Constructed Wetlands as a Decentralized Treatment Option for Domestic Wastewater: A Systematic Review (2015–2024)

Domínguez-Solís, Diego; Martínez-Rodríguez, María Concepción; Ramírez-Escamilla, Héctor Guadalupe; Campos-Villegas, Lorena Elizabeth; Domínguez-Solís, Roman

doi:10.3390/w17101451

Abstract

Constructed wetlands (CWs) attempt to simulate the physicochemical and biological processes that occur within a natural wetland and have been employed in recent decades for wastewater treatment. This work aims to review the use of CWs for domestic wastewater treatment in undeveloped or developing areas, including the amount of literature produced, the type of constructed wetland, the vegetation, the substrate, and the social benefits that have been achieved, through a qualitative methodology where different articles are collected from the Scopus and Web of Science databases after a strict revision by means of the PRISMA method (Preferred Reporting Items of Systematic Reviews and Meta-Analyses) and CASP (Critical Appraisal Skills Program). A total of 49 articles were selected, and co-occurrence and density maps were obtained; following this, three main themes and the five keywords with the highest correlation were identified. The literature analyzed in this work exposes different types of CWs where not only the hybrid, vertical, and horizontal flow systems stand out, but also the floating and aerated wetlands, which present high removal efficiencies. Additionally, new substrate materials, such as olote, palm shells, and coconut peat, and the ornamental plants usually used, such as Phragmites australis and Thypha latifolia, are discussed; however, new studies with vegetation that has been little studied but has a high potential to be implemented in areas with silvicultural characteristics stand out: Duranta repens, Pennisetum pedicellatum, and Pistia stratiotes. In conclusion, there is an advancement in the research of these systems, new configurations, substrates, and vegetation to treat domestic wastewater; in addition, these studies present an opportunity to continue studying the installation of CWs at the household level; however, compared to the other areas of application mentioned above, its implementation requires a greater challenge, since it requires a compact design and easy handling.

Keywords:

wastewater; wetland; vegetation; organic load; reuse

1. Introduction

Constructed wetlands are systems designed to treat various types of wastewater. Their implementation increases the availability of treated water and contributes to environmental restoration. Vymazal [1] describes CWs as systems that mimic natural wetland processes, incorporating aquatic plants, substrate materials, and water. According to Luna-Pabello and Ramírez-Carrillo [2], a constructed wetland (CW) is a sustainable technology that reduces the concentration of key pollutants to regulatory standards through physicochemical processes. Gómez [3] emphasizes that their structure resembles shallow ponds, where substrate occupies most of the volume and serves as a support for macrophyte aquatic plants. Therefore, CWs are human-engineered zones that replicate natural wetland mechanisms for pollutant removal via controlled physical, biological, and chemical processes. These systems aim to reproduce natural decomposition processes through aquatic vegetation, microorganisms, and substrate materials. The use of this alternative seeks to replicate natural processes and leverage biotic factors for wastewater purification. This eco-technology enhances water availability, mitigates water stress, and counteracts biodiversity loss.

Initial research on subsurface-flow wetlands for wastewater treatment began in the 1950s in Germany, where studies demonstrated that emergent plants and sand within a simulated wetland reduced pollutant levels. Between the 1970s and 1980s, such systems were used exclusively for domestic or municipal wastewater, but from the 1990s onwards, their application has expanded to all wastewater types [4]. García [5] notes that subsurface-flow CWs with sand substrates originated in Europe and are now employed worldwide. Today, they are widely adopted in developed countries, such as Germany, England, France, Denmark, Poland, and Italy. However, Kivaisi [6] argues that CWs hold greater potential in warm tropical and subtropical regions like Mexico, where higher biological activity enhances contaminant removal efficiency.

This study proposes a systematic review to compile and analyze the evidence on CW performance while emphasizing their social and environmental impact in undeveloped or developing areas. In this regard, the differential value of this systematic review lies not only in its rigorous methodology but also in offering an integral and context-driven perspective on CWs as sustainable solutions. Special attention is given to their application in rural and semi-urban settings, where these systems transcend technical functions by fostering environmental awareness, strengthening community engagement, and creating green spaces [7,8]. The 2015–2024 timeframe was selected based on two criteria: contemporary relevance and the surge in recent research. Since 2015, interest in sustainable, decentralized water treatment technologies has grown significantly, aligning with the United Nations Sustainable Development Goals (SDGs), particularly SDG 6: Clean Water and Sanitation, this marked a turning point where nature-based solutions like CWs are prioritized [9,10].

The objective of this research is to present a review of constructed wetlands as a promising, sustainable, and decentralized alternative for domestic wastewater treatment in economically constrained and space-limited developing regions. The findings aim to serve as a foundation for future CW implementation.

2. Methodology

To ensure a clear and precise methodology that supports the rigor of this study, Figure 1 shows the research process:

Figure 1. Applied Methodology. Source: Author’s own research.

2.1. Criteria for Inclusion and Exclusion

The databases used for the literature review were Scopus and Web of Science, which provide complete and high-quality literature suitable for systematic reviews [11].

Keywords and Boolean operators used in the search included “constructed wetland”, “water”, “domestic”, and “performance”. The initial stage focused on establishing criteria for language, publication type, and timeframe. Further selection criteria include studies in English and Spanish as well as articles published between 2015 and 2024. Applying these criteria reduced the number of articles to 154.

2.2. Quality Assessment and Data Extraction

First selection stage: Duplicate articles (those present in both databases) and open-access articles with unavailable full texts were excluded, reducing the final article count to 119.

Second selection stage: The objective of this stage was to ensure that selected articles addressed the central theme and research question, prioritizing case studies over review papers. To achieve this, a thorough screening of each article’s title, abstract, and conclusions was conducted. This evaluation process reduced the final article count to 78.

