Search Results (25)

Human activities and economic development require large amounts of water and energy. The analysis of the nexus between water and energy flows can improve the understanding of the quantitative relationship between the two resources and guide actions and policies to obtain better results with lower risks. This article aimed to analyse and evaluate the use of rainwater in urban environments and its relationship with the water–energy nexus through a literature review. The PRISMA guidelines were used to structure the research, and the RStudio programme was used for the bibliometric analysis. A total of 118 articles published between 2013 and 2023 were identified in the Scopus and Web of Science databases, of which 30 met the eligibility criteria and were included in the review. The risk of bias in the studies included was assessed by two independent reviewers, and disagreements were resolved by consensus. The results were synthesized in a narrative and descriptive way, and organized in a table containing the authors, year, country, and main findings. The studies were grouped according to the theme addressed and the results related to the use of rainwater and the water–energy nexus were compared. The results indicate that the main use of rainwater is for non-drinkable purposes, to reduce the demand for potable water, lessen the pressure on water resources and contribute to environmental sustainability. Climate change can affect rainfall regimes and, consequently, the feasibility of systems. By decentralizing water supply services, the use of rainwater can save drinking water. When assessing energy savings, the use of rainwater is not always the best option, as system configurations and pump specifications are determining factors. Regarding the environmental impacts, all stages of the urban water cycle consume energy for their operation, and the environmental impact is directly related to the energy source used. Policies and regulations focused on rational use, water conservation, demand reduction, and tax incentives for the installation of rainwater harvesting systems, together with awareness campaigns, are necessary for the widespread adoption of rainwater harvesting systems. Finally, there is consensus regarding saving drinking water, but there is still a lack of studies and specifications regarding energy savings. The findings highlight the need for future longitudinal and simulation-based studies to strengthen knowledge of water–energy nexus dynamics in buildings. Full article

Small decentralized water supply systems are often sensitive to local pollution and require a clear understanding of recharge conditions and the hydrodynamics within the water resource catchment. This study develops a conceptual hydrogeological model for the Šmarna Gora area based on geological mapping, long-term monitoring of chemical parameters, and stable isotope analyses (δ¹⁸O, δ²H) of precipitation and groundwater. The study was initiated in response to rising pollutant concentrations in the drinking water. Estimates of transit time (TT) and mean residence time (MRT) were used to characterize recharge, mixing processes, and differences between the SG and ZAVRH wells, the existing and alternative water supply wells. Isotope data show that the aquifer is predominantly recharged during colder periods and that Mediterranean air masses have become an increasingly important source of precipitation, suggesting a shift in precipitation patterns. The results indicate that SG has longer TT (6–8 months) and MRT (up to 1–2 years). In contrast, ZAVRH shows shorter TT and MRT (4–6 months), and lower pollutant concentrations. The hydrogeological regime in the catchment of the ZAVRH well is characterized by a dynamic, fast-flowing system with limited storage and more intensive dilution of contaminants by infiltrating water, whereas the catchment of the SG well functions as a deeper and more buffered aquifer with prolonged groundwater residence and a more direct hydraulic linkage to the contaminant source. The findings distinguish two hydrogeological regimes and provide a basis for planning water supply solutions and protection measures. Full article

This study presents a short-term, IoT-enabled sensor-based assessment of treated municipal water and decentralized groundwater in Bragança, northeastern Portugal. Two drinking-water supply contexts were compared: treated surface-water-derived municipal water from the public supply system and groundwater from a decentralized supply system serving part of a higher education campus. Five sampling points were monitored during three campaigns between January and March 2026. At each point, pH, electrical conductivity, temperature, oxidation–reduction potential, and total dissolved solids were recorded at 10 s intervals over approximately 10 min monitoring windows using a multiparameter probe integrated into an IoT-enabled data acquisition workflow. Microbiological analyses were performed on groundwater samples as complementary information. Treated municipal water showed lower mineralization, narrower parameter ranges, and higher oxidation–reduction potential, reflecting source-water characteristics, treatment, and operational control. Groundwater showed higher mineralization, lower oxidation–reduction potential, and greater variability among sampling points and campaigns, consistent with stronger local hydrogeochemical and operational influences. The repeated short-interval readings provided more detailed physicochemical profiles than isolated spot measurements, although the short monitoring windows do not represent continuous long-term high-frequency monitoring. Overall, the results support standardized IoT-enabled sensor-based monitoring as a complementary tool for short-term water-quality assessment and indicate the need for longer seasonal datasets and laboratory confirmation. Full article

