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Article

Enhancing Greywater Treatment: High-Efficiency Constructed Wetlands with Seashell and Ceramic Brick Substrates

by
Adriano P. Feitosa
1,
Kelly Rodrigues
1,
Waleska E. Martins
1,
Sara M. P. R. Rodrigues
1,
Luciana Pereira
2,3,4,* and
Glória M. M. Silva
1
1
Graduate Program in Environmental Technology and Management, IFCE, Federal Institute of Ceara, Fortaleza-Ceará 60000-000, Brazil
2
CEB, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
3
LABBELS, Associate Laboratory, 4710-057 Braga, Portugal
4
LABBELS, Associate Laboratory, 4800-058 Guimarães, Portugal
*
Author to whom correspondence should be addressed.
Appl. Sci. 2024, 14(19), 9011; https://doi.org/10.3390/app14199011 (registering DOI)
Submission received: 27 August 2024 / Revised: 19 September 2024 / Accepted: 4 October 2024 / Published: 6 October 2024
(This article belongs to the Special Issue Application of Biological Processes in Waste Treatment and Valorisation)
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Abstract

:

Featured Application

This research underscores the effectiveness of using seashells and ceramic bricks as substrates in vertical flow CW for greywater treatment. The findings are particularly relevant for rural and semi-arid regions, where these low-cost, sustainable systems can enhance water quality. The study also provides valuable insights into optimizing macrophyte age and substrate materials, offering practical solutions for decentralized wastewater treatment in underserved areas. This technology can be particularly beneficial for decentralized wastewater treatment in communities with limited access to advanced infrastructure, offering a practical solution for improving water quality and sustainability in resource-constrained environments.

Abstract

Constructed wetland (CW) systems have been recognized as a sustainable technology for wastewater treatment that can be easily integrated into the local natural environment, offering both low cost and high efficiency. In this study, synthetic greywater was treated using a vertical subsurface flow CW operated in batch mode with 7-day cycles across two phases, operated in parallel: I, non-vegetated, and II, vegetated, with Echinodorus subalatus. The mixed filter bed was composed of seashells, ceramic brick fragments, and sand. No statistically significant differences (p > 0.05) were observed between the non-vegetated and vegetated phases for most parameters. The removal efficiencies of organic matter, anionic surfactants, and total phosphorus in the non-vegetated versus vegetated phases were (91.0 ± 3.8)% versus (94.0 ± 1.1)%; (71.9 ± 14.1)% versus (60.0 ± 9.5)%; and (35.2 ± 4.6)% versus (40.2 ± 15.5)%, respectively. Phosphorus removal exceeded values reported in the literature for both phases, primarily due to the calcium present in the seashells, which increased the electrical conductivity and hardness of the effluent compared to the influent. The macrophyte exhibited leaf desiccation, possibly due to contact with greywater and its young age (30 days), which may have negatively impacted the system’s performance during the vegetated phase.

1. Introduction

The lack of access to clean water is a critical issue affecting billions of people globally. According to the United Nations Children’s Fund and the World Health Organization [1], approximately 2.2 billion people do not have access to safe drinking water services, 4.2 billion lack adequate sanitation, and 3 billion are without basic handwashing facilities. Additionally, it is estimated that 785 million people, representing 10% of the global population, still lack basic water services, with 144 million relying on untreated water, a situation of significant concern.
Water scarcity exacerbates this precarious situation, as water is an essential resource for life. Sustainable management of water resources has become one of the most critical issues of the 21st century, directly impacting water availability [2,3]. Many challenges associated with water scarcity stem from inadequate conservation and protection of water sources. In addition to the deforestation of springs and riparian forests, the pollution of water bodies, particularly through the discharge of untreated or partially treated sewage into natural waters, is identified as the primary contributor to the degradation of water quality [3,4]. Therefore, investing in sanitation and sewage treatment is a crucial strategy for enhancing water supply.
Wastewater treatment plants (WWTPs) are designed to replicate, within a compact space and timeframe, the natural self-purification processes of watercourses [2,4]. Various technologies have been developed to treat water resources, aiming to restore and preserve their physical, chemical, and biological characteristics. Among these, constructed wetland (CW) systems are particularly notable due to their sustainability [5]. CW systems are sustainable and decentralized technologies, effective in improving water quality, and can treat a range of effluents, including domestic sewage, storm water, leachate, and industrial wastewater [5]. They offer significant advantages, such as lower costs for implementation, operation, and maintenance compared to traditional treatment methods. The recent review by Santos et al. [5] examined the impact of substrate type, plant selection, and operational criteria such as hydraulic load and hydraulic retention time (HRT) on CW performance, highlighting the promising use of construction waste and biochar as effective, cost-efficient alternatives due to their adsorption properties and ease of use to enhance efficiency. Their review also provides key insights into how design and operational choices affect CW effectiveness.
The selection of appropriate substrates in wetland systems is crucial for optimizing treatment efficiency, as these substrates play a significant role in biofilm formation [5]. While sand and gravel are commonly used, alternative substrates such as waste materials—specifically, ceramic bricks from construction and seashells from shellfish farming—offer a means to recycle these by-products [5]. Shellfish farming by-products have demonstrated potential for treating wastewater, especially those with high phosphorus content. However, research on using seashells in effluent treatment technologies, particularly within nature-based systems, remains limited [6].
Incorporating endemic macrophytes into wetland systems for wastewater treatment represents a novel advancement in this emerging technology [5,7]. However, selecting plant species for CW requires careful consideration for each specific case. Macrophytes play a vital role in CW systems by enhancing wastewater treatment through nutrient uptake, oxygen transfer, biofilm support, sedimentation, toxin transformation, and hydraulic flow regulation. Effective selection and management of macrophytes are essential for maximizing the efficiency and sustainability of these systems. It is recommended to use native plants or those well adapted to the local climate and environmental conditions. Endemic macrophytes may provide superior performance compared to exotic macrophytes, which are traditionally employed in these systems [5,7].
In rural and semi-arid areas, the lack of access to advanced wastewater treatment technologies poses significant challenges, as conventional centralized systems are often impractical due to economic and infrastructural limitations. These regions typically suffer from water scarcity, further intensifying the need for greywater reuse and effective, low-cost treatment solutions. CW systems, particularly those using vertical subsurface flow, offer a promising alternative due to their low operational costs and ability to treat wastewater effectively in decentralized settings. Despite their potential, there is a noticeable gap in research concerning the use of such systems, specifically for greywater treatment in these areas, where sustainable and affordable solutions are crucial. Brazil, with its favorable climatic conditions and a significant deficit in wastewater treatment infrastructure in some areas, is particularly well suited for broader application of CW technology [5,7]. However, CW remain relatively underexplored and underutilized in the country, primarily confined to scientific research and small-scale wastewater treatment projects [5]. Addressing this gap, the present study evaluates the feasibility of a vertical subsurface flow CW system using alternative substrates, such as seashells and ceramic bricks, which are both cost-effective and sustainable. Additionally, the study explores the role of native macrophytes, specifically Echinodorus subalatus, in enhancing treatment efficiency. This investigation holds particular relevance for rural and semi-arid regions, where low-cost, decentralized wastewater treatment solutions are urgently needed. Therefore, the objective of this study was to assess the feasibility of treating greywater using a CW system with vertical subsurface flow on a bench scale. This system employed a mixed filter bed of seashells and ceramic bricks, which was evaluated for its treatment efficiency both with and without the presence of the native macrophyte species Echinodorus subalatus.

