Decentralized Water Treatment Research Articles

Flow-through inactivation of pathogenic Escherichia coli by titanium suboxide reactive electrochemical membranes: Unlocking the coupled mechanics of electrochemical and subcellular alterations

Limited mass transfer controlled by diffusion and unexplored disinfection mechanisms at the subcellular alternation respond to different electrochemical reactions always obstacles the electrochemical disinfection decentralized water treatment. Here, a large-scale reactive electrode membrane composed of titanium suboxide (TiSO-REM) was pioneered for pathogen inactivation and mechanism exploration. Complete bacteria inactivation (>7.1 log reduction) was achieved after 20 min of electrolysis at 1440 L m−2 h−1 (LMH) and 15 mA cm−2. Electrostatic adsorption facilitated the interaction of pathogens with oxidants in the electrode boundary layer by enhancing the adhesion of Escherichia coli at anode surface, resulting in 25 % improvement in removal. Subcellular alternation of waterborne pathogens depended on specific electrochemical mechanisms. Direct electron transfer (DET) unbalanced intracellular metabolism by excessive intracellular reactive oxygen species accumulation. While more violent electro-generated •OH annihilated the whole cells with disorderly alternation which also effectively reduced the risk of bacterial regeneration with no bacterial resuscitation. The study also provides a universal model to develop sustainable technologies for pathogen inactivation and precise regulation of inactivation efficiency from a mechanistic perspective for a wide range of engineering applications like water disinfection and bio-safety control.

Life cycle assessment and techno-economic analysis of nanotechnology-based wastewater treatment: Status, challenges and future prospectives

BackgroundWater pollution is a pressing concern stemming from both natural and anthropogenic activities. The challenges associated with water treatment technologies are adsorption (fouling and corrosion of the adsorbent), flocculation (increased sludge generation and high operation cost), ion exchange (high cost and improper ion removal), chemical precipitation (sludge generation), and membrane technologies (membrane fouling and storage). These technologies have been overstretched and struggle to meet increasingly stringent water quality standards. More recent progress has been made in using nanotechnology for wastewater treatment. Nano-technology offers several advantages over traditional technologies. Many nano-based technologies support reuse, require less space, produce fewer toxic intermediates, and are adaptable to support the emerging concept of decentralized water treatment. An essential aspect of this review is a detailed techno-economic analysis, assessing the long-term viability of nanotechnology-based wastewater treatment methods from an economic standpoint. MethodsThis review outlines the current state of nanotechnology in wastewater treatment, addressing environmental and economic aspects, challenges, and future potential. Significant findingsUnderstanding the sustainability and feasibility of these innovative technologies is crucial for their successful integration into wastewater treatment practices, ensuring a more effective and environmentally friendly approach to water remediation.

Pervious Concrete and Pervious Mortar as Water Filter in Decentralized Water Treatment– a Review

Decentralized water treatment system is water treatment carried out by the community on a household-scale. One of the technologies that have been developed to gain freshwater is the pervious concrete filter (PCF). This study aims to provide the researchers with an understanding of the pervious concrete filter as a potential filter technology in water treatment. The method used is a literature review from several papers and reports related to pervious concrete from past to present. PCF is a filter made from a mixture of aggregate, cement, and water with a specific ratio. PCF has enough water and air permeability due to interconnected macro pores. Some properties such as porosity, permeability, and pores size determine the ability of PCF to remove the contaminants in the water. These properties were controlled mostly by the aggregate size, aggregate-cement ratio, water-cement ratio, etc. According to its characteristic, the PCF shows a prospect to be used as water filter mainly in a decentralized water treatment system. Besides, the understanding of PCF is a basis to develop a pervious mortar filter that slightly different in the aggregate sizes used in this composite.

Low-Cost Antibacterial Ceramic Water Filters for Decentralized Water Treatment: Advances and Practical Applications.

