Freshwater Scarcity Research Articles

Research on the application of hydrophilic modified covalent organic framework membranes in seawater desalination

Given the global challenge of freshwater scarcity, the importance of seawater desalination technology has grown. This study examines the efficiency and role of hydrophilic-modified covalent organic framework (COF) membranes in seawater desalination through molecular simulations. Incorporating hydrophilic groups like -SO3H into N2COF membranes and optimizing their structure significantly improved water permeability and salt ion retention. Non-equilibrium molecular dynamics (NEMD) simulations showed that hydrophilic modifications enhance water permeability while preserving salt ion interception efficacy. Furthermore, adjusting the membrane's stacking method could further enhance its seawater desalination performance. The simulations confirm the high-efficiency desalination capability of hydrophilic-modified COF membranes and offer crucial theoretical guidance for designing and preparing high-performance desalination materials.

Potential impacts of saline groundwater pumping on seawater intrusion in a coastal aquifer system

ABSTRACT Desalination plants employing feed water sourced from saline groundwater (SGW) are a feasible approach to tackle freshwater scarcity and seawater intrusion (SWI). Available studies lacked comprehensive analysis quantifying the impact of pumping from a coastal aquifer, on changes in solute transport mechanism. This study investigates the impact of different rates of SGW pumping on the solute transport in a coastal aquifer. A regional-scale model resembling the Upper Floridan aquifer was modelled using SEAWAT to quantify SWI variables. The study found that the length of intrusion of toe (Ltoe), width of mixing zone (WMZ) and residual salt mass (RSM) varied with dispersivity values. The ratio of saltwater to freshwater influx was unaffected by dispersivity values. Significant decrease in the toe-length occurred when the pumping rate was highest and the dispersivity was lowest. The WMZ was found to be the most sensitive SWI variable towards varying dispersivity, with 65% difference for higher pumping rates. The mid-bottom region was experiencing substantial modifications, leading to an inclined response at increased pumping rates, which suggested that the diluting process was primarily taking place in the bottom portion. This study gives insight into saline wedge movement in a coastal aquifer system which will benefit in the design of SGW well system for desalination plants.

New graphite fins efficacy on conical solar distiller performance: Experimental study with thermal, exergy, economic, and sustainability analysis

The pressing issue of freshwater scarcity in remote areas has stimulated the development of the performance of solar distillers as a means of desalinating saltwater. This was done by incorporating efficacy new graphite fins with basin of the conical solar distiller. The new graphite fins are characterized by their high thermal properties, so they represent thermal storage materials and are used to increase the surface area to absorb solar radiation and transfer heat. To get the optimal height of new graphite fins that achieve highest freshwater production, four different heights 1, 2, 3, and 4 cm of the new efficacy graphite fins were studied. To achieve this, three conical distillers were built with the same dimensions, the first is a classical conical distiller (CCD), and the second and third are the modified conical distiller with graphite fins (MCD-GF). The results presented that incorporating the new efficacy graphite fins that have 3 cm height with the basin of conical solar distiller represents a good choice, that causes improves the freshwater production, energy efficiency, exergy efficiency, and sustainability index by 97.37, 94.37, 574.1, and 18.6 % as compared to CCD. In addition, it reduces the cost of producing fresh water by 48.26 %.

Testing the performance of tubular solar still with flat basin, cords wick basin, and various angle of inclinations

Freshwater scarcity is a growing concern due to population expansion and industrial development. Solar stills offer a solution for generating potable water, although production volumes are limited. This research aims to address this challenge by improving the yield, thermal efficiency, and cost-effectiveness of freshwater production in tubular solar stills (TSS). We propose a novel approach that incorporates wick materials within the TSS design. This method involves creating a specific number of cuts (cracks) in a secondary basin liner positioned 2.5 cm above the original liner within the still. The upper liner is extended with wick, and wicking cords are suspended from edges and openings of this liner. These cords continuously remove saltwater, ensuring a consistently moist wick surface. The design of the wick cords optimizes water utilization and minimizes energy waste. The cords extract precisely the amount of saline water needed for evaporation, eliminating the loss or overflow of hot water. This approach maximizes wick efficiency without sacrificing freshwater production. The study investigates the performance of the TSS using 32 wick cords in conjunction with jute wick material. This modification to the conventional TSS offers a simple and cost-effective method to enhance productivity. Additionally, the glass cover of the still is tilted at an angle to facilitate the collection of distilled water droplets. ICWTSS was used as a code name for the modified TSS. After that, three distinct inclination angles (2°, 4°, and 6°) were examined, and the effectiveness of ICWTSS at each angle was contrasted with that of CSS. With a 6° angle of inclination, the ICWTSS showed a 67 % thermal efficiency and a 257 % increase in production over CSS.