2. Material and Methods

2.1. CW System and Characteristics of the Support Bed

The CW system was constructed at the Environmental Technology Laboratory of the Federal Institute of Education, Science, and Technology of Ceará (IFCE), Fortaleza campus (coordinates: 3°44′47″ S, 38°32′08″ W), and featured a mixed filter bed comprised waste from the shellfish industry and from construction. The experiment was designed with one non-vegetated (Figure 1a) and one vegetated bed (Figure 1b), and both reactors were run in parallel under the same conditions to assess the impact of vegetation on greywater treatment efficiency. The system comprised two rectangular base reservoirs, each measuring 42 × 29 × 27 cm, with a total volume of 30 L. The filter media included ceramic bricks, construction debris, and bivalve mollusk shells from Anomalocardia brasiliana, sourced from shellfish harvesting in Acaraú, Ceará. These materials were pre-washed with running water to eliminate coarse impurities. The materials were layered in the following sequence from the base: brick fragments (8.80 cm), seashells (8.80 cm), and medium sand (Ø 2.00 mm) (4.4 cm), creating a bed with a usable volume of 11.20 L and a porosity of 41%.
The Echinodorus subalatus seedlings were collected from a marsh area in the locality of Jacundá, municipality of Aquiraz, Ceará (3°53′57″ S, 38°25′29″ W) and transported in plastic bags to the laboratory, where they were washed with tap water. Dried and decomposed leaves were pruned, and the seedlings were placed in 1 L plastic beakers containing a nutrient solution composed of (g/L): H3BO3 (0.3), MoO3.H2O (0.13), CaCl2 (0.13), MnCl2 (0.35), KH2PO4 (0.02), KCl (0.15), NaNO3 (0.07), (NH4)2SO4 (0.07), CuSO4.5H2O (0.35), ZnSO4 (0.35), FeSO4 (0.04), and MgSO4 (0.04). The plants were maintained under artificial lighting using 15 W fluorescent lamps with a 12 h photoperiod at 24 °C for approximately 15 days before being planted in the wetland. Echinodorus subalatus was planted with 20 cm spacing between individuals, resulting in a density of 18 plants/m2. Figure 1c illustrates the layout of the wetland system, both with and without vegetation.

2.2. Operation of the Constructed Wetland System

The study was carried out over 98 days, divided into two phases, operated in parallel, non-vegetated (Phase I) and vegetated (Phase II), with each phase consisting of 7 cycles of 7 days each. The system was operated at controlled environment temperature (~24 °C). During Phase II, a 12 h photoperiod was implemented. Each operational cycle encompassed the periods of influent distribution, treatment, and discharge, with the discharge occurring at the end of each cycle. Following discharge, the wetland rested for 1 h before commencing the next cycle.
A gravity-fed reservoir (25 L) positioned at a height of 0.20 m provided synthetic greywater (SGW) to the CW through 12.70 mm internal diameter polyvinyl chloride (PVC) piping. The water was distributed via a perforated horizontal pipe with three 4 mm diameter holes located above the sand layer. Drip irrigation was used to deliver the influent, with an average flow rate of 0.09 L/min. A PVC drainage pipe (12.70 mm internal diameter) at the CW’s bottom collected the treated effluent at the outlet. This pipe was equipped with a valve to control and adjust the flow when emptying the system.

2.3. Synthetic Greywater

The greywater was prepared following the methodology outlined by Abed and Scholz [8] and adapted by Bermudez [7], with the substitution of hygiene and cleaning products by sodium dodecylbenzene sulfonate (C18H29O3SNa). The formulation included the following components per liter of an artesian well water: soluble starch (1 g), sodium bicarbonate (1.25 g), microcrystalline cellulose (0.20 g), ammonium chloride (3.10 g), magnesium chloride (0.20 g), calcium chloride (0.20 g), sodium chloride (1 g), yeast extract (1.25 g), potassium phosphate (2.50 g), sucrose (10 g), and linear alkylbenzene sulfonate (LAS) (0.30 g). This mixture was then combined with 25 L of water in the feeding reservoir and manually homogenized.

2.4. Analytical Methods

Physical and chemical determinations were carried out, in triplicate, to characterize both the SGW feeding the system (influent) and the effluent from the CW during each operating cycle. The parameters tested included pH, electrical conductivity (EC), hardness, dissolved oxygen (DO), total dissolved solids (TDS), total suspended solids (TSS), chemical oxygen demand (COD), phosphorus (P), surfactant (LAS), ammonia (NH4+), nitrite (NO2−), and nitrate (NO3−). The methodologies used were performed according to APHA [9], except for nitrate, which was conducted as per Rodier [10].
Macrophyte growth was monitored weekly by assessing leaf count, shoot emergence, leaf and flower development, plant count, and height measurements, as per Bermudez [7].

2.5. Statistical Analysis

The data related to the physical and chemical parameters of the influents and effluents from the treatment system were analyzed using descriptive statistical tests to assess central tendency, range, and dispersion. For the analyzed parameters, maximum and minimum values, averages, and standard deviations were calculated. Statistical analysis of the obtained data was performed using PAST, statistics software, version 2.17c, using analysis of variance (ANOVA), followed by Tukey’s test at 5% significance (p < 0.05), to assess the significance of differences in removal efficiencies between planted and unplanted beds during the monitoring period. The assumptions of normality and homogeneity of variance were verified prior to performing ANOVA. The Shapiro–Wilk test was applied to check the normality of the data, while Levene’s test was used to assess homogeneity of variances.