Access to clean water remains challenging for people living in underdeveloped regions, rural areas, and remote locations. In the absence of centralized water treatment systems, point-of-use (POU) solutions are necessary. Ceramic water filters (CWFs) have emerged as a practical and affordable option for decentralized water treatment. This review focuses on recent advances in antibacterial CWFs, including preparation methods, filtration performance, and applications. The review highlights the significance of preparation techniques, material choices, and additives in determining CWF properties and performance. Despite virus and chemical contaminant removal limitations, ongoing research on nanofillers and antibacterial additives shows promise for enhancing the CWF performance. The cost-effectiveness, ease of production, and low operational requirements of CWF make it a viable solution for decentralized drinking water systems, particularly in resource-limited areas. Studies have demonstrated the efficacy of CWFs in reducing water contaminants, but proper maintenance and user training are crucial to optimal performance.

Microalgae-Mediated Biosorption for Effective Heavy Metals Removal from Wastewater: A Review

Environmental contamination by heavy metals poses significant threats to terrestrial and aquatic ecosystems, necessitating the development of effective remediation strategies. Conventional methods for heavy metal removal exhibit limitations, including inadequate efficiency and elevated costs. In this context, microalgae have emerged as a promising bioremediation approach due to their robust metal-binding capabilities, specifically through biosorption. This review comprehensively examines the role of microalgae in addressing heavy metal pollution, with a primary focus on their effective removal from wastewater. Microalgae offer wastewater purification potential across diverse sources and capitalize on wastewater as a growth matrix, yielding valuable bioproducts, biomaterials, and bioenergy. Their versatility allows them to thrive in various wastewaters, facilitating effective contaminant removal. This study also investigates the application of microalgae in decentralized water treatment systems (DWTSs), where the decentralized nature of these systems proves advantageous in addressing heavy metal contaminants directly at the point of generation or use. This approach holds particular significance in regions where centralized systems face obstacles due to geographical constraints, inadequate infrastructure, or financial limitations. DWTSs not only provide a decentralized solution for heavy metals removal but also prove advantageous in disaster relief scenarios and rapidly growing urban areas.

Nitrate electro-bioremediation and water disinfection for rural areas

Nitrate-contaminated groundwater is a pressing issue in rural areas, where up to 40 % of the population lacks access to safely managed drinking water services. The high costs and complexity of centralised treatment in these regions exacerbate this problem. To address this challenge, the present study proposes electro-bioremediation as a more accessible decentralised alternative. Specifically, the main focus of this study is developing and evaluating a compact reactor designed to accomplish simultaneous nitrate removal and groundwater disinfection. Significantly, this study has established a new benchmark for nitrate reduction rate within bioelectrochemical reactors, achieving the maximum reported rate of 5.0 ± 0.3 kg NO3− m−3NCC d−1 at an HRTcat of 0.7 h. Furthermore, thein-situ generation of free chlorine was effective for water disinfection, resulting in a residual concentration of up to 4.4 ± 1.1 mg Cl2 L−1 in the effluent at the same HRTcat of 0.7 h. These achievements enabled the treated water to meet the drinking water standards for nitrogen compounds (nitrate, nitrite, and nitrous oxide) as well as pathogens content (T. coliforms, E. coli, and Enterococcus). In conclusion, this study demonstrates the potential of the electro-bioremediation of nitrate-contaminated groundwater as a decentralised water treatment system in rural areas with a competitive operational cost of 1.05 ± 0.16 € m−3.

Deployment of interpretable machine learning in a water treatment device - feasibility exploration of performance enhancement

