A Review of Low-Cost Point-of-Use Water Treatment Solutions Addressing Water Access and Quality in Resource-Limited Settings

Abstract

Access to safe, clean drinking water is a critical challenge across many resource-constrained settings, especially in developing economies. Large-scale water treatment technologies are often available in urban areas, whereas such centralized systems are unavailable in rural and remote areas due to high infrastructure costs, rugged terrains, and maintenance challenges. To address this challenge, point-of-use (PoU) water treatment systems can fill this critical gap. This study critically evaluates the role low-cost PoU water treatment solutions play as a promising alternative to address water access and quality aspects in remote rural areas. The study explores the present state of global water sources, the challenges of water scarcity and pollution, and the limitations of existing large-scale treatment technologies. It highlights the motivation behind PoU systems and provides an in-depth analysis of various low-cost technologies, including operational principles, performance efficiency, and economic viability. Embedded in this study is a concise evaluation of the sustainability of these solutions in addressing water access and quality challenges in resource-limited regions. Finally, the study proposes solutions and perspectives on improving PoU systems and scale-up of the systems for large-scale applications to facilitate increased access to clean and safe water.

1. Introduction

The provision of safe drinking water is a fundamental human right, yet more than two billion people worldwide still lack reliable access to it, particularly in low-income regions often with limited resources and infrastructure [1]. Water is not only essential for human health and survival but also plays a crucial role in economic development and poverty reduction. Sustainable Development Goal (SDG) 6 underscores the need for access to clean water and sanitation for all. However, the quality and availability of water are increasingly compromised by pollution, overuse, and changing climatic patterns [2]. In regions with scarce resources, the challenges of providing clean water are further aggravated by financial constraints, poor infrastructure, and geographical isolation [3]. These challenges, alongside the ever-growing demand for water, have led to a global water crisis, placing millions at risk of consuming unsafe water. Water contamination is aggravated by discharge of industrial effluent, agricultural runoff, and poor sanitation practices. These contaminate the water sources with harmful pathogens, chemicals, and heavy metals [4]. This widespread contamination of water supplies is linked to serious health risks, including waterborne diseases such as diarrhea, cholera, typhoid, and dysentery, leading to high morbidity and mortality, particularly in children under five years of age [5].

To address water quality challenges, large-scale centralized water treatment plants are widely used in urban areas. These systems have proven effective at delivering clean water to populations with robust infrastructure and financial resources [6]. However, such systems are often impractical in remote or rural regions, which constitute resource-limited settings. These areas have limited resources and therefore cannot afford the high costs of installation, operation, and maintenance, skilled plant operators, and reliable energy supplies. Additionally, the infrastructure required to distribute treated water from central plants to individual households is often lacking, leaving vulnerable populations dependent on untreated or contaminated water sources [7].

To address these limitations, point-of-use (PoU) water treatment technologies have gained considerable attention as a potential solution for improving local water quality at the household or community level [8,9]. Unlike large-scale systems, PoU technologies focus on treating water immediately before consumption, ensuring that contaminants are removed just before use. These systems are useful in remote areas where centralized treatment facilities are limited or non-existent. PoU systems include a range of low-cost technologies, such as ceramic filters, biosand filters, solar disinfection (SODIS), and chlorine tablets, all of which aim to provide safe drinking water with minimal infrastructure requirements [10]. PoU systems are primarily advantageous due to their affordability, simplicity, and adaptability to various environmental and economic settings. Most of these technologies are designed to be user-friendly, requiring little to no technical expertise to operate and maintain [11,12]. They are also typically low maintenance, often requiring only periodic cleaning or simple filter replacements. Moreover, PoU systems can be rapidly deployed in emergency situations, such as during natural disasters or disease outbreaks, where immediate access to clean water is critical [13]. Despite their promise, however, the effectiveness and sustainability of low-cost PoU technologies are still a subject of ongoing research and debate. The consistent removal of contaminants and potential environmental impacts are the key areas of concern regarding these systems [14]. A few studies have assessed the cost and environmental sustainability of four PoU water disinfection technologies through techno-economic and life cycle analyses. One such study reported that chlorination and silver-nanoparticle ceramic filters were the most affordable and sustainable options for rural and low-income settings, while UV-based systems were costly and energy-intensive [14]. Further research is necessary to determine possible ways to enhance the performance of PoU technologies in field applications [15].

Although several studies have demonstrated the performance of PoU technologies, comprehensive reviews of the various low-cost PoU water purification systems are lacking. The present study endeavored to fill this gap. Firstly, the study provides an overview of global water sources, scarcity, and pollution issues. Then it critically evaluates the current large-scale treatment technologies and their limitations. It thereafter delves into the different types of low-cost PoU technologies, examining their principles of operation, performance efficiency, economic feasibility, and sustainability. Finally, the study proposes new approaches and considers future perspectives on improving PoU systems and scaling them up to significantly expand access to potable water. As such, the application of PoU makes a crucial contribution to the attainment of SDG 6 (clean water and sanitation) and SDG 3 (good health and wellbeing), among other global development goals. Relevant data for the past 10 years (2015 to 2025) on Scopus search engines were obtained for this review. A comprehensive search was conducted to assess relevant information for this review. During the search, appropriate keywords and phrases such as “point of use”, “household water treatment”, “adsorption”, “water filtration”, “limited water resource”, and “water disinfection” were used. The study did not consider sources of water (surface water, groundwater, rainwater, etc.) in the inclusion criteria. The selected PoU systems are discussed in Section 4.