3. Results and Discussion

3.1. Characterization of the Synthetic Greywater

The physical and chemical characteristics of the SGW that fed the CW are presented in Table 1.
The average concentration of organic matter in terms of COD in the greywater was 843.7 mg/L, which is intermediate compared to the range of 22.9 to 1307 mg/L reported by Bani-Melhem and Al-Kilani [11], with higher values linked to excessive use of cleaning chemicals and food residues [12]. The average TDS of 700 mg/L and EC of 1430.0 µS/cm were higher than the maximum values reported by Uthirakrishnan et al. [12], which were 650.0 mg/L and 650.0 µS/cm, respectively. This increase is likely due to the water used in preparing the synthetic greywater, similar to Baracuhy [13], who observed an average EC of 3280.0 µS/cm, attributed to the use of groundwater, which generally has higher salt concentrations [14].
The concentration of nitrate in the greywater was relatively low, at 3.4 mg/L, compared to 8.9 mg/L reported by Abed and Scholz [8]. In contrast, ammoniacal nitrogen was higher, 20.0 mg/L, significantly exceeding the 0.4 mg/L found by those authors. The level obtained is more consistent with the values reported by Liao et al. [15] (<14.0 mg/L), as higher nitrogen concentrations are typically associated with dark greywater from kitchen sinks [15,16]. The phosphorus concentration in the greywater was (35.3 ± 4.4) mg/L, which is within the reported range of 0.062–57 mg/L [15]. This variation is influenced by the intensity of detergent, soap, and other cleaning products containing phosphates used in kitchens, bathrooms, and laundries [15,16]. The pH values of greywater generally range from over 9.0, due to heavy use of cleaning products, to between 6.0 and 8.2, due to the presence of amino acids [16,17]. The average pH in this study was (6.83 ± 0.20), consistent with the typical range for such discharges.
Products like laundry detergents, dishwashing detergents, and fabric softeners contribute to the presence of anionic surfactants in wastewater, with LAS being the most commonly used in these formulations, accounting for an annual global production of 4 million tons [18]. When these discharges are not properly managed, LAS can become adsorbed onto suspended particles and sediment in water bodies [19].