Machine learning (ML) provides a promising tool for predictive control and unattended operation of water treatment processes, especially in decentralized water supply due to its high variability of water quality and scarcity of manpower. However, model deployment after ML development is a challenge that hinders their implementation. Herein, this study constructed a novel electrocoagulation membrane cathode reactor (ECMCR) as an example of decentralized water treatment due to its highly integratable. Nine ML models were established to determine the ECMCR operational current density (CD) and the Bayesian technique was employed for adaptive hyperparameters tuning of each ML model. Light gradient boosting machine (LightGBM) with turbidity, humic acid (HA), pH, temperature and time as input performed best (R2 = 0.99, MSE = 0.0004) during training, whereas the random forest (RF) was effective and robust for test data (R2 = 0.98, MSE = 0.0056) with same inputs. The mean decrease impurity (MDI) and Shapley Additive exPlanation (SHAP) method indicated that the RF model made predictions based primarily on influent turbidity, which implied a correct “understanding” of the RF model. Finally, the model was deployed to the ECMCR to explore the regulation capability, and the HA removal and turbidity removal of the ECMCR increased by 23.68 % and 23.83 %, respectively. The results demonstrate that ML technology could assist in achieving the desired performance of drinking water treatment devices without manual involvement.

Oxygen vacancy-rich Ag/CuO nanoarray mesh fabricated by laser ablation for efficient bacterial inactivation

The contamination of drinking water by microbes is a critical health concern, underscoring the need for safe, reliable, and efficient methods to treat pathogenic microorganisms. While most sterilization materials are available in powder form, this presents safety risks and challenges in recycling. Herein, this study reports the preparation of an innovative copper oxide supported silver monolithic nanoarray mesh with abundant oxygen vacancies (Ag/CuO-VO) by laser ablation. The instantaneous high temperature caused by laser ablation preserves the material's original structure while generating oxygen vacancies on the CuO surface. The Ag/CuO-VO mesh demonstrated a remarkable ability to inactivate over 99% of Escherichia coli (E. Coli) within 20 min. The oxygen vacancies in the Ag/CuO-VO enhance interactions between oxygen species and the Ag/CuO-VO, leading to the accumulation of large amounts of reactive oxygen species (ROS). The generated ROS effectively disrupt both layers of the bacterial cell wall - the peptidoglycan and the phospholipid - as confirmed by Fourier Transform Infrared (FTIR) spectroscopy, culminating in cell death. This research presents a monolithic material capable of inactivating pathogenic microorganisms efficiently, offering a significant advancement in water sterilization technology.

Approaching easy water disinfection for all: Can in situ electrochlorination outperform conventional chlorination under realistic conditions?

Electrochlorination has gained research interest for its potential application as decentralized water treatment. A number of studies have displayed promising efficiency for water disinfection. However, a comprehensive comparison of in situ electrodisinfection to existing disinfection techniques, particularly under realistic water composition and flow rates, still needs additional research efforts. The aim of this study is to evaluate in situ electrochlorination while comparing the treatment with conventional chemical chlorination for point-of-entry decentralized disinfection at the household level. An electrochemical flow cell reactor was operated in a single pass mode considering water flow and water consumption for a household of four family members. Disinfection efficiency assessment of both electrochemical and chemical chlorination was conducted using bacterial and viral surrogates, E. coli and MS2 bacteriophage. Furthermore, a techno-economic analysis was conducted, using the levelized cost of water, to compare two electrochemical chlorination scenarios (i.e., electrical grid energy use, and solar panel powered system) and benchmarked against the baseline treatment of chemical chlorination. The findings revealed increased inactivation efficiency of in situ electrochlorination over conventional chlorination (p-value < 0.05). The synergetic impact of radicals and chlorine, and/or contribution of high chlorine concentration at acidic pH near anode surface were identified as key factors that could enhance disinfection performance of in situ electrochlorination. The techno-economic analysis demonstrated that electrochemical treatment, when operated using renewable energy sources, is not only a more environmentally sustainable approach, but also emerges as a more economically feasible solution for decentralized water treatment application. The results highlight that in situ electrochlorination is a more advanced alternative to decentralized water chlorination. However, further fundamental research on products and by-products formation under various water matrices is required.