Damage to urban water supply infrastructure can rapidly compromise access to safe water and force households to rely on alternative sources of uncertain quality. This study presents a case-based assessment of water quality and emergency household-level treatment options in Mykolaiv, Ukraine, following conflict-induced disruption of the centralized water supply system. Water samples collected from selected groundwater and distribution-network points were analyzed for physicochemical, organoleptic, and microbiological indicators, including total dissolved solids, hardness, sulfates, chlorides, iron, permanganate oxidizability, total microbial count, and E. coli. The results showed elevated mineralization, increased sulfate and chloride concentrations, high hardness, organic load indicators, and episodic microbiological contamination in several samples. A low-cost four-stage household treatment procedure combining chemical oxidation, thermal treatment, sorption, and short-term preservation was evaluated as a preliminary emergency approach. The procedure improved odor, taste, hardness, iron content, permanganate oxidizability, and microbiological safety; however, it did not fully reduce total dissolved solids, sulfates, or chlorides to drinking-water standards. Therefore, the treated water should be considered non-potable and suitable mainly for limited domestic and hygienic uses unless additional desalination or blending is applied. The study highlights both the potential and the limitations of simple household-level interventions under emergency water supply disruption and emphasizes the need for decentralized treatment support, monitoring, and long-term infrastructure recovery. Full article

Manganese pollution in surface water has been a new concern in decentralized drinking water treatment. The dissolved manganese cannot be effectively removed by the traditional ultrafiltration (UF) process, but will cause severe membrane fouling. To address such issues, an innovative gravity-driven membrane (GDM) coupled with a dynamic manganese oxide (MnOx) film on the membrane surface was proposed, with hopes of enhancing manganese removal and alleviating membrane fouling. The results demonstrated that pre-coating a dynamic MnOx film on the membrane surface of a GDM system would effectively reduce start-up time for removing iron and manganese pollutants, without affecting the flux stabilization of the GDM. Effective manganese removal (~80%) primarily depended on the adsorption and auto-catalytic oxidation facilitated by the pre-coating of MnOx. Furthermore, the MnOx film notably enhanced organic pollutant removal efficiency. Additionally, the MnOx coated on the membrane surface acted as a skeleton, promoting the gradual formation of a biocake layer with a heterogeneous and porous structure, which benefited the flux stabilization of the GDM. In particular, the fine and homogeneous MnOx-M derived from the backflushing water of the mature manganese sand filter exhibited precise and uniform coating on the membrane surface, effectively mitigating the irreversible pore plugging caused by organic matter penetration and thereby enhancing stable flux by ~16.3% compared to the control. This study offered a novel strategy to enhance the purification efficiency of GDM system treating manganese pollution and was expected to contribute to the technological advancement of decentralized water supply scenarios. Full article