3.2. Operation and Performance of the CW with the Studied Substrates

The variations in COD concentrations in both the influent and effluent, as well as the system’s efficiency during the non-vegetated phase (Phase I) and the vegetated phase (Phase II), are presented in Figure 2. The system demonstrated similar removal efficiencies for organic matter in terms of COD across both phases, with percentages of (94.0 ± 1.1)% in the vegetated phase and (91.0 ± 3.8)% in the non-vegetated phase. Statistical analysis confirmed no significant difference between the two phases (p = 0.38; p > 0.05). The concentrations of COD in the treated effluent were (50.0 ± 10.8) mg/L for the vegetated phase and (74.8 ± 29.8) mg/L for the non-vegetated phase. In the vegetated phase, the presence of plants likely contributed to enhanced treatment efficiency through the development of microbiota on the plant roots, which aids in organic matter assimilation and increases bed oxygenation, promoting degradation by aerobic and facultative microorganisms [20]. Conversely, the non-vegetated system showed greater variability in COD concentrations, ranging from 40.0 mg/L in the 5th cycle to 132.0 mg/L in the 6th cycle, whereas the vegetated phase had a narrower range from 38.0 mg/L in the 9th cycle to 65.5 mg/L in the 14th cycle. This suggests that vegetation may stabilize and improve the consistency of treatment performance.
Table 2 presents the removal efficiencies of organic matter reported in various studies on greywater treatment using vertical flow wetlands across different cycle times. The average removal of organic matter, as measured by COD, was higher than the 88.4% achieved by Bermudez [7] in a similar wetland system operated on a pilot scale with the same 7-day cycle time for greywater treatment, despite the slightly lower temperature in our study compared to Bermudez’s [7] pilot system (25–30 °C). This suggests that Echinodorus subalatus used in both systems is not adversely affected by the lower temperatures in the controlled environment (~24 °C) of this study, nor by the temperature fluctuations in Bermudez et al.’s research [7], which lacked temperature control.
Though there are high organic matter concentrations in greywater, as compared with other waters, CW has demonstrated effective performance with their treatment. For instance, Sotiropoulou et al. [21] reported successful treatment of laundry greywater using a vertical flow wetland with a sand bed and vegetated with Zantedeschia aethiopica, operating with varying hydraulic loads (15.9 to 63.7 mm/day) in 24 h cycles. The authors reported removal efficiencies between 92.0% and 97.0%, noting that while the highest hydraulic load reduced efficiency, optimal performance was achieved at a hydraulic load of 15.9 mm/day, resulting in a 97.0% removal. The laundry water had an organic matter concentration varying from 500.0 to 2500.0 mg COD/L, depending on the operational phase.
Kotsia et al. [22] also achieved a high COD removal rate of 96% in greywater treatment using CW, and this removal was similar regardless of the plant used. On the other hand, Nema et al. [23] obtained removal efficiencies that ranged from 46.7% to 55.4%, and the fluctuation in removal percentages was likely due to the type of macrophyte used, with the best efficiency using Hymenocallis littoralis and the worse with Phragmites australis. Notwithstanding the lower removal percentages compared to other studies, it is important to note that the cycle time was only 0.5 days (Table 2).
Interestingly, the concentration of TDS and EC increased from influent to effluent. TDS values were (680 ± 33.3) mg/L (Phase I) and (719 ± 14.0) mg/L (Phase II) in the influent, and (904 ± 46) mg/L (Phase I) and (920 ± 2.0) mg/L (Phase II) in the effluent. Similarly, EC rose from (1256 ± 67) µS/cm (Phase I) and (1452 ± 23) µS/cm (Phase II) in the influent to (1807 ± 93) µS/cm (Phase I) and (1842 ± 49) µS/cm (Phase II) in the effluent. This increase in TDS and EC may be attributed to ions released from the bed materials, such as carbonate, bicarbonate, chloride, and calcium, among others [24].
Calcium carbonate present in shells and bricks can gradually leach into water over time, resulting in an increase in calcium ion concentration and, consequently, water hardness [24,25], as observed in this study. The total hardness measured in the influent exhibited similar values across both phases: in the phase non-vegetated phase (Phase I), hardness in the influent ranged from 100.0 mg/L to 175.0 mg/L, with a mean of (125.5 ± 23.8) mg/L, and, during the vegetated phase (Phase II), it ranged from 100.0 to 160.0 mg/L, with a mean of (135.7 ± 23.9) mg/L. Regarding the effluent, hardness values were also close across both phases, ranging from 400 to 505 mg/L in the non-vegetated phase with a mean of (457.1 ± 37.3) mg/L, and from 400 to 505 mg/L, with a mean of (444.3 ± 31.7) mg/L in the vegetated phase.
Elevated hardness and EC values can compromise the performance of these systems. High EC indicates increased salinity, which can stress macrophytes [13,26]. Increased hardness, driven by higher calcium concentrations, can impact aquatic organisms by reducing epithelial permeability, affecting nutrient availability, and altering biogeochemical processes in wetlands. This reduction in permeability can hinder passive diffusion and increase the energy required for osmoregulation [27]. The increase in Ca++ and Mg++ can also influence the pH of the environment, as these ions can neutralize acids and bases present in the environment, especially in closed systems like CW [28]. However, in this study both influent and effluent showed stability in pH values throughout the operational cycles, with average values of 6.93 and 7.02, respectively, in the non-vegetated phase and 6.83 and 6.98 in the vegetated phase, respectively, in the vegetated phase, remaining very close to neutral conditions. It is considered ideal for pH to remain between 6.50 and 8.00 to favor nitrification and denitrification processes [29,30]. Additionally, the final effluent complied with the pH limits set by Brazilian legislation CONAMA Nº 430/2011 [31], which is between 5.0 and 9.0 for discharge into receiving water bodies.
In Phases I and II, the system demonstrated an ammonium nitrogen removal efficiency of (32.4 ± 9.7)%, with the average ammonia concentration decreasing from 56.8 ± 2.4 mg/L in the influent to (38.4 ± 5.4) mg/L in the effluent. During Phase I, the effluent ammonium nitrogen values exhibited greater stability, ranging from 31.6 to 47.2 mg/L, in contrast to Phase II, where values fluctuated between 43.1 and 66.1 mg/L, indicating a tendency towards nutrient production in this latter phase. The low efficiency of ammonium nitrogen removal can be attributed to the brief emptying time of the wetland (1 h), which likely limited natural aeration. This is reflected in the recorded average dissolved oxygen levels of (0.77 ± 0.58) mg/L in Phase I and (1.60 ± 0.15) mg/L in Phase II, conditions that are insufficient to support the nitrification process. Nitrification, mediated by ammonia-oxidizing bacteria such as Nitrosospira, Nitrosomonas, and Nitrosococcus, and nitrite-oxidizing bacteria such as Nitrospira, Nitrobacter, and Nitrococcus, was likely inhibited, hindering the conversion of ammonia to nitrate [32]. Therefore, the average influent nitrate concentration (3.40 ± 0.50 mg/L), which was relatively low to begin with, was entirely removed in both operational phases. This complete removal is likely due to absorption by macrophytes, although denitrifying bacteria may also convert nitrate to gaseous nitrogen in anoxic areas within the bed [32].