Magnetically separable MnFeCoNiCu-based high entropy alloy nanoparticles for photocatalytic oxidation of antibiotic cocktails in different aqueous matrices

Destroying persistent organic pollutants via photocatalytic advanced oxidation processes is critical for sustainable water management. In spite of the tremendous progress in developing highly effective and durable photocatalysts in recent decades, inferior optical absorption and rapid charge recombination considerably restrict their application on a commercial scale. In order to address these issues, herein we have constructed MnFeCoNiCu-based high entropy alloy (HEA) nanoparticles (NPs), through a facile and straightforward procedure, and showcase its superiority over conventional photocatalysts in degrading some typical antibiotics (viz., sulfamethoxazole, SMX; ofloxacin, OFX; and ciprofloxacin, CFX). The equimolar HEA-NPs feature n-type semiconducting properties, improved light trapping ability, and reduced charge recombination. Consequently, a high degradation of 95 %, 94 %, and 89 % for SMX, OFX, and CFX, respectively, can be achieved in the presence of MnFeCoNiCu NPs under visible light illumination, without any serious risks of secondary contamination. In order to better evaluate the photocatalytic performance of MnFeCoNiCu NPs, particularly from a practical perspective, the removal of antibiotic pollutants from multicomponent systems is also investigated. The average treatment efficiency for a ternary mixture of SMX, OFX, and CFX in different aqueous matrices decreases in the order of deionized water (∼82 %) < tap water (∼86 %) < river water (∼78 %) < hospital wastewater (∼60 %) < domestic wastewater (∼57 %) < pharmaceutical industry wastewater (∼47 %). Further, the expended HEA-NPs can be conveniently recovered from the reaction system by applying an external magnetic field, allowing recurrent usage, without any substantial alteration in their microstructure and performance. These demonstrations of satisfactory photocatalytic activity under a diverse spread of realistic environmental conditions, excellent durability, and inexpensive retrieval endorse the application potential of MnFeCoNiCu NPs in decentralized water treatment systems.

Industry 4.0 as a strategy to contribute to the water supply universalization in developing countries

Access to safe water is still a challenge. Millions of people worldwide, mainly in rural and remote regions, still do not have access to safe drinking water. Point-of-use and decentralized water treatment systems have the potential to improve their livelihood, especially if these technologies are combined with the advantages brought by the Fourth Industrial Revolution. This paper presents and discusses opportunities for convergence between water treatment mainly using membrane separation processes and technologies related to Industry 4.0, focusing on a scenario of decentralized systems installed in developing countries. Emphasis is given to membrane-based applications due to their advantages of ease of operation, small area requirements, and reduced implementation time while maintaining a great capacity to produce high water quality regardless of raw water characteristics. Literature suggests that Industry 4.0 can be considered an ally to better support water management in remote and rural regions. Treatment units can now be integrated into digital cyber-physical systems to promote a greater comprehension of local necessities and provide transparent and effective communication, faster actions, or even remote and automatic operation, contributing to the capacitation of local operators and the performance and conservation of the infrastructure. It is also possible to monitor many parameters of water quality, ensuring process integrity and safe water. These advancements may result in affordable, adaptive, and resilient solutions, but it is necessary to consider the perspective of the Human Right to Water and Sanitation – unfortunately, not always present – and the difficulties inherent to developing countries.

Use of recycled aggregates as filter support and filter media for decentralized water filtration systems

Clean drinking water is crucial for maintaining public health and can be considered a fundamental right of people. Unfortunately, access to potable water is limited for residents of developing and underdeveloped countries, especially in rural communities. Conventional treatment systems for such regions are challenging in terms of installation, operation, and maintenance. An emerging problem of rapid urbanization and proliferating construction industry is huge quantities of Construction and Demolition (C & D) waste, which needs proper reuse and/or disposal. A simultaneous solution to these twin problems is the formulation of a decentralized water filtration system using C & D waste aggregates. In the current study, small-scale (5-lt capacity), decentralized water filtration systems were designed and tested for the treatment of surface water samples. Fresh aggregates were replaced by C & D waste aggregates progressively in the drainage media, support media, and filter media; resulting in a total of seven test filtration devices. The effectiveness of such filters was evaluated for treating river water samples. It was found that the filters prepared with C & D waste aggregates were successful in the removal of turbidity, total solids, and total dissolved solids (TDS). Removal efficiencies up to 98% for turbidity, 86% for total solids, and 61% for the TDS were observed for different combinations of fresh and recycled aggregates in these filters. The results also show that filters made with only recycled aggregates can also yield high levels of contaminant removal and cleaner water. Further, the color and odor of the raw water were also significantly improved. These results show that C & D waste can be successfully incorporated into decentralized water treatment systems and can result in high-quality water through low-cost and low-tech, easy-to-maintain/operate devices.

Decentralized approach toward organic pollutants removal using UV radiation in combination with H2O2-based electrochemical water technologies

The current literature lacks a comprehensive discussion on the trade-off between pollutant degradation/mineralization and treatment time costs in utilizing UV light in combination with H2O2-based electrochemical advanced oxidation processes (EAOPs). The present study sheds light on the benefits of using the photoelectro-Fenton (PEF) process with UVA or UVC for methylparaben (MetP) degradation in real drinking water. Although light boosts the photodegradation of refractory Fe(III) complexes and the photolysis of H2O2 (with UVC only), the energy-intensive nature of light-based treatments is acknowledged. To help tackle the high energy consumption issue, a novel approach was employed: partial application of UVA or UVC light after a predetermined electro-Fenton electrolysis time. The proposed treatment approach yielded satisfactory comparable results to those obtained from the application of PEF/UVA or PEF/UVC in terms of total organic carbon removal (ca. 100%), with notably lower energy consumption (ca. 50%). The study delves into the combined method's feasibility, analyzing pollutant degradation/mineralization process and overall energy consumption. The research identifies possible degradation routes based on intermediate detection and radical quenching experiments. Finally, toxicological assessments evaluate the toxicity levels of MetP and its intermediates. The findings of this study bring meaningful contributions to the fore and point to the highly promising potential of the proposed approach, in terms of sustainability and cost-effectiveness, when applied for decentralized water treatment.

Sustainable, decentralized water treatment system fabricated from domestic waste materials and ultrafast-reduced graphene oxide

The demand for fresh water will increase in the coming decades as the world population grows. While large-scale water purification plants will serve highly populated areas, the demand of fresh water will continue to grow even in remote and potentially under-developed locations. In this work, it has been shown that fresh water can be produced from seawater or polluted water using waste paper and direct solar exposure, without the need of electricity during water purification. The highly efficient solar evaporation system proposed here, which is based on graphene/cellulose aerogels, can be fabricated quickly without highly technical skills, requiring only a microwave oven, graphene oxide samples, and cellulose fibers obtained from packaging (i.e., waste paper and polyethylene foams). The produced aerogels show high photo-thermal conversion, excellent hydrophilicity and low thermal conductivity, properties that are conducive to evaporation rates as high as 1.83 kg m−2 h−1, photo-thermal efficiency of 92%, and stability for more than 40 operation cycles. Despite using waste materials, these performance metrics are superior to those reported for most materials to date, and are a consequence of the manufacturing process described here. Field tests confirmed that 1 m2 of the as-prepared aerogels can produce between 6.44 and 11.27 kg of fresh water from seawater or polluted water in a 12-hour period, which is the daily amount of drinking water required for three adults based on World Health Organization projections.

Recycled membrane for drinking water treatment with high iron and manganese concentrations