Constructing Co3O4 nanosheet arrays anode as durable and efficient electrocatalyst for simultaneous chlorine evolution and carbamazepine degradation in the marine environment

The electrochemical chlorine evolution reaction (CER) is an essential and valuable technology for converting Cl− to Cl2 in industrial-scale applications. However, under the background of freshwater scarcity, seawater electrolysis for Cl2 generation becoming highly demanded. Meanwhile, pollutant degradation in the ocean is still challenging, especially in coastal and offshore seawaters. Herein, we provide a facile approach for constructing a highly efficient system for simultaneous Cl2 evolution and organic contaminant abatement utilizing Co3O4 nanosheet arrays decorated carbon cloth (Co3O4/CC) anode in the marine environment. The fabricated Co3O4/CC electrode achieved a considerably low potential of 1.55 V to reach a current density (j) of 10 mA cm−2 and long-term stability of 12 h at 100 mA cm−2 in seawater (pH = 2). Meanwhile, the practical environmental remediation results attested that the Co3O4 nanosheet arrays possess an outstanding Carbamazepine (CBZ) degradation efficiency of 100 % within 6 min accompanied with a k value of 0.358 min−1 in real seawater, demonstrating the integrity and reusability. The overall findings offer new insight into designing highly active CER catalysts with efficient pollutant degradation in the marine environment.

Supplemental greenhouse lighting increased the water use efficiency, crop growth, and cutting production in Cannabis sativa.

The expanding cannabis production sector faces economic challenges, intensified by freshwater scarcity in the main US production areas. Greenhouse cultivation harnesses sunlight to reduce production costs, yet the impact of greenhouse light levels on crucial production components, such as plant growth, branching, and water use efficiency (WUE), remains poorly understood. This study aimed to assess the effects of combined sunlight and supplemental lighting on the crop's main production components and leaf gas exchange of Cannabis sativa 'Suver Haze' in the vegetative stage. Within a greenhouse, LED lighting provided at intensities of ~150, 300, 500, and 700 µmol m-2 s-1 (18-hour photoperiod), combined with solar radiation, resulted in average daily light integrals of 17.9, 29.8, 39.5, and 51.8mol m-2 d-1. Increasing light levels linearly increased biomass, leaf area, and the number of branches per plant and square meter, with respective rates of 0.26g, 32.5 cm2, and 0.41 branches per mole of additional light. As anticipated, crop evapotranspiration increased by 1.8-fold with the increase in light intensity yet crop WUE improved by 1.6-fold when comparing the lowest and highest light treatments. Moreover, water requirements per unit of plant biomass decreased from 0.37 to 0.24 liters per gram when lighting increased from ~18 to 52mol m-2 d-1, marking a 35% reduction in evapotranspiration. These results were supported by increments in leaf photosynthesis and WUE with light enhancement. Furthermore, our findings indicate that even 52mol m-2 d-1 of supplemental lighting did not saturate any of the crop responses to light and can be economically viable for cannabis nurseries. In conclusion, light supplementation strongly enhanced photosynthesis and plant growth while increasing WUE. Additionally, a comprehensive discussion highlights the shared physiological mechanisms governing WUE in diverse plant species and their potential for water conservation under enhanced lighting conditions.

The efficiency of chlorophyll fluorescence as a selection criterion for salinity and climate aridity tolerance in barley genotypes.

