The results of the BOD analysis of the phytore-mediation system throughout the 107 days of the research period are shown in Fig (3). The BOD data indicated that most of the BOD removal occurred due to the microorganism activity in the medium. Wastewater from sewage treatment plants often contains organic materials that are decomposed by microorganisms, which use oxygen in the process. The amount of oxygen consumed by these organisms in breaking down the waste is known as the biochemical oxygen demand or BOD.

The pattern for BOD was fluctuating due to the irregular entry of sewage treatment water every day. In the first 5 days, the removal percentage was 31.94%, which increased to 41.37% on the 19th day. It dropped to 15.95% and 14.23% on days 33^th and 47^th, respectively. It started to rise on day 61st with the third highest reading over 178 days with a reading of 68.38%. The highest removal percentage was on the 96th day with a reading of 90.87%. On the 107th day, the removal percentage decreased to 57.94%. The lowest and greatest BOD values are clearly visible in the data. During Week 8, the lowest BOD reading was obtained, with a surprisingly low number of 14.23%. In contrast, the greatest BOD measurement came on day 96, when the BOD value increased to a significant 90.87%. This substantial reduction in BOD reflects the efficiency of the treatment system in significantly improving the water quality. At the end of January (day 33), the average weather is 31° and rises to 33° in early February on average. Temperature stress affects the geographical distribution of plants and reduces plant productivity, thus deteriorating the effectiveness of the plants. If plants are stressed or die due to the contaminants, their metabolic activity, including respiration, can decrease, resulting in less oxygen consumption and has given effect on aquatic plants as depicted (Fig. 4).

Fig. (3). Removal performance of BOD by phytoremediation system.

Fig. (4). Condition of lepironia articulata sp. in February.

It was observed in February that some trees in tank 2 had died as shown in Fig (4). The dead plants might increase in pollutants inside the tank and affect the actual pollutants value in tanks. The trunk becomes yellowish and the roots of the tree become damaged. Some plants can take up contaminants through their roots and translocate them to above-ground parts. This process may reduce the availability of contaminants in the water or soil, potentially leading to reduced microbial activity and oxygen consumption. In some cases, contaminants may have phytotoxic was effects, harming the plants' health. Lepironia Articulata sp. is an aquatic plant that can absorb a lot of BOD. It is supported by a previous study that stated 99.94% removal of BOD5 can be removed by Lepironia articulata and Scirpus grossus [19].

The result proved that the synergic utilization of plants selected has led to significant improvements in BOD removal of the sewage. The data showcases both an initial reduction and a remarkable reduction over a longer period, highlighting the positive impact of plