With the growing concerns over water scarcity and depleting groundwater levels in Pakistan due to population growth, climate change, and inefficient use of water resources, the water demand has also increased. The worst figures are provided by the sixth Sustainable Development Goal (SDG) of the UN Agenda 2030 "Clean Water and Sanitation," with over 733 million people residing in countries under severe water stress. Rainwater harvesting can help solve the domestic water problem that we have just tagged as a local issue. It is the most sustainable approach, in which the rainwater from rooftops, land surfaces, or rock catchments is collected and stored via scientific techniques. Rainwater harvesting has great potential for groundwater recharge and to combat problems of water crisis, urban flooding, and insecurity in local sources. This system stores rainwater trapped in these catchment areas, which is then passed through activated carbon filters to remove all impurities within. The clean rainwater is further conveyed to recharge wells and infiltrated safely into the groundwater table. The initial results suggest that using the rainwater harvesting system to increase groundwater recharge rates is an efficient way to improve water sustainability in different communities. This project combines rainwater harvesting with state-of-the-art filtration methods to help save water and take a step toward the sustainable management of groundwater resources.

Floating wetlands are artificially constructed platforms that support aquatic vegetation growing hydroponically. These systems are considered a nature-based solution (NBS), leveraging the natural processes of plants, microbes, and associated microorganisms to filter and enhance water quality by removing pollutants such as nutrients, heavy metals, and organic contaminants. In Macau SAR, China, a coastal city with significant water bodies, floating wetlands offer a promising solution to mitigate water pollution. Macau faces considerable environmental challenges due to urban runoff, industrial discharge, and limited natural wetlands. The implementation of floating wetlands can effectively address these issues. This study aims to evaluate the use of floating wetlands for the remediation of water pollution, particularly eutrophication, in both freshwater and coastal wetlands. A pilot-scale floating platform, made of bamboo and coconut fibers, was set up as a base for the vegetation. Local coastal mangrove species such as Kandelia obovata and Aegiceras corniculatum, along with freshwater wetland plants like Thalia dealbata, Canna sp., and Iris sp., were anchored between the bamboo tubes and secured with coconut fibers and polyethylene nets. Nutrient concentrations in the surrounding waters were measured before deployment and monitored thereafter. The growth conditions of the plants and the biodiversity within the floating wetlands are also being monitored. Biofilm from the roots of the plants will be collected and processed for sequencing to identify associated microorganisms involved in phytoremediation. We expect that the presence of floating wetlands will improve water quality and biodiversity in the system. Acknowledgments: Calheiros C.S.C. is thankful to Strategic Funding UIDB/04423/2020, UIDP/04423/2020, and LA/P/0101/2020 through national funds provided by FCT.

This study evaluates the effectiveness of MnFe2O4/g-C3N4 spinel ferrites nanoparticles, synthesized using Chrysopogon zizanioides (C. zizanioides) root powder as the base material, in removing Pb (II) from contaminated water through the adsorption process. Firstly, the nanoparticles were synthesized using the co-precipitation method. The MnFe2O4/g-C3N4 nanoparticles were characterized using various techniques, such as Fourier-transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer–Emmett–Teller (BET) surface area analysis, dynamic light scattering (DLS), zeta potential measurement, Raman spectroscopy (RAMAN), and vibrating sample magnetometry (VSM). These analyses confirmed the successful synthesis and revealed the magnetic properties of the nanoadsorbent.

The adsorption capacity of the C. zizanioides/MnFe2O4/g-C3N4 nanoparticles was then tested, demonstrating a high removal efficiency for Pb (II) from contaminated water. The effects of various parameters on the adsorption process, including pH, adsorbent dosage, contact time, initial Pb (II) concentration, and temperature, were investigated. Kinetic studies revealed that the adsorption process followed a pseudo-second-order model with a coefficient of determination of 97.32%, indicating a strong correlation. Additionally, the Freundlich isotherm model best described the adsorption of Pb (II) by the nanoparticles. Thermodynamic studies indicated that the adsorption of Pb (II) was an endothermic and spontaneous process. This study also examined the desorption capability and reusability of the nanoadsorbent over multiple cycles, finding that it could be effectively regenerated and reused, with a high percentage of recovery of adsorbed Pb (II). Additionally, a machine learning algorithm was developed to predict and optimize the adsorption process, providing further insights and improving the efficiency of Pb (II) removal.

Disinfection By-Products (DBPs) are generated through the interaction of the free chlorine added during the drinking water (DW) disinfection process with natural organic matter (NOM) that may be part of the raw water. The most common DBPs found in DW include trihalomethanes, haloacetic acids, haloacetonitriles and haloketones. The presence of DBPs in DW can lead to several consequences for human health due to their high toxicity; thus, their reduction is crucial to achieve better water quality worldwide. For this purpose, NOM can be removed at the early stages of the treatment process, or the DBPs can be removed at the end of the process.

In this work, photocatalysis was investigated as a potential removal alternative for 4-chloro-L-phenylalanine (Cl-phe), a known precursor of some of the most incident DBPs in DW. For this purpose, several metal layered double hydroxides (LDHs) were synthesized by the co-precipitation method, combining iron with zinc (ZnFe), copper (CuFe), cobalt (CoFe), nickel (NiFe) and manganese (MnFe), and their photocatalytic potential was assessed. Additionally, their performance was compared to commercial titanium dioxide (TiO₂). A 10 mg/L solution of Cl-phe (the highest possible concentration of NOM in DW) was used for the photocatalysis tests, with a load of 200 mg/L, a pH of 7 and UV-A light. TiO₂ was able to completely remove Cl-phe with 2 h of UV-A light exposure. As for the LDH catalysts, CoFe and MnFe did not show an effect on the removal of Cl-phe, whereas CuFe and NiFe showed a greater affinity during the adsorption phase rather than under UV-A light. In contrast, ZnFe was able to remove the Cl-phe by photocatalysis, leading to a removal of 45% with 2 h of UV-A light exposure.

Funding: EU—H2OforAll Horizon project (GA 101081963); FCT—CERES unit, with Refs. UIDB/00102/2020 and UIDP/00102/2020.

This study develops a Severity Heat Map to analyse the spatiotemporal dynamics of exceptional rainfall in Portugal over 42 hydrological years (1981/1982–2022/2023) using the ERA5-Land reanalysis dataset. By employing four upper quantiles (Q95, Q99, Q99.5, Q99.9), this research identifies exceptional rainfall events and analyses their occurrences, cumulative impacts, and intensity. The ERA5-Land data, validated against local meteorological records, provide a robust foundation for assessing regional variations and temporal changes. The results reveal significant regional variations and temporal changes in exceptional rainfall. While overall cumulative rainfall has decreased, the most exceptional events have intensified in severity. This trend is particularly evident when comparing two subperiods: 1981/1982–2001/2002 and 2002/2003–2022/2023. The innovative Severity Heat Map visualises these changes, illustrating combined characteristics of exceptional rainfall. It shows significant increases in frequency and intensity, particularly in coastal and urban areas. The Severity Heat Map was created using a 2x2 matrix, considering two variables: the mean annual number of occurrences of exceptional rainfall and the mean annual cumulative rainfall above the threshold. Higher severity was assigned to areas where both variables exhibited increased values in the more recent subperiod. This visualisation highlights regions experiencing heightened severity, offering a comprehensive view of the evolving landscape of exceptional rainfall in Portugal. This tool is crucial for understanding the broader impacts of climate change on regional hydrological systems. The findings indicate that despite a decrease in overall rainfall, the intensity and severity of exceptional events have increased, reflecting the broader impacts of climate change. These insights are vital for informing risk management and sustainable development strategies aimed at mitigating the impacts of exceptional weather events in Portugal. The Severity Heat Map approach provides valuable insights for informed decision making in risk management and sustainable development, tailored to the changing patterns of exceptional rainfall in the country.

Membrane-based separation technology has been extensively utilized in desalination, owing to its high efficiency and lower energy consumption. Unlike traditional polyether sulfone membranes, the novel composite membrane features distinct physicochemical structures and properties. The incorporation of carbon-based nanomaterials like activated carbon, carbon nanotubes, and graphene oxide enhances the membrane's separation performance, resistance to diverse feed waters, and operational lifespan. The present study investigated the desalination performance of nanocomposite polyether sulfone (PES) membranes embedded with activated carbon (PES-AC), multi-walled carbon nanotubes (PES-CNT), and graphene oxide (PES-GO) in aqueous solutions of NaCl and Na₂SO₄. Salt rejections were evaluated using a dead-end filtration cell assembly. The PES-AC, PES-CNT, and PES-GO membranes demonstrated salt rejection rates of 42%, 51%, and 60%, respectively, for NaCl aqueous solution at 0.8 MPa. The salt rejection performance for Na₂SO₄ was 47%, 53%, and 58% for the PES-AC, PES-CNT, and PES-GO membranes, respectively. In conclusion, embedding carbon-based nanomaterials significantly enhanced the salt rejection performance of PES membranes, positioning them as a promising solution for advanced treatment of saline water. In conclusion, the integration of carbon-based nanomaterials into polyether sulfone (PES) membranes has markedly improved their salt rejection capabilities. This advancement not only meets the increasing demand for efficient desalination technologies but can also foster the development of sustainable and cost-effective water treatment solutions. Therefore, these modified PES membranes have the potential to significantly contribute to the global effort to provide clean and safe drinking water from saline sources.

