Utilising Fragrant Roots to Purify Wastewater From Fish Habitats and Reintroducing It to the Pond

Domestic wastewater is among the most significant sources of pollution in aquatic environments, particularly rivers [1]. Approximately 57% of river pollution originates from domestic wastewater discharges [2], [3]. River water, however, remains an essential resource for various purposes, including agricultural and landscape irrigation, washing vehicles and equipment, and other non-potable applications [4], [5], [6], [7]. The discharge of untreated domestic wastewater deteriorates water quality and negatively affects plant growth and agricultural productivity when contaminated water is used for irrigation [8], [9], [10], [11]. Given the increasing volume of domestic wastewater and its high pollution potential, the development of effective and sustainable wastewater treatment technologies has become a priority. Numerous studies have proposed simple and practical treatment technologies capable of improving wastewater quality through different treatment approaches [2], [3], [4], [5], [11].

One of the most promising environmentally friendly approaches is the application of aquatic plants as phytoremediation agents [12], [13]. Constructed wetlands planted with aquatic vegetation remove pollutants through a combination of physical filtration, sedimentation, microbial degradation, and plant uptake [14]. Among various aquatic plants, Vetiver grass (Vetiveria zizanioides), locally known as fragrant root grass, has attracted considerable attention because of its rapid growth, extensive root system, and wide availability [15]. Besides its traditional use for handicrafts and ornamental purposes, vetiver has demonstrated excellent capability in removing pollutants from wastewater [16], [17], [18]. These characteristics make vetiver a promising plant for producing treated effluent suitable for non-potable reuse, particularly in urban environments.

This study focuses on the treatment of domestic greywater to increase the availability of treated effluent for urban water reuse. Greywater refers to wastewater generated from sinks, kitchens, bathrooms, and laundry activities, excluding wastewater containing human excreta [19]. Greywater accounts for approximately 70–75% of the total domestic wastewater generated in households [20]. In many urban areas, this wastewater is discharged directly into drainage systems and eventually reaches nearby rivers without adequate treatment [21]. Consequently, a substantial amount of potentially reusable water is wasted, contributing to environmental degradation.

Integrated Water Resources Management (IWRM) promotes a coordinated approach that integrates environmental, social, and economic considerations in sustainable water-resource management [22]. Effective implementation of IWRM requires balancing stakeholder interests and multiple sustainability objectives [23].

In this study, water quality was evaluated using nine parameters: pH, odour, colour, turbidity, total dissolved solids (TDS), nitrate (NO$_3$$^-$), nitrite (NO$_2$$^-$), fecal coliform, and iron (Fe). The physicochemical and microbiological parameters were analyzed using standard water and wastewater examination procedures [24], [25], [26], [27], [28], [29], [30], [31], [32], [33]. The treated water quality was evaluated according to the Indonesian Minister of Health Regulation No. 2 of 2023 [34]. This study proposes a simple and cost-effective constructed wetland model that can improve greywater quality using vetiver plants. Owing to its low cost, simple design, and ease of operation, the proposed system has strong potential for application in household-scale and community-based wastewater treatment.

Constructed wetlands have received considerable attention as environmentally friendly and sustainable wastewater treatment technologies [20]. These systems mimic natural wetlands by using vegetation, soil media, and microorganisms to remove contaminants from wastewater. Previous studies have demonstrated that vetiver plants effectively remove various pollutants, including dissolved nitrogen, phosphorus, sulfate, and heavy metals such as arsenic (As) and cadmium (Cd). Dyamanagowdru and Lokeshappa [20] reported that constructed wetlands planted with Vetiveria zizanioides and Canna siamensis achieved high pollutant removal efficiencies at hydraulic retention times of four and six days. Their study reported removal efficiencies of 96% for turbidity, 29% for TDS, 65% for total suspended solids (TSS), 70% for biochemical oxygen demand (BOD), 80\% for chemical oxygen demand (COD), 53% for chloride, 50% for nitrate, and 55% for phosphate, demonstrating the effectiveness of vetiver-based constructed wetlands for wastewater treatment.