2. Water Sources, Scarcity, and Pollution

2.1. Global Water Sources

Water, the most abundant resource on Earth, is characterized by a highly unequal distribution. Freshwater, which is essential for drinking, agriculture, and industry, accounts for only about 3% of the Earth’s total water, and the remaining amount is mainly saline [16]. Groundwater constitutes 30.1% of the total available freshwater globally [17] and is mainly used in areas where surface water is either scarce or contaminated. High dependence on groundwater has resulted in challenges regarding the over-extraction and depletion of these vital resources, particularly in regions affected by recurrent droughts [18,19]. Surface water accounts for 10% of the available freshwater worldwide and is crucial for supporting agriculture, urban water supply, and industrial activities [18]. However, in most developing economies, surface water sources are often affected by pollution and overuse, further straining their sustainability [20]. Atmospheric water constitutes only 0.04% of the Earth’s total water and plays an essential role in the hydrological cycle by replenishing surface and groundwater through precipitation [21]. However, arid and semi-arid lands constitute nearly 41% of the world’s total land size and face variable rainfall patterns, which often lead to prolonged droughts and water scarcity [22]. Therefore, developing countries in sub-Saharan Africa and parts of Asia face significant challenges in managing their water resources, exacerbated by climate change and increasing population. The uneven distribution of freshwater resources, coupled with growing demand, highlights the urgent need for sustainable water management practices to ensure reliable access to clean water.

2.2. Water Scarcity

Water scarcity is a critical issue in many developing countries. In many parts of the world, many people still lack clean drinking water, particularly in arid and semi-arid regions, with limited water sources and inadequate infrastructure [23], leading to physical and economic water scarcity [24]. Emile and co-workers reported physical and economic water scarcity in developing regions such as sub-Saharan Africa, South Asia, and parts of the Middle East [25]. This is attributed to erratic rainfall patterns, and prolonged droughts, exacerbated by climate change, have strained already limited water resources, making physical scarcity a persistent issue. Economic water scarcity is evident in rural and underserved communities, where water infrastructure is either outdated or nonexistent, leading to unreliable access to clean water. In areas that lack surface water, over-reliance on groundwater has led to its depletion in many areas, adding further stress to her water systems [23,26]. Addressing water affordability in developing countries is essential to combat the broader issue of water scarcity. This requires a combination of improved water management practices, sustainable infrastructure development, and climate adaptation strategies to enable provision of equitable and reliable water access.

2.3. Water Pollution

Water pollution remains a critical challenge in many developing nations due to factors such as rapid urbanization, industrialization, and insufficient waste management systems. In many developing countries in sub-Saharan Africa and South-East Asia, poor infrastructure and weak regulatory enforcement have led to widespread pollution of water bodies, severely impacting public health and the environment [27,28]. Microbial contamination from untreated sewage is a major concern in developing nations, contributing to waterborne diseases like cholera, diarrhea, and typhoid [1,29]. Agricultural runoff, laden with fertilizers and pesticides, results in eutrophication, which depletes oxygen in water bodies and damages aquatic ecosystems [30]. Additionally, industrial pollutants such as heavy metals and toxic chemicals are often discharged into rivers and lakes without proper treatment, further degrading water quality [31]. Improper storage practices further exacerbate water contamination. Clean water, after treatment, is often re-contaminated during storage in open or unclean containers, exposing it to pathogens and environmental contaminants [32]. Poor hygiene during water handling and biofilm formation inside storage containers also contribute to this problem [33].

PoU water treatment systems offer a practical solution to addressing water contamination, especially in resource-limited settings. These systems treat water at the point of use, making them an effective way to remove pollutants from water already compromised by storage issues or environmental exposure. The flexibility of PoU systems allows them to address specific contaminants depending on the technology used, including microbial pathogens, chemical pollutants, and heavy metals. PoU systems are cost-effective, user-friendly, and scalable, making them suitable for developing countries that lack centralized water treatment infrastructure. Their effectiveness in improving water quality at the household level, even in areas with significant pollution, makes them a vital part of the solution to water contamination in these regions.

3. Water Treatment Technologies

3.1. Existing Large-Scale Technologies and Their Limitations

Large-scale water treatment technologies are essential for providing safe drinking water, especially in urban areas where the population density is high, and distribution networks are well established. These systems are effective but face several limitations, particularly in resource-limited settings. The centralized water treatment system involves processes such as screening, coagulation and flocculation, sedimentation/clarification, advanced treatment (reverse osmosis, ultrafiltration, adsorption), disinfection, storage, and distribution. The limitations of large-scale water treatment technologies are presented in

Table 1. Key unit operations in centralized water treatment systems and limitations.