Third selection stage: This stage involved a meticulous evaluation of the methodology, results, and findings presented in each article to ensure they provided substantial information on the type of wetland, vegetation, and substrate used for domestic wastewater treatment, and the location type where the system was implemented. This rigorous screening yielded 49 articles (Scopus: n = 28; Web of Science: n = 21). A detailed summary of the article selection process following the PRISMA method is presented in Table 1 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses).

Table 1. Article selection process using the PRISMA method (Preferred Reporting Items of Systematic Reviews and Meta-Analyses).

The quality of the articles was assessed using the Critical Appraisal Skills Program (CASP), a tool that provides a systematic framework for evaluating the methodological robustness of diverse study types. CASP employs a structured guide to assess key aspects such as methodology, data analysis, and presentation of findings [12]. The tool identifies methodological strengths and weaknesses through key questions grouped into three sections: (1) internal validity, (2) results, and (3) applicability.

Each reviewed article underwent a detailed assessment based on parameters outlined in the CASP criteria: methodological rigor, validity of findings, suitability of experimental methods, and clarity of research design. Documents and articles categorized as low-quality were excluded, while studies classified as moderate- and high-quality were included in the analysis. This appraisal ensured the credibility, applicability, and replicability of the final selected studies.

2.3. Data Analysis

A qualitative analysis of the selected articles (n = 49) was conducted using VOSviewer software (version 1.6.17) [13]. A co-occurrence map and a density map were generated based on keyword frequency and correlation strength. Redundant singular/plural terms were consolidated to refine the dataset. Additionally, Bibliometrix 4.0.1 was employed to produce a graphical representation of research output on CWs for domestic wastewater treatment from 2015 to 2024.

For the second analysis, data on wetland type, vegetation, substrate, and pollutant removal efficiency in treated water were extracted to discuss findings, with emphasis on high-impact results. The application sites of the CWs were examined with the aim of making recommendations and analyzing design advances for their implementation.

3. Results

We present a detailed overview highlighting the main characteristics of CWs used in domestic wastewater treatment as a decentralized system to reduce the adverse environmental effects of polluted water discharge and as a social and economic benefit. This overview provides significant information on the effectiveness of these treatment systems and the type of structure employed in different locations where they have been applied; the following eight CW types were found: Horizontal Subsurface Flow Constructed Wetlands (HSFCWs), Vertical Subsurface Flow Constructed Wetlands (VSFCWs), Hybrid Constructed Wetland (HCWs), Up-flow Compact Constructed Wetland (UCCWs), Partially Saturated Vertical Flow Wetlands (PSVFs), Flow Surface Constructed Wetlands (FSCWs), Floating Constructed Wetlands (FCWs), and Tidal Flow Constructed Wetlands (TFCWs).

Table A1 in Appendix A compiles the 49 articles selected for this review, summarizing their contributions to the study of CWs in domestic wastewater treatment. It details the type of wetland system, treatment efficiency findings, and the primary social benefit of each implementation.

The bibliometric data analysis adhered to a rigorous application of the CASP checklist, employing three key criteria to assess the validity and robustness of the results sourced from Scopus and Web of Science. The final column of Table A1 categorizes the studies based on a detailed evaluation of methodologies and outcomes. Studies classified as moderate quality provided adequate contextual recovery but lacked sufficient methodological detail to ensure replicability, while those rated as high or medium quality met these criteria, offering a robust foundation for future research.

3.1. Geographic Context

The geographic context of CW research for domestic wastewater treatment is critical for understanding system variability and efficacy across rural and semi-urban regions. Figure 2 highlights the countries with the highest research productivity: China, Brazil, Mexico, and India, collectively contributing over 40% of the reviewed literature.

Figure 2. Productivity of work related to the use of CW in domestic wastewater treatment.

3.2. Annual Productivity

Following the established methodology, 49 articles spanning the period 2015–2024 were selected. This number reflects the rigorous application of inclusion and exclusion criteria, ensuring the methodological quality and thematic relevance of the analyzed studies. By focusing on the constructed wetlands with documented social impact in rural, school, and marginalized urban contexts, the selection was intentionally narrowed to prioritize medium- and high-quality research, aligning with the study’s objectives.

As illustrated in Figure 3, a significant increase in research output on this topic emerged starting in 2018. Of the total number of articles, over 60% of the articles were published within the last 5 years. To date, 2020 and 2024 have been the most productive years, featuring case studies that emphasize CWs as decentralized systems in schools and small communities. Notably, some studies explore their application at the household level, featuring implementations based on compact designs, which opens a new area of opportunity for their deployment.

Figure 3. Annual scientific production of research works related to the use of constructed wetlands for domestic wastewater treatment.

3.3. Topics Related to CW Implementation

Figure 4 illustrates the keyword co-occurrence map derived from the reviewed literature, identifying three primary thematic clusters: The green cluster groups terms related to the structure and functionality of constructed wetlands, including flow types, construction materials, and biological processes. The red cluster represents concepts associated with treatment efficiency and system performance. The blue cluster encompasses terms linked to contaminants and wastewater sources, indicating a focus on the removal of specific pollutants.

Figure 4. Keyword concurrency map obtained from Vosviewer. Source: Author’s own research.

3.4. Types of Constructed Wetlands

CWs can generally be classified based on criteria such as vegetation type, hydrology, and water flow direction [14]. The use of this eco-technology has gained momentum as an alternative for contaminated effluent treatment, being an ecological and economic option in terms of operation and maintenance. A review of the different types of constructed wetlands is an essential tool for advancing the knowledge and application of this technology in domestic wastewater treatment, enabling design optimization, identification of improvement areas, and promotion of sustainable development. Figure 5 summarizes the diverse CW configurations employed in domestic wastewater treatment: HSFCWs, VSFCWs, HCWs, UCCWs, PSVFs, FSCWs, FCWs, and TFCWs.