Previous research [3] reviewed different types of constructed wetlands, including free-water surface flow wetlands, subsurface-flow wetlands, hybrid systems, and floating-treatment wetlands, to identify suitable wastewater treatment technologies for developing countries. The study concluded that hybrid constructed wetlands provide superior treatment performance because they effectively reduce TSS and COD by 93% and 85.65%, respectively. In addition, Typha angustifolia was identified as an effective plant species for improving wastewater quality in constructed wetland systems.

Another study [35] evaluated a full-scale subsurface-flow constructed wetland installed in a residential area. The treatment system consisted of a wastewater filtration tank, a storage tank, and a constructed wetland measuring 2 $\times$ 1 $\times$ 0.65 m³ with a treatment capacity of approximately 0.6 m³/day. The wetland was planted with iris species using sand, gravel, and recycled plastic bottles as supporting media. The results showed that a hydraulic retention time of three days significantly improved wastewater quality, particularly by reducing BOD, compared with untreated influent wastewater.

Although numerous studies have demonstrated the effectiveness of constructed wetlands using vetiver and other aquatic plants, most have focused on domestic or industrial wastewater. Limited attention has been given to greywater generated from fishpond operations, despite its considerable environmental impact. Furthermore, few studies have systematically evaluated the combined effects of hydraulic retention time, flow rate, and plant density using a laboratory-scale physical model. Therefore, this study addresses these research gaps by investigating the performance of a vetiver-based constructed wetland for treating fishpond greywater under different operational conditions. The findings are expected to contribute to the development of simple, low-cost, and nature-based wastewater treatment technologies suitable for decentralized water reuse applications.

Waste is discarded material from human activities that has lost its value or utility. There are two types of liquid waste: industrial and household. Liquid waste from household activities typically consists solely of organic matter, making it amenable to simple treatment to remove pollutants [29]. Liquid waste is water that contains organic pollutants or comes from:

(1) Household activities, such as bathing, washing clothes, using the toilet, and cooking.

(2) Commercial activities such as hotels, resorts, villas, vacation homes, offices, and supermarkets that produce liquid waste.

(3) Industrial activities that produce wastewater, such as liquid waste from industries, agriculture, livestock farming, etc.

(4) Rainwater that falls through rooftops, drainage channels, and road surfaces. Based on the nature of the waste, the wastewater treatment process can be divided into three categories [30]:

(1) Physical Process

This process is carried out mechanically without the addition of chemicals. It involves filtration, sedimentation, and flotation.

(2) Chemical process

This process is carried out by utilising chemicals to neutralise pollutants.

(3) Biological Processes. This process removes pollutants using microorganisms. In practice, this treatment process does not operate independently but is often implemented alongside other methods.

To clarify how the variables in this study interact, a conceptual framework was developed based on the study's problems and objectives. The variables in this study include the following [31]:

(1) Free variables:

(a) Number of fragrant root stems (50, 100, 150)

(b) Number of discharges (1000, 1500, 2000) litres/day

(c) Duration of stay (2 days, 4 days, 7 days), based on the type of plant used in the wetland, namely Vetiver (Vetiveria zizanoides).

(2) The selected parameters, namely as follows:

(a). pH

(b). Odor

(c). Color

(d). TDS

(e). Turbidity

(f). NO$_3$$^-$

(g). NO$_2$$^-$

(h). Fecal coliform

(i). Fe

This research was conducted at home, and the test results were then sent to the Jasa Tirta Malang Laboratory for further testing. This activity included collecting tilapia wastewater samples, analysing the initial and final water, and analysing the water output from the wetland. This physical model was made on a scale of 1:150, adjusting to the available space in the house, including:

(a) Water Reservoir

(b) Filter 2 wetland filter boxes

Figure 1 explains the preparations and tools before observation, such as:

(a) Sampling from the research location into bottles

(b) Tilapia pond

(c) Fragrant root plants with residence time, variation in the number of fragrant root stems, and variation in flow rate.

(d) Output with variations in days, discharge, and number of fragrant root stems.

To achieve treated effluent quality standards, research was conducted using the model illustrated in Figure 2, which utilises soil as a medium for wetland plants. All treatments are similar to phytoremediation, except that these use soil submerged in water.

Description of the Waste Treatment Process in Figure 2, such as:

(1) Treated effluent as input entering the tilapia pond

(2) Tilapia pond

(3) Tilapia pond wastewater

(4) Fragrant root wetlands (model scale) that use tilapia pond wastewater

(5) The output from wetlands that use wastewater is treated effluent that will re-enter the tilapia pond.

Wetlands are areas where the soil is saturated with water, either permanently or seasonally. These areas are sometimes partially or completely flooded by shallow water and are classified as wetlands, including swamps (e.g., mangrove swamps), marshes, and peatlands. The water that floods wetlands can be classified as freshwater, brackish water, or saltwater. In this case, we work using a scale model in the laboratory (see Figure 2).

All the greywater used in this study was sourced from the same fish pond and freshly collected for each experiment. Before each new run, the water was mixed to maintain consistency for that particular test. Water quality was not monitored over time; the study focused only on the water used in each setup. At the beginning of each experiment, the primary water quality parameters were measured to document the initial conditions. Since each test was conducted only once without replication, the influent values were presented as single data points for each scenario rather than as averages. These values allow me to compare how the treatment performed under various retention times, flow rates, and plant densities.

Standard analytical methods were used to assess water quality, following typical lab procedures. Turbidity, pH, and TDS were all measured using calibrated portable meters and for Fecal coliforms, established culture-based methods were used. However, this study does not assess measurement uncertainty or instrument precision, which likely contributed to the variability of the results. In the future, it would be sensible to include detection limits for each method and perform replicate measurements to enhance the analysis.

Given the study's general focus on domestic wastewater treatment in urban areas, it is necessary to provide an overview of the locations where the technology will be applied. This community service project is located in a housing complex in Malang City, East Java, namely Pondok Harapan Indah (Poharin). Specifically, this housing complex is located on Jalan Terusan Sigura-gura, Karangbesuki Village, Sukun District, Malang City. This location was chosen because the housing complex is quite old, having been established in 1981. This indicates that population density is relatively high, resulting in substantial domestic wastewater generation. So far, there has been no adequate greywater treatment facility in Poharin. Still, at least residents have initiated the construction of fish ponds to utilise greywater (see Figure 3). This idea has motivated researchers to support domestic wastewater treatment initiatives.

Each experimental condition was conducted only once, due to time and resource constraints, in a controlled laboratory environment. The experiments were not repeated, so the figures in the tables are from single trials rather than averages over several runs. These data illustrate how retention time, flow rate, and plant density affect outcomes, but they are not suitable for drawing broad statistical conclusions. Thus, to present the observed patterns rather than make generalised statements.

This section presents the results for water quality parameters, including pH, color, turbidity, TDS, NO$_3$$^-$, NO$_2$$^-$, Fe, odor, and fecal coliforms. Water quality is influenced by water discharge, the number of fragrant roots, and retention time. The test results are presented using line graphs, as shown below. The results presented in this section correspond to single experimental runs for each treatment condition and are intended to demonstrate comparative performance trends among the tested scenarios. The influent water quality values reported for each test condition represent initial measurements taken at the start of each experimental run and are intended to characterize the input conditions rather than capture temporal variability.

Table 1 shows that, with 50 fragrant root stems and each increased with the addition of water, from 7.30 to 7.80 across different retention periods. However, Figure 4 shows that, with 100 fragrant root stems and each additional water addition, the pH value increases from 7.30 to 7.85 across different retention periods. Meanwhile, the results for the pH parameter indicate that, with 150 fragrant root stems and each addition of water, the pH value increases from 7.30 to 7.90 across different retention periods.