Technology	Mode of Operation	Limitations	References
Coagulation, Flocculation, and Sedimentation	Coagulants such as aluminum sulfate are added to water to aggregate particles into flocs, which then settle down, thus cleaning the water	Chemical dependency Residual chemicals (e.g., aluminum) Generate waste by-products in the process Less efficient at low temperatures	[34,35]
Reverse Osmosis (RO)	This technique uses a semi-permeable membrane to remove dissolved salts, heavy metals, and other contaminants by applying pressure.	High energy demand Membrane fouling Produces brine waste, that requires intensive pretreatment Expensive maintenance and replacement of membranes	[36,37,38,39]
Ultrafiltration (UF)	A membrane-based process that filters out particulates, bacteria, and viruses using pressure.	High initial setup costs Ineffective for dissolved chemicals Membrane fouling Poor decontamination performance for potentially toxic elements Susceptible to bacterial growth and subsequent contamination, leading to water quality issues if not properly maintained	[40]
Disinfection by UV, Ozonation, and Chlorination	Exposes water to ultraviolet light, chlorine, or ozone, which kills or inactivates pathogens.	Requires reliable power supply Human error in disinfectant dosing Formation of disinfection by-products (DBPs) which are carcinogenic to humans. No residual disinfection, so recontamination can occur.	[41,42]

.

3.2. The Motivation for Point-of-Use Systems

Point-of-use (PoU) water treatment systems are becoming increasingly popular, particularly in underdeveloped countries where access to clean and safe water remains a significant challenge. These systems treat water at the point where it is consumed, such as in homes or small communities, rather than through large, centralized water treatment plants. Several factors motivate the adoption of PoU systems, and they are discussed below.

(a)

Addressing Limited Access to Centralized Water Treatment

In many regions, particularly rural and peri-urban areas of developing countries, centralized water treatment plants are often absent or unreliable due to infrastructure challenges, high costs, and limited government capacity. PoU systems provide a viable solution by allowing households to treat their own water directly from local sources such as rivers, lakes, or wells [43]. This helps ensure that even in areas far from urban centers, people can have access to treated drinking water.

(b)

Affordability and Low Infrastructure Requirements

Unlike large-scale water treatment facilities, PoU systems typically require minimal infrastructure and can be implemented at a lower cost. Technologies such as ceramic filters, solar disinfection (SODIS), and biosand filters are relatively affordable and require little maintenance, making them accessible to low-income households [44]. This cost-effectiveness is crucial in resource-limited settings, where budgets for water infrastructure development are often constrained.

(c)

Flexibility and Adaptability

PoU systems offer flexibility in their application, allowing them to fit specific needs and available resources of a community. For example, regions with high solar exposure may benefit from solar-powered water disinfection systems, while areas with abundant clay materials may prefer ceramic filters. This adaptability ensures that communities can select the most appropriate technology based on their local environmental and socio-economic conditions [45].

(d)

Reduction of Waterborne Diseases

In regions with poor sanitation and water quality, the prevalence of waterborne diseases like cholera, diarrhea, and typhoid remains high. PoU systems effectively reduce microbial contaminants at the point of consumption, helping to lower the incidence of these diseases. Studies have shown that PoU technologies, such as chlorine dispensers and ceramic filters, can reduce diarrheal diseases by up to 35% in low-income areas [46].

(e)

Minimizing Water Contamination during Storage

One of the key challenges in water distribution, particularly in developing countries, is contamination during storage and handling. Even if water is initially treated, it can become contaminated by pathogens or chemicals during transportation or in storage containers [47]. PoU systems help mitigate this by allowing water to be treated just before consumption, ensuring its quality is maintained until it reaches the end user.

(f)

Sustainability and Environmentally Friendly Solutions

Many PoU systems, such as biosand filters and solar disinfection, rely on natural processes and require little to no external energy, making them environmentally friendly and sustainable. These technologies can be used for extended periods with minimal maintenance or energy costs, unlike large-scale water treatment plants, which often rely on electricity and chemicals [48]. This sustainability aspect makes PoU systems particularly appealing for communities seeking long-term, eco-friendly solutions to their water challenges.

(g)

Empowering Local Communities

Implementing PoU systems empowers local communities to take ownership of their water supply and decrease their reliance on centralized authorities. This can be particularly important in areas where government resources are stretched thin or where centralized systems are prone to inefficiencies and failures. By managing their own water treatment solutions, communities can ensure that their specific needs are met, and that water quality is maintained at a household level [49,50].

4. Low-Cost Point-of-Use Water Treatment Systems

4.1. Types of PoU Technologies, Principle of Operation, and Performance Efficiency

Point-of-use technologies treat water at the exact place where it is used or consumed. On-site drinking water treatment systems are installed near water outlets, showers, and dispensers so that water can be purified just before being used for cooking, bathing, or drinking. The systems are designed for easy operation and require minimal maintenance. Key accessible technologies include filtration, disinfection, flocculation, coagulation, reverse osmosis, and ion exchange units; these are discussed further. Common PoU systems and their applications are illustrated in Figure 1.

4.1.1. Filtration Systems

Filtration is a physical process that removes suspended solids, colloids, and pathogens by size exclusion, whereby particles larger than the pore size of the filter are retained within the system while the fluid passes through. Filtration systems can function in two different modes of operation: dead-end filtration and cross-flow filtration.