In the 3rd, 4th, 5th, and 6th cycles of the vegetated phase, it was observed that the effluent ammonium nitrogen concentrations were higher than the influent concentrations. This anomaly may be attributed to several factors, including potential accumulation or desorption of N-NH4+ within the system during these cycles, fluctuations in system performance, or variations in the biological activity of the vegetated bed. Additionally, temporary imbalances in nutrient uptake or microbial activity may have contributed to these unexpected results. Figure 3a illustrates the variations in ammonium nitrogen and phosphorus concentrations across the cycles of Phases I and II.
For phosphorus, the average removal efficiencies were (35.2 ± 4.6%) in Phase I and (40.2 ± 15.4)% in Phase II (Figure 3b). The vegetated phase achieved a maximum phosphorus removal efficiency of 70.4% in its first cycle. The effluent phosphorus concentrations in the non-vegetated phase ranged from 18.2 to 27.3 mg/L, with a mean of (22.4 ± 3.0) mg/L. In contrast, the vegetated phase had a lower average effluent phosphorus concentration of (20.8 ± 4.9) mg/L, ranging from 27.2 to 11.5 mg/L. The system demonstrated exceptional performance in phosphorus removal. Typical phosphorus removal efficiencies in vertical wetlands are under 20%, which aligns with the 10% to 30% range reported by Metcalf and Eddy [33,34] for secondary biological systems. The enhanced removal efficiency observed in this study may be attributed to the inclusion of marine shells and bricks in the filter bed, which likely contribute to improved phosphorus retention due to the composition of these materials. Bivalve shells, which contain significant amounts of CaO (51.0–54.7%), are known for their ability to retain phosphorus, achieving removal rates of nearly 90.0% [35,36]. However, in this study, phosphorus removal cannot be solely attributed to adsorption by the substrates. The total mass of phosphorus removed was 2.08 mg, whereas the adsorption capacities of the shells and bricks are 0.001 mg/g and 0.002 mg/g, respectively [7]. Given these adsorption capacities, the maximum phosphorus that could theoretically be removed by the shells and bricks would be 0.015 g and 0.022 g, respectively. This indicates that the observed phosphorus removal exceeds what could be accounted for by adsorption alone. Thus, with the layers of shell and brick alone, a maximum of 73.5 mg/g of support material would have been retained, a value that exceeds the phosphorus adsorption capacities of 0.015 g and 0.022 g for shells and bricks, respectively. This suggests that phosphorus removal was likely due to microbial activity, plant uptake, or the formation of phosphorus precipitates through biochemical reactions in the medium [37]. The increase in effluent hardness, associated with the wear of seashells, may also indicate the formation of calcium precipitates.
Indeed, in most of the CW systems, phosphorus removal efficiency remains relatively low, but performance may be enhanced through the use of alternative substrates, particularly those rich in calcium, iron, and aluminum, which can form insoluble complexes with phosphorus [36]. Materials with high adsorption capacities can further optimize wetland performance. For instance, Žibienė et al. [37] demonstrated that a vertical flow wetland using a dolomite (CaMg(CO3)2) bed achieved a 21% increase in phosphorus removal compared to one with a sand bed, underscoring the significance of substrate selection for improving treatment efficiency. Other materials with high phosphorus adsorption capabilities, such as expanded clay, aluminum sludge, and oyster shells, have also been suggested [38,39].
The use of adsorbent materials as substrates typically plays a more pivotal role than biological absorption in phosphorus removal within constructed wetlands [40,41]. While vegetated wetlands generally exhibit enhanced phosphorus absorption, achieving permanent nutrient removal and contributing to efficiencies ranging from 4.72% to 59.6% [38,42], this study found no significant difference in phosphorus removal between the vegetated phase (40.17 ± 0.15)% and the non-vegetated phase (34.42 ± 3.07%) (p = 0.6586; p > 0.05). Similarly, no significant statistical difference was observed in the removal of the anionic surfactant between phases I and II (p = 0.2500; p > 0.05), with removal efficiencies of (71.9 ± 14.1)% and (60.0 ± 9.5)% in the non-vegetated and vegetated phases, respectively. In Phase I (without vegetation), the final effluent anionic surfactant concentrations ranged from 0.7 to 2.3 mg/L, with a mean of (1.4 ± 0.7) mg/L, and, in Phase II (with vegetation), ranged from 0.9 to 2.8 mg/L, with a mean of (1.8 ± 0.6) mg/L. The removal efficiency observed in the unplanted systems suggests that physical processes such as adsorption or biofilm formation on the gravel surface play a significant role in LAS removal. The overall average removal efficiency of (64 ± 16.9)% indicates that the system effectively removed this substance. Interestingly, Bermudez [7], while operating two pilot-scale CW with 7-day cycles and vegetated with Echinodorus subalatus in a bed composed of sand, shells, and bricks, achieved a 94.1% removal of LAS despite a significantly 100 times higher influent concentration. Adsorption onto the media was the primary mechanism for LAS removal. This discrepancy in removal efficiency compared to the current study may be attributed to the use of pure surfactant in this research, whereas Bermudez [7] used shampoo and liquid soap as the source of the surfactant.
Pérez-Lopez et al. [42] reported a 90% removal of 83.0 mg/L of LAS using agave fiber as a substrate in a CW vegetated with Schoenoplectus americanus and operated under continuous flow with an HRT of 15 days. They attributed the primary removal mechanism to the adsorption of LAS onto the filter bed material. Similarly, Thomas et al. [43] achieved a 95% removal of LAS from an influent concentration of 10 mg/L in a CW system treating domestic wastewater. This system was vegetated with Pragmites australis, Thypha latifolia, Salix viminalis, Iris, and Juncus effusus in a gravel bed, and operated an HRT of 13.8 days. The study also highlighted adsorption onto the filter bed as the principal removal pathway.