The description of the odor parameters shows that with 50 bars of fragrant roots and each addition of water flow at different retention periods, the odor value can be reduced from 2 to 0.97, as shown in Table 2 and Figure 5. The results of the odor parameter description show that, with 100 fragrant root stems and each addition of water discharge at different retention periods, the odor value can be reduced from 2 to 0.91. The results of the odor parameter description indicate that, with 150 fragrant root stems and each addition of water discharged at different retention periods, the odor value can be reduced to 0.77.

The results of the color parameter description show that with 50 fragrant root stems and each addition of water discharge at different retention periods, the color value can be reduced from 34.63 to 11.9 TCU, as shown in Table 3 and Figure 6. The results of the color parameter description show that, with 100 fragrant root stems and each additional water discharge at different retention periods, the color value can be reduced from 34.63 to 11.5 TCU. The results of the color parameter description show that with 150 fragrant root stems and each addition of water discharge at different retention periods, the color value can be reduced from 34.63 to 10.6 TCU.

The TDS parameter description results show that, with 50 bars of fragrant roots and each addition of water, the TDS value decreases from 332 to 192 mg/L, as shown in Table 4 and Figure 7. The results of the TDS parameter description show that, with 100 fragrant root stems and each additional water discharge at different retention periods, the TDS value can be reduced from 332 to 179 mg/L. The results of the TDS parameter description indicate that, with 150 fragrant root stems and each water discharge at different retention periods, the TDS value can be reduced from 332 to 175 mg/L.

The results of the turbidity parameter description indicate that, with 50 fragrant root bars and each water discharge addition at different retention periods, the turbidity value can be reduced from 119 to 6.42 NTU, as shown in Table 5 and Figure 8. The results of the turbidity parameter description show that, with 100 fragrant root stems and each additional water discharge at different retention periods, the turbidity value can be reduced from 119 to 5.68 NTU. The results of the turbidity parameter description indicate that, with 150 fragrant root stems and each additional water discharge at different retention periods, the turbidity value can be reduced from 119 to 5.44 NTU.

The description of the NO$_3^-$ parameter indicates that, with 50 fragrant root bars and each addition of water, the NO$_3^-$ parameter description indicate that, with 100 fragrant root stems and each additional water discharge at different retention periods, the NO$_3^-$ parameter description indicate that, with 150 fragrant root stems and each additional water discharge at different retention periods, the NO$_3^-$ concentration increased from 1.412 to 2.319 mg/L.

The NO$_2^-$ parameter description results show that, with 50 fragrant root bars and each water discharge at different retention periods, the NO$_2^-$ parameter description show that with 100 fragrant root stems and each addition of water discharge at different retention periods, the NO$_2^-$ parameter description show that with 150 fragrant root stems and each addition of water discharge at different retention periods, the NO$_2^-$ value can increase from 0.0086 to 0.0922 mg/L.

The results of the fecal coliform parameter description show that with 50 fragrant root stems and each addition of water discharge at different retention periods, the fecal coliform value can be reduced from 260 to 101 CFU/100ml, as shown in Table 8 and Figure 11. The results of the fecal coliform parameter description show that with 100 fragrant root stems and each addition of water discharge at different retention periods, the fecal coliform value can be reduced from 260 to 91 CFU/100ml. The description of Fecal coliform parameters shows that with 150 fragrant root stems and each addition of water, the Fecal coliform value can be reduced from 260 to 85 CFU/100ml.

The results of the Fe parameter description indicate that, with 50 fragrant root stems and each additional water discharge at different retention periods, the Fe value can be reduced from 0.0585 to 0.0265, as shown in Table 9 and Figure 12. The results of the Fe parameter description indicate that, with 100 fragrant root stems and each additional water discharge at different retention periods, the Fe value can be reduced from 0.0585 to 0.0265. The results of the Fe parameter description indicate that, with 150 fragrant root stems and each additional water discharge at different retention periods, the Fe value can be reduced from 0.0585 to 0.0286.