Figure 5. Type of constructed wetlands used in domestic wastewater treatment. Source: Author’s own research.

3.5. Types of Pretreatments Prior to Entering CW

According to Garibay et al. [15] and Luna-Pabello y Aburto-Castañeda [16], to increase the lifespan of CWs, it is essential to apply pretreatment to facilitate the removal of easily settleable suspended solids, thus preventing their rapid accumulation and clogging. The most widely used pretreatments are septic tanks and sedimentation tanks, as illustrated in Figure 6. Therefore, it is a key stage for improving system efficiency and preventing operational problems and excessive solid accumulation.

Figure 6. Types of pretreatments for CW-treated domestic wastewater. Source: Author’s own research.

3.6. Vegetation Used

Figure 7 summarizes the most frequently used plant species in CWs, as identified in the systematic review. Phragmites australis, Typha latifolia, Saggitaria latifolia, and Cyperus papyrus stand out due to their high prevalence, attributed to their adaptability to diverse hydrological conditions and efficiency in pollutant removal. Other species, though less common, have also been documented for their unique phytoremediation capabilities, which are discussed in greater detail in the following section. These findings emphasize the importance of selecting vegetation based on target contaminants and site-specific CW conditions.

Figure 7. Type of vegetation and number of times they were used in the literature review. Source: Author’s own research.

3.7. Substrate Used

Figure 8 shows the types of substrates most used in CWs according to the systematic review carried out. Other materials, such as sand and zeolites, also show considerable use, and some studies have also explored alternative materials, such as palm shells, coco peat, corn cobs, and biochar, for their potential in the removal of specific pollutants.

Figure 8. Type of substrate and number of times used in the reviewed literature. Source: Author’s own research.

4. Discussion

This analysis provides a renewed perspective on the use of constructed wetlands (CWs) for domestic wastewater treatment, particularly in rural, semi-urban, and marginalized urban contexts. It discusses suitable implementation sites, social benefits, and the structural components of CWs—vegetation and substrate. The importance of this technology lies in its low operational and maintenance costs compared to conventional systems. Based on the reviewed literature, CWs have evolved from complementary processes in large-scale treatment plants to decentralized solutions for household-level water recycling. This review emphasizes compact CW designs that utilize unconventional substrates derived from repurposed local raw materials, enhancing their replicability in space-constrained areas or regions with similar environmental conditions.

4.1. Geographical Relevance

Only the four main countries concentrate the highest production of articles. This is mainly associated with the use of CWs as sustainable alternatives in developing areas, where conventional treatment infrastructure is often infeasible or unaffordable [17].

In China, CWs have emerged as a promising eco-technology for wastewater treatment. Their growing popularity is due to their pollutant-removal efficiency, low operational and maintenance costs, and capacity to enhance water quality and restore ecosystems, particularly along the eastern coast [18,19].

In Brazil, CWs are widely deployed for domestic wastewater treatment, with emphasis in decentralized settings. Research focuses on optimizing the removal of contaminants and nutrients such as total nitrogen, organic matter, and suspended solids. These strategies have proven effective in the Brazilian context, maximizing treatment capacity and promoting sustainable waste management in tropical climates [20,21].

In India, CWs are employed as accessible and sustainable technologies for treating domestic wastewater in small-scale facilities with limited economic resources, such as in schools and rural communities. These strategies promote the rehabilitation of contaminated water bodies, aquifer recharge, and sustainable water use in agriculture [22,23].

In Mexico, CWs are implemented as low-cost, sustainable alternatives in marginalized rural and urban zones. They integrate technologies such as septic tanks and biofilters, using locally sourced materials, achieving treatment efficiencies that enable water reuse for irrigation, domestic activities, and green spaces. These systems comply with national and international standards, improving water quality and sustainability in areas lacking conventional infrastructure [24,25].

4.2. Application Sites and Benefits

The application of CWs promotes water reuse and environmental conservation. According to Fernández-Ramírez et al. [26] and Masoud et al. [27], employing these systems for contaminant removal can greatly benefit developing countries that do not have sufficient infrastructure to meet wastewater demand.

CWs can be deployed in various settings (Figure 9). For this analysis, we categorize them into four groups: schools or research centers, semi-urban communities, rural communities, and household-level treatment. Dividing the discussion in this way underscores the broader benefits achieved beyond merely treating domestic wastewater.

Figure 9. CW Application Sites for Domestic Wastewater Treatment.

4.2.1. School or Research Center

Sudarsan et al. [28] and Visiy [29] note that CWs are favored in academic settings (schools and research centers) due to their low cost, minimal maintenance requirements, high removal efficiencies, and ecological benefits. In water-scarce areas, Sharma et al. [22] and Hua et al. [30] highlight these nature-based solutions as sustainable methods—the treated effluent can be reused for onsite activities or agricultural irrigation [31]. Benefits include environmental awareness, wastewater reuse, landscape enhancement, community engagement, interdisciplinary education, etc.

4.2.2. Semi-Urban Communities

In semi-urban contexts, CWs have proven viable for water reuse and environmental improvement. Wu et al. [32] and Li et al. [33] evaluated their efficiency in urban parks, emphasizing landscape and recreational benefits as an environmental service. Nguyen et al. [34] studied CWs in university dormitories for irrigation water quality, while Obeng et al. [35] demonstrated contaminant removal efficiency—both cases also highlighting educational opportunities and environmental awareness. These studies showcase CWs’ technical performance and their potential to generate social and environmental benefits in community spaces, supporting sustainable, resilient semi-urban environments and contributing to decentralized solutions aligned with the 2030 Agenda.

