Introduction

Annually approximately 70 million tonnes of synthetic dyes is generated each year globally, primarily utilized in the manufacturing of textiles, cosmetics, and leather. About 30 to 150 thousand tonnes of dye-containing wastewater is released into the water bodies (Zou & Wang, 2017). Nowadays, the world is fascinated by using various synthetic dyes, and azo dye is famous for its applications. Nearly 70% of dyes were used as a coloring material in multiple industries, categorized under the azo group (Benkhaya et al., 2020). Azo dyes are substances that contain one or more azo linkages and are made up of a diazotized amine coupled to an amine or a phenol. Aromatic amines are the primary precursors of azo colors (Chung, 2016). In the past, at least 3000 azo dyes were used in the paper and pharmaceutical sectors, printing inks, paints, varnish, lacquer, and wood stains. Azo dyes are also used as colorants in synthetic and natural textile fibers, hair dyes, waxes, petroleum, plastics, and leather (Chung, 2016). The azo compounds have antibacterial, antiviral, antifungal, and cytotoxic properties in addition to their typical coloring activity (Ali et al., 2018). The azo double-bound groups are harmful and difficult to degrade in nature, potentially leading to significant environmental concerns and harming public health. Therefore, azo dye effluent must be treated before being released into aquatic bodies (Li et al., 2016).

Metanil yellow as an azo dye is used in various sectors, viz., food, pharmaceutical, leather, paper, textile, and chemical laboratories. Metanil yellow (a non-permitted food color) has been used as a food additive in making sweets, spices, pulses, beverages, and soft drinks to enhance their appearance (Kourani et al., 2020). Consumption of metanil yellow for a more extended period stimulates oxidative stress, prevents the indigenous antioxidant system, and produces free radicals. Moreover, it has a toxic impact on the digestive, excretory, reproductive, cardiovascular, and nervous systems, respectively (Ghosh et al., 2017). The presence of the azo group in metanil yellow blocks the sunlight in the aquatic environment, which affects the photosynthetic organisms and their activity (Ramadhani et al., 2020). The byproduct of the azo group, i.e., aromatic amine, causes various disorders like allergic, mastitis, skin irritation, gene alteration, etc. (Yaseen & Scholz, 2017). Although many researchers have developed methods like coagulation, chemical precipitation, electro-Fenton, electrochemical oxidation, and other advanced oxidation processes (Matyszczak et al., 2020) for the effective treatment of synthetic dye wastewater, all corresponding concern high operational and maintenance cost, vast applications of chemicals and electrical energy are the shortcomings of these methods.

Constructed wetlands (CWs) are considered sustainable and cost-effective approaches that undergo both phytoremediation and microbial remediation while treating various wastewaters (Muduli et al., 2022). The use of CWs for dye removal and textile wastewater is under investigation. Multiple researchers have reviewed the effectiveness of CWs in treating textile wastewater and dye removal (Dogdu & Yalcuk, 2016; Haddaji et al., 2019; Oon et al., 2020); however, very scanty literature is available covering all seasons. Under anaerobic conditions, the azo bond (present in the azo dye) can be broken easily to undergo the decolorization process; further, primary amine as a product can be degraded under aerobic conditions (Tee et al., 2015). Therefore, combining aerobic and anaerobic processes is advisable for complete dye degradation. Treatment of the metanil yellow dye using water hyacinth and specific bacterial strains like Bacillus sp. AK1 and Lysinibacillus sp. AK2 has been studied (Anjaneya et al., 2011; Guerrero-Coronilla et al., 2019).