3.3. Assessment of Echinodorus Subalatus Growth and Development

Echinodorus subalatus measured 20 cm when introduced into the wetlands, a height below the recommended ideal range of 25 to 60 cm for perennial plants of this species [44], since the plants used in this study were younger and therefore smaller. However, Brisson and Chazarenc [45] suggest that using younger individuals is preferable for wetland systems, as they tend to assimilate a greater number of contaminants during their growth phase. They also noted that at the senescence stage, the decomposition of macrophytes can release nutrients into the environment, potentially influencing the microbial dynamics. Higher nutrient release can reduce microbial diversity, negatively impacting wastewater treatment in constructed wetlands.
During the operation of the system, desiccation of leaf edges was observed, although new small leaves emerged without fully developing, leading to limited plant decomposition. Symptoms such as chlorosis (yellowing) and leaf curling, which are early indicators of senescence, were noted. These symptoms can arise from nutrient imbalances or toxicity in greywater [46]. It is possible that greywater exerted a toxic effect on the plants, as similarly reported by Marcelino and Morais [47], who operated a small-scale, shallow vertical flow CW for dairy industry effluents (COD (3014.3 ± 37.9) mg/L; pH (4.25 ± 0.05)). They observed growth inhibition and subsequent death of Pistia stratiotes (water lettuce), which was replaced by Eichhornia crassipes (water hyacinth) due to its better adaptation. This suggests that the sensitivity of macrophyte species to specific environments can significantly influence the performance of the system, highlighting the importance of species selection. Forgiarini and Rizzi [48] also operated a vertical subsurface flow CW and observed a partial loss of the planted macrophytes in their system, which was fed with domestic wastewater containing 464.2 mg BOD/L (789.14 mg COD/L). Over a period of 45 days, Colocasia esculenta experienced a 100% loss of the initially planted individuals (five replacements), Typha sp. had a 33% loss (two replacements), and Pennisetum purpureum experienced a 66% loss (three replacements). This decline in plant survival was attributed to the effects of the wastewater and the low temperatures (12 to 16 °C).
In the present study, the average temperature in the laboratory where the wetland was installed was approximately 24 °C, which is higher than the temperatures reported by Forgiarini and Rizzi [48]. Over the 49 days of operation with the vegetated system, there was no total loss of individuals. However, the average number of leaves per plant decreased from 10 to 4 by the end of the experiment, and no new leaves were observed to sprout. This suggests that Echinodorus subalatus endured the imposed conditions relatively well, without requiring the replanting of new individuals in the system. Additionally, Forgiarini and Rizzi [48] noted that the optimal age for macrophytes used in constructed wetlands should be between 60 and 90 days. In this study, Echinodorus subalatus was planted at just 30 days old, which is below the recommended age. This may have contributed to the lack of a significant difference in the system’s performance between the vegetated and non-vegetated phases. It is important to note that the Echinodorus subalatus individuals did not exhibit any increase in height, remaining at 20 cm, the same as at the start of the experiment. This stagnation in growth suggests that the composition of the greywater, combined with the young age of the plants (30 days), may have restricted the optimal development of the macrophytes, thereby limiting the system’s ability to achieve greater pollutant removal. Consequently, planting Echinodorus subalatus at an age of 30 days or younger is not recommended, as it did not significantly enhance greywater treatment.

4. Conclusions

This study evaluated the performance of a vertical flow CW system with Echinodorus subalatus for greywater treatment, demonstrating that the use of seashells and ceramic bricks as alternative substrates is both feasible and sustainable. These materials facilitated effective removal of most monitored variables, with phosphorus removal rates around 35% in Phase I (non-vegetated) and circa 40% in Phase II (vegetated), notably surpassing the 20% efficiency commonly reported for such systems, possibly due to the inclusion of calcium-rich substrates, which facilitated phosphorus precipitation. The high phosphorus removal rate was attributed to the adsorption capacity of the substrates and potential phosphorus precipitation associated with calcium from the seashells. Ammonium nitrogen removal was low across both phases, likely due to the long cycle time (7 days) and short resting time (1 h), which may have limited natural aeration and inhibited the nitrification process. Despite the system’s capability to achieve good removal percentages for organic matter (COD: ~91 in Phase I and ~94% in Phase II), anionic surfactant (~72% in Phase I and ~60% in Phase II), and phosphorus, the young age of the Echinodorus subalatus plants may have limited their performance due to their susceptibility to pollutants, as evidenced by leaf desiccation and chlorosis. The use of more mature macrophytes is recommended to enhance resilience to pollutants and improve treatment efficiency.
The findings support the continued use and development of this technology, particularly in rural and semi-arid areas. However, further research into optimizing macrophyte age and other operational parameters is needed to achieve even better performance and maximize the benefits of CW for greywater treatment.