The central coast of Vietnam, characterized by diverse terrain and climate, provides a good natural laboratory for studying beach cusps' complex formation and evolution. This study investigates the key hydrodynamic and morphological parameters that strongly influence beach cusps' formation and evolution mechanism. First, to quantify the morphological characteristics of beach cusps, high-resolution Unmanned Aerial Vehicle (UAV) imagery was captured weekly at multiple sites along the My Khe coast. Key 2D and 3D features of the beach cusp, including cusp spacing, depth, amplitude, and elevation, were extracted from these images and validated using detailed one-meter digital elevation models (DEMs). Concurrently, incident wave characteristics, including wave heights, wave periods, and wave directions, were recorded at each location. Moreover, important hydrodynamic and morphological parameters were collected, such as water level, tidal components, and sediment characteristics. The primary factors driving beach cusp formation and evolution mechanisms are better clarified by examining the spatial and temporal variability of cusp features in relation to hydrodynamic and morphodynamic conditions. A notable finding is the strong relationship between cusp spacing and changes in incident wave direction and energy induced by headlands. The curved coastline sheltered by headlands experiences reduced incident wave angle and energy, resulting in smaller and shallower cusps than exposed areas. The most pronounced beach cusp is recorded in the transition from the protected to the exposed coastline. A conceptual model of the beach cusp was then constructed in a coupled XBeach and Delft3D model. The model integrates field observations and theoretical models that can be used to explore the relationship between incident wave patterns, sediment characteristics, and coastal geomorphology, which contribute to the development of rhythmic shoreline patterns.

Water is a vital component of life systems, highly essential for all life forms. Human water exhaustion is of two types: direct and indirect. Like other natural resources, water demand evaluation is crucial for survival. With increased consumption pressure, “Water scarcity” is globally recognized. The only way out is to change water usage patterns, not only to reduce pollution loads but also to safely meet future needs. The water footprint (wf) measure, an indicator of conservational sustainability, is valid in water assessment and management. In regions of old municipal systems that are not maintained and have never been updated, urban flooding is a common occurrence each rainy season. Traditional methods of growing cereals, predominantly rice and wheat, have made conditions worse. In such environments, introducing ecological water use is fundamental. The evaluation of water in a certain system of production in a given scenario is regularly required. In this study, Indus River Basin (IRB), Pakistan was selected to apply the conception of ‘wf’ using GIS technology. This plotting will help to demonstrate statistics about water: depletion, stress, and exploitation in definite space and time. The green, blue, and grey components of ‘wf’ scheming will make available the estimation of precipitation, ground reserves, the water table, and contamination ratios generated during domestic, commercial, industrial, and agriculture practices conducted. This study will surely allow for a circumstantial baseline of water resource management, refrain from floods, and the ability to meet future demands for farming, food supplies, and economic development in the region. Its a method of assuming, accomplishing, and executing new sustainable processes of water use, measurement, management, and conservation, thereby avoiding life-threatening urban flooding, over evaporation in farms during roasting weather, and extensive drilling for performing daily tasks in each sector. This addresses the issues of increasing demand for excessive water from ground assets and subsequent energy costs.

The formation, maintenance, and development of beach cusps are among the most challenging morphological and physical processes in hydrodynamics and coastal morphology. Many unanswered questions remain despite extensive research, data collection, measurement, and modeling of these coastlines. A study of the My Khe coastal region revealed that beach cusps, ranging from 150 to 200 meters, mainly form during the transitional period from the southwest monsoon to the northeast monsoon. To gain further insight, a two-dimensional numerical experiment model for beach cusp formation was constructed using the elevation and hydrodynamic data of the area in the Xbeach model. Simulation results show the crescent-shaped cusps' initial formation and subsequent development trends from an initially flat state during the transitional period. The horn and bay features of the beach cusps first formed in the offshore area. The size and spacing of these cusps match the observed scales in reality. The initial period, when the water level first rises, is when the formation and development of the cusps seem most pronounced. As the water level increases, the cusps shift gradually towards the shore. This process is hypothesized to repeat when the sea level drops in the next cycle. As a result, a series of cusps gradually moves towards the shore.

The global proliferation of the sugar industry has led to the production of large amounts of untreated effluent being released into the environment, prompting the exploration of energy-saving technologies like microbial desalination cells (MDCs). Despite the proven efficiency of MDCs in wastewater treatment and desalination, their performance is hindered by the high cost and toxicity of the cathode catalysts. MDCs powered by an algal cathode offer an alternative solution by enhancing the effectiveness of the oxidation–reduction reaction and eliminating the need for expensive catalysts and aeration at the cathode. The main aim of this study is to evaluate the efficiency of a Scenedesmus obliquus-inoculated photosynthetic MDC (PMDC) in the cathode chamber in comparison to a traditional aerated MDC. It focuses on using sugar industry effluent as an anolyte to enhance the electricity production when treating sugar industry wastewater and achieve simultaneous desalination. This study assesses the performance of MDCs and PMDCs in terms of wastewater treatment, energy generation, and desalination. The results indicate that the PMDC outperformed the MDC throughout the experiment by achieving 21.6% desalination, an average voltage of 275.9 mV, 73.8% anode COD removal, and a maximum power density of 6.8 mW/m², exceeding the performance efficiency of the MDC by 6.43%, 27.5%, 18.5%, and 112.5%, respectively. These results demonstrate that PMDCs are more effective than MDCs in producing electricity, desalinating water, and treating wastewater. Furthermore, PMDCs have the potential to remove nutrients while producing algal biomass, making them a viable alternative for water and wastewater treatment.