Membrane recycling by oxidative treatment is one alternative to minimize the impacts of the disposal of end-of-life (EoL) reverse osmosis (RO) membranes. In parallel, iron (Fe) and manganese (Mn) contamination in surface and groundwater is increasing. This study aims to develop recycled membranes that retain dissolved Fe and Mn from water for supply purposes. EoL RO membranes were recycled with sodium hypochlorite (NaClO, 10–12%) solution at exposure dose between 4000−80,000 ppm∙h to produce a recycled membrane with high flowrate and high Fe and Mn rejection. EoL RO treated by 40,000 ppm·h showed water permeability of 54.30 L∙h−1∙m−2∙bar−1 and Fe and Mn rejection of 99% and 65%, respectively. Potability for Mn (> 98%) was enhanced by integrating pre-oxidation stage with NaClO (5 mg∙L−1 of Cl- and pH 8) to the recycled membrane process. Recycled module performance was evaluated for water treatment from Paraopeba River on pilot scale, in continuous operation (51 h) and pressure of 1 bar. At pilot scale, recycled membrane obtained a water permeability of 40.33 L∙h−1∙m−2∙bar−1, like a moderately open ultrafiltration membrane. Fe and Mn removals were > 99% and > 90%, respectively, with high color and turbidity removal efficiency. Membrane recycling cost was predicted to be US$ 4.08/m², and the capital (CapEX) and operating (OpEX) expenditures for the single-household system was US$ 671.18 and US$ 22.52 to m3·day−1 of treated water. Therefore, the recycled membrane was shown to be efficient in removing dissolved Fe and Mn, and it is promising for decentralized water treatment.

Synergistic, adaptive, continuous-flow, and low-carbon solar evaporation and electrochemical treatment (SEET) system – a combined numerical and experimental study

A synergistic, adaptive, continuous-flow, and low-carbon solar evaporation and electrochemical treatment (SEET) system was proposed and researched for energy-efficient and sustainable decentralized water treatment. The hybrid system integrated anodic oxidation with solar evaporation to enhance organic degradation and optimize mass transport through the photo-thermal effect. A novel four-step numerical simulation method was proposed to design the system and examine the water evaporation process and mass transport of salts and organics. A case study was implemented, revealing that system parameters related to evaporation and organics degradation exhibited strong interdependence. The relationships between these parameters were well-established, and adaptive water flow rate ranges were also identified to prevent salt accumulation while ensuring efficient organic degradation. The adaptability demonstrated the system's potential for use in varying influent scenarios. A prototype of the system was constructed, and the experimental data matched well with the simulation results. In the experiments, the local water temperature reached 45–50 °C in the continuous-flow mode under one sun condition, resulting in a 2–5 times reduction in outlet organic concentrations compared to traditional electrochemical systems. Energy analysis confirmed that the system primarily relied on clean and sustainable solar energy, maintaining a low carbon footprint. In conclusion, this innovative approach offers significant potential for addressing the clean drinking water crisis and enhancing pollutant removal in future decentralized water treatment systems.

Effect of a Permanganate-Bearing Reactive Oxidant on Flocs in Electrocoagulation: Transformations and Interfacial Interactions.

The electrocoagulation/ultrafiltration (ECUF) process is expected to address the issues of current wastewater increments and complex water reuse. However, the underlying mechanism associated with flocs remains unclear in the ECUF system, especially in the upgraded permanganate-bearing ECUF (PECUF) system. Herein, flocs and their formation, response to organic matter (OM), and interfacial features in the PECUF process were systematically explored. Results demonstrated that permanganate contributed to the rapid start-up of the coagulation process by forming MnO2 and blocking the ligand-metal charge transfer process between adsorbed Fe(II) and solid-phase Fe(III). The response of flocs to natural OM (NOM) exhibited obvious time- and particle size-dependent characteristics. Based on this, the optimal NOM adsorption window was found to be in the interval of 5-20 min, whereas the optimal NOM removal window was located at the 20-30 min interval. Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek theory revealed the underlying principle of the PECUF module for optimizing UF performance. On the one hand, it reduced the inherent resistance of the cake layer by modifying the colloidal solution, which guaranteed a small drop (15%) in initial flux. On the other hand, it enhanced the repulsive force among suspended particles to achieve a long-term antifouling effect. This study may provide insights into the selection and performance control of on-demand assembly modules in decentralized water treatment systems.