4.2.3. Rural Communities

The use of CWs in rural communities has been extensively studied due to their ability to provide decentralized, low-cost, and environmentally sustainable solutions. Research by Fu et al. [36] and Gong et al. [37] confirms that effluents treated through these systems meet national standards, encouraging water reuse and reducing environmental pollution. Other studies, such as that by Rahi et al. [38], emphasize the benefit of treated water availability for community agriculture. Meanwhile, Kasenene et al. [39] and Micek et al. [40] highlight the critical role of CW systems in rural areas to ensure access to clean water, underscoring their effectiveness in safeguarding sensitive ecosystems. Additionally, it is worth noting that these systems can utilize locally available resources as substrates, further enhancing their cost-effectiveness for reusing water in domestic or agricultural applications.

4.2.4. Treatment at the Household Level

While many studies focus on community-scale CW implementation, this work also emphasizes their application at the household level through compact designs that utilize low-cost, readily available materials. The installation of these systems offers a practical solution for areas with intermittent water supply, enabling treated water to be reused in daily activities such as patio washing, garden irrigation, and toilet flushing, as highlighted by Garzón-Zuñiga et al. [24]. Furthermore, Andreo-Martinez et al. [31] note that CW systems help prevent aquifer contamination in isolated households lacking access to public sewage networks, positioning them as a viable decentralized alternative for greywater treatment in individual homes. This approach reinforces local sustainability efforts [41]. Collectively, such studies underscore the feasibility and accessibility of CWs for efficient domestic water management.

4.3. Removal Efficiency

The implementation of various types of CWs (Table 2) has led to the generation of data highlighting their advantages, particularly reflected in their pollutant removal rates. This analysis does not seek to identify a superior system but rather provides a comparative overview to evaluate the performance of different configurations under varying conditions. Such an approach yields a broader understanding of the expected variability in each system’s performance. This empirical evidence is crucial for the operational planning of CWs.

Table 2. Types of constructed wetlands and their definitions.

4.3.1. HSFCWs

HSFCWs have demonstrated variable efficiencies in contaminant removal. Sudarsan et al. [28] reported high removal percentages of BOD₅ (75.99%) and COD (76.16%), while Garzón-Zúñiga et al. [24] found higher percentages for BOD₅ (88%) and COD (83%). Other studies, such as those by Wu et al. [32] and Andreo-Martínez et al. [31], show high NH₄⁺-N removal levels (98.9% for both). Regarding the reduction of solids and phosphorus, Kasenene et al. [39] reported efficiencies of 97.4% for TSS and 49.8% for TDS, respectively. Ali et al. [70] found high removal percentages of TDS (83%), TSS (82%), and NH₃ (84%). These data indicate that HSFCWs are effective in treating organic matter and nitrogen, although phosphorus removal can be limited. This is mainly due to the type of material used, since, according to Gao et al. [71], phosphorus removal depends on substrate adsorption.

4.3.2. VSFCWs

VSFCWs generally achieve better results in organic matter and nitrogen removal compared to HSFCWs. Fu et al. [36] reported a BOD₅ removal rate of 80.1%, while García-Ávila et al. [72] documented an efficiency of 80.69%. In terms of bacterial reduction, Tibebu et al. [73] found efficiencies of 98.7% for heterotrophic bacteria and 96.2% for total coliforms, which were higher than those reported for HSFCWs. Similarly, Thalla et al. [74] concluded that VSFCWs exhibit a 7.14% higher overall removal efficiency, demonstrating their superior capacity for pollutant elimination compared to other systems. Nonetheless, it is important to evaluate the life cycle of this type of CW to ensure the required total treatment time [75].

4.3.3. FSCWs and FCWs

Studies on FSCWs and FCWs show that they can achieve efficient removals in certain parameters; Li et al. [33] reported a NH₃-N removal of 92.31%, although with a lower phosphorus removal (38.8%) with respect to other parameters. Magaña-López et al. [25] found that these wetlands achieve significant reductions in turbidity (98.8%) and color (89.4%); this configuration can be effective for certain pollutants. Its performance is usually lower in the removal of organic matter compared to HSFCWs and VSFCWs.

4.3.4. HCWs

HCWs have demonstrated high effectiveness in removing organic matter and nutrients. Ávila et al. [63] reported near-total removal of TSS, BOD₅, and NH₄⁺-N (98–99%), Almeida-Naranjo et al. [48] similarly documented removal efficiencies of 86.8% for COD and 96.4% for NH₄⁺. However, other studies have revealed lower efficiencies for phosphorus; for instance, Lavrnić et al. [49] reported 40–43% COD and 72–74% TSS removal, and Magalhaes et al. [41] highlighted that these wetlands can reduce BOD₅ by 50% under passive conditions (i.e., without external inputs). In terms of heavy metal removal, Huong et al. [76] achieved efficiencies of up to 79.4% for Cu and 71.5% for Pb. Overall, the reviewed studies indicate that HCWs are highly effective in removing organic matter and nitrogen, with variable efficiency for parameters such as phosphorus and heavy metals.

4.3.5. UCCWs, PSVFs, and TFCWs

UCCWs have demonstrated high efficiency in nitrogen removal. Zhou et al. [77] reported 99.1% NH₄⁺-N removal, while Chen et al. [55] documented values ranging from 82.7% to 44.1% for organic matter removal. Boog et al. [54] highlighted the influence of factors such as porosity and hydraulic permeability. On the other hand, PSVFs have shown lower removal compared to other wetlands. Nakase et al. [57] reported efficiencies of 35% for NH₄⁺-N and 47% for TP, indicating less effective performance than other systems. Furthermore, Wang et al. [66] compared TFCWs and HSFCWs, finding that TFCWs achieved higher NH₄⁺-N (96.47%) and COD (69.46%) removal rates compared to horizontal flow CWs. These results align with Hamisi et al. [62], who emphasized the superior nitrogen removal efficiency of such configurations. The comparative analysis of these constructed wetland types underscores that UCCWs and TFCWs deliver enhanced performance in nitrogen and organic matter removal, whereas systems like PSVFs demonstrate more limited efficiencies.