Literature related to metanil yellow (acid yellow 36) removal using CWs is inadequate; furthermore, the use of ornamental species in the constructed vertical flow wetlands (CVFWs) is the uniqueness of this study. Dracaena reflexa is an ornamental species that has been used in the present study instead of wetland species. The main aim for choosing Dracaena reflexa is to undergo phytoremediation of textile wastewater, as it can withstand various environmental conditions and is simple to propagate by stem cuttings. Moreover, the root system of Dracaena has a propensity to develop micro-aerobic regions, contributing to the continuous degradation of organic matter (Dadrasnia & Pariatamby, 2016). In addition, the availability of native wetland species, especially in the arid and semi-arid areas, is challenging, where ornamental plants can play a vital role in wastewater management.

The present study uses CVFWs, which provide proper aeration (Hussein & Scholz, 2018) for the dye removal. This work aims to monitor and assess the Dracaena-based CVFWs’ potentiality for treating synthetic wastewater contaminated with metanil yellow, chemical oxygen demand (COD), and nutrients like NH4+-N and PO43−-P, respectively. The related objective was to (i) monitor the treatment efficiency (dye and other physicochemical contaminants) of the CVFWs operated in different seasons, (ii) kinetics of dye and nutrients removal, (iii) statistical analysis to validate pollutant removal, (iv) characterize the compounds present in the inlet and outlet water samples using Fourier transform infrared (FTIR), (v) elemental and oxide accumulation study of Dracaena by using X-ray fluorescence (XRF), (vi) compare the efficiency of the systems concerning the different concentration of dye mixture, and (vii) study the impact of synthetic dye mixture on the plant development.

Material and methods

Lab-scale CVFW setup, design, and operation

The experimental setups were made from opaque PVC pipes (to prevent algae growth) with a 4-inch diameter and 24-inch height (for providing space for grow of the plant root), providing an empty volume of 4.94 l. Each system was filled with two different natural media in layers with a particle size of 25–35 mm (gravels) and 8–12 mm (pea gravels) from bottom to up to support the plant species. CVFWs like CVFW-1, CVFW-2, and CVFW-3 were planted with the ornamental plant species named Dracaena reflexa except control system to study the influence of plant species on the treatment efficiency. The whole experimental setup was shown (Fig. 1). After plantation (single plant in each CVFW), the CVFWs were kept for 2 months to stabilize. The daily inlet dye mixture (synthetic wastewater) was 24 h for different CVFWs. This batch-scale experimental setup was located (21.7590° N, 72.1443° E) within the Council of Scientific and Industrial Research-Central Salt And Marine Chemicals Research Institute (CSIR-CSMCRI) Bhavnagar district of Gujarat. The system is exposed to ambient meteorological conditions. The CVFWs undergo vertical down-flow movement of wastewater. The outlet samples were collected every day (10 AM, with 24-h interval) from the outlet valve present at the bottom of each CVFW and were analyzed based on three seasons (summer, 02.03.2020 to 14.07.2020; monsoon, 17.07.2020 to 30.09.2020; and winter, 27.10.2020 to 24.11.2020), and the sample collection was stopped from 25 March to 7 June 2020 due to nationwide lockdown imposed by the Government of India for COVID-19 pandemic.

Fig. 1
figure 1

Schematic diagram of the experimental setup treating the textile dye wastewater

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Characteristics of wastewater

Metanil yellow (acid yellow 36) is a commercial azo dye used in this study. The stock solution (1000 ppm) of the dye was prepared. The required concentrations for our investigation, i.e., 5 ppm, 50 ppm, and 100 ppm of volume 2 l, were prepared from the stock solution. In each dye concentration (i.e., 5, 50, 100 ppm), an equal amount of nutrients, i.e., diammonium hydrogen phosphate and potassium nitrate, were added. The dye mixtures were prepared inside the laboratory at a temperature of about 25 °C by mixing all compounds properly (Table 1). During this study, all the used chemicals were analytical grade.

Table 1 Wastewater composition
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Water quality analysis

Inlet and outlet samples were sampled and analyzed correctly. Parameters like pH and TDS were measured on the spot immediately after sampling, and the remaining parameters (COD, color removal, chlorophyll estimation, nitrate, phosphate, and ammonium) were analyzed as per the procedure prescribed (APHA, 2017; Mohanty et al., 2015; Ray et al., 2014a). BOD analysis for water samples was not conducted as COD typically oxidizes more organic compounds chemically rather than biologically (Lee et al., 2016).