Rapid and even disruptive innovations are needed to make cities fit for the future. The particular challenge will be to transform existing urban spaces in order to increase climate resilience. Along these lines, rainwater harvesting has taken place insufficiently to date, even when Sponge City concepts are implemented. Thus, the concept presented here addresses existing urban neighborhoods and proposes to collect rainwater from nearby rooftops and treat it in decentral treatment units called “City Water Hubs” (CWH) equipped with modular coupled low-energy technologies to produce various customized “City Water” qualities, and store it until it can be used or distributed. A feasibility study with a focus on the campus area at the main building of the Leibniz University of Hannover, the determined rainwater qualities, and the results from investigations with two laboratory test plants provided the basis for the technical design of the pursued concept. The feasibility study showed how sufficient rainwater for irrigation purposes can be made available for the listed large university park even under extreme dry and heat wave conditions. If large portions of the roof area (11,737 m²) of the university’s main building were activated, even in a dry year with only 49.8% of the average precipitation, only 19.8% of the harvested stormwater would be needed for irrigation. The rainwater samples showed TSS concentrations of up to 7.54 mg/L, COD of up to 58.5 mg/L, and NH₄ of up to 2.21 mg/L, which was in line with data reported in the literature. The treatment technologies used for the two pilot plants are proven approaches for stormwater treatment and were composed as follows: (1) gravity-driven membrane filtration (GDM) and (2) slow sand filter with integrated activated carbon (AC) layer. The treatment with both (1) and (2) clearly improved the rainwater quality. The GDM reduced turbidity by 90.4% and the Sand/AC filter by 20.4%. With regard to COD, the studies for GDM did not show a clear elimination trend; the Sand/AC filter reduced the COD by 77%. Taken together, decentralized low-energy rainwater treatment can reliably provide quality-assured City Water for any specific use. Regarding the treatment design, GDM is preferable and can be better operated with downstream UV disinfection, which might be needed to reduce the pathogenic load, e.g., for local heat control measures. The research steps presented here will pioneer the development of a city-wide rainwater harvesting infrastructure on the way of establishing stormwater as a resource for a new wing of urban water supply. The presented findings will now result in the implementation of a full-scale CHW on the campus to ensure long-term irrigation of the listed park, relieving the public drinking water supply. Full article

Providing everyone with safe drinking water is a moral imperative. Yet, sub-Saharan Africa seems unable to achieve “safe drinking water for all” by 2030. This sad situation calls for a closer examination of the water supply options for both rural and urban populations. Commonly, two main aspects are considered: (1) behavioural responses to available or potential water supply options, and (2) socio-economic acceptability. These aspects determine the feasibility and the affordability of bringing safe drinking water as a basic good and human right to everyone. There is a broad consensus that achieving the UN Sustainable Development Goal 6.1 is mostly a financial issue, especially in low-income settings. This communication challenges this view as water is available everywhere and affordable treatment options are well-known. It considers the decentralized water supply model as a reference or standard approach in low-income settings rather than as an alternative. Here, the medium-sized city of Bangangté in the western region of Cameroon is used to demonstrate that universal safe drinking water will soon be possible. In fact, during the colonial period, the residences of the elite and the main institutions, including the administrative quarter, churches, and hospital, have been supplied with clean water from various local sources. All that is needed is to consider everyone as important or accept safe drinking water as human right. First, we present a historical background on water supply in the colonial period up to 1980. Second, the drinking water supply systems and water demand driven by population growth are discussed. Finally, a hybrid model for the achieving of universal access to clean drinking water, and preconditions for its successful implementation, are presented. Overall, this communication calls for a shift from safe drinking water supply approaches dominated by centralized systems, and presents a transferable hybrid model to achieve universal clean drinking water. Full article

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. Full article

The growing demands for affordable and applicable technologies for decentralized safe drinking water provision have instigated technical innovations in the water filtration industry. Adsorptive filtration appears to be the most affordable, resilient, and socially acceptable solution for households and small communities worldwide. However, water filtration devices have not yet been widely implemented due to lack of awareness for the efficiency of such systems using locally available materials. Water filtration has the potential to secure universal access to safe drinking water by 2030. This special issue has elucidated the applicability, benefits, constraints, effectiveness, and limitations of metallic iron as filter material for safe drinking water provision. Tools to make rainwater a primary water source are also presented together with ways to transform existing centralized water management systems into decentralized ones (sectorization). The knowledge is applicable to a wide variety of situations on a global scale. Full article