4.4. Vegetation Influence

According to Tejeda et al. [78] and Sandoval-Herazo et al. [79], plants play a key role within a CW by facilitating pollutant uptake, system oxygenation, and water quality improvement. Within the reviewed studies, the use of Phragmites australis stands out due to its ability to enhance pollutant removal [31,32,63]. The high efficiencies observed in systems employing this vegetation align with findings by Milke et al. [80], as this plant exhibits a remarkable capacity to accumulate diverse nutrients and heavy metals, outperforming other plant species commonly used in CWs.

Species such as Typha latifolia have demonstrated effectiveness in removing organic pollutants and nutrients [38,81]. This is similar to what was found by Sandoval-Herazo et al. [80], who mention that this aquatic plant adapts easily and grows healthily despite being exposed to high contaminant concentrations. The plant Saggitaria latifolia is a species with good abundance in tropical and subtropical climates that can reduce operation and maintenance costs due to its availability, size, and handling. It is widely recommended for decentralized treatment [25,82]. On the other hand, Cyperus papyrus is a species native to tropical climates but can tolerate low temperatures, and due to its characteristics, it has shown high percentages of contaminant removal [24].

Among species warranting special mention, Duranta repens, Pennisetum pedicellatum, and Pistia stratiotes stand out. While scarcely studied in CWs, these species offer aesthetic benefits and represent novel aquatic vegetation alternatives for local wastewater treatment systems targeting both conventional and emerging contaminants [23,73,74]. Their use presents opportunities for future research to expand the diversity of plants employed in decentralized wastewater treatment, tailoring systems to local conditions and optimizing system efficiency.

4.5. Substrate Influence

The type of substrate used in constructed wetlands significantly influences their performance. According to Wang et al. [83], common substrates in CWs include activated carbon, ceramsite, gravel, and modified materials. Firstly, gravel has been widely used in various studies due to its capacity to provide support for vegetation and facilitate contaminant retention [24,81]. If better adsorption of organic matter and ammoniacal nitrogen is desired, biochar in aerated systems is a good alternative [77]. For the removal of heavy metals and ammonium, zeolite offers significant advantages [38,41]. Additionally, in coastal or rural areas, materials such as palm oil endocarp, corn cobs, and coconut peat, which possess a porous physical structure that facilitates infiltration and water retention, allow for improved contaminant adsorption at a low cost, as they are considered waste materials [84]. On the other hand, the use of diatomite, vermiculite, and hydrotalcite, according to Fu et al. [36], has demonstrated good results in contaminant removal, although acquiring them might require a larger economic budget than the aforementioned materials. Based on the reviewed studies, considering the reported removal efficiency of various contaminants and the cost, the combination of zeolite with gravel and corn cob is an ideal option, as it balances structural stability, vegetation support, and a high adsorption capacity for heavy metals and ammonium.

5. Conclusions

After a rigorous screening and review of 49 articles on constructed wetlands (CWs) for domestic wastewater treatment obtained from the Web of Science and Scopus databases, the main characteristics of these systems were identified. The main characteristics of these systems can be highlighted as follows: pollutant removal efficiency, social benefits, and adaptability; their application is wide in undeveloped or developing areas of countries, such as China, India, Brazil, and Mexico, as well as in schools, semi-urban and rural communities, and households, which demonstrates their capacity for water resource management and as an environmental service. In terms of efficiency, the different types of CW configurations have shown different percentages of pollutant removal. Firstly, it was found that the VSFCWs are the most efficient in the removal of organic matter and nitrogen, while the HSFCWs and HCWs show a high capacity for the reduction of suspended solids and BOD₅; UCCWs and TFCWs are not usually used but are recommended since their characteristics increase the removal of nutrients and organic matter.

Vegetation plays a crucial role in the efficiency of the system; in this review, the use of Phragmites australis and Typha latifolia is highlighted for their capacity to absorb nutrients and heavy metals. In addition, Duranta repens, Pennisetum pedicellatum, and Pistia stratiotes were identified as emerging species with a high potential to be used in CWs. On the other hand, the type of substrate has a significant influence on the retention and absorption of pollutants. From the exhaustive review carried out, typical materials such as zeolite, biochar, and tezontle and innovative ones such as olote, palm shells, and coconut peat were reported; the latter could be obtained at no cost in coastal or rural regions since they are considered as waste.

The importance of constructed wetlands (CWs) is highlighted as a viable alternative for wastewater treatment in areas with limited space and economic resources, contributing to the achievement of SDG 6. Their implementation in semi-urban and rural settings is promoted as a sustainable solution that offers both social and environmental benefits. Based on this review, it is recommended to continue researching the long-term performance of these systems and to explore new configurations and reusable materials that can enhance their efficiency in pollutant removal, particularly at the household level. Such efforts can foster collective awareness and drive a cultural shift towards more responsible water management.

Author Contributions

Writing—original draft preparation, D.D.-S.; conceptualization, D.D.-S.; methodology, D.D.-S. and H.G.R.-E.; validation, M.C.M.-R.; software, H.G.R.-E.; investigation, M.C.M.-R. and R.D.-S.; formal analysis, L.E.C.-V. and R.D.-S.; data curation, L.E.C.-V. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data sharing not applicable.

Conflicts of Interest

The authors declare no conflicts of interest.

Appendix A

Table A1. Content of reviewed articles.