Dead-end filtration is the most common mode used in gravity-driven membrane (GDM) filters. In this process, the feed stream flows perpendicularly to the membrane surface, passing through it as filtrate/permeate (Figure 2). Particles and aggregates that are blocked by the membrane accumulate to form a filter cake. Dead-end filtration is widely used in point-of-use water treatment systems, including household water purifiers and community-scale ultrafiltration units, due to its simplicity, low energy requirement, and effectiveness in removing pathogens.

In cross-flow filtration, the feed solution flows parallel to the membrane surface (Figure 3). This allows a portion of it to pass through as purified water (permeate) while the remaining water carries away retained particles in a separate stream (concentrate). This continuous flow reduces the buildup of contaminants on the membrane surface, thereby enhancing long-term performance.

There are several PoU filtration technologies, which include the following:

(a)

Ceramic filters and sediment cartridges

Ceramic filtration is one of the water filtration methods that utilizes a porous ceramic material to trap and remove contaminants from water. The ceramic filters have tiny pores that trap and remove bacteria, sediment, and other microorganisms from water. Water passes through the ceramic filter by gravity. Similarly, a sediment filter is another form of physical filtration that removes suspended solids from water, such as insoluble impurities, thereby reducing water turbidity. Ceramic pot filters produced from locally available materials have been used to reduce pathogenic organisms such as E. coli from water. The study concluded that high-flow ceramic pot filters exhibit high filtration rates and significant log reduction values (LRV) for E. coli [51]. Ceramic disc filters coated with nano-TiO₂ showed effectiveness in the removal of E. coli from water [52]. Meanwhile, biochar-clay composite ceramic filter (BCF), fabricated from a mixture of clay and sawdust, have demonstrated effective removal of total hardness (42.5%), total dissolved solids (45.8%), and turbidity (67%) compared to clay-made ceramic filter (14.8, 17.6, and 56%), respectively. Ceramic filters made from recycled paper fiber (green fiber) and those made from combustible material (starch and rice husk) depicted higher water flow rates than the flow rates of regular ceramic filters currently in use [53]. Figure 4 illustrates ceramic and sediment cartridge filters.

Bacterial log reduction values (LRVs) are used to quantify bacterial removal efficiency, to determine the performance of ceramic filters. LRV is calculated using the equation below:

$$LRV={log}_{10}{(C}_{in})-{log}_{10}{(C}_{eff})$$

(1)

where $C_{in}$ and $C_{eff}$ (CFU/mL) represent the E. coli concentrations in the untreated and treated water, respectively.

(b)

Biosand Filters

A biosand filter (BSF) is a modern take on traditional slow sand filters, designed to remove pathogens and suspended solids from water through biological and physical processes that take place in a sand column covered with a biofilm. Biosand filters improved by the addition of iron-sand mixture have been found to have the highest removal efficiency for contaminants. Household slow sand filters present average turbidity removal efficiencies of 75% or greater, often reaching removals above 90% while bacteria removal is an average LRV between 1 and 2 [11,54,55]. Although the BSF has been widely used and studied, its effectiveness can be improved by, (i) integration of nanotechnology such as incorporating silver nanoparticles into the sand layer to enhance the disinfection capabilities; and (ii) the use of alternative porous materials instead of sand that have large surface area to volume ration resulting in improved pollutant removal and reduced filter clogging.

(c)

Gravity-based membrane systems

Gravity-based membrane filtration is a decentralized water treatment technology designed to harness the force of gravity to filter water through a filter membrane. The central component of the GDM filter is a membrane with a pore size of 20–40 nm. Water is filtered through the membrane at a very low pressure (10–150 mbar) and remarkably, this system does not require backflushing, cleaning, or electricity to allow sustainable operation without clogging [56]. Low-pressure membrane systems like microfiltration and ultrafiltration have been employed as PoU systems in areas that lack electricity or where electricity costs are prohibitive (Figure 5). For such areas, gravity-driven membrane systems are a suitable alternative for sustainable water purification [57,58]. The effectiveness of gravity-driven membrane (GDM) filters is typically evaluated based on flux and removal efficiency. The key formula used for flux calculation is:

$$J={\displaystyle \frac{V}{A.t}}$$

(2)

where J represents the permeate rate (L m⁻² h⁻¹), V is the permeate volume (L), A is the filtration area (m²), and t is the duration of permeate collection (h).

Permeability is often used to compare membrane performance under different transmembrane pressure (TMP). The permeate flow through the membranes can be described by Darcy’s law, which explains that the water flow (flux) through the membrane is directly proportional to the applied pressure.

$$J=k\Delta P$$

(3)

where k is the permeability constant containing structural factors such as porosity and viscosity, and ΔP is the applied transmembrane pressure (TMP).

For gravity-driven systems, TMP is determined by hydrostatic pressure:

$$\Delta P=\rho gh$$

(4)

where ρ is water density (kg/m³;), $g$ is gravitational acceleration (m/s²), and h is water column height (m).

Contaminant removal efficiency is calculated using Equation (5)

$$\left(\eta \right)(\%)={\displaystyle \frac{{(C}_0-C_t)}{C_0}}\times 100$$

(5)

where $C_0$ and $C_t$ denote the initial and final concentration of the contaminant (mg L⁻¹).