Chemical contaminants from water

The inlet and outlet water samples were analyzed using FTIR (Perkin Elmer, Model: Spectrum GX) (Ladwani, 2016) to see the presence of functional groups.

Biochemical characterization of Dracaena

Roots and stem from each CVFW were collected and analyzed during summer and winter for different biochemical characteristics. For ash content, the oven-dried roots and stem samples were kept in the muffle furnace at 500 °C for 30 min. Further, the ash was dissolved in distilled water, and the filtrate was analyzed to determine the nutrient uptake (nitrogen, phosphorous). The chlorophyll concentrations (chlorophyll-a, chlorophyll-b, and total chlorophyll) were undertaken for leaf samples, where the leaf was collected under dark conditions and was analyzed.

Elemental analysis

The dried pulverized forms of plants (roots and stem) and media (composite sample: both gravels and pea gravel) samples were pressed to form homogeneous pellets using boric powder as a binder and further analyzed using “wavelength dispersive X-ray fluorescence spectrometer” (WDXRF, Model: Bruker S8 TIGER II) delivers with its high sense technology for all elements from “Be to Am.” Elemental compositions of the samples were analyzed by “complete analysis vac 34 mm” methods (Muduli et al., 2022).

Kinetic study

First-order kinetics model (Gajewska et al., 2020) was used to study the removal rate of the pollutants (COD, NH4+-N, and PO43−-P) and dye through the systems. Microsoft Excel-2010 was used for the evaluation of decomposition rate.

Statistical analysis

The statistical analysis was undertaken using Statistical Package for Social Sciences (SPSS) (Ver 22) (Ray et al., 2014b, 2019). Mann–Whitney U test was used to elucidate whether any significant difference exists between seasons concerning parameters. The principal component analysis (PCA) was undertaken to explain the inter-relationship between different parameters. The mean and standard deviation was calculated using Microsoft Office Excel 2010. The experimental data were collected in triplicates, and the mean was considered for interpretation with an experimental error within ± 5%.

Results and discussion

Meteorological observations

Meteorological data like ambient air temperature, rainfall, and humidity were recorded (India Meteorological Department, 2020) and analyzed during the study, as they significantly influence the efficiency of the CWs during wastewater treatment (Yin et al., 2017). The ambient air temperature varied from 22.95 to 32.7 °C during the study, representing the local steppe climate. The average (± SD) ambient air temperatures for summer, winter, and monsoon were 28.7 ± 2.6, 29.7 ± 0.7, and 25.6 ± 1.9 °C, respectively. The rainfall was observed only in monsoon and varied from 0 to 1.4 mm, whereas the average (± SD) humidity for summer, monsoon, and winter were 69.9 ± 12.9, 78.7 ± 6.8, and 36 ± 5.4%, respectively.

Performance of the CVFWs for pollutant removal

During wastewater treatment, removing pollutants like dye, COD, PO43−-P, and NH4+-N is a primary concern (Hussein & Scholz, 2018). During the study, the concentrations of the above pollutants were measured for both inlet and outlet water samples (Table 2). Over the study period, the inlet water quality showed not much variation for all the CVFWs (control, CVFW-1, CVFW-2, and CVFW-3) as they were prepared in the laboratory. In contrast, outlet water showed variation, especially for all the CVFWs planted with Dracaena, highlighting its role and dependence on meteorological factors.