In this study, vetiver-based constructed wetlands were evaluated as a nature-based solution for treating greywater from fish pond operations. The treatment system effectively reduced organic matter, turbidity, TDS, and fecal coliform concentrations, demonstrating the potential of vetiver-planted wetlands to improve greywater quality. Table 10 summarizes the treatment performance. These findings are consistent with previous studies on hybrid constructed wetlands and vetiver-based treatment systems, which reported effective removal of organic matter, suspended solids, and nutrients under various hydraulic loading conditions [7-13]. With appropriate design and operation, constructed wetlands planted with macrophytes such as vetiver can significantly improve water quality, making treated greywater suitable for irrigation and other non-potable applications. Furthermore, constructed wetlands have been widely recognized as reliable, low-energy, and cost-effective technologies for decentralized wastewater treatment [8].

The constructed wetland evaluated in this study was a laboratory-scale physical model, approximately 1:150 of a potential full-scale system. Laboratory-scale experiments are valuable for investigating treatment mechanisms and identifying critical operational parameters; however, they cannot fully replicate the hydraulic complexity of field-scale wetlands. Scaling down may alter flow distribution, hydraulic retention time, media packing characteristics, and root-zone interactions, resulting in hydraulic behavior that differs from that of full-scale systems. Consequently, the findings should be regarded as preliminary design guidance rather than direct predictions of field performance. Future pilot-scale and full-scale investigations are recommended to validate hydraulic performance, treatment efficiency, and long-term operational stability under real environmental conditions.

Beyond the measured improvements in water quality, the observed reductions in organic matter, nutrients, suspended solids, and microbial contaminants have important environmental implications. Implementation of this treatment system in residential communities or small settlements could substantially reduce pollutant discharge into rivers and drainage systems. Lower organic and nutrient loading would reduce eutrophication risks, improve dissolved oxygen concentrations, and enhance ecological conditions for aquatic organisms. Therefore, the significance of this study extends beyond pollutant removal efficiencies by demonstrating the potential contribution of nature-based wastewater treatment systems to sustainable environmental management.

The observed treatment performance can be explained through several complementary mechanisms, including physical filtration, sedimentation, microbial biodegradation within biofilms, and rhizosphere-mediated pollutant transformation. In subsurface-flow constructed wetlands, the filter media retain suspended particles while simultaneously providing attachment surfaces for biofilm development. Meanwhile, vetiver roots improve oxygen transfer within the rhizosphere, creating favorable microenvironments for microbial activity and nutrient transformation. Similar mechanisms have been reported in previous investigations demonstrating the effectiveness of vetiver-planted wetlands for degrading organic pollutants under controlled hydraulic loading conditions [9].

The present findings are also consistent with recent investigations of constructed wetlands for decentralized water reuse. Previous field and pilot-scale studies have demonstrated that constructed wetlands effectively improve greywater quality while substantially reducing conventional pollutants and fecal indicator bacteria under appropriate operating conditions [8], [9], [11]. Moreover, hybrid constructed wetlands have shown superior treatment performance by combining aerobic and anoxic treatment zones, thereby enhancing nutrient removal efficiency and improving treatment stability under variable hydraulic conditions [3], [7].

An increase in nitrate or nitrite concentrations observed during certain treatment stages is likely associated with enhanced nitrification. Increased oxygen availability within the wetland media promotes the microbial oxidation of reduced nitrogen compounds into nitrate. This process commonly occurs as organic matter concentrations decline and aerobic conditions become more favorable [31]. Consequently, elevated nitrate concentrations should not necessarily be interpreted as treatment failure but rather as possible evidence of nitrogen transformation within the wetland. For a more comprehensive assessment of nitrogen removal, future studies should evaluate total nitrogen (TN) in addition to individual nitrogen species.

The reduction in fecal coliform concentrations further demonstrates the capability of vegetated constructed wetlands to reduce microbial contamination through multiple mechanisms, including physical filtration, microbial attachment to biofilms, predation by indigenous microorganisms, natural bacterial die-off, and unfavorable environmental conditions within the rhizosphere [31]. Nevertheless, although fecal coliform concentrations decreased considerably, the treated effluent should not be considered suitable for direct human consumption. Additional disinfection processes may still be required depending on local water reuse regulations and the intended end use. Recent reviews emphasize that pathogen removal in constructed wetlands may vary according to operational conditions and therefore recommend integrating wetlands within a multi-barrier treatment strategy to ensure microbiological safety [34], [36].