In the Near East and North Africa (NENA) region, crop production is being affected by various abiotic factors, including freshwater scarcity, climate, and soil salinity. As a result, farmers in this region are in search of salt-tolerant crops that can thrive in these harsh environments, using poor-quality groundwater. The main staple food crop for most of the countries in this region, Tunisia included, is barley. The present study was designed to investigate the sensitivity and tolerance of six distinct barley genotypes to aridity and salinity stresses in five different natural field environments by measuring their photosynthetic activity. The results revealed that tolerant genotypes were significantly less affected by these stress factors than sensitive genotypes. The genotypes that were more susceptible to salinity and aridity stress exhibited a significant decline in their photosynthetic activity. Additionally, the fluorescence yields in growth phases J, I, and P declined significantly in the order of humid environment (BEJ), semi-arid site (KAI), and arid environment (MED) and became more significant when salt stress was added through the use of saline water for irrigation. The stress adversely affected the quantum yield of primary photochemistry (φP0), the quantum yield of electron transport (φE0), and the efficiency by trapped excitation (ψ0) in the vulnerable barley genotypes. Moreover, the performance index (PI) of the photosystem II (PSII) was found to be the most distinguishing parameter among the genotypes tested. The PI of sensitive genotypes was adversely affected by aridity and salinity. The PI of ICARDA20 and Konouz decreased by approximately 18% and 33%, respectively, when irrigated with non-saline water. The reduction was even greater, reaching 39%, for both genotypes when irrigated with saline water. However, tolerant genotypes Souihli and Batini 100/1B were less impacted by these stress factors.The fluorescence study provided insights into the photosynthetic apparatus of barley genotypes under stress. It enabled reliable salinity tolerance screening. Furthermore, the study confirmed that the chlorophyll a fluorescence induction curve had an inflection point (step K) even before the onset of visible signs of stress, indicating physiological disturbances, making chlorophyll fluorescence an effective tool for identifying salinity tolerance in barley.

Barriers and drivers to the development of an effective water reuse chain: insights from an Italian water utility

AbstractWidespread adoption of water reuse technologies is critical to the development of a circular economy and to reduce the pressure on increasingly scarce freshwater resources. However, the adoption of water reuse technologies involves a complex and multi-level decision-making process, influenced by different factors that hinder or support such adoption, namely barriers and drivers. The present research provides a first identification of such factors from a value chain perspective. To do so, the paper first conceptualises the water reuse value chain, including the actors and stages required to bring collected wastewater to the reuse destination. It then conducts an exploratory case study in the context of an Italian water utility facing increasing water stress. External barriers such as societal perceptions and lack of demand for recycled water emerge as particularly influential in hindering the adoption of water reuse technologies. Drivers emerge from both the external and internal environment, with the level of water scarcity and the effectiveness of collaboration and coordination between different institutional and policy actors being particularly strong. Barriers and drivers are found to be of varying relevance depending on the characteristics of the facilities and the reuse value chain analysed, including the operational status of the reclamation facility, the type of final reuse, and the roles in the value chains. The paper provides relevant implications for academics, policymakers, and adopters of water reuse technologies for a more circular and environmentally sustainable water sector, offering useful insights for decision-makers in related sectors. Graphical abstract

All‐In‐One Self‐Floating Wood‐Based Solar‐Thermal Evaporators for Simultaneous Solar Steam Generation and Catalytic Degradation

AbstractSolar‐driven steam generation has emerged as a sustainable technology for addressing freshwater scarcity. However, significant challenges still exist in developing high‐performance, multifunctional evaporators that are adept at both efficiently evaporating water and degrading pollutants, primarily because of the trade‐offs among functional designs. Here, a self‐floating solar evaporator is reported by functionalizing balsa wood with solar‐thermal conversion material carbon nanotubes and catalytic manganese dioxide (MnO2) nanoflowers for simultaneous solar evaporation and pollutant degradation. MnO2 nanoflowers are rich in oxygen vacancies that can effectively activate peroxymonosulfate to generate reactive oxygen species for efficient organic pollutant degradation. A distinctive non‐wetted porous interior structure and a precisely targeted water pathway are spontaneously established in the multifunctional evaporator, ensuring fast water supply, thermal insulation, efficient mass transfer, and high buoyancy. The resulting evaporators successfully combine an impressive evaporation rate of 2.74 kg m−2 h−1, a high pollutant degradation efficiency (98.3% for 100 mg L−1 tetracycline and 97.4% for 200 mg L−1 Methyl orange), and stable self‐floating and self‐standing capabilities that ensure long‐term operation stability even in complex real‐world environments. This work provides an approach to design multifunctional solar evaporators, ensuring strong alignment with practical requirements while expanding their potential application scenarios.