Table 2 Performance of the Dracaena-based constructed vertical flow wetland (CVFW) system during different seasons
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Substantial dye removal was observed during the study period, maximum in summer, slightly lesser in winter, and the least in monsoon, respectively (Table 2). The dye removal in CVFW-3 is less than in CVFW-2, which may be due to the stress of a more significant inlet concentration of dye on Dracaena. Dye removal was achieved due to phytoremediation activities and media adsorption. Here the CVFWs with Dracaena can efficiently remove dye (37.1–76.8%) as compared with the previous study reported, i.e., 18–92%, treating other dyes (BR46, AB113, and mixture of BR46 and AB113) using common reed (a wetland plant species) (Hussein & Scholz, 2018). The relationship between ambient air temperature, air humidity, and dye removal during the study period is shown in Fig. 2. During summer, dye removal coincides with temperature due to the increased metabolism of plants and microbes in the wetland system. However, in monsoon, high air humidity hampers the dye removal efficiency. In winter, less humidity accelerated the dye removal. Seasonal variation of COD, dye, NH4+-N, and PO43−-P concentrations in different CVFWs were shown (Figs. 3 and 4).

Fig. 2
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Relationship of temperature (°C) and air humidity (%) with a COD removal (%), b dye removal (%)

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Fig. 3
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Variation of COD and dye concentrations in different CVFWs a summer; b monsoon; c winter; d summer; e monsoon; f winter

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Fig. 4
figure 4

Variation of NH4+-N and PO43−-P concentrations in different CVFWs a summer; b winter; c summer; d monsoon; e winter

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The inlet COD variation may be due to changing dye concentrations for different CVFWs; however, substantial COD removal was observed during the study period, maximum in winter, slightly lesser in summer, and the least in monsoon, respectively (Table 2). The COD removal in CVFW-3 is less than in CVFW-2, which may be due to the stress of a more significant dye concentration on Dracaena. The COD removal was observed in CVFWs with the Dracaena plant highlighting its phytoremediation characteristics. Here the CVFWs with Dracaena can efficiently remove COD (50.5–72.3%) as compared with the previous study reported (Hussein & Scholz, 2018), i.e., 37–82%, treating other dyes using common reed. The relationship between ambient air temperature, air humidity, and COD removal during the study period is shown in Fig. 2. During summer, COD removal coincides with temperature, which may be due to the increased metabolism of plants and microbes in the wetland system; however, high air humidity hampers COD removal efficiency in monsoon. An increase in temperature would lead to a rise in carbon and nitrogen removal and vice versa. In winter, decreasing humidity accelerated the dye removal.

In this study, CVFWs could efficiently remove nutrients like PO43−-P (19.5–58.2%) and NH4+-N (93.1–96.7%) (Table 2). In summer, the PO43−-P removal efficiency was more than the other two seasons; the reason may be the higher rate of evapotranspiration and nutrient uptake (Nandakumar et al., 2019). Media adsorption and chemical precipitation may be the other reason for PO4-P reduction. Here gravels (low in cost and collected locally) worked as reactive media as it contains Al, Ca, and Fe having a better affinity for phosphorus (Yin et al., 2017). The composite sample was collected at the end of the experiment and the elemental composition for gravels (control—Al: 48,900 ppm, Ca: 127,000 ppm, Fe: 78,400 ppm; CVFW-1—Al: 49,700 ppm, Ca: 142,000 ppm, Fe: 75,300 ppm; CVFW-2—Al: 43,800 ppm, Ca: 124,000 ppm, Fe: 74,900 ppm; CVFW-3—Al: 40,700 ppm, Ca: 115,000 ppm, Fe: 74,700 ppm) was analyzed using WDXRF. Better NH4+-N removal was achieved, which may be due to proper aeration enhancing the nitrification activities. The vertical hydraulic flow pattern and the rhizosphere zone of Dracaena enhanced the oxygen level. However, NO3−-N concentration increased, which may be resulted from ammonia oxidation. The average TDS outlet concentration slightly exceeds the inlet (Table 2), observed in an earlier study (Hussein & Scholz, 2018). The average pH and DO values were given for both inlet and outlet water samples (Table 2). Overall the treatment performance of the wetland system was higher in both summer and winter, followed by the monsoon, where temperature and humidity play a vital role.