Author Contributions

Conceptualization, A.P.F. and G.M.M.S.; methodology, A.P.F., W.E.M. and S.M.P.R.R.; validation, G.M.M.S., K.R. and L.P.; formal Analysis, G.M.M.S., K.R. and L.P.; investigation, A.P.F., G.M.M.S., K.R., L.P., S.M.P.R.R. and W.E.M.; resources, G.M.M.S., K.R. and W.E.M.; data Curation, A.P.F., G.M.M.S. and K.R.; writing, A.P.F.; writing—review and editing, G.M.M.S., K.R. and L.P.; supervision, G.M.M.S. and K.R.; project administration, G.M.M.S.; funding acquisition, G.M.M.S. and K.R. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The raw data required to reproduce these findings will be made available upon request.

Acknowledgments

The authors express their acknowledgments to the funding agencies Coordination for the Improvement of Higher Education Personnel (CAPES), to the Ceará Foundation for Scientific and Technological Development (FUNCAP), and to the Environmental Technology Laboratory (LATAM) of the Federal Institute of Professional Education, Science, and Technology. We also acknowledge the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of the UIDB/04469/2020 unit and LABBELS—Associate Laboratory in Biotechnology, Bioengineering, and Microelectromechanical Systems, LA/P/0029/2020.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. United Nations Children’s Fund and World Health Organization. Progress on Household Drinking Water. Sanitation and Hygiene 2000–2017. Special Focus on Inequalities. New York, 2019; pp. 1–140. Available online: https://www.who.int/publications/i/item/9789241516235 (accessed on 24 August 2024).
  2. Tundisi, J.G.; Matsumara-Tundisi, T.A. Água (Water); Scienza: São Carlos, SP, Brazil, 2020; pp. 1–130. [Google Scholar] [CrossRef]
  3. UNEP. A Snapshot of the World’s Water Quality: Towards a Global Assessment; United Nations Environment Programme: Nairobi, Kenya, 2016; pp. 1–162. [Google Scholar]
  4. Stamatelatou, K.; Tsagarakis, K.P. Sewage Treatment Plants: Economic Evaluation of Innovative Technologies for Energy Efficiency; IWA Publishing: London, UK, 2015; pp. 1–337, Number 104536. Available online: https://library.oapen.org/handle/20.500.12657/43789 (accessed on 24 August 2024).
  5. Santos, J.; Rodrigues, S.; Magalhães, M.; Rodrigues, K.; Pereira, L.; Marinho, G. A state-of-the-art review (2019–2023) on constructed wetlands for greywater treatment and reuse. Environ. Chall. 2024, 16, 100973. [Google Scholar] [CrossRef]
  6. Wani, A.K.; Akhtar, N.; Mir, T.U.G.; Rahayu, F.; Suhara, C.; Anjli, A.; Chopra, C.; Singh, R.; Prakash, A.; El Messaoudi, N.; et al. Eco-friendly and safe alternatives for the valorization of shrimp farming waste. Environ. Sci. Pollut. Res. 2024, 31, 38960–38989. [Google Scholar] [CrossRef] [PubMed]
  7. Bermudez, V.M.S. Wetland System Built with Native Macrophyte Echinodorus Subalatus for Gray Water Treatment. Ph.D. Thesis, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, Brazil, 2022. Available online: http://repositorio.ufc.br/handle/riufc/69601 (accessed on 24 August 2024).
  8. Abed, S.N.; Scholz, M. Chemical simulation of greywater. Environ. Technol. 2016, 37, 1631–1646. [Google Scholar] [CrossRef] [PubMed]
  9. American Public Health Association (APHA). Standard Methods for the Examination of Water and Wastewater, 23rd ed.; American Public Health Association: Washington, DC, USA, 2005; pp. 1–9750. ISBN 978-087553-287. [Google Scholar]
  10. Rodier, J. Análisis de las Aguas (Spanish Edition); Omega: Barcelona, Spain, 1990. [Google Scholar]
  11. Bani-Melhem, K.; Al-Kilani, M.R.A. Comparison between iron and mild steel electrodes for the treatment highly loaded greywater using an electrocoagulation technique. Arab. J. Chem. 2023, 16, 105119. [Google Scholar] [CrossRef]
  12. Uthirakrishnan, U.; Manthapuri, V.; Harafan, A.; Chellam, P.V.; Karuppiah, T. The regime of constructed wetlands in greywater treatment. Water Sci. Technol. 2022, 85, 3169–3183. [Google Scholar] [CrossRef]
  13. Baracuhy, V.S. Monitoring Gray Water Quality and Socio-Environmental Assessment of Users in an Agricultural Production Unit in Cabaceiras-PB. Master’s Thesis, Federal University of Campina Grande, Paraíba, Brazil, 2014. Available online: http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/17022 (accessed on 24 August 2024).
  14. Paulo, P.L.; Azevedo, C.; Begosso, L.; Galbiati, A.F.; Boncz, M.A. Natural systems treating greywater and blackwater on-site: Integrating treatment. reuse and landscaping. Ecol. Eng. 2013, 50, 95–100. [Google Scholar] [CrossRef]
  15. Liao, Y.; Wam, Z.; Cao, X.; Jiang, L.; Feng, L.; Zheng, H.; Ji, F. The importance of rest phase and pollutant removal mechanism of tidal flow constructed wetlands (TFCW) in rural grey water treatment. Chemosphere 2023, 311, 137010. [Google Scholar] [CrossRef]
  16. Gholami, M.; O’Sullivan, A.D.; Mackey, H.R. Nutrient treatment of greywater in green wall systems: A critical review of removal mechanisms, performance efficiencies and system design parameters. J. Environ. Manag. 2023, 345, 118917. [Google Scholar] [CrossRef]
  17. Oteng-Peprah, M.; Acheampong, M.A.; Devries, N.K. Greywater characteristics. treatment systems. reuse strategies and user perception-a review. Water Air Soil Pollut. 2018, 229, 255. [Google Scholar] [CrossRef]
  18. Júnior, R.M.; Passoni, C.M.; Santos, M.F.; Bernardes, F.S.; Magalhães Filho, F.J.C.; Paulo, P.L. Assessment of surfactant removal capacity and microbial community diversity in a greywater-treating constructed wetland. Resources 2023, 12, 38. [Google Scholar] [CrossRef]
  19. Hampel, M.; Mauffrett, A.; Pazdro, K.; Blasco, J. Anionic surfactant linear alkylbenzene sulfonates (LAS) in sediments from the Gulf of Gdask (southern Baltic Sea. Poland) and its environmental implications. Environ. Monit. Assess. 2012, 184, 6013–6023. [Google Scholar] [CrossRef] [PubMed]
  20. Sezerino, P.H.; Santos, M.O.; Pelissari, C.; Celis, G.S.; Philipp, L.S. Horizontal constructed wetlands applied on decentralized wastewater treatment. Rev. Eng. Const. Civil 2015, 2, 1–10. [Google Scholar]
  21. Sotiropoulou, M.; Stefanatou, A.; Schiza, S.; Petousi, I.; Stasinakis, A.S.; Fountoulakis, M.S. Removal of microfiber in vertical flow constructed wetlands treating greywater. Sci. Total. Environ. 2023, 858, 159723. [Google Scholar] [CrossRef] [PubMed]
  22. Kotsia, D.; Deligianni, A.; Fyllas, N.M.; Stasinakis, A.S.; Fountolakis, M.S. Converting treatment wetlands into “treatment gardens”: Use of ornamental plants for greywater treatment. Sci. Total. Environ. 2020, 744, 140889. [Google Scholar] [CrossRef] [PubMed]
  23. Nema, A.; Prasad, R.; Sharma, D.; Yadav, K.; Chistian, R.A.; Hibrahim, H. Performance evaluation of different macrophytes in small-scale vertical flow constructed wetlands for greywater treatment using principal component analysis. Can. J. Chem. Eng. 2023, 101, 1321–1334. [Google Scholar] [CrossRef]
  24. Faisal, A.A.H.; Taha, D.S.; Hassan, W.H.; Lakhera, S.K.; Ansar, S.; Pradhan, S. Subsurface flow constructed wetlands for treating of simulated cadmium ions-wastewater with presence of Canna indica and Typha domingensis. Chemosphere 2023, 338, 139469. [Google Scholar] [CrossRef]
  25. Pinheiro, V.S. Application of Dissolved Air Flotation for Treating Hard Water in the Seridó/RN Region. M.Sc. Thesis, Federal University of Pernambuco, Recife, Brazil, 2011. [Google Scholar]
  26. Khalifa, M.E.; El-Reash, Y.G.A.; Ahmed, M.I.; Rizk, F.W. Effect of media variation on the removal efficiency of pollutants from domestic wastewater in constructed wetland systems. Ecol. Eng. 2020, 143, 105668. [Google Scholar] [CrossRef]
  27. Zak, D.; Hupter, M.; Cabezas, A.; Juransiski, G.; Audet, J.; Kleeberg, A.; Goldhammer, T. Sulphate in freshwater ecosystems: A review of sources, biogeochemical cycles, ecotoxicological effects and bioremediation. Earth Sci. Rev. 2021, 212, 103446. [Google Scholar] [CrossRef]
  28. Teir, S.; Eloneva, S.; Fogelholm, C.-J.; Zevenhoven, R. Stability of calcium carbonate and magnesium carbonate in rainwater and nitric acid solutions. Energy Convers. Manag. 2006, 47, 3059–3068. [Google Scholar] [CrossRef]