(d)

Reverse Osmosis

A point-of-use reverse osmosis (RO) system is a water filtration unit that is connected to a single fixture (such as under the kitchen sink) and uses the process of reverse osmosis to remove contaminants from the water supplied to that fixture. The system employs reverse osmosis where pressure forces water through a semi-permeable membrane, resulting in a stream of treated water, called permeate, and a stream of rejected water called concentrate or brine. Moreira and co-workers studied the use of recycled RO membranes as the alternative for groundwater treatment at the POU [60] and reported that after the membranes were cleaned by chemical oxidation (NaOCl), permeability increased from 4.5 to 50.4 L.m⁻².h⁻¹.bar⁻¹ and salinity rejection decreased from 99.4 to 11.6%. The performance of a reverse osmosis (RO) membrane is evaluated using several key parameters, including flux, salt rejection, and recovery rate. The flux or permeation rate of the membrane can be determined using Equation (2). Salt rejection indicates how effectively the membrane removes dissolved salts as shown in Equation (6).

$$SR={\displaystyle \frac{(C_f-C_p)}{C_f}}\times 100\%$$

(6)

where SR represents the salt rejection (%), $C_f$ is the feed water concentration (ppm or mg/L), and $C_p$ is the permeate concentration (ppm or mg/L)

The recovery rate measures the percentage of feed water that has been converted into permeate and is given by Equation (7).

$$RR={\displaystyle \frac{V_P}{V_f}}\times 100\%$$

(7)

where RR denotes the recovery rate (%), $V_P$ represents the volume of permeate (L), and $V_f$ represents the volume of feed water (L).

4.1.2. Adsorption Systems

Adsorption is one of the methods that can be used to remove a wide range of dissolved pollutants, such as toxic metal ions, pesticides, disinfection by-products, and industrial solvents from water. The contaminants, such as dissolved organic and inorganic substances, accumulate on the surface of a solid (adsorbent), forming a molecular or atomic film (adsorbate). The adsorption can either be physical or chemical adsorption, also known as physisorption and chemisorption, depending on the forces of attraction between the adsorbent and the adsorbate. Adsorbents such as biosorbents [61], activated carbon and biochar [62,63], clays and minerals [64], polymers, nanoparticles, and composites [65] with high adsorption uptake capacity have been successfully employed to remove hazardous pollutants from wastewater. Low-cost adsorbents such as rice husk, ash, and activated carbon, and fruit peels such as banana peels, lemon peels, and pomegranate peels, have shown ability to capture new pollutants such as pharmaceuticals and personal care products (PPCPs), pesticides, dyes, and heavy metals [66]. The adsorption capacity ($q_e$) on the adsorbent can be calculated as,

$$q_e={\displaystyle \frac{{(C}_0-C_e)V}{m}}$$

(8)

where V is the solution volume (L), $C_0$ and $C_e$ represent initial and equilibrium concentration of the adsorbate (mg L⁻¹), and m is the adsorbent mass (g).

4.1.3. Disinfection Systems

Disinfection is the process of inactivation, elimination, or killing of pathogenic microorganisms in water to make it safe for human consumption. Processes of water disinfection include chemical disinfection and solar disinfection by UV and are discussed further.

(a)

Chemical disinfection

Chemical disinfection is the process of eliminating pathogens such as viruses and parasites in water to make it portable. The process involves adding a chemical to water to react with organic matter and harmful microorganisms. Chemicals that are mostly used for chemical disinfection are chlorine, chlorine dioxide, chloramines, and ozone. Chlorination of water is achieved at the household level using chlorine-releasing tablets such as Waterguard and Aquatabs tablets. These tablets release free chlorine in water, hence destroying bacteria and viruses. A key benefit of free chlorine is that it disinfects the water and maintains chlorine residuals that will remain in the water as it travels through the distribution system. Ozone disinfection, on the other hand, occurs by damaging the cell membrane and protoplasm of microorganisms, which impedes cell re-activation in bacteria, coliform, viruses, and protozoa. Ozone is best used as a primary disinfectant prior to chlorination [67].

(b)

Solar disinfection

Solar disinfection (SoDis) is a low-cost and efficacious disinfection technology that involves exposure of water to UV radiation and thermal heating from sunlight to inactivate microbes in contaminated water. The procedure typically entails the containment of water within polyethylene terephthalate (PET) bottles and exposure to sunlight for 6–48 h. Solar disinfection can be enhanced using visible light active photocatalysts to enhance the disinfection efficiency [68]. Numerous studies have proven the effectiveness of SoDiS in improving water quality. SoDiS application shows potential for the remediation of contaminants of emerging concern (CECs) such as pharmaceutically active compounds, personal care products, and pesticides in groundwater matrices, with removal efficiencies higher than 90% [15]. The study also confirmed that the addition of TiO₂ as a photocatalyst significantly enhances the performance of SoDis by up to three orders of magnitude because of increased adsorption and photocatalytic degradation.