Groundwater vulnerability assessment of elevated heavy metal contamination related health hazard in coastal multi-aquifers of Sundarban Biosphere Reserve, India

The concept of groundwater (GW) vulnerability emerged as a response to the escalating contamination of GW globally. Over recent decades, both scholars and policymakers have extensively utilized GW vulnerability assessments to safeguard groundwater from pollution. Within the Sundarban Biosphere Reserve (SBR), inhabitants residing near coastal aquifers face significant challenges, notably the scarcity of fresh water during the hot and dry season. Furthermore, there is a concern regarding the presence of heavy metals (HMs) in this region, adversely impacting GW quality. In both Indian and global contexts, HM contamination, including arsenic (As), fluoride (F‾), and nitrate (NO3–), and its repercussions on human health (HH) in coastal districts, represent critical issues. In light of these challenges, this study aims to assess GW vulnerability and its implications for HH in SBR utilizing the Hazard Quotient (HQ) approach. Fifteen hydro-geochemical parameters have been selected for this research endeavor. Various statistical indices, such as “groundwater quality index (GWQI)”, “degree of contamination (CD)”, “index of ecological risk (ERI)”, and “human health hazard index (HHHI)”, have been employed to accomplish the study objectives. Piper's and Box plot diagrams were utilized to assess hydrogeochemical properties and GW quality. The findings reveal average concentrations of HMs, such as As, NO3–, and F‾ in the study area, to be 0.204 mg/l, 6.28 mg/l, and 0.79 mg/l, respectively. Among all variables, a positive correlation of 0.876 is observed between electrical conductivity (EC) and sodium ions (Na+). Eventually, the outcomes of this study can provide valuable insights for planners and policymakers to make informed decisions regarding the sustainable management of water resources.

Manipulating 2D Membrane Interlayer Channels with Accelerated Mass-Transfer Behavior to Boost Solar Desalination.

The scarcity of fresh water necessitates sustainable and efficient water desalination strategies. Solar-driven steam generation (SSG), which employs solar energy for water evaporation, has emerged as a promising approach. Graphene oxide (GO)-based membranes possess advantages like capillary action and Marangoni effect, but their stacking defects and dead zones of flexible flakes hinders efficient water transportation, thus the evaporation rate lag behind unobstructed-porous 3D evaporators. Therefore, fundamental mass-transfer approach for optimizing SSG evaporators offers new horizons. Herein, a universal multi-force-fields-based method is presented to regularize membrane channels, which can mechanically eliminate inherent interlayer stackings and defects. Both characterization and simulation demonstrate the effectiveness of this approach across different scales and explain the intrinsic mechanism of mass-transfer enhancement. When combined with a structurally optimized substrate, the 4Laponite@GO-1 achieves evaporation rate of 2.782kg m-2 h-1 with 94.48% evaporation efficiency, which is comparable with most 3D evaporators. Moreover, the optimized membrane exhibits excellent cycling stability (10 days) and tolerance to extreme conditions (pH 1-14, salinity 1%-15%), verifies the robust structural stability of regularized channels. This optimization strategy provides simple but efficient way to enhance the SSG performance of GO-based membranes, facilitating their extensive application in sustainable water purification technologies.