  29. Miloslav, S.; Cooper, J.E. The influence of soil pH on denitrification: Progress towards the understanding of this interaction over the last 50 years. Eur. J. Soil Sci. 2002, 53, 345–354. [Google Scholar] [CrossRef]
  30. Ma, Y.; Zheng, X.; Fang, Y.; Xu, K.; He, S.; Zhao, M. Autotrophic denitrification in constructed wetlands: Achievements and challenges. Bioresour. Technol. 2020, 318, 123778. [Google Scholar] [CrossRef] [PubMed]
  31. Brasil. Ministério do Meio Ambiente (MMA). Resolução nº 430. de 17 de Março de 2011; Conselho Nacional do Meio Ambiente (CONAMA): Brasília, Brazil, 2011; Available online: https://www.legisweb.com.br/legislacao/?id=114770 (accessed on 24 August 2024).
  32. Punyapwar, S.; Mutnuri, S. Diversity and functional annotation of microorganisms in French vertical flow constructed wetland treating greywater. World J. Microbiol. Biotechnol. 2020, 36, 148. [Google Scholar] [CrossRef] [PubMed]
  33. Vymazal, J. Removal of nutrients in various types of constructed wetlands. Sci. Total. Environ. 2007, 380, 48–65. [Google Scholar] [CrossRef] [PubMed]
  34. Metcalf, L.; Eddy, H.P. Wastewater Engineering: Treatment and Resource, 5th ed.; McGraw-Hill: New York, NY, USA, 2016; p. 2018. [Google Scholar]
  35. Cheng, G.; Li, Q.; Su, Z.; Sheng, S.; Fu, J. Preparation, optimization, and application of sustainable ceramsite substrate from coal fly ash/waterworks sludge/oyster shell for phosphorus immobilization in constructed wetlands. J. Clean. Prod. 2018, 175, 572–581. [Google Scholar] [CrossRef]
  36. Deng, S.; Chen, Y. A study by response surface methodology (RSM) on optimization of phosphorus adsorption with nano spherical calcium carbonate derived from waste. Water Sci Technol. 2019, 79, 188–197. [Google Scholar] [CrossRef]
  37. Žibien, G.; Dapkien, M.; Kazakeviien, J.; Radzeviius, A. Phosphorus removal in a vertical flow constructed wetland using dolomite powder and chippings as filter media. J. Water Secur. 2015, 1, 46–52. [Google Scholar] [CrossRef]
  38. Yang, Y.; Zhao, Y.; Liu, R.; Morgan, D. Global development of various emerged substrates utilized in constructed wetlands. Bioresour. Technol. 2018, 261, 441–452. [Google Scholar] [CrossRef]
  39. Nguyen, T.A.H.; Ngo, H.H.; Guo, W.S.; Nguyen, T.H.H.; Soda, S.; Vu, N.D.; Pham, T.T. White hard clam (Meretrix lyrata) shells media to improve phosphorus removal in lab-scale horizontal sub-surface flow constructed wetlands: Performance. removal pathways. and lifespan. Bioresour. Technol. 2020, 312, 123602. [Google Scholar] [CrossRef]
  40. Almuktar, A.A.A.N.; Suhail, N.A.; Scholz, M. Wetlands for wastewater treatment and subsequent recycling of treated effluent: A review. Environ. Sci. Pollut. Res. 2018, 25, 23595–23623. [Google Scholar] [CrossRef]
  41. Wu, S.; Kuschk, P.; Brix, H.; Vymazal, J.; Dong, R. Development of constructed wetlands in performance intensifications for wastewater treatment: A nitrogen and organic matter targeted review. Water Res. 2014, 57, 40–55. [Google Scholar] [CrossRef]
  42. Pérez-Lopez, M.E.; Arreaola-Ortiz, A.E.; Zamora, P.M. Evaluation of detergent removal in artificial wetlands (biofilters). Ecol. Eng. 2018, 122, 135–142. [Google Scholar] [CrossRef]
  43. Thomas, R.; Gough, R.; Freeman, C. Linear alkylbenzene sulfonate (LAS) removal in constructed wetlands: The role of plants in the treatment of plants the treatment of a typical pharmaceutical and personal care product. Ecol. Eng. 2017, 106, 415–422. [Google Scholar] [CrossRef]
  44. Matias, L.Q.; Soares, G. Morphology and micromorphology of the seed coats of species of Echinodorus (Alismataceae) from Brazilian Northeastern. Bol. Mus. Para. Emílio Goeldi Ciênc. Nat. 2009, 4, 165–173. [Google Scholar] [CrossRef]
  45. Brisson, J.; Chazarenc, F. Maximizing pollutant removal in constructed wetlands: Should we pay more attention to macrophyte species selection? Sci. Total. Environ. 2009, 407, 3923–3930. [Google Scholar] [CrossRef]
  46. Tan, S.; Sha, Y.; Sun, L.; Li, Z. Abiotic Stress-Induced Leaf Senescence: Regulatory Mechanisms and Application. Int. J. Mol. Sci. 2023, 24, 11996. [Google Scholar] [CrossRef]
  47. Marcelino, G.C.; Morais, A.A. Analysis of a prototype of constructed wetlands in the treatment of industrial dairy effluents. Res. Soc. Dev. 2022, 11, 12811830520. [Google Scholar] [CrossRef]
  48. Forgiarini, F.R.; Rizzi, E.S. Efficiency of different macrophytes in the removal of biodegradable organic matter in constructed wetland with vertical flow in subtropical climate. Sci. Eng. J. 2016, 25, 79–86. [Google Scholar] [CrossRef]
Applsci 14 09011 g001
Figure 1. Images of the non-vegetated (a) and vegetated (b) operated CW, and scheme of the CW system operated with the detail of Echinodorus subalatus, in the vegetated phase (c).
Figure 1. Images of the non-vegetated (a) and vegetated (b) operated CW, and scheme of the CW system operated with the detail of Echinodorus subalatus, in the vegetated phase (c).
Applsci 14 09011 g001
Applsci 14 09011 g002
Figure 2. COD removal efficiency in the system during the non-vegetated phase (Phase I) and the vegetated phase (Phase II).
Figure 2. COD removal efficiency in the system during the non-vegetated phase (Phase I) and the vegetated phase (Phase II).
Applsci 14 09011 g002
Applsci 14 09011 g003
Figure 3. Variation in (a) ammonium nitrogen (N-NH4+) and (b) total phosphorus (P) concentrations, along with their removal efficiency over time during the phases without vegetation (Phase I) and with vegetation (Phase II).
Figure 3. Variation in (a) ammonium nitrogen (N-NH4+) and (b) total phosphorus (P) concentrations, along with their removal efficiency over time during the phases without vegetation (Phase I) and with vegetation (Phase II).
Applsci 14 09011 g003
Table 1. Characterization of the greywater that fed the constructed wetland.
Table 1. Characterization of the greywater that fed the constructed wetland.
ParameterMinimumMaximumAverage
pH6.617.116.83 ± 0.20
EC (μS/cm)1256.01452.01430.0 ± 60.4
Hardness (mgCaCO3/L)100.0175.0135.7 ± 23.5
COD (mg/L)713.71030.0843.7 ± 95.0
Phosphorus (mg/L)29.639.835.3 ± 3.4
Ammonium (mg/L)9.733.820.5 ± 6.4
Nitrate (mg/L)2.84.13.4 ± 0.5
Nitrite (mg/L)51.560.357.7 ± 2.6
LAS (mg/L)3.46.14.3 ± 0.9
DO (mg/L)1.23.11.9 ± 0.5
TS (mg/L)136016141498 ± 82
TDS (mg/L)628736700 ± 32
TSS (mg/L)640897751 ± 80
EC—electrical conductivity; COD—chemical oxygen demand; LAS—linear alkylbenzene sulfonate; DO—dissolved oxygen; TS—total solids; TDS—total dissolved solids; TSS—total suspended solids.
Table 2. Organic matter removal efficiency, measured as COD, reported in the literature for vertical flow wetlands operated at various cycle times for greywater treatment.
Table 2. Organic matter removal efficiency, measured as COD, reported in the literature for vertical flow wetlands operated at various cycle times for greywater treatment.
ReferenceColonizing SpeciesInfluent
COD
(mg/L)		Cycle Time (Days)Efficiency
(%)
This studyEchinodorus subalatus843.7 794.0
Bermudez [7]Echinodorus subalatus1851.7788.4
Sotiropoulou et al. [21]Zantedeschia aethiopica500–2500192.0–97.0
Kotsia et al. [22]Pittosporum tobira 
Polygala myrtifolia
Hedera helix (ivy)		350796.0
Nema et al. [23]Hymenocallis littoralis
Phragmites australis
Canna indica
Colocasia esculenta		143.30.5055.4
46.7
52.5
50.6
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Feitosa, A.P.; Rodrigues, K.; Martins, W.E.; Rodrigues, S.M.P.R.; Pereira, L.; Silva, G.M.M. Enhancing Greywater Treatment: High-Efficiency Constructed Wetlands with Seashell and Ceramic Brick Substrates. Appl. Sci. 2024, 14, 9011. https://doi.org/10.3390/app14199011

AMA Style

Feitosa AP, Rodrigues K, Martins WE, Rodrigues SMPR, Pereira L, Silva GMM. Enhancing Greywater Treatment: High-Efficiency Constructed Wetlands with Seashell and Ceramic Brick Substrates. Applied Sciences. 2024; 14(19):9011. https://doi.org/10.3390/app14199011

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Feitosa, Adriano P., Kelly Rodrigues, Waleska E. Martins, Sara M. P. R. Rodrigues, Luciana Pereira, and Glória M. M. Silva. 2024. "Enhancing Greywater Treatment: High-Efficiency Constructed Wetlands with Seashell and Ceramic Brick Substrates" Applied Sciences 14, no. 19: 9011. https://doi.org/10.3390/app14199011

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