4.1.4. Hybrid Water Treatment Systems

Hybrid water treatment involves the combination of two or more water treatment systems, for instance, pairing physical filtration methods, such as ceramic filters, with chemical disinfection like chlorination or UV treatment to ensure microbial safety while maintaining overall system efficiency. Electrocoagulation systems have been used in tandem with UV, O₃, and H₂O₂ to remove various organic and inorganic pollutants and to ensure that the effluent is of high quality prior to discharge into the aquatic environment. By combining electrochemical and advanced oxidation technologies, a hybrid system has been developed. Hybrid systems such as ozone-assisted electrocoagulation, for instance, peroxi-electrocoagulation photo-electrocoagulation, and ozone-photo-Fenton, were applied to improve the quality of wastewater [69]. Figure 6 depicts hybrid water treatment systems and the advantages of their use, and

Table 2. Comparison of the point of use of water treatment technologies.

POU Technology	Mechanism	Strengths	Limitations	Example Applications	References
Filtration	Physical removal of particles and microbes using barriers like ceramic filters	Effective at removing sediments, microbes, and some pollutants.	Limited effectiveness for dissolved contaminants (such as chemicals).	Household filters, portable units.	[53,70]
Disinfection	Inactivates or kills pathogens using chemicals (e.g., chlorine) or physical methods solar disinfection	Very effective post-treatment against bacteria and viruses.	Ineffective for removing physical particles or some chemicals.	Direct exposure to sunlight, UV lamps, chlorination kits.	[41,42]
Adsorption	Uses adsorbents such as activated carbon to trap and remove contaminants.	Excellent for removal of organic chemicals, odors, and tastes. Flexibility in terms of pollutant removal in the aqueous solution. Regenerative ability	Limited for microbes and heavy sediments.	Charcoal filters, advanced units.	[71,72]
Reverse osmosis	Uses pressure to force water through a semi-permeable membrane to remove dissolved salts, heavy metals, and contaminants.	Efficient in removal of a wide range of contaminants, including salts and pathogens.	Too much wastage of water, and requires frequent maintenance	Under-sink and portable RO units	[60]
Hybrid Systems	Combines multiple methods (for example filtration + UV or adsorption + disinfection).	Comprehensive treatment and removes multiple contaminants at once.	More complex and costly than single-method systems.	Advanced household and community systems.	[69,73]

provides a summary of PoU systems, mechanisms of operation, strengths, and limitations.

4.2. Economic Viability and Sustainability of the Systems

In low-income nations, PoU water treatment methods serve as a practical solution in areas lacking piped water networks or where existing water treatment and delivery systems are inadequate [74,75]. Cost-effective inorganic substances, such as mineral-based or silicate waste materials, show potential as suitable alternatives in producing affordable ceramic membranes, thus notably lowering material expenses. Compared to centralized water treatment setups, ceramic pot filters have been proven to be more economical and environmentally friendly [76].

Disinfection solutions or tablets that release active agents represent one of the most efficient and low-cost mobile options for water purification [77]. Chlorination delivers a lasting disinfectant barrier, crucial for preserving water safety during household storage, where recontamination risks exist. A key issue highlighted in multiple studies is the formation of various disinfection by-products (DBPs) during chlorination, which may pose health hazards. Despite chlorine’s affordability, it requires constant replenishment, leading to recurring household expenses. Moreover, user preferences influence chlorination adoption, as some individuals may favor more convenient methods that avoid frequent purchases [78].

Biochar, made from pyrolysis of agricultural and forest residues, is economically viable as waste biomass is converted into carbon-rich filtration media with a potential for water decontamination [79]. The use of biochar economically at scale requires that conversion systems such as gasifiers are located near the contaminated water sources to reduce transportation costs. Additionally, its low cost, high adsorption capacity, environmental benefits, and ability to be regenerated and reused make it sustainable and potentially suitable for continuous large-scale water treatment.

Gravity-driven filtration avoids the need for pumps or chemical additives, prolongs membrane lifespan, and minimizes energy consumption for filtration, ensuring continued operation during periods of limited resources [80]. Implementing gravity-based filtration at centralized plants is both technically and economically viable under multiple conditions, dependent on energy pricing, stable flow rates, and membrane durability. In such settings, traditional UF is replaced with gravity filtration, thereby boosting the reliability of centralized drinking water systems.

Adsorption is widely regarded as one of the most effective pollutant removal techniques for wastewater due to its adaptable nature, easy system design, reuse of materials, regeneration potential, low expense, and environmentally friendly attributes, making it both well-researched and extensively implemented [81]. These adsorbents can also be derived from eco-friendly sources, offering additional sustainability advantages.

Table 3. Performance efficiencies of different point-of-use water treatment systems.