Unveiling 4500 years of environmental dynamics and human activity at Songo Mnara, Tanzania

Coastal East Africa has undergone massive transformations through the Late Holocene, with a combination of changes in sea level, increasing human settlement, and ensuing use of coastal resources. A comprehensive multi-proxy analysis, including pollen, phytolith, charcoal, stratigraphy, particle size, and geochemical data from sedimentary cores extracted from mangrove ecosystems combined with soils from archaeological contexts, provided valuable insights into vegetation dynamics, environmental changes, and human interactions within the mangrove ecosystem of Songo Mnara Island, Tanzania over the last 2590 BCE (4540 cal yr BP). The bottommost layers indicate a lack of vegetation, as deduced from the presence of coral rags and high calcium and carbonate content, possibly due to high mid-Holocene sea-level. Evidence of mangrove taxa suggests a decrease in sea level, enabling the establishment of mangroves from around 2590 BCE. A brief period of sea-level rise occurred between 90 BCE and 320 CE before sea-level fell until 1570 CE. Significant evidence of human activity is recorded from around 1400 CE indicated by increased charcoal, crop phytoliths, and evidence of marine resource utilisation. The timing of this human-environment interaction is also linked to the time of lower sea level. However, there was evidence suggesting human abandonment of the island from around 1500 CE. This coincided with a subsequent rise in sea levels and potentially prolonged drought conditions spanning from 1570 to 1700 CE. These factors likely contributed to a shortage of food resources in the area, impacting both agricultural practices due to the scarcity of natural freshwater and the accessibility of marine food resources. From 1700 CE to the present, fluctuations in sea level have been observed, with a signal of recent sea-level rise in tandem with shifts in mangrove, terrestrial herbaceous taxa and fire activity.The low sedimentation rates within mangrove areas suggest that the mangroves on Songo Mnara Island may not keep pace with the current rate of sea-level rise.

Wastewater irrigation beneath the water table: analytical model of crop contamination risks

Wastewater irrigation alleviates freshwater scarcity. However, conventional (near)surface irrigation techniques directly expose crops to contaminants. Irrigating wastewater into shallow phreatic zones to raise the water table enhances groundwater evapotranspiration, while using the vadose zone as a bioreactor that attenuates contaminants through dilution, adsorption, and biodegradation. Nevertheless, contaminants may spread across the groundwater, soil, and vegetation. In this study, we focus on the crop contamination risks, and derive a simple analytical model to estimate crop solute uptake. Although crops are not directly exposed to the irrigated wastewater, contaminants (and nutrients) may spread to the root zone. Results show that crop contamination is primarily determined by the root zone water balance, and by solute dispersion and biogeochemical reaction parameters. The model contributes towards identifying hydrogeologically and climatically suitable locations for phreatic zone wastewater irrigation, determining acceptable levels of irrigation water quality, and evaluating crop contamination hazards against the fertigative value of wastewater.

Condensation of water on PDMS-coated copper surfaces for fresh water harvesting

With an increased need to solve fresh water scarcity for humanity in many places around the world, dew water harvesting is one promising approach to improve the situation. While condensation from humid air has been a research topic for many years, it is still unclear how surface wettability influences the condensation efficiency and the fresh water harvest. In this work, we contribute to bridging this knowledge gap by comparing the condensation efficiency of PDMS-coated hydrophobic and uncoated hydrophilic surfaces. We characterize the humid air velocity field to enable comparability of the present results on condensation efficiency with the results gained at other conditions. In addition, the surface wetting behavior prior to and after the condensation experiment is investigated to analyze the PDMS-coating longevity and allow to draw conclusions on their suitability for long term use in condensation applications.

Exergy, exergo-economic, environmental and sustainability analysis of pyramid solar still integrated hybrid nano-PCM, black sand, and sponge