The establishment of decentralized drinking water systems in urban areas is technically and financially feasible, and these ‘off-grid’ systems can complement investment in traditional piped water systems. However, users often see ‘off-grid’ systems as the second-best option, compared to citywide piped water systems. Thus, although they are designed to improve access to water and reduce inequality, they can be perceived by users as infrastructural manifestations of extant inequality. In this paper, we present original research on the perceptions of users in Cimahi, Indonesia, surrounding their access to water and willingness to use and maintain ‘off-grid’ infrastructure. The majority of respondents used groundwater and packaged water as their primary water sources, and paid approximately twice the maximum tariff of piped water service. We interpreted the survey data with the theory of planned behavior framework and determined that respondents demonstrated a willingness to pay fees for ‘off-grid’ water systems, participate in water supply programs, and switch to new water sources. These intentions were affected by their attitude towards the behavior, subjective norm, and perceived behavioral control to various degrees. The findings are useful for those designing strategies to introduce novel water delivery systems aimed at improving water access for diverse and disadvantaged socioeconomic groups in urban areas in the Global South. Full article

Biological and chemical contamination of natural water bodies is a global health risk for more than one billion people, mostly living in low-income countries. Innovative, affordable, and efficient decentralized solutions for safe drinking water supply are urgently needed. Metallic iron (Fe⁰)-based filtration systems have been described as such an appropriate solution. This communication focuses on the Kanchan arsenic filter (KAF), presented in the early 2000s and widely assessed during the past decade. The KAF contains iron nails as the Fe⁰ source and is primarily designed to remove As from polluted tube well waters. Recent independent works assessing their performance have all reported on a high degree of variability in efficiency depending mostly on the following factors: (1) the current operating conditions, (2) the design, and (3) the groundwater chemistry. This communication shows that the major problems of the KAF are two-fold: (1) a design mistake as the Fe⁰ units disturb the operation and functionality of the biosand filter, and (2) the use of poorly characterized iron nails of unknown reactivity. This assertion is supported by the evidence that the very successful community filter designed by the Indian Institute of Technology Bombay works with iron nails and has been efficient for many years. Replacing iron nails by more reactive Fe⁰ materials (e.g., iron fillings and steel wool) should be tested in a new generation KAF. It is concluded that a methodological or systematic approach in introducing and monitoring the efficiency of KAF should be used to test and disseminate the next generation KAF worldwide. Moreover, better characterization of the Fe⁰ materials including their intrinsic reactivity is required. Full article

Gravity-driven membrane (GDM) filtration is one of the promising technologies for decentralized water treatment systems due to its low cost, simple operation, and convenient maintenance. The objective of this study was to evaluate the permeability of submerged GDM filtration with three different membranes, i.e., polyethersulfone and polyvinylidene difluoride ultrafiltration (PES-UF and PVDF-UF) and polytetrafluoroethylene microfiltration membrane (PTFE-MF). The GDM system was operated using lake water for about one year. The determined average permeability values were high for PVDF-UF (192.9 L/m²/h/bar (LMH/bar)) and PTFE-MF (80.6 LMH/bar) and relatively lower for PES-UF (46.1 LMH/bar). The observed higher permeability for PVDF-UF and PTFE-MF was thought to be related to the rougher surface of these two membranes compared to PES-UF. The fouling layers of PVDF-UF and PTFE-MF were characterized by high biomass and the presence of a number of nematodes, while PES-UF showed a thin fouling layer with no nematode. The relatively high and fluctuated permeability of PVDF-UF and PTFE-MF could thus be attributed to the high biological activity of nematodes making the fouling layer more loose and porous. This was supported by a good linear relationship among the permeability, biomass concentration, and the number of nematodes in the fouling layers. These results provide important insights into membrane selection as a critical factor affecting the flux performance of the GDM filtration system for a decentralized drinking water supply. Full article