Influent water quality may also influence the interpretation of treatment efficiency. In short-term laboratory studies, variations in influent characteristics can substantially affect removal efficiencies because treatment performance is strongly dependent on initial pollutant concentrations. Therefore, future investigations should clearly report the influent sampling strategy, confirm whether influent samples originate from a homogeneous and well-mixed source, and present the mean values together with standard deviations for each experimental condition. Such information would improve the reproducibility of the study and facilitate comparisons with other decentralized greywater treatment systems.

A comparison between the present study and recent investigations of constructed wetlands for greywater treatment is presented in Table 11.

This study evaluated the performance of a laboratory-scale constructed wetland during relatively short hydraulic retention times under controlled experimental conditions. Therefore, the findings should be interpreted as evidence of short-term treatment effectiveness rather than confirmation of long-term operational reliability. The long-term performance of constructed wetlands may be influenced by several factors, including media clogging, plant growth and harvesting cycles, seasonal climatic variations, and changes in microbial communities. Recent long-term studies have demonstrated that treatment efficiency can vary considerably across seasons and different stages of plant development. Consequently, monitoring under both wet and dry seasonal conditions is necessary before the system can be considered suitable for continuous year-round operation [11].

Based on the present findings and previous studies, three practical recommendations can be proposed. First, influent flow and pollutant loading should be stabilized through simple equalization or sedimentation units before entering the constructed wetland. Such pretreatment can minimize hydraulic shock loading and improve treatment stability. Second, hydraulic retention time and vetiver planting density should be optimized to achieve an appropriate balance between physical filtration and biological pollutant removal, as supported by previous pilot-scale studies and reviews on constructed wetlands for water reuse [9], [13], [20]. Third, where higher microbiological safety is required, constructed wetlands should be integrated with additional treatment processes, such as disinfection, as part of a multi-barrier treatment strategy for reclaimed water reuse [34], [36].

The results indicate that vetiver-based constructed wetlands represent a promising low-energy and environmentally sustainable technology for polishing greywater generated from fish habitat facilities. However, because the present investigation was conducted over a relatively short experimental period, additional pilot-scale and long-term studies are required to evaluate treatment stability, hydraulic performance, seasonal variability, media longevity, and long-term operational efficiency.

From both policy and practical perspectives, the proposed treatment system supports the increasing adoption of decentralized wastewater management, particularly in rural areas, peri-urban communities, and locations where centralized wastewater treatment infrastructure is unavailable or economically impractical. The findings provide baseline design information regarding hydraulic retention time, vetiver planting density, and expected treatment performance that may assist engineers, planners, and decision-makers in implementing nature-based wastewater treatment technologies. Furthermore, this study supports the integration of constructed wetlands into sustainable water resource management policies aimed at reducing diffuse water pollution. Accordingly, the treated effluent should be regarded as a valuable water resource suitable for restricted non-potable reuse, such as landscape irrigation and environmental applications, rather than as water intended for unrestricted human consumption.

This study has several limitations that should be considered when interpreting the findings. First, the experiments were conducted without replication, with each treatment evaluated only once. Consequently, the results should be interpreted as preliminary trends rather than statistically validated conclusions, as treatment variability and reproducibility could not be assessed. Therefore, this study should be regarded as a pilot investigation intended to evaluate the feasibility and preliminary performance of a vetiver-based constructed wetland for greywater treatment. Future studies should incorporate appropriate experimental replication and statistical analyses to validate the observed treatment trends and improve the robustness of the conclusions.

Second, although the influent greywater originated from the same fish pond and was mixed before each experimental run, natural variations in greywater composition may still have occurred and were not continuously monitored. Such fluctuations in influent quality may have affected treatment efficiency. Future investigations should include systematic monitoring of influent characteristics, standardized homogenization procedures, and replicated sampling to better quantify variability and improve the reliability of treatment performance assessments.