A sustainable and cost-effective technique for desalinating water with solar energy to alleviate the freshwater scarcity is the solar still. In this study, four different cases including the case-I: conventional solar still (CSS), case-II: CSS with fins and black sand, case-III: CSS with fins, hybrid enhanced nano PCM, black sand and sponges, case-IV: CSS with fins, hybrid enhanced nano PCM, crushed stone and sponges have been comprehensively investigated in terms of thermal, productivity, exergy, economic, environmental and sustainability point of view. The assessments were executed at the Rajshahi (latitude: 24°22′N, longitude: 88°36′E), Bangladesh. Later, the performance case-III was investigated by using river (Padma) water and discolored water, respectively. Average thermal efficiency on daily basis of case-III is about 32.44 % and 6.47 % higher than case-II and case-IV due to the improved heat storing configuration. In addition, cases-II, III, and IV all had exergy efficiency improvements of 18.89 %, 74.75 %, and 53.54 %, correspondingly in comparison to case-I. For cases I, II, III, and IV, the payback periods are 185, 159, 126, and 135 days, accordingly. In cases-I, II, III, and IV, modified SS results in cost-per-litre reductions of 73.5 %, 77.29 %, 81.89 %, and 80.63 %, correspondingly, as compared to market prices. Cases-I, II, III, and IV's energy production factors are 0.137, 0.099, 0.138, and 0.195 yr−1, respectively. The research also supports the claim that adding fins, sponges, black sand, and hybrid enhanced nano-PCM to CSS results in a higher sustainability index.

Nondestructive testing on concrete-based treated wastewater

Recycled wastewater in construction presents an opportunity to ease freshwater scarcity while advancing sustainability. This study investigated the influences of cement-type and treated wastewater source on setting time and mechanical properties of cement paste and mortar. Three cement types: ordinary Portland cement (CEM I), CEM III/A, and CEM IV/A-P, were encountered. Four plants treated wastewater versus potable water as control were included. Fifteen mixes were encountered; every 5 mixes addressed certain cement types along with specified treated water types. Two phases were designed: Phase I for pastes toe value setting time and Phase II for the mortar to evaluate the flexural and compressive strengths of tool 90 specimens, 6 at 2 and 28 days of age. The significant impact of both variables was observed. CEM III/A displayed the fastest setting among the other mixes, while CEM I was the slowest. Wastewater accelerated setting versus distilled water. The mechanical performance also varied based on the cement–wastewater combination. CEM IV/A-P provided optimal strength enhancement up to 50% in flexural and 35% in compressive strength with wastewater compared to CEM I control. Results were attributed to cement–water interactions influencing hydration and microstructure, while CEM I underperformed with wastewater, CEM III/A, and CEM IV/A-P benefits, especially at early ages. Considerable variability highlights the complex interplay of factors governing performance. Coupled chemical-microstructural analysis was recommended to elucidate underlying mechanisms. Overall, tailored cement–wastewater selection shows promise for sustainable concrete, pending further optimization and durability testing. The study provides a platform for context-specific development of eco-efficient construction materials utilizing locally available resources.

Fresh, hardened, durability and microstructure properties of seawater concrete: A systematic review

Seawater concrete (SWC) is an environmentally friendly construction material that addresses freshwater scarcity concerns by utilising seawater as a mixing water source. This review study comprehensively examines SWC by focusing on its fresh properties, hardened properties, seawater composition, microstructure and porosity, hydration process, durability, test methods and electrical resistivity. The study analyses the influence of additives and admixtures on SWC’s performance by considering constituents such as cement, aggregates and seawater. It also explores the impact of manufacturing techniques, including mix design. The potential of SWC is revealed and compared with that of conventional concrete by evaluating and comparing their mechanical properties, such as compressive strength, modulus of elasticity, stress-strain behaviours, tensile strength and flexural strength. This study primarily aims to thoroughly examine the characteristics of SWC in its fresh and hardened states. It also assesses the advantages and drawbacks of seawater as a mixing water source. Moreover, this study delves into the impact of seawater composition on crucial aspects, such as the hydration process, microstructure and porosity of concrete. It also used various test methods to explore SWC durability, including resistance to chloride ingress, sulphate attack and carbonation. Furthermore, the importance of electrical resistivity for corrosion prevention is discussed in this study. The carbon-negative cement production and carbonation curing of seawater concrete underscore groundbreaking advancements, emphasizing sustainability and climate mitigation in the construction industry. Overall, this study aims to enhance the comprehension of SWC and provide valuable insights for engineers, researchers and policymakers in concrete technology.