First-order kinetics model

The first-order kinetics model was used as a reliable tool to investigate the efficiency of a working system related to contaminant removal. Gajewska et al. (2020) have mentioned the first-order kinetics model for a vertical flow constructed wetland in their study.

$$\frac{{C}_{Out}}{{C}_{In}}={e}^{\frac{{-K}_{A}}{q}}$$
(1)

By solving Eq. (1), we can get

$${K}_{A}=-q\mathrm{ln}\frac{{C}_{Out}}{{C}_{In}}$$
(2)

where KA: decomposition rate constant in m/d; Cout: outlet concentration in mg/l; Cin: inlet concentration in mg/l; and q: hydraulic loading rate in m d−1.

Using Eq. (2), we calculated the decomposition rate constants for various parameters like COD, dye, PO43−-P, and NH4+-N for different seasons. From Table 3, we found a remarkable removal rate, i.e., 0.33, was achieved by CVFW-1, especially in the summer season compared to the control system. However, both systems have been treated with the same concentration of dye mixture. This result indicated that plant species planted in CVFW-1 significantly contributed to the removal rate. From the decomposition rate constant value calculated for the other two systems named CVFW-2 and CVFW-3 treated with 50 and 100 ppm dye, respectively, we realized that CVFW-2 had greater KA value, i.e., 0.34, during summer as compared to the other three systems. This result indicated that using Dracaena, we can treat dye mixture up to 50 ppm. Concentration more than 50 ppm may create a stressful condition for that plant species. Moreover, during summer, high ambient temperature provides a favorable condition to the plant species to treat the dye mixture.

Table 3 First-order kinetics
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By analyzing the KA value of COD for four CVFWs, i.e., control, CVFW-1, CVFW-2, and CVFW-3, we observed a greater KA, i.e., 0.308, by CVFW-2. From this result, we may conclude that the winter season may be providing favorable conditions to that plant species for the removal of COD. During the experiment, excellent performance was observed for removing NH4+-N by all systems. KA value of NH3-N varies between 0.6 and 0.9 for all CVFWs. Between two seasons, i.e., summer and monsoon, the out-standing KA value of NH3-N, i.e., 0.81, was achieved during summer. The design and configuration of all the systems and rhizospheric bacteria present around the root zones of plant species is the key contributor to the oxidation of NH4+-N. Decomposition rate constants for PO43−-P of all seasons by all the four reactors were studied, and we got to know that KA was found to be between 0.1 and 0.2. CVFW-3 achieved higher removal during summer. Both phyto-accumulation and adsorption by gravels used inside the CVFWs contributed towards PO43−-P removal.

Statistical analysis

Mann–Whitney U test

In this study, the removal of various water pollutants during treatment using different CVFWs was considered to see whether seasonal variance has any impact on them or not using the “Mann–Whitney U test,” and the variations are shown (Table 7, supplementary file). Significant (p < 0.05) dye removal was observed for CVFW-1 (summer-monsoon) and CVFW-2 (summer-monsoon and monsoon-winter). Similarly significant COD removal was observed for control (summer-monsoon), CVFW-1 (summer-monsoon and monsoon-winter), CVFW-2 (summer-monsoon and monsoon-winter), and CVFW-3 (summer-monsoon and monsoon-winter). Significant differences were observed in the case of dye, COD, and PO43−-P removal, highlighting the impact of seasonal variation, whereas NH4+-N removal is independent of meteorological factors.

Principal component analysis

The PCA used in the present study helped to concise the information collected to a lesser set of critical, independent variables (Fig. 5). It was used to establish the relationship within the experimental variables (air temperature, pH, air humidity, COD, dye, DO, NH4+-N, and PO43−-P) during the treatment. All the above variables were described with three components. Component-1 describes 28.09 of the cumulative variance with an eigenvalue of 2.24. It comprises of variables like air temperature, pH, air humidity, and dye, showing a positive correlation and highlighting the dye removal dependency on meteorological factors. Similarly, component-2 describes 46.29 of the cumulative variance and eigenvalue of 1.45. Here it comprises variables like COD and dye, highlighting the COD value that includes dye. Component-3 contains DO, NH4+-N, and PO43−-P, which shows the dependency of NH4+-N removal on DO and PO43−-P uptake by Dracaena and media adsorption.