Author	Year	CW Type	Findings (Efficiency)	Social Benefit	Quality Assessed
[28]	2015	HSFCW	The average efficiencies reported were 75.99% for BOD₅, 76.16% for COD, 57.34% for TDS, 62.08% for para nitrate, 58.03% for phosphate, and 57.83% for para potassium.	The use of CWs has created environmental awareness among students, staff, and other residents of the municipality.	High
[63]	2015	HCW	The average removal efficiency was 98–99% for TSS, BOD₅, and NH₄-N.	The study proved to be a very robust eco-technology for wastewater treatment and reuse in small communities.	High
[85]	2015	HSFCW	Removal efficiencies of 48% and 48.9% for BOD₅, 38.9% and 28.5% for TP, and 52.7% and 55.4% for COD, respectively.	The study demonstrated the efficiency of different types of vegetation for a community in Chiapas, Mexico, showing the possibility of water reuse.	Moderate
[24]	2016	HSFCW	The removal efficiencies obtained from the application were as follows: 83% for COD, 88% for BOD₅, 82% for N-NH₄⁺, and 15% for P-PO₄⁻	The study demonstrated the efficiency of different types of vegetation for a community in Chiapas, Mexico, showing the possibility of water reuse.	High
[32]	2016	HSFCW	High removal of COD (97.2%), NH₄⁺-N (98.9%), and TN (85.8%).	Demonstrated the feasibility of using CW in parks and promoted environmental awareness for the treatment of domestic wastewater.	Moderate
[22]	2016	VSFCW	The BOD₅ concentration decreased by 84.21% (from 180–190 mg/L in the influent to less than 30 mg/L in the effluent), meeting the limits established for discharge of water into surface water bodies.	This study provides an economical and sustainable method for wastewater treatment, which is particularly relevant in areas with limited water resources.	High
[31]	2016	HSFCW	Pollutant reduction: BOD5 (96.4% the first year, 92.0% in the second), COD (84.6%, 77.7%), TSS (94.8%, 89.9%), TN (79.5%, 66.0%), NH₄⁺-N (98.8%, 86.6%) and TP (83.7%, 82.8%).	This study offers an effective and low-cost solution for wastewater treatment in isolated communities, helping to prevent contamination of aquifers and comply with environmental regulations.	Moderate
[77]	2017	UCCW	Results showed that the addition of biochar achieved a much higher removal of chemical oxygen demand (COD) (94.9%), ammoniacal nitrogen (NH₄⁺-N) (99.1%), and total nitrogen (TN) (52.7%).	This study proposes an effective and appropriate strategy for the treatment of domestic wastewater with low C/N ratio, a common condition in certain types of wastewaters.	Moderate
[30]	2017	HSFCW	The study showed that the average total nitrogen (TN) removal efficiency was 45.2%.	This study highlights the potential of horizontal subsurface flow constructed wetlands to effectively treat domestic wastewater, particularly in areas with limited resources.	Moderate
[36]	2018	VSFCW	The average total removal rates determined in the test period for TSS, COD, BOD₅, TN, NH₃-N, and TP were 85.3%, 82.4%, 80.1%, 47.5%, 51.0%, and 61.8%, respectively.	The proposed constructed wetland system offers an effective and sustainable solution for domestic wastewater treatment in rural areas.	High
[81]	2019	HSFCW	COD values of 16.6 mg O₂/L and TSS of 0.40 mg/L were achieved in the treated water without disinfection.	This study demonstrates that greywater treatment using a constructed wetland system combined with UV disinfection is a viable and efficient alternative for the agricultural reuse of treated wastewater.	Moderate
[54]	2019	UCCW	The most important factors affecting performance include porosity, hydraulic permeability, and dispersion length of the fast flow field.	This study provides deeper insights into aeration mechanisms in mechanically aerated constructed wetlands, which can enhance the efficiency of pollutant removal, such as COD and NH₄-N.	High
[57]	2019	PSVF	N-NH₄ (35%), Norg (16%), TN (25%), and TP (47%) were removed in greater quantities in the vegetated systems.	The study underscores the advantages of using vertical partially saturated constructed wetlands (VPS) for domestic wastewater treatment, particularly in tropical climates.	High
[74]	2019	HSFCW and VSFCW	VSFCW showed an overall removal efficiency higher than HSFCW by 7.14%.	This study demonstrates that constructed wetlands (CWs) are a sustainable and cost-effective alternative for the tertiary treatment of domestic wastewater, owing to their low operational costs and reliance on locally available materials.	High
[72]	2019	VSFCW	BOD₅ contaminant removal capacity of 80.69%, COD of 69.87%, NH₄⁺-N of 69.69%, and TP of 50%.	Effective solutions for wastewater treatment have been presented using the promising technology of vertical subsurface flow constructed wetlands, which stand out for their low construction cost and minimal operational requirements.	Moderate
[38]	2020	HSFCW	The presence of P. australis significantly improved the removal efficiencies of COD (86,0%), BOD₅ (85.6%), NH₄-N (82.1%), PO₄-P (59.6%), and TSS (65.5%).	Water for reuse in the community’s agriculture.	High
[48]	2020	HCW	The average removal efficiencies were 86.8%, 96.4%, and 57.0% for COD, NH₄⁺, and PO₄³⁻, respectively.	The adequate selection of the plants used in CWs plays a decisive role in the successful implementation and operation of this technology type.	High
[49]	2020	HCW	COD and TSS removal were similar between the two systems, ranging from 40–43% and 72–74%, respectively.	Hybrid systems can be implemented in universities for irrigation of experimental gardens or energy crops, promoting sustainability on campus.	High
[37]	2020	HCW	The HV-SFCW composite system proved to be the most efficient in COD (46.7%), TN (58.1%), and TP (53.7%) removal.	The treated effluent complies with national standards, enhancing the quality of environmental discharges and promoting its reuse.	High
[34]	2020	VSFCW	The removal efficiencies for TSS, COD, BOD₅, NH₄-N, and Tcol were 71%, 73%, 79%, 91%, and 70%, respectively, and the FWS was less efficient in removing pollutants than the VF.	Improvement of water quality for irrigation or secondary uses, promoting sustainability.	High
[76]	2020	HCW	HCW: Not specified. - HCW-1: Cu (73.5%), Pb (71.5%). - HCW-2: Cu (79.4%), Pb (67.8%). - HCW-2 with earthworms showed higher efficiency in BOD5 reduction. (>70%).	This approach optimizes the use of substrates and natural organisms, providing a low-cost and easy-to-implement solution for wastewater treatment in academic and industrial settings.	Moderate
[84]	2020	HSFCW	Reduction of 61% in TN, 21% in TP, 63% in NO₃-N (HRT1), 55% in NO₃-N (HRT2), 23% in NH₃-N (HRT1), 24% in NH₃-N (HRT2), 23% in PO₄-P (HRT1), and 11% in PO₄-P (HRT2).	Use of local plants and natural processes to manage high-salinity wastewater.	High
[86]	2020	HCW	Showed 100% confidence in the removal of BOD₅, COD, and TSS, similar to the two-stage systems.	Production of a high-quality effluent, with low concentrations of solids, organics, and nutrients, suitable for discharge or reuse.	High
[40]	2020	HCW	Reductions of 96–99% in BOD₅ and COD, 90–94% in TP, 80–87% in TSS, and 73–86% in TN were achieved.	Environmental protection in sensitive areas, such as national parks, through effective and natural treatment of wastewater.	High
[39]	2021	HSFCW	Reductions of up to 97.4% in TSS, 95.9% in turbidity, 94.3% in fecal coliforms, 91.7% in nitrate, BOD₅, and ammonium, and 49.8% in phosphate were achieved.	Provision of high-quality treated water for domestic use in vulnerable rural communities.	High