The increase in nitrate and nitrite concentrations observed under certain experimental conditions suggests that nitrification may have occurred within the constructed wetland. As organic matter decreased and hydraulic retention time increased, oxygen-rich microenvironments likely developed around vetiver roots and within the filter media, promoting the oxidation of reduced nitrogen compounds. However, because dissolved oxygen, oxidation–reduction potential (ORP), and ammonium concentrations were not measured, this interpretation remains a plausible hypothesis rather than a confirmed mechanism. Future studies should directly monitor these parameters to better understand nitrogen transformation pathways within the wetland system.

The results also demonstrated that treatment performance generally improved with increasing hydraulic retention time and higher vetiver planting density. Nevertheless, several effluent quality parameters, particularly turbidity, colour, and fecal coliform, did not consistently comply with the applicable treated effluent standards. Consequently, the treated water should not be considered suitable for potable use or other applications involving direct human contact. Instead, it may be appropriate for restricted non-potable reuse, such as landscape irrigation, irrigation of non-food crops, or other applications permitted under local regulations. Where higher water quality is required, additional treatment processes, including filtration, sedimentation, or disinfection, should be incorporated. These findings indicate that the proposed vetiver-based constructed wetland is more suitable as a pre-treatment or polishing unit than as a standalone treatment system for producing high-quality reclaimed water.

Finally, the present investigation was conducted under laboratory-scale conditions over a relatively short experimental period. Consequently, the influence of seasonal variation, long-term hydraulic performance, media clogging, plant growth dynamics, and operational stability could not be evaluated. Future research should therefore include pilot-scale and full-scale field investigations with extended monitoring periods, repeated experiments, comprehensive water quality analyses, and long-term performance evaluations. Such studies will provide a more reliable basis for optimizing system design and supporting the wider implementation of vetiver-based constructed wetlands for sustainable greywater treatment and reuse.

Greywater generated from tilapia pond operations contains organic matter, suspended solids, nutrients, and microbial contaminants that require appropriate treatment before being discharged into receiving water bodies. This study evaluated the performance of a laboratory-scale constructed wetland planted with Vetiveria zizanioides (vetiver grass) using submerged soil media under different hydraulic loading rates, planting densities, and hydraulic retention times.

The results demonstrated that the vetiver-based constructed wetland effectively improved greywater quality. The highest treatment performance was achieved with 150 vetiver stems and a hydraulic retention time of seven days. Under these conditions, the treated effluent met the applicable treated effluent quality standards for pH (7.90), nitrate (2.319 mg/L), nitrite (0.0922 mg/L), iron (0.0286 mg/L), and TDS (175 mg/L). However, several parameters, including odor (0.77), colour (10.6 TCU), turbidity (5.44 NTU), and fecal coliform (85 CFU/100 mL), did not fully comply with the required treated effluent quality standards. These findings indicate that the proposed treatment system is effective in improving greywater quality but is more suitable as a pre-treatment or polishing unit rather than as a standalone treatment system for producing water suitable for unrestricted reuse.

The study also demonstrates that vetiver-based constructed wetlands represent a promising nature-based and low-energy technology for decentralized greywater treatment in aquaculture and small-community settings. In addition to reducing pollutant concentrations, the system has the potential to decrease contaminant discharge into surrounding aquatic environments, thereby supporting more sustainable water resource management.

Nevertheless, this study has several limitations. The experiments were conducted under laboratory-scale conditions without experimental replication, and the influent water quality was not continuously monitored throughout the study. Consequently, the findings should be regarded as preliminary and should not be directly extrapolated to full-scale applications. Future research should include replicated experiments, continuous influent monitoring, pilot- and field-scale investigations, long-term performance evaluation under seasonal conditions, and additional treatment processes, such as filtration or disinfection, to improve microbial removal and expand opportunities for safe non-potable water reuse.