Elution and disinfection of silver and zinc nanoparticles in co-fired ceramic water filters

Ceramic water filters (CWFs) are decentralized water treatment technologies commonly used in resource-restricted geographies. Inclusion of silver nanoparticles (AgNP) assists with disinfection but can substantially increase costs. This research investigates AgNP supplementation with zinc oxide (ZnO) as a low-cost bactericide alternative. CWF disks were impregnated with varying AgNP and/or ZnO concentrations and challenged against Escherichia coli. Effluent bacteria were enumerated and monitored over 72 h while eluted metal concentrations were measured and scaled according to surface area to establish ‘pot-equivalent’ estimates (0–50 ppb Ag and 0–1200 ppb Zn). Ag addition correlated to subsequent measured release values, though Zn impregnation did not. Background Zn was thus evidently present. Meanwhile, the eluted metal concentration related to disinfection: a CWF with a pot-equivalent elution estimate of 2 ppb Ag and 156 ppb Zn achieved a Log Removal Value (LRV) of 2.0 after 60 min of filtration and 1.9 after 24 h of storage while a CWF with a pot-equivalent elution estimate of 20 ppb Ag and 376 ppb Zn achieved LRVs of 3.1 and 4.5 after the same filtration and storage times, respectively. Clay elemental composition may therefore impact filter performance more than previously considered This trend was further confirmed by batch experiments with Ag and Zn in concentrations of 0–20 ppb Ag and 0–800 ppb Zn, respectively: bacterial regrowth was only observed when Ag and Zn were each below 5 ppb and 160 ppb while 1 ppb Ag and 800 ppb Zn maintained complete disinfection for 72 h. Increased Zn concentrations thus reduced Ag required to maintain disinfection over time. Overall, it is recommended to include Zn with Ag for CWF to improve short-term and long-term disinfection efficacy and associated water safety.

Arsenic Removal by Adsorbents from Water for Small Communities’ Decentralized Systems: Performance, Characterization, and Effective Parameters

Arsenic (As), a poisonous and carcinogenic heavy metal, affects human health and the environment. Numerous technologies can remove As from drinking water. Adsorption is the most appealing option for decentralized water treatment systems (DWTS) for small communities and household applications because it is reliable, affordable, and environmentally acceptable. Sustainable low-cost adsorbents make adsorption more appealing for DWTS to address some of the small communities’ water-related issues. This review contains in-depth information on the classification and toxicity of As species and different treatment options, including ion exchange, membrane technologies, coagulation-flocculation, oxidation, and adsorption, and their effectiveness under various process parameters. Specifically, different kinetic and isotherm models were compared for As adsorption. The characterization techniques that determine various adsorbents’ chemical and physical characteristics were investigated. This review discusses the parameters that impact adsorption, such as solution pH, temperature, initial As concentration, adsorbent dosage, and contact time. Finally, low-cost adsorbents application for the removal of As was discussed. Adsorption was found to be a suitable, cost-effective, and reliable technology for DWTS for small and isolated communities. New locally developed and low-cost adsorbents are promising and could support sustainable adsorption applications.

The importance of user acceptance, support, and behaviour change for the implementation of decentralized water technologies

Decentralized water treatment technologies could help in addressing global key water issues. Their successful implementation, however, depends on users’ positive valuation and, depending on the technology, ‘passive’ use (rooted in acceptance), ‘engaged’ use (rooted in support) or ‘active’ use (rooted in behaviour change). Although users’ valuation of a technology is contingent on its characteristics, positive valuation and use usually also require supporting promotion activities. Here we review the literature on psychological determinants of use as well as change techniques to promote use, and propose a user-focused theory of change to guide promotions. Our review highlights a lack of (conclusive) evidence on both psychological determinants and effective change techniques. We call on environmental and health psychologists to intensify their research on ‘passive’, ‘engaged’ and ‘active’ use of decentralized water treatment technologies and encourage engineers, practitioners and psychologists to intensify collaboration to ensure that technologies, implementation and promotions are optimally integrated. Decentralized water treatment technologies could help in addressing global key water issues. This Perspective reviews the literature on the psychological determinants of acceptance, support and behaviour change related to decentralized water treatment technologies and proposes a user-focused theory of change to guide the promotion of these technologies.