[87]	2021	HSFCW	Removal efficiencies were 76% for BOD₅, 62% for DOC, and 50.7% for total nitrogen (TN).	Provision of sustainable and efficient technology for wastewater treatment on small and medium-sized dairy farms.	High
[41]	2021	HCW	The removal efficiency was 90% for COD, while BOD showed an approximately 50% lower reduction without the cooking component (GWL).	Improves the sustainability and efficiency of CW systems for domestic greywater treatment; offers a decentralized system alternative at the household level.	Moderate
[73]	2022	VSFCW	98.7% for heterotrophic bacteria in E-1. 96.2% for total coliforms in E-1. 92.9% for fecal coliforms in E-1.	This hydroponic treatment system shows promising potential for pathogen removal from wastewater in developing countries.	High
[88]	2022	VSFCW	Biological oxygen demand (BOD₅) and ammonia were 74.2%, 87.9%, and 82.1%, respectively.	Construction waste was highlighted as a possible and efficient substitute for expanded material in CW systems.	High
[33]	2022	FSCW, VSFCW, and FCW	The total NH3-N removal rate of the wetland system was up to 92.31% on average. The total TP level removal rate was 38.8%.	Integrating landscape features into wetland design not only improves water quality but also provides environmental and economic benefits, contributing to sustainable urban landscapes.	High
[29]	2022	VSFCW	Over 90% removal for fecal bacteria, over 80% for TSS, over 70% for phosphates, and over 60% for organic matter.	Potential replacement of sand with biochar in constructed wetlands, which can improve treatment efficiency and promote sustainability.	Moderate
[89]	2022	HSFCW	Removal efficiencies: BOD₅ (71.83%), COD (73.75%), TSS (82.77%), NH4-N (80.29%), and PO4-P (59.49%).	This system is suitable for domestic wastewater treatment in rural settlements in arid environments.	Moderate
[55]	2022	UCCW	COD (83.6% in warm season, 66.3% in cold season), NH₄⁺-N (82.7% in warm season, 44.1% in cold season), and TN (76.8% in warm season, 43.8% in cold season).	Combination of aeration and vegetation, which can be especially useful in cold seasons, improves wastewater treatment in rural areas and cold climates.	High
[82]	2023	HSFCW	COD removal rates ranged from 68.4% to 80.4% (CW6), from 54.3% to 66.6% (CW1) under high HLR, and from 68.5 to 88.9% (CW6).	Improved water quality through on-site treatment on campus, generating environmental awareness among students.	Moderate
[66]	2023	TFCW and HSFCW	The TFCW system showed better removal efficiencies during the stable phase: COD, 69.46%; NH₄⁺-N, 96.47%; and total phosphorus (TP), 57.38%. In comparison, the HFCW system had lower efficiencies: COD, 61.43%; NH₄⁺-N, 84.99%; and TP, 46.75%.	Attractive technique for the treatment of pollutants as a compact ecological system.	High
[90]	2023	VSFCW	BOD₅, COD, and TSS in raw wastewater were 89%, 58%, and 88%, respectively.	It provides a model applicable to different types of treatment systems, benefiting communities with diverse technologies and capabilities.	High
[20]	2023	VSFCW	The efficiencies obtained were as follows: COD (85–86%, no significant difference), N-NH₄⁺ (74% vs. 68%, significant difference), NT (71% vs. 74%, significant difference for 25 cm), and TSS (91% vs. 63%, significant difference for TAH of 40 mm and 100 mm d⁻¹).	The recommended operating conditions are suitable for different climates, maximizing performance and improving the landscape of the installation site, integrating harmoniously with the environment.	Moderate
[35]	2023	HSFCW	For both hydraulic loading rates, the highest removal efficiencies recorded were BOD₅ (73.97%), COD (71.89%), TSS (90.82%), TP (71.13%), and TN (49.41%). Palm Kernel Shells (PKS) achieved the highest coliform removal (98.6%).	This approach favors the development of accessible and effective technologies for wastewater treatment, contributing to public health and environmental sustainability.	High
[25]	2023	FSCW and HSFCW	Results were obtained in the subsurface flow wetland with Sagittaria latifolia (SSFCW-SL), with removals of turbidity, color, and COD of 95.9%, 89.4%, and 95.7%, respectively. The free water surface wetland with S. latifolia (FFCW-SL) achieved removals of 98.8%, 74.2%, and 89.7%, respectively.	Promotes a species with good abundance in the region, which allows for reduced operating and maintenance costs due to its availability, size, and management.	High
[91]	2024	Two types of constructed wetlands were used: HSFCW and VSFCW.	The optimum pH for nitrogen removal is 7.0–7.5. Intermittent systems outperform continuous systems, achieving higher NH₄⁺-N (99.09% vs. 94.58%), TN (+32%), and TP (54.1% vs. 45.5%) removal.	Constructed wetlands offer a sustainable and low-cost solution for wastewater treatment, improving water quality and contributing to public health and the environment in agricultural communities.	High
[45]	2024	HCW	Average COD, TN, NH₃-N, and TP removal rates in the VHCW were 73.68%, 57.19%, 81.21%, and 72.71%, respectively.	The VHCW system is ideal for decentralized wastewater treatment in rural areas. Its design allows gravity flow without the need for additional power, which reduces operating costs and optimizes the use of space.	Moderate
[92]	2024	Two types of constructed wetlands were used: HSFCW and VSFCW.	Biochemical Oxygen Demand (BOD₅): Average removal 87.5%. Chemical Oxygen Demand (COD): Average removal of 77.3%. Total Nitrogen (TN): Efficiency significantly influenced by temperature and hydric load (HL).	It reduces land occupation compared to traditional wetlands and does not require additional energy, since it operates by gravity.	High
[70]	2024	HSFCW	Reductions: TDS 83%, TSS 82%, BOD₅ 82%, COD 81%, chloride 80%, sulfate 77%, NH₃ 84%, and fats 74%.	This system is economical, ecologically sustainable, and does not require complex infrastructure, making it ideal for rural communities or areas with limited resources.	Moderate
[21]	2024	FSCW	High efficiencies from the start: total solids 80%, COD 93%, NTK 98%, and orthophosphate 97%.	Improved water quality in communities using decentralized treatment systems.	High
[23]	2024	FCW	Reduction of several contaminants, including total nitrogen (78.9%), ammonia (90.2%), total phosphorus (86.9%), DOC (92.8%), BOD₅ (94.8%), TDS (70.7%), and TSS (93.6%).	CW contributed to the reduction of pollutants in the wastewater, having a direct impact on its quality and plant growth.	High
[93]	2024	HSFCW in a small community.	Removal efficiencies up to 91%, 94%, 98%, 52%, 73%, 78%, and 75% for BOD₅, TSS, total phosphorus, nitrates, nitrites, ammonium, and total nitrogen, respectively.	Promotes sustainable agricultural practices in rural areas.	High
[42]	2024	HSFCW	The reduction was between 86.36 and 562.50%; in water hyacinth, it was between 91.30 and 737.50%, and in lotus, it was between 91.30 and 737.50%.	Aesthetic and environmental benefit.	High
[94]	2024	VSFCW	The system achieved maximum removals of BOD₅, COD, TDS, TSS, nitrates, phosphates, phosphate pentoxide, phosphorus, and E. coli of 56.01%, 82.87%, 30, 61%, 90.40% 17, 26%, 35.80%, 36, 19%, 40.64%, and 90.28%, respectively.	Recycle water in other types of activities, generating a positive impact on the community.	High
[58]	2024	Pilot scale PSVF for domestic wastewater treatment.	The systems achieved >95% in BOD₅ and TSS and 60–80% in TN.	Alternative wastewater treatment in a system with lower operating and maintenance costs.	Moderate