Fig. 5
figure 5

Principal component analysis highlighting the relationship within the experimental variables (air temperature, pH, air humidity, COD, dye, DO, NH4+-N, and PO43−-P) during the treatment

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FTIR spectral analysis

By analyzing both inlet and outlet samples of different CVFWs, i.e., control, CVFW-1, CVFW-2, and CVFW-3, by FTIR, we observed the presence of various functional groups and their intensities (Table 4). The comparative study of inlet and outlet of the wastewater (dye mixture) of concentration 5 ppm treated by control and CVFW-1, as shown in Fig. 6 (supplementary file), stated a remarkable change in the intensity of the functional group. A great shifting in intensity was noticed for the peak azide (2160–2120 cm−1) in CVFW-1 compared to control. This better result in CVFW-1 may be due to phyto-accumulation and media absorption. From FTIR peak at 3340.92 cm−1 of the outlet of control, i.e., N–H stretching, primary amine, we may predict that the formation of primary amine, a byproduct of the azo group, prevents further degradation process of dye.

Table 4 Infrared frequencies and identified functional groups from FTIR spectra
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By analyzing FTIR peaks of both inlet and outlet of CVFW-2, we observed no significant change in intensity of the azide group. But the peak at 1262.87 cm−1 (alkyl aryl ether, aromatic ester) found in the inlet was absent in the outlet and the peaks at 1159.89, 1087.48, 1017.86, 887.84, 819.03, 755.55, 687.62, and 621.97 cm−1 were found in the outlet. We may predict that the functional group alkyl aryl ether and aromatic ester has got transformation during treatment to produce the alcohol, alkenes, aliphatic ethers, and various fluoro compounds.

By investigating the FTIR peak of both inlet and outlet of CVFW-3, we may state that a slight shift in intensity for the azide group has occurred (Fig. 7, supplementary file). Besides it, peaks (1260.71, 1021.81, 867.02, 806.61, 751.51, 632.99 cm−1) disappeared in the outlet.

Elemental and oxide accumulation by Dracaena

The potential of Dracaena concerning elemental and oxide accumulation during treatment was observed in the present study while treating 262 l of wastewater from summer to winter, where composite samples were considered for analysis of root and stem. Metallic elements, viz., Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Pd, V, and W, and non-metallic elements, viz., Na, Mg, Si, P, S, Cl, K, Ca, Br, and Sr, were detected from root and stem of CVFW-1, CVFW-2, and CVFW-3, respectively (Table 5). Metallic element accumulation was observed for Mn (root—48%, stem—75.1%), Co (root—100%, stem—100%), Cu (root—30.3%, stem—7.7%), and Mo (root—100%, stem—100%) in CVFW-1, respectively. Accumulation in roots was observed for Cr (61.6%) and Ni (31.3%), whereas Al (25.7%) accumulation was observed in the stem. Similarly, nonmetallic element accumulation was observed for Na (root—34.5%, stem—89.4%), Mg (root—32.3%, stem—50.4%), Si (root—8.6%, stem—4.7%), S (root—28.1%, stem—65.3%), and Br (root—41.7%, stem—100%) in CVFW-1, respectively. Accumulation in stem was observed for P (58.3%), Cl (69.2%), K (5%), and Ca (63.7%). CVFW-1 accumulated oxides in both roots (CaO, MgO, Na2O, K2O, P2O5, MnO, SO3, V2O5, SrO, CuO, Cr2O3, NiO, MoO3, and CoO) and stem (SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, TiO2, P2O5, MnO, SO3, V2O5, SrO, CuO, ZnO, MoO3, CoO), respectively (Table 5). Similarly, the elements and oxides for CVFW-2 and CVFW-3 are shown in Table 4. Overall in CVFW-2, the accumulation was observed to be more than CVFW-1 and CVFW-3. Moreover, the element accumulation was observed to be maximum in the stem compared with roots for all the Dracaena-based wetlands. For oxides, accumulation was observed to be more in roots. The source of these elements and oxides may be largely from the media used in the wetlands, and some might be from the chemicals used to prepare the synthetic wastewater. The accumulation by Dracaena proves to be a potential plant species, which may be used in treating real textile dye wastewater (that contains both dye and other toxic elements).

