tank of each area.

Originality/value

The proposed methodology is essential in decision making for the distribution of drinking water in refugee camps in short-term needs. The model adds important value to the literature as the proposed problem has no solution in the literature before.

Forward osmosis treatment of effluents from dairy and automobile industry - results from short-term experiments to show general applicability

Forward osmosis (FO) is a potential membrane technology to treat wastewater energy efficiently with low fouling. In laboratory-scale experiments, six effluents from a dairy and an automobile production plant were tested to find out if FO is an applicable treatment technology. Permeate flux and reverse salt flux were determined in nine test series with three subsequent 5 h experiments each. In between, the membrane was cleaned with deionized water. Membrane performance tests before each experiment were used to monitor membrane performance and fouling. Samples were analysed and the T/M-value was introduced to indicate which substances caused fouling. Dairy cheese brine was a suitable DS. Here, permeate fluxes were 21.0 and 15.1 L/(m²·h). Automobile cooling tower water and wastewater from cathodic dip painting were also used as DS. However, permeate fluxes were below 1.1 L/(m²·h). The tested FS, reverse osmosis concentrate from dairy wastewater treatment, rinsing water and wastewater from automobile cathodic dip painting, as well as wastewater from automobile paint shop pre-treatment, showed good performance regarding the permeate flux of between 7.9 and 19.4 L/(m²·h). Membrane performance test showed that some of the effluents lead to permeate flux reduction due to fouling. Different cleaning-in-place methods were examined. Eventually, permeate flux was restored.

Electrocatalytic Reduction of Nitrate Using Magnéli Phase TiO2 Reactive Electrochemical Membranes Doped with Pd-Based Catalysts

This research focused on synthesis, characterization, and application of point-of-use catalytic reactive electrochemical membranes (REMs) for electrocatalytic NO₃^- reduction. Deposition of Pd-Cu and Pd-In catalysts to the REMs produced catalytic REMs (i.e., Pd-Cu/REM and Pd-In/REM) that were active for NO₃^- reduction. Optimal performance was achieved with a Pd-Cu/REM and upstream counter electrode, which reduced NO₃^- from 1.0 mM to below the EPAs regulatory MCL (700 μM) in a single pass through the REM (residence time ∼2 s), obtaining product selectivity of <2% toward NO₂^-/NH₃. Nitrate reduction was not affected by dissolved oxygen and carbonate species and only slightly decreased in a surface water sample due to Ca²⁺ and Mg²⁺ scaling. Energy consumption to treat surface water was 1.1 to 1.3 kWh mol^-1 for 1 mM NO₃^- concentrations, and decreased to 0.19 and 0.12 kWh mol^-1 for 10 and 100 mM NaNO₃ solutions, respectively. Electrocatalytic reduction kinetics were shown to be an order of magnitude higher than catalytic NO₃^- reduction kinetics. Conversion of up to 67% of NO₃^-, with low NO₂^- (0.7-11 μM) and NH₃ formation (<10 μM), and low energy consumption obtained in this study suggest that Pd-Cu/REMs are a promising technology for distributed water treatment.

Forward Osmosis Application in Manufacturing Industries: A Short Review

Forward osmosis (FO) is a membrane technology that uses the osmotic pressure difference to treat two fluids at a time giving the opportunity for an energy-efficient water and wastewater treatment. Various applications are possible; one of them is the application in industrial water management. In this review paper, the basic principle of FO is explained and the state-of-the-art regarding FO application in manufacturing industries is described. Examples of FO application were found for food and beverage industry, chemical industry, pharmaceutical industry, coal processing, micro algae cultivation, textile industry, pulp and paper industry, electronic industry, and car manufacturing. FO publications were also found about heavy metal elimination and cooling water treatment. However, so far FO was applied in lab-scale experiments only. The up-scaling on pilot- or full-scale will be the essential next step. Long-term fouling behavior, membrane cleaning methods, and operation procedures are essential points that need to be further investigated. Moreover, energetic and economic evaluations need to be performed before full-scale FO can be implemented in industries.