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Figure 1. Applied Methodology. Source: Author’s own research.

Figure 2. Productivity of work related to the use of CW in domestic wastewater treatment.

Figure 3. Annual scientific production of research works related to the use of constructed wetlands for domestic wastewater treatment.

Figure 4. Keyword concurrency map obtained from Vosviewer. Source: Author’s own research.

Figure 5. Type of constructed wetlands used in domestic wastewater treatment. Source: Author’s own research.

Figure 6. Types of pretreatments for CW-treated domestic wastewater. Source: Author’s own research.

Figure 7. Type of vegetation and number of times they were used in the literature review. Source: Author’s own research.

Figure 8. Type of substrate and number of times used in the reviewed literature. Source: Author’s own research.

Figure 9. CW Application Sites for Domestic Wastewater Treatment.

Table 1. Article selection process using the PRISMA method (Preferred Reporting Items of Systematic Reviews and Meta-Analyses).

Table 2. Types of constructed wetlands and their definitions.

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Section		Description
Identification		Database: Scopus y Web of Science Timeframe: 2015–2024 Topics: “constructed wetland”, “water”, “domestic”, “performance”
Selection and eligibility	1	Total number of articles (n = 154)	Duplicated article (n = 26) Other reasons (n = 9)
	2	Eligible articles (n = 119)	Excluded articles (n = 41)
	3	Eligible articles (n = 78)	Excluded articles (n = 29)
Inclusion		Eligible articles (n = 49)

Types of CWs	Description	Author
HSFCWs	They use a horizontal flow of water through a porous medium, promoting filtration and contaminant removal.	[31,42,43,44]
VSFCWs	This type of CWs operate with a vertical flow of water through the substrate, improving aeration and nutrient removal.	[20,45,46,47]
HCWs	They combine features of different types of constructed wetlands to optimize wastewater treatment.	[48,49,50,51,52,53]
UCCWs	They are designed to take up little space, employing an upward flow through the support medium for contaminant removal.	[19,54,55,56]
PSVFs	They maintain an unsaturated zone to enhance the removal of nitrogenous compounds and promote substrate aeration.	[57,58,59,60]
FSCWs	They operate with a flow of water over the surface, providing habitat for aquatic species and promoting natural purification processes.	[21,25,61,62]
FCWs	They use floating plants to absorb pollutants and improve water quality in natural or artificial water bodies.	[23,63,64,65]
TFCWs	They mimic tidal flow by alternating flooding and drainage periods to enhance oxygenation and pollutant removal in water.	[66,67,68,69]