Table 5 Elemental and oxide accumulation by Dracaena in the wetlands during the study period
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Wastewater effect on Dracaena

The biochemical components of plants were studied as they played a vital role in textile dye wastewater treatment and taking nutrients (nitrogen, phosphorous). The growth of the Dracaena plant was monitored in terms of ash content, chlorophyll (a, b, and total), and inorganic salts (nitrogen and phosphorous) within a gap of 9 months, from summer to winter (Table 6). A substantial increase in chlorophyll concentrations was observed for CVFW-1 and CVFW-2 with no physical stress on plant growth. In contrast, decreased chlorophyll in CVFW-3 shows plant stress imposed due to higher inlet dye concentration. The root ash content has increased for all CVFWs, whereas stem ash content is only observed to be decreased in CVFW-3.

Table 6 Biochemical characteristics of Dracaena of CVFWs
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Conclusions

In this study, the performance of different “constructed vertical flow wetlands” treating textile dye wastewater (metanil yellow as dye) is investigated for 9 months (covering three seasons). The CVFWs planted with Dracaena efficiently removed contaminants like dye, COD, NH4+-N, and PO43−-P from the wastewater and the removal performance largely depends on meteorological factors. The CVFWs’ overall performance is similar for summer and winter, and least in monsoon. Significant dye removal was observed during the study period, maximum in summer (control, 44.3%; CVFW-1, 75.1%; CVFW-2, 76.1%; CVFW-3, 46%), but lesser in winter (control, 45; CVFW-1, 73.1%; CVFW-2, 76.8%; CVFW-3, 42.6%) and the least in monsoon (control, 40.8%; CVFW-1, 63.5%; CVFW-2, 51.6%; CVFW-3, 37.1%), whereas COD removal was observed to be highest in winter (64.4%, CVFW-1; 72.3%, CVFW-2; 62.5%, CVFW-3) followed by summer (61.8%, CVFW-1; 70.5%, CVFW-2; 59.4%, CVFW-3) and monsoon (50.5%, CVFW-1; 57.2%, CVFW-2; 51%, CVFW-3). Nutrients ranged between 52.1 and 64.4% (PO43−-P) and 56.6 and 71.6 (NH4+-N). CVFW-1 and CVFW-2 performed well, showing no stress on Dracaena, whereas CVFW-3 showed lesser performance, which may be due to plant stress resulting from a higher inlet concentration of dye. Dye removal was achieved due to phytoremediation activities and media adsorption. Dracaena proved to be efficient in dye removal and other pollutants; however, exceeding dye concentrations (> 50 mg/l) may pose stress. The first-order kinetic model was used to evaluate the decomposition rate constant. Higher KA values were achieved for dye removal in summer for all CVFWs. Various functional groups were characterized using FTIR from the inlet and outlet water samples of different CVFWs. The pollutant removal efficiency concerning seasons was validated statistically. Dye, COD, and PO43−-P removal showed significant differences, highlighting the impact of seasonal variation, whereas NH4+-N removal is independent of meteorological factors. The Dracaena of the wetlands accumulated various elements and oxides with no stress on its health. Apart from wetland species, there are various robust ornamental plants that can be tested for textile dye wastewater treatment.