Measuring the benefits of using market based approaches to provide water and sanitation in humanitarian contexts

The use of cash transfers and market based programming (CT/MBP) to increase the efficiency and effectiveness of emergency responses is gaining prominence in the humanitarian sector. However, there is a lack of existing indicators and methodologies to monitor activities designed to strengthen water and sanitation (WaSH) markets. Gender and vulnerability markers to measure the impact of such activities on different stakeholders is also missing. This study identifies parameters to monitor, evaluate and determine the added value of utilising CT/MBP to achieve WaSH objectives in humanitarian response. The results of the work revealed that CT/MBP can be used to support household, community and market level interventions to effectively reduce transmission of faeco-oral diseases. Efficiency, effectiveness, sustainability, appropriateness and equity were identified as useful parameters which correlated to widely accepted frameworks against which to evaluate humanitarian action. The parameters were found to be directly applicable to the case of increasing demand and supply of point of use water treatment technology for a) disaster resilience activities, and b) post-crisis response. The need for peer review of the parameters and indicators and pilot measurement in humanitarian contexts was recognised.

Vibrational Spectroscopy as a Promising Toolbox for Analyzing Functionalized Ceramic Membranes

Ceramic materials find use in many fields including the life sciences and environmental engineering. For example, ceramic membranes have shown to be promising filters for water treatment and virus retention. The analysis of such materials, however, remains challenging. In the present study, the potential of three vibrational spectroscopic methods for characterizing functionalized ceramic membranes for water treatment is evaluated. For this purpose, Raman scattering, infrared (IR) absorption, and solvent infrared spectroscopy (SIRS) were employed. The data were analyzed with respect to spectral changes as well as using principal component analysis (PCA). The Raman spectra allow an unambiguous discrimination of the sample types. The IR spectra do not change systematically with functionalization state of the material. Solvent infrared spectroscopy allows a systematic distinction and enables studying the molecular interactions between the membrane surface and the solvent.

Quantitative design of emergency monitoring network for river chemical spills based on discrete entropy theory

Field monitoring strategy is critical for disaster preparedness and watershed emergency environmental management. However, development of such is also highly challenging. Despite the efforts and progress thus far, no definitive guidelines or solutions are available worldwide for quantitatively designing a monitoring network in response to river chemical spill incidents, except general rules based on administrative divisions or arbitrary interpolation on routine monitoring sections. To address this gap, a novel framework for spatial-temporal network design was proposed in this study. The framework combines contaminant transport modelling with discrete entropy theory and spectral analysis. The water quality model was applied to forecast the spatio-temporal distribution of contaminant after spills and then corresponding information transfer indexes (ITIs) and Fourier approximation periodic functions were estimated as critical measures for setting sampling locations and times. The results indicate that the framework can produce scientific preparedness plans of emergency monitoring based on scenario analysis of spill risks as well as rapid design as soon as the incident happened but not prepared. The framework was applied to a hypothetical spill case based on tracer experiment and a real nitrobenzene spill incident case to demonstrate its suitability and effectiveness. The newly-designed temporal-spatial monitoring network captured major pollution information at relatively low costs. It showed obvious benefits for follow-up early-warning and treatment as well as for aftermath recovery and assessment. The underlying drivers of ITIs as well as the limitations and uncertainty of the approach were analyzed based on the case studies. Comparison with existing monitoring network design approaches, management implications, and generalized applicability were also discussed.

Effects of Boiling Drinking Water on Diarrhea and Pathogen-Specific Infections in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis

Globally, approximately 2 billion people lack microbiologically safe drinking water. Boiling is the most prevalent household water treatment method, yet evidence of its health impact is limited. To conduct this systematic review, we searched four online databases with no limitations on language or publication date. Studies were eligible if health outcomes were measured for participants who reported consuming boiled and untreated water. We used reported and calculated odds ratios (ORs) and random-effects meta-analysis to estimate pathogen-specific and pooled effects by organism group and nonspecific diarrhea. Heterogeneity and publication bias were assessed using I2, meta-regression, and funnel plots; study quality was also assessed. Of the 1,998 records identified, 27 met inclusion criteria and reported extractable data. We found evidence of a significant protective effect of boiling for Vibrio cholerae infections (OR = 0.31, 95% confidence interval [CI] = 0.13-0.79, N = 4 studies), Blastocystis (OR = 0.35, 95% CI = 0.17-0.69, N = 3), protozoal infections overall (pooled OR = 0.61, 95% CI = 0.43-0.86, N = 11), viral infections overall (pooled OR = 0.83, 95% CI = 0.7-0.98, N = 4), and nonspecific diarrheal outcomes (OR = 0.58, 95% CI = 0.45-0.77, N = 7). We found no evidence of a protective effect for helminthic infections. Although our study was limited by the use of self-reported boiling and non-experimental designs, the evidence suggests that boiling provides measureable health benefits for pathogens whose transmission routes are primarily water based. Consequently, we believe a randomized controlled trial of boiling adherence and health outcomes is needed.