PoU System	Feed/Process Conditions	Performance (LRV or % Removal Efficiency)	Reference
Flocculation Disinfection by PUR sachets	10 L water treated with 1 PUR sachet; mixed for 5 min; allowed to settle; filtered through cloth; left to stand for 20 min for disinfection	>5 LRV for virus; 4 LRV for Cryptosporidium and 3.6 LRV for Giardia. >99% arsenic removal and >8.2 LRV of E. coli.	[54]
Gravity-based membrane	-	E. coli (>7 LRV). Hollow fiber filter showed Cryptosporidium oocysts (>3.9 LRV) removal Ceramic filter showed Bacteria removal of (>4 LRV)	[54]
Biosand Filters	0.95 m tall biosand filter; media: 5 cm rocks, 5 cm gravel, 50 cm river sand; 20 L batch with ≥8 h pause between uses.	94.4% (fecal coliform)	[82]
	Surface water parameters: pH (7.1), temperature (28 °C), turbidity (112 NTU), E. coli 4.8 log	Turbidity removal efficiencies ranging between (51–92%) and (98.6–98.8%) for the biosand filter and Modified biosand filter, respectively. Removal efficiency of E. coli (99.8%)	[83]
Coagulation	-	Coagulation with iron and alum salts reduced viruses from 1 to 5 LRV	[84]
Ceramic Filters	The initial flow rate of the filters was 51 mL/min for BCF	Biochar-clay composite ceramic filter (BCF) fabricated with clay and sawdust showed removal efficiencies of 42.5% (total hardness), 45.8% (total dissolved solids), and 67% (turbidity)	[85]
	-	Silver-impregnated ceramic filters exhibit up to 5 LRV of bactericidal activity	[10]
	-	Over 90% removal efficiency for pharmaceutically active compounds (PhACs), personal care products, (PCPs) and pesticides	[15]
		15% green fiber ceramic filters achieved a high bacterial removal efficacy (LRV > 4)	[53]
	0.5 g/L silver-doped titanium dioxide catalyst, 180 min of solar irradiance	Disinfection using solar photocatalysis resulted in 88.4–100.0% disinfection efficiency	[68]
Filtration using membrane filters	0.0117 wt% impregnated AgNPs.	Woven fabric microfiltration membranes that were impregnated with silver nanoparticles demonstrated 100% (2500–77,000 CFU/100 mL) E. coli removal efficiency	[57]
Reverse Osmosis Membrane	4–10 bar, Feed flow—2.4 L/min	Salinity rejection from 99.4 to 11.6%	[60]

highlights the efficiency levels of various PoU water treatment technologies.

4.3. Social Acceptance of PoU Technologies

The social acceptance of point-of-use (PoU) water treatment technologies in rural communities varies significantly depending on factors such as awareness, cultural beliefs, affordability, and trust in the technology. Despite PoU systems such as chlorine disinfection becoming widely accepted in many developing regions due to their ability to provide safe drinking water without reliance on centralized infrastructure, adoption rates are currently inconsistent. Studies indicate that community engagement, empowerment, and a sense of ownership enhance the acceptance and sustainability of these PoU technologies [86]. Another recent study done in Nigeria highlighted the need for education on safe water treatment including chlorination and its benefits [87].

Table 4. Social acceptance of the different POU systems.

POU System	User Experience and Challenges	Reference
Chlorination	Users of chlorine tablets were satisfied with the treatment methods and the taste of the treated water, although it was different from what they were used to.	[88]
	Some communities harbored fears that chlorine could cause illness, infertility, or other adverse effects. Many users also struggled with determining the proper chlorine dosing.	[77]
Solar Disinfection	The households’ willingness to accept and adopt a SODIS was high (97%). In Bolivia, Peru, and Indonesia, taste and odor influenced the acceptance of solar water disinfection (SODIS) treatment, with some users associating treated water with discomfort or rejecting it despite its advantages. These perceptions are likely shaped by cultural norms and preferences related to water quality.	[89,90,91]
	Users of the solar disinfection method reported that the treated water had a better taste, the method was simple to use, and they appreciated that it helped improve their health. However, a noted challenge was the limited availability of clear plastic bottles and the need to remember to refill them for future use	[88]
POU Water filters—Hollow Fiber Filters	Continuous training, follow-up visits, and maintenance protocols are essential to ensure long-term efficacy of these PoU systems and enhance health benefits.	[92]
Gravity-Driven Membrane Filters	Although the initial cost of purchasing and installing a gravity-driven membrane (GDM) system is high, it is viewed as economically beneficial in the long run when compared to the recurring expense of bottled water. Additionally, households recognize indirect savings through reduced incidences of diarrheal disease in young children.	[93]
Biosand Filters	In a study that involved 131 respondents, willingness to pay for and use the biosand filter (BSF) was high at 98.1%, especially among households previously affected by waterborne diseases. Acceptance was also strong, with 89.6% viewing the BSF as a reliable protection against contamination. Additionally, 90.6% expressed positive cultural adaptation.	[94]

provides a summary of the social acceptance of PoU systems.

5. Outlook and Future Perspectives

Point-of-use (PoU) water treatment technologies offer strong potential in tackling global water quality issues, particularly in isolated and underserved regions. With the growing need for safe water, technological progress, and creative solutions are anticipated to be key in delivering clean drinking water. The enhancements outlined below can significantly improve both the efficiency and practicality of PoU systems.