Assessment of synthetic series to design the capacity of flow regulation reservoirs

Freshwater scarcity is perceived as a global systemic risk. Intending to reach water secutiry, flow regulation reservoirs are alternatives to improve streamflow and water storage, especially in places where demand exceeds water availability during periods of drought. However, the unavailability of historical series of flows in watersheds makes the adequate design of reservoirs difficult. To overcome such difficulties, synthetic series of flows are currently being generated for the specific sections of the watercourses where these structures are to be designed. The present study aimed to evaluate two methods of generating synthetic series of flows applied to design the capacity of flow regulation reservoirs in conditions of limited data. A monitored hydrological region (Itapemirim River Basin, Espírito Santo, Brazil) and synthetic flow series generated according to the methodologies of Rodrigues (2017) and Cesconetto (2021) were used. The methodologies were tested by cross-validation, and the results were compared using graphs and statistical indicators to the results obtained with observed data, measured in fluviometric reference stations. After analyzing the statistical indicators, such as the coefficient of determination (R2), the Nash-Sutcliffe efficiency index (NSE), and the reservoir design quality index (IQD), it was concluded that the method proposed by Cesconetto (2021) showed a tendency to under-design the capacities of the reservoirs, mainly for lower flows to be regularized (β < 0.75). The method proposed by Rodrigues (2017) performed better than the method proposed by Cesconetto (2021) for the design of the capacity of flow regulation reservoirs under conditions of limited data in the Itapemirim River Basin.

Comparative analysis of greywater recycling and rainwater harvesting as supplementary water sources for conventional urban and tourist resort water supplies

Freshwater scarcity combined with high water demand from rapid urbanization, population growth, and changing consumption has resulted in increasing stress on urban water supply systems. Seasonal fluctuations in the population of tourist destinations are especially evident in tourist resorts. Greywater recycling and rainwater harvesting have been proposed as the most widely used valuable strategies to address water scarcity. By taking the conventional water supply system and the water supply of tourist resorts as examples, this study systematically compares and analyzes the advantages and limitations of greywater recycling and rainwater harvesting by enumerating the stress of water supply in different systems, discussing the benefits of both strategies and comparing the differences when using them for tourist destinations. The results showed that pumping systems or elevated tanks used to meet the water supply needs of high-rise buildings pose energy challenges. The water use characteristics of tourist resorts cause it to be closely related to the seasonal influx of tourists. Greywater recycling is more effective than rainwater harvesting in mitigating tourist resorts' water shortage problem. Suggestions for ways to implement these strategies for different regions are also given to make informed decisions about water distribution efforts. This study provides a reference for sustainable urban water resource management.

Black Silver-Decorated liquid metal nanofillers coupled with Glycerol-Modified hydrogel composites for high efficiency solar steam generation and thermoelectric conversion

Solar-driven interfacial evaporation (SDIE) holds great potential in alleviating global freshwater scarcity, which requires the design of efficient energy conversion devices. Herein, a quadruply engineered hydrogel-based evaporator is developed based on multipath regulation of the four key processes involved in SDIE, i.e., heat generation, energy utilization, water transportation, and evaporation. Surface-tailored liquid metal nanoparticles (EGaIn@Ag NPs) with a high photothermal conversion efficiency (PCE) of 30.4 % serve as the nanofiller to produce heat efficiently. Vertically aligned microchannels are constructed in the poly(vinyl alcohol) (PVA) hydrogel through directional freezing to accelerate water transportation. Glycerol is introduced to the PVA matrix to synergistically a) prevent heat loss from the interface to bulk water, and b) modulate the bonding state of water in the hydrogel to reduce the vaporization enthalpy. Such an elaborate design achieves a rather high evaporation rate of 3.26 kg m−2h−1 under 1 sun illumination. The hydrogel evaporator (EGaIn@Ag/PVAG) is applicable in treating real seawater and dye-contaminated sewages, showing favorable desalination durability and self-cleaning property. The synergistic design also imparts the hydrogel with thermoelectric power generation capabilities. This work offers a new insight into the synergistic design of SDIE devices, which is expected to inspire innovations in solar energy conversion and utilization.