Enhanced flux performance of polyamide composite membranes prepared via interfacial polymerization assisted with ethyl formate

A novel thin film composite (TFC) polyamide reverse osmosis membrane was prepared via the interfacial polymerization of m-phenylene diamine (MPD) in aqueous phase and 1,3,5-trimesoyl chloride (TMC) in organic phase on a polysulfone ultrafiltration support by assisting with ethyl formate as a co-solvent added in the organic phase. The ethyl formate added in the organic phase is intended to form a narrow miscibility zone, which leads to the thicker reaction zone. The multi-layered loose polyamide structure with larger pore size was formed due to the thicker reaction zone and lower content of MPD. The enhanced hydrophilicity of the membrane was proved by the decreased water contact angle. Water flux was measured at 1.6 MPa with 2,000 ppm NaCl aqueous solution. Compared to the TFC membrane prepared without ethyl formate, the water flux across the TFC membrane with ethyl formate in the organic phase increased with the increased ethyl formate content (from 23 to 45 L/(m² h)) and the salt rejection remained at a high level (>90%). The ethyl formate can be used as a co-solvent to effectively enhance the performance of the TFC membrane.

Influence of extreme concentrations of hydrophilic pore-former on reinforced polyethersulfone ultrafiltration membranes for reduction of humic acid fouling

To address the issue of membrane fouling by ubiquitous humic substances, a hydrophilic pore-former-blended polyethersulfone UF membrane was successfully synthesized via the phase inversion method. For the first time, extremely high concentrations of polyvinylpyrrolidone (PVP), up to 20 wt%, were tested as the hydrophilic pore-former in order to determine the optimum concentration for humic acid fouling. Intrinsic membrane parameters such as permeability and selectivity were evaluated using a cross-flow UF filtration setup. Interestingly, as little as 1 wt% added PVP can significantly improve membrane permeability. That tiny amount of added PVP increased membrane flux to 1107 L/m²h·bar from zero flux, with over 90% rejection of humic acid. In addition, pure water permeation increased to over 2400 L/m²h·bar without sacrificing humic acid rejection (around 90%) when 10 wt% PVP was added; pure water permeation decreased to around 1000 L/m²h·bar as added PVP was increased to 20 wt%. The order of water flux increased with the amount of added PVP up to 20 wt% during humic acid fouling while maintaining membrane selectivity. However, the membrane with 10 wt% added PVP showed the best fouling resistance in terms of flux recovery ratio (98%), total flux loss, reversible fouling ratio, and irreversible fouling ratio. Therefore, the addition of 10 wt% PVP is recommended considering cleaning efficiency and the moderately high flux during humic acid fouling for field operation in wastewater reclamation and water treatment processes.

A novel gravity-driven nanofibrous membrane for point-of-use water disinfection: polydopamine-induced in situ silver incorporation

We report a facile method for preparing silver-loaded membranes for point-of-use disinfection and disaster relief applications. A bio-inspired material, polydopamine, was coated onto a highly porous nanofibrous polyacrylonitrile substrate. We then take advantage of the redox properties of polydopamine to form silver nanoparticles in situ. These nanoparticles were uniformly distributed on the surface of nanofibers with no apparent agglomeration at a silver loading up to 4.36 wt.% (cPAN-Ag1.5). The silver-incorporated membrane cPAN-Ag1.5 achieved a high pure water flux of 130 Lm⁻² h⁻¹ at 10-cm water head, demonstrating the feasibility of energy-efficient gravity-driven filtration and eliminating the need for electrical power. The strong anti-bacterial activity and high physical rejection of the membrane led to an excellent disinfection power, with no viable bacterial cells detected in its permeate water. The membrane exhibited >7 log reduction for E. coli and >6 log reduction for B. subtilis. The strategy reported here provides an efficient and green route to synthesize point-of-use membranes. Combining their excellent permeability and disinfection effectiveness, these membranes offer an ideal solution to water supply in disaster-affected areas.