5.1. Metal–Organic Frameworks and Nanomaterials

The creation and utilization of customized materials with enhanced properties, such as nanomaterials and metal–organic frameworks (MOFs), show great potential. These materials exhibit high efficiency in eliminating pollutants like heavy metals and harmful microorganisms. Their outstanding adsorption abilities and photocatalytic features contribute to the development of more efficient filtration technologies. The MOFs possess remarkable traits, including large surface area, adjustable pore dimensions, and high porosity, which make them suitable for water purification; however, their broad application is hindered by costly production and complex synthesis processes [95]. Future investigations should emphasize affordable production methods, eco-friendly ligands, and scalable approaches such as mechanochemical and microwave-assisted synthesis. Enhancing automation and integrating hybrid processes could improve production efficiency, positioning MOFs as key components in clean water solutions. At present, nanotechnology applications in water treatment are mostly confined to lab or pilot-scale due to financial constraints, technical challenges, high setup costs, and potential risks to health and the environment. Another major hurdle is the insufficient understanding of the underlying mechanisms of nanomaterials used in water purification.

5.2. Enhancing the Efficiency and Affordability of Ceramic Water Filters

Reducing costs and enhancing treatment effectiveness are key future trends for expanding ceramic membrane applications in water treatment. It is essential to design not only newer, more affordable ceramic membrane variants that offer comparable or improved performance, but also to establish more process strategies that boost efficiency, supporting broader implementation. Creating ceramic filters that maintain steady water flow while ensuring ongoing contaminant removal remains highly desirable yet challenging. Fouling is an unavoidable issue in ceramic water filters (CWFs) after prolonged usage, primarily due to sediment accumulation and/or particle blockage. Extended performance evaluation of CWFs made with refined formulations should be carried out and analyzed under actual environmental and regional conditions. As water pollutants grow more intricate, additional studies are necessary to grasp their behavior, the formation of by-products, associated toxicity, and risk analysis during point-of-use (POU) treatment, along with potential improvements to enhance the field-level performance of these technologies.

5.3. Integrating Advanced Technologies for Enhanced PoU Systems

Incorporation of cutting-edge technologies such as nanofiltration, improved oxidation processes, and membrane bioreactors is predicted to boost the effectiveness and efficiency of PoU systems. This equipment offers improved removal of contaminants such as pathogens, heavy metals, and emerging impurities. For instance, advanced oxidation processes (AOPs) have shown great potential in degrading persistent organic pollutants and pathogens, making them a promising option for PoU applications. The AOPs are promising technologies for treating water containing pollutants with extreme chemical stability and/or low biodegradability.

5.4. Advancing PoU Systems Through Integrated and Sustainable Approaches

The integration of PoU systems to combat physical, chemical, and biological treatment pollutants is a growing trend. For instance, systems integrating adsorption and photocatalysis demonstrate improved removal rates for a variety of pollutants, including emerging contaminants like pharmaceuticals and perfluoroalkyl and polyfluoroalkyl substances (PFAs). More studies are needed exploring natural coagulants and bio-based adsorbents as low-cost, biodegradable alternatives. These materials contribute to reducing environmental footprints while maintaining performance.

5.5. Integration of IoT-Enabled Devices in Water Treatment

Embracing modern technologies such as IoT-enabled devices for real-time water quality monitoring and data analytics are being integrated into PoU systems. This includes the use of sensors and smart devices to monitor and manage water quality and water resources in real time. This facilitates timely maintenance and troubleshooting, user confidence, and enhances operational efficiency. The use of IoT devices enhances smart water management and leads to efficient water use.

5.6. Application of Point-of-Use Technologies for Emerging Contaminants

The future of point-of-use (PoU) water treatment is likely to shift considerably as emerging contaminants such as pharmaceuticals, microplastics, and nanoparticles become more rampant in water sources. Existing PoU technologies have primarily focused on removing common pathogens and chemical impurities, but the increasing detection of these complex contaminants is pushing researchers towards more advanced point-of-use water treatment solutions such as magnetic nanoparticle filtration, electrochemical disinfection and solar photocatalytic systems.

6. Conclusions

PoU water treatment systems are essential in the global effort to provide potable water. This review has examined various technologies used in PoU systems, including biosand filters, ultraviolet (UV) purifiers, ceramic filters, reverse osmosis (RO) systems, and activated carbon filters, along with emerging nanofiltration and advanced oxidation processes. These systems have shown significant effectiveness in contaminant removal. However, there is a need to integrate different PoU systems, particularly through hybrid approaches, to maximize elimination efficiencies for a wide range of contaminants, reduce energy consumption, promote sustainable water management, and enhance water recovery rates. The accessibility and affordability of PoU systems are central to their extensive implementation, especially in undeveloped regions in which centralized and advanced water treatment facilities and technology may be limited. Innovations in low-cost materials and scalable manufacturing processes are vital to bridge this gap. Future research should focus on integrating PoU systems with smart technologies that provide real-time monitoring and improved management, ensuring consistent water quality and system performance. Sustainability is another critical aspect of future PoU systems. Utilizing environmentally friendly materials, energy-cost-effective designs, and renewable energy sources minimizes environmental pollution and supports SDG, which focuses on clean water and sanitation, as well as SDG 13, which deals with climate Action. Finally, major advancements have been made in the enhancement and deployment of PoU water treatment systems; ongoing research, innovation, and collaboration are necessary to solve the evolving limitations of water contamination and scarcity. By leveraging PoU technologies, we can make sure that safe and potable water is accessible to all, thereby enhancing public health and quality of life worldwide.