Freshwater Scarcity Research Articles

Graphene crown pore for efficient heavy metal ion Removal: Protonated vs. Non-protonated

The rapid progression of industrialization has significantly intensified the contamination of water resources by heavy metal ions, thereby exacerbating the global challenge of water scarcity. Aiming at solving this pressing issue of worldwide freshwater scarcity, nanomaterial and nanotechnology show a pivotal alternative in wastewater treatment. In this study, we construct distinct graphene nanosheets with varying shaped and sized pores (named as graphene crown pores) and assess the protonation of the pore edges to the heavy metal ion removal capacity. Employing molecular dynamics (MD) simulations, we demonstrate that protonated graphene nanopores exhibit exceptional water permeability and outstanding ion rejection rates. Moreover, our free energy calculations confirm that water molecules encounter a lower energy barrier compared to ions when traversing through graphene crown pores. Furthermore, the non-protonated graphene pores allow faster water permeance while compromising the ion rejection, yielding a dissatisfactory performance of metal ion removal. Detailed analysis suggest that the protonated pore endows the pore with a positively charged center, obstructing the passage of heavy metal ions. Therefore, our findings not only propose the protonated graphene crown pores for efficient heavy metal ion removal but also reveal the corresponding molecular mechanism, which is useful for future application of such membranes for heavy metal ion removal.

Wicking-controlled interfacial water content for highly efficient solar desalination

Solar-driven interfacial evaporation offers a potential solution to address global freshwater scarcity. However, the water-thermal-vapor-salt imbalance issue severely affects the operating efficiency of the evaporator. This research examines the correlation among water supply height, spontaneous wicking rate, and interfacial water content. Subsequently, an engineering strategy is proposed to control the water concentration gradient within a two-dimensional solar absorber with vertical water supply channels. The results demonstrate that the hydrophilicity and internal structure of the material exert a crucial influence on the transport of bulk water. Specifically, longitudinal stripes within the water-conducting material promote a faster wicking rate and higher wicking height. This phenomenon occurs due to the combined effects of capillary forces and gravity, leading to a gradual decrease in liquid saturation along the capillary direction within the water-conducting material. By optimizing the water supply height and rate, the evaporation interface achieves a remarkable water evaporation rate of 1.50 kg m−2h−1. Building on this success, a novel configuration for a flow desalination evaporator is proposed, capable of sustaining the same evaporation rate even when operating continuously for 9 h in saltwater with a mass concentration of 20 %. Overall, this study emphasizes the importance of water and heat balance at the evaporative interface, reconciling conflicting requirements of interface flow and evaporation rate. These findings contribute to the development of highly efficient and reliable evaporators for sustainable freshwater generation.

Desalination brines as a potential vector for CO2 sequestration in the deep sea

Freshwater scarcity, driven by population growth and climate change, is increasingly mitigated by seawater desalination, globally. As an energy-intensive process, desalination is a substantial source of atmospheric CO2. Nevertheless, desalination may hold a potential for ocean-based atmospheric carbon removal. Here we describe, for the first time, the carbonate chemistry of desalination brines near the submerged marine outfalls of a large desalination plant, their unique CO2 buffering capacity, and potential for deep sea carbon sequestration. We show that reverse osmosis acts as a carbon concentration factory and that the high-density brine plumes could create a vector for long-term CO2 removal to the deep sea below the seasonal thermocline. At present desalination capacity, we estimate that Desalination Assisted Carbon Concentration (DACC) and Carbon Dioxide Removal (CDR) could potentially remove 3.8 Mton CO2/year globally, with a negligible contribution to ocean acidification. This mechanism partially mitigates the high carbon print associated with desalination. SynopsisDesalination reject brines pose environmental challenges upon disposal to sea, but due to their unique properties, may become an opportunity for long-term carbon sequestration.

Iron diselenide/carbon black loaded mushroom-shaped evaporator for efficiently continuous solar-driven desalination

Solar-driven desalination is an environmentally sustainable method to alleviate the problems of freshwater scarcity and the energy crisis. However, how to improve the synergy between the photothermal material and the evaporator to achieve high photothermal conversion efficiency simultaneously, excellent thermal management system and good salt resistance remains a challenge. Here, a mushroom-shaped solar evaporation device is designed and fabricated with iron diselenide/carbon black (FeSe2/CB) coated cellulose acetate (CA) film as mushroom surface and cotton swab as mushroom handle, which presented high solar-driven evaporation and excellent salt resistance. Thanks to the unique photothermal effect and the synergistic effect, the FeSe2/CB composites enabled a promising photothermal conversion efficiency of up to 65.8 °C after 180 s. The mushroom-shaped evaporation device effectively overcomes water transport and steam spillage channel blockage caused by salt crystallization through its unique vertical transport water channels and conical air–water interface. When exposed to real sunlight, the solar evaporation rate of the steam generation structure reached as high as 2.03 kg m−2 h−1, which is more than 13 times higher than natural evaporation. This study offered new insights into the higher solar-driven evaporation rate and salt-blocking resistance of the FeSe2/CB mushroom-shaped solar evaporation device for solar-powered water production.

Ruthenium Oxide Nanoparticles Immobilized on Ti3C2 MXene Nanosheets for Boosting Seawater Electrolysis.

Seawater electrolysis represents a viable alternative for large-scale synthesis of hydrogen (H2), which is recognized as the most promising clean energy source, without relying on scarce fresh water. However, high energy cost and harmful chlorine chemistry in seawater limited its development. Herein, an effective catalyst based on a ruthenium nanoparticle-Ti3C2 MXene composite loaded on nickel foam (RuO2-Ti3C2/NF) with an open, fine, and homogeneous nanostructure was devised and synthesized by electrodeposition for high performance and stable overall seawater splitting. To drive a current density of 100 mA cm-2, the RuO2-Ti3C2/NF electrode required a small overpotential of 85 and 351 mV for HER and OER in 1 M KOH with only a slight increase in 1 M KOH seawater (156 and 378 mV for, respectively, HER and OER). An assembled RuO2-Ti3C2/NF-based two-electrode cell required an overpotential of only 1.84 V to acquire 100 mA cm-2 in 1 M KOH seawater and maintained its activity for over 25 h. This low cell voltage effectively prevented chlorine electrochemical evolution without anode protection. These promising results open up new avenues for the effective conversion of abundant seawater resources to hydrogen fuel.

Biofilm dynamic changes in drip irrigation emitter flow channels using reclaimed water

Reusing reclaimed water through drip irrigation offers an effective way to overcome freshwater scarcity. However, biofilm accumulation in the flow channel of drip emitters is the primary obstacle. So far, biofilm development in the emitters remains largely unknown. Here, industrial computed tomography was used to quantify the emitter biofilm developments. Results showed that biofilm typically accumulated in the inlet of the emitter flow channel and decreased toward the flow direction. Biofilm was also typically accumulated in dead areas having low flow velocities, such as edge, corner, and adjacent surface zones in flow channels. The dynamics of the emitter biofilm variation mechanisms were also elucidated. Specifically, particle and nutrient transport appeared to be dominant in shaping the initial biofilm formation (i.e., 5% emitter clogging degree), resulting in biofilm abundant in the inlet of the flow channel. However, it changed the hydraulic conditions in emitter flow channels, increased local water shear stress, which made the biofilm easier to be washed away in the inlet, and caused biofilm to grow faster in the middle and outlet regions of the flow channel at 20% emitter clogging degree. At 50% clogging degree, biofilm in inlet regions grew faster again. Finally, some biofilm control approaches such as water quality management and emitter flow channel structure optimization were proposed. This study provided a better understanding of biofilm formation mechanisms in the emitter flow channels, which is critical for designing appropriate biofilm control technologies and will facilitate the reuse of reclaimed water in agricultural irrigation.

Highly dispersed ultrasmall BiOCl nanoclusters on graphene sheets as high-performance anion-capture electrode for hybrid capacitive deionization

BiOCl nanomaterials, because of their unique layered structure and fascinating physicochemical properties, have attracted enormous attention as anode material for capacitive deionization (CDI) towards the relief of global freshwater scarcity. However, the synthesis of ultrasmall BiOCl nanoclusters remains a considerable challenge, while the effect of crystalline surfaces on the Cl− ion intercalation/deintercalation has not yet been explored so far. In this work, highly dispersed BiOCl nanoclusters with the predominant exposure of (110) and (101) planes on graphene sheets (BiOCl@G) are fabricated by nanoconfinement and air-plasma strategy. On one hand, the ultrasmall BiOCl nanoclusters with size of ∼3 nm significantly increased their atomic utilization and electrochemical active sites, whereas the preferred crystalline planes of (110) and (101) favored the Cl− intercalation/deintercalation process within BiOCl. On the other hand, the dominant mesopores, along with a large interlayer distance (∼0.4 nm) between exfoliated graphene sheets, ensured the fast ion transport-adsorption at BiOCl/solution interface. With these novel structural features, the BiOCl@G possesses excellent figure-of-merits in terms of the Cl−-adsorption capacity (109.8 mg g−1), adsorption rate (0.110 mg g−1 s−1), energy consumption, and CDI cycling stability. These results provide new fundamental insights for developing high performance BiOCl-graphene nanocomposites used in CDI desalination and beyond.

Investigation of conical passive solar still by incorporating energy metrics, efficiency, and sensitivity analyses for sustainable solar distillation

The application of solar energy technology to solve the freshwater scarcity problem of society will contribute to the sustainable development goal of the United Nations. It will also recede the dependency on fossil fuels. This paper deals with the investigation of conical passive solar still (CPSS) by incorporating energy metrics, efficiency, and sensitivity analyses. Fundamental equations have been obtained from the thermal modelling of CPSS followed by experimental validation. The coefficient of correlation for water temperature is about 0.96, for condensing surface temperature is about 0.99 and for freshwater yield is also 0.99. The present work involves diverse monthly weather conditions for the performance analysis of CPSS. In the present work, a MATLAB-based computational code is used to compute hourly freshwater output, exergy, and energy assessment for their yearly results. Afterward, energy metrics and different efficiencies were computed, and the outcomes were compared with recent investigations. Finally, the energy payback time has been lowered by 161.40%. The energy production factor and life cycle conversion efficiency for CPSS were improved by 61.71% and 28.20%, respectively, compared with the conventional solar still. The comparative study of daily thermal efficiency reveals that the efficiency of CPSS is higher by 51.47% than V-type solar still.

WATER QUALITY PARAMETERS PREDICTION OF TIGRIS RIVER USING SENTINEL-2 DATA AND LASSO REGRESSION

Abstract. Water-related issues have become a growing concern due to the impact of human activities and climate change unpredictability, and Iraq faces a significant challenge with freshwater scarcity and poor quality. Field measurements are expensive, while remote sensing is a cost-effective alternative. This study aimed to monitor the water quality of the Tigris River in Baghdad using Sentinel-2 satellite images. The study employed the least absolute shrinkage and selection operator (LASSO) and field data from 14 different stations during 2018 and 2019 to measure water quality parameters, including temperature (Temp), electrical conductivity (Cond), total dissolved solids (TDS), potential of hydrogen (pH), turbidity (Turb), Chlorophyll-a (Chl_a), Blue-Green Algae (BGA), and Dissolved Oxygen (DO). The incorporation of spectral indices significantly improved the models’ effectiveness, with R2 greater than 0.8, except for Cond, which was 0.73. Water Quality Index (WQI) based on Iraqi standards was estimated and showed that the river water quality was categorized as poor and very poor. This approach can enhance water resource management and decisionmaking in areas where traditional monitoring approaches may be challenging and costly.

Influence of desalination concentrate medium on microalgal metabolism, biomass production and biochemical composition

AbstractReverse osmosis is currently the most promising method for addressing freshwater scarcity in numerous nations, enabling the production of drinkable water for human consumption. This process, however, generates a byproduct stream, known as desalination concentrate (DC), that is enriched with high concentrations of salts such as Na+ and Cl−, moderate levels of SO42−, Mg2+, Ca2+ and K+ and trace levels of Si, Fe3+, NO3− and PO43−, which can be suitable and valuable for microalgal metabolism and growth. Salt concentration in DC can significantly influence microalgal growth via effects through osmotic shock, salt stress and cellular ionic ratios. Under certain conditions, these salinity changes can have a positive impact on microalgal metabolism, such as the synthesis of lipophilic compounds that include lipids, fatty acids and carotenoids. This mini‐review aims to provide up‐to‐date information of recent studies conducted towards the use of DC as a potential substrate for microalgal cultivation as well as to summarize the response mechanism of microalgae when cultured in DC. Several laboratory‐based studies have examined the effect of different DC concentrations on the biochemical composition of microalgae grown either in photobioreactors or in raceway ponds. These studies have uncovered significant effects of DC on the synthesis of proteins, amino acids and phycocyanin in freshwater species like Chlorella vulgaris and Arthrospira platensis, where DC tends to hinder these processes. Conversely, experiments with halophilic Dunaliella salina and marine Nannochloropsis gaditana have demonstrated that increasing DC concentration can positively influence the production of β‐carotene, lipids and specific saturated fatty acids (C16:0 and C18:0), suggesting that these species can adapt to a broader range of DC salinities. Cultivating salinity‐tolerant microalgae in DC would greatly reduce the production cost of algal‐based products, offering a promising approach to enhance the profitability of desalination and microalgal industries. © 2023 Society of Chemical Industry (SCI).

ASSESSMENT OF THE CURRENT SPATIOTEMPORAL VARIATIONS OF TOTAL SUSPENDED SOLID ON THE SURFACE WATERS OF KUALA PERLIS, PERLIS

Rivers are vital water sources for human existence and environmental health. Due to freshwater scarcity, monitoring river water quality is crucial, especially concerningtotal suspended solids (TSS), which pose potential risks to health and the environment. Despite this importance, there is a lack of assessment of spatiotemporal TSS variation in Malaysia, particularly in Sungai Kuala Perlis. This study aims to evaluate spatial-temporal TSS variations in the surface water of Kuala Perlis, Perlis. Sampling points were GPS recorded in December 2021. Five sites were established for morning, afternoon, and evening sampling. Water samples were collected and subjected to gravimetric analysis using the American Public Health Assessment (APHA) standard. ANOVA (p=0.05) in SPSS version 26 found TSS ranges of 110.67 mg/L -177.67 mg/L, 27.67 mg/L – 132 mg/L, and 78 mg/L – 304.67 mg/L for morning, afternoon, and evening, respectively. Surprisingly, no significant mean TSS differences were found for temporal (p>0.05) or spatial (p>0.05) variations. Factors influencing TSS variation such as water flow, salinity, and anthropogenic activities, were discussed. These findings inform researchers, governments, and NGOs for future planning in Kuala Perlis, promoting river health and eco-friendly management

Dissolution Manufacturing Strategy for Designing Efficient and Low Cost Polymeric Solar Water Evaporator

AbstractThe scarcity of fresh water is a pressing issue globally, and solar water evaporation technology has emerged as a leading method for producing fresh water. However, the preparation of solar evaporators is hindered by high costs, complexity, and environmental concerns. In this work, a solar evaporator with hierarchical porous structure is prepared using a simple, low‐cost, and environmentally friendly dissolution manufacturing strategy. Excellent photothermal conversion capability and salt drainage performance are found owing to its hierarchical porous structure. The prepared sample exhibits a water evaporation rate of 2.19 kg m−2 h−1 and achieves evaporation efficiency of 84.3% under one sun. Furthermore, the evaporation rates of the samples in seawater and methylene blue are 2.04, and 1.98 kg m−2 h−1, respectively. The evaporation rate remains stable after ten evaporation cycles. The strategy also overcomes the dimensional limitations of traditional methods, as large‐size samples prepared by this strategy are successfully evaluated for evaporation experiments with natural seawater under sunny weather, and the quantity of water collected is ≈170 g in 6 h. The proposed strategy will offer not only sustainable water purification technologies, but also new routes for solar water evaporation, solar steam generation, and photothermal drive fields.

Poly(arylene ether)s-Based Polymeric Membranes Applied for Water Purification in Harsh Environment Conditions: A Mini-Review.

Confronting the pressing challenge of freshwater scarcity, polymeric membrane-based water treatment technology has emerged as an essential and effective approach. Poly(arylene ether)s (PAEs) polymers, a class of high-performance engineering thermoplastics, have garnered attention in recent decades as promising membrane materials for advanced water treatment approaches. The PAE-Based membranes are employed to resist the shortages of most common polymeric membranes, such as chemical instability, structural damage, membrane fouling, and shortened lifespan when deployed in harsh environments, owing to their excellent comprehensive performance. This article presents the advancements in the research of several typical PAEs, including poly(ether ether ketone) (PEEK), polyethersulfone (PES), and poly(arylene ether nitrile) (PEN). Techniques for membrane formation, modification strategies, and applications in water treatment have been reviewed. The applications encompass processes for oil/water separation, desalination, and wastewater treatment, which involve the removal of heavy metal ions, dyes, oils, and other organic pollutants. The commendable performance of these membranes has been summarized in terms of corrosion resistance, high-temperature resistance, anti-fouling properties, and durability in challenging environments. In addition, several recommendations for further research aimed at developing efficient and robust PAE-based membranes are proposed.

Preparation of polypropylene with photothermal conversion and hydrophilicity by one-step impregnation for efficient interfacial water evaporation

Solar-driven interfacial water evaporation is a technology that is currently attracting significant interest for tackling freshwater scarcity. However, the creation of porous membranes with photothermal conversion and hydrophilicity remains a challenging task. This study utilizes melt-blown polypropylene nonwoven (PP), a substrate with high porosity, low cost and high yield, to prepare evaporation membranes exhibiting photothermal conversion properties. The PP surface was treated with a one-step impregnation method to produce both shell and nanoparticles containing MnO2−x. The addition of MnO2−x grants the PP membranes both photothermal conversion and hydrophilicity simultaneously. Sunlight absorption efficiency of PP membranes covered with MnO2−x (M-PP) is 85.83%, and its hydrophilicity and porosity enable it to form an ultra-thin layer of water during evaporation, promoting rapid escape of vapors. Evaporation rate of M-PP membranes reach 1.02 kg m−2 h−1, much higher than that of PP and bulk water. In addition, M-PP membranes have excellent corrosion resistance, which is potentially valuable in treating wastewater and desalinating seawater.

Mapping of scientific production on actions, projects and challenges to deal with fresh water scarcity

The concern over water is due to the increase in population, which has led to an increase in water consumption. Given the context of water scarcity, it is necessary to direct efforts towards preventing this occurrence. One way to meet demand is through technology for water reuse. In this sense, the research proposal was to conduct a systematic and integrative review of the literature on technology transfer related to water, with a focus on water reuse. A total of 33 articles on the subject were selected. The main findings were that research is focused on promoting water reuse and addressing concerns about water consumption. The research highlights the importance of public policies related to water consumption and reuse, as well as the need to understand the population's awareness and acceptance of such aspects. One alternative to meet the water scarcity crisis is through desalination, but progress is needed to overcome the barrier of high energy consumption and waste generation. Regarding technology transfer, sharing knowledge on a global level is necessary for effective technology transfer and satisfactory results.

Dynamic decision-making for inspecting the quality of treated sewage

Given the scarcity of fresh water, aquatic ecosystems influence climate change. Municipal wastewater pumped into the sewage treatment system could then begin to be re-utilized, balancing how fresh water can be reused with how to fully utilize the potential value of water resources. The crux of the drainage standard is that the decision-making model is accurate and effective for detecting the quality of treated sewage and improving sewage treatment measures. The proposed method called PRBF-SVM(Parallel Radial Basis Function Support Vector Machine) predicts the classification of disposed sewage and provides an effective and efficient solution for detecting water quality. To solve the decision-making problem in municipal wastewater systems, a relevant decision model is set up to combine multi-attributes, and parallel grid search and cross-validation are employed to obtain the optimal model on the training data. Experimental results show that the proposed method improves the accuracy of classification prediction, which is higher than that of the original algorithm. In addition, the performance of the run-time and accuracy are perfect, compared to logistic regression, decision tree, random forest, KNeighbours, XGboost, and AdaBoost methods on the same dataset. PRBF-SVM can be used to determine whether sewage is disposed of to meet the post-treatment drainage standard.

Green recycling of waste poly(ethylene terephthalate) into Ni‐MOF nanorod for simultaneous interfacial solar evaporation and photocatalytic degradation of organic pollutants

AbstractInterfacial solar evaporation is regarded as the promising technology to mitigate freshwater scarcity. However, when polluted water is used, toxic pollutants might accumulate in the bulk water. Herein, we report the production of Ni‐MOF nanorod from waste poly(ethylene terephthalate) and fabricate bifunctional Ni‐MOF‐based evaporators. Owing to high light absorption and photothermal conversion, low thermal coefficient, and vaporization enthalpy, it shows an exciting evaporation rate (2.25 kg m−2 h−1) with good flexibility/durability, rated as one of most advanced evaporators. Density functional theory and COMSOL results show that the combination of nickel‐sites in Ni‐MOF and local heat plays a crucial role in peroxymonosulfate activation to produce reactive species. Thereby, it exhibits the high degradation activity of tetracycline. In outdoor, the freshwater production reaches 5.54 kg m−2 per day, and the tetracycline removal efficiency is 91%. This work provides a sustainable approach to produce solar evaporators capable of freshwater production and contaminant degradation.image

Starch hydrogel with Poly(ionic liquid)s grafted SiO2 for efficient desalination and wastewater purification

Solar-driven interface evaporation is promising to alleviate the fresh water scarcity in an economical and sustainable way. However, most of currently reported photothermal conversion materials (PMs) are time-consuming costly, inefficient, or complex preparation process, which causes low utilization efficiency, and difficult to be practical for large-scale application. To solve this problem, a facile and green strategy for preparing hydrogel evaporator (SiO2-PILs/starch) by grafting poly(ionic liquid)s onto silica and doping it with starch is proposed. Benefiting from the broad solar absorption (ca.91 %), strong hydrophilic, and superb salt tolerance and stain resistance of SiO2-PILs/starch. Under 1 sun irradiation, the SiO2-PILs/starch achieves a remarkable solar evaporation efficiency of 91.72 % in pure water and 81.45 % in 20 wt% NaCl solution, respectively. In particular, SiO2-PILs/starch exhibited outstanding long-term salt stability (8 h) and crystalline salt can be self-cleaned in the dark environment. It is worth noting that the prepared hydrogel also possesses a satisfied evaporation efficiency of 75.84 % in oily wastewater (3 wt% n-hexadecane solution) due to its excellent water retention. These properties of SiO2-PILs/starch may provide desperately needed solution for efficient desalination and guaranteed high applicability and durability in practice.

A loofah-based all-day-round solar evaporator with phenolic lignin as the light-absorbing material for a highly efficient photothermal conversion

Solar interfacial evaporation has received widespread attention as an emerging and sustainable approach to solve freshwater scarcity. However, traditional photothermal conversion materials, which are crucial components of solar evaporators, are mostly petroleum-based and are thus non-eco-friendly and expensive. This paper reports the application of aminated phenolated lignin as an efficient photothermal material and elucidates the photothermal conversion mechanism of lignin. By regulating the number of grafted conjugated structures in a simple process, a controllable and efficient photothermal conversion efficiency can be obtained. The biodegradable loofah is utilized as a water transmission layer, and thus an all-biomass solar evaporator was successfully obtained. Additionally, the evaporator enabled an all-day-round seawater desalination by releasing thermal energy stored in the polyethylene glycol loaded in the loofah sponge. The obtained evaporator did not only exhibit a high evaporation efficiency of up to 97.6% with an evaporation rate of 1.75 kg m−2h−1 under 1 sun, but also showed excellent cost-effectiveness (280 g h−1 $−1), which is superior to that of previously reported evaporators. Furthermore, the evaporator delivered an excellent salt-resistant performance after 25 cycles, which is conducive to long-term practical applications. The prepared evaporator with the characteristics of cost effectiveness, energy conservation, environmental friendliness, ease of preparation, stability, great evaporation efficiency has a great potential in solar evaporation applications.

Coping with Water Stress: Ameliorative Effects of Combined Treatments of Salicylic Acid and Glycine Betaine on the Biometric Traits and Water-Use Efficiency of Onion (Allium cepa) Cultivated under Deficit Drip Irrigation.

Freshwater scarcity is a major global challenge threatening food security. Agriculture requires huge quantities of water to feed the ever-increasing human population. Sustainable irrigation techniques such as deficit drip irrigation (DDI) are warranted to increase efficiency and maximize yield. However, DDI has been reported to cause water stress in plants. The study aimed to investigate the influence of the exogenous application of salicylic acid alone (SA) or in combination with glycine betaine (GB) on the growth, yield quality, and water-use efficiency of onions under different DDI treatments (100%, 70%, and 40% field capacity (FC)). Spray treatments (sub-treatments) were as follows: T1: (distilled water), T2: (1.09 mM SA), T3: (1.09 mM SA + 25 mM GB), T4: (1.09 mM SA + 50 mM GB), and T5: (1.09 mM SA + 100 mM GB). Our results indicated that T2 slightly ameliorated the effects of water stress by improved plant heights, leaf number, pseudostem diameter, bulb quality, and nutrient content of onion bulbs, especially under the 70% FC treatment. However, T3 recorded the poorest results on leaf number, pseudostem diameter, and bulb quality under the 70% and 40% FC treatments. Generally, our results indicated that onions could tolerate moderate water stress (70% FC) without severely affecting the growth and yield of onion. In conditions where freshwater is a limiting factor, a DDI treatment of 40% FC is recommended.