Rural China faces a shortage of safe drinking water. There are significant challenges associated with small centralized water supply systems and decentralized water supply systems. Many rural residents use point-of-use water treatment systems to ensure the safety of their drinking water. The actual water purification effect and applicability of these water treatment systems in small centralized and decentralized water supply systems need to be determined urgently. In this study, the water quality index (WQI) method was applied for the first time in rural areas to evaluate the effectiveness of point-of-use water treatment systems. A total of 67 reverse osmosis water treatment systems were tested. The rate of compliance with drinking water standards of the decentralized water supply was low (37%). Compared with untreated water, the use of a reverse osmosis water treatment system improved the rate of compliance with drinking water standards, but this effect was not satisfactory (8%). Among the factors potentially affecting the purified water quality of point-of-use water treatment systems (e.g., service time of the water treatment system, service time of the filter element, and type of water source), the service time of the filter element had the most significant influence on the water quality. If the filter element had not been replaced for a long period, the removal effect of the water treatment system on the total hardness, sulfide, copper, and ammonia nitrogen was significantly affected, reducing the quality of the purified water. To ensure the safety of drinking water, it is recommended to replace the filter element of a reverse osmosis water treatment system at least once a year. Full article

Development of coalbed methane (CBM) projects is critical to the achievement of climate change goals because it will help facilitate coal-to-gas transitions in Asia-Pacific countries with low conventional gas reserves. However, growth in CBM in these regions will necessitate strategic, sustainable approaches to produced water management. We posit that it may be possible to deliver synergistic water, energy, and health benefits by reusing CBM-produced waters as potable water supply in water-stressed coal-bearing regions. The goal of this study is to probabilistically evaluate life cycle costs and benefits of using reverse osmosis to treat CBM-produced water in the Damodar Valley coalfields in eastern India. Two treatment configurations are assessed, namely, centralized, and decentralized (i.e., in-home). We find that both configurations offer good cost-effectiveness based on two separately computed metrics to account for the value of health improvement benefits (i.e., disability-adjusted life years (DALYs) averted or monetized health benefits). We also observe that centralized systems are more cost-effective than decentralized, because they reduce capital cost and use-phase energy consumption per unit-volume treated. Average estimated values for the cost–benefit ratio are <0.5 and 1.0 for centralized and decentralized, respectively. Normalizing by anticipated health benefits, cost-effectiveness metrics are <$30/DALY for the centralized system versus <$200/DALY for the decentralized system. These results are highly sensitive to the value of statistical life and baseline water access. A related analysis taking into account both CBM-produced waters and mine waters revealed that deployment of reverse osmosis (RO) could provide drinking to approximately 3.5 million people over 20 years in the Damodar Valley region. These results have interesting implications not only for the study region but also for other CBM-producing countries experiencing chronic severe water stress. Full article

Installation of decentralized water-treatment plants is an ideal option to supply safe drinking water for rural communities. Presently in Sri Lanka, over 3.6 million villagers face acute water-quality problems, and chronic kidney disease of unknown etiology (CKDu) is also prevalent among this community. Most of the drinking water in these villages is unpalatable due to high hardness and salinity. As an interim measure, reverse-osmosis (RO) water-treatment plants are introduced to provide safe water. However, due to deficient electrolytes, RO-treated water tastes unpleasant to some consumers; hence, people refuse it after prolonged use. The operation, maintenance, and management of RO plants are other major problems. Aimed at providing safe drinking water to the rural sector in a cost-effective manner, in this study, we fabricated an automated drinking-water purification system based on nanofiltration (NF) membrane technology, which can remove divalent cations, dissolved organic carbon (DOC) and pathogens efficiently, and monovalent ions partially, and thus keep electrolytes to some degree. Ten commercial NF membranes were tested in a laboratory, for solute and DOC removal efficiency and robustness. The DF-90 membrane showed the highest removal of DOC and hardness, and it was therefore selected, to design a pilot NF drinking-water treatment plant. The adhered DOC by the membrane can be cleaned by NaOH solution (pH = 12). The pilot NF drinking-water treatment plant has been in use since September 2018, and it shows excellent performance of removing DOC, TDS, hardness, fluoride, and pathogens in groundwater, and the permeate water of the NF plant has been well-accepted by the stakeholders of the society. The dominant genus of source water, and throughout the two processes (NF and RO), is Pseudomonas, and their difference is significant in the concentrates of the NF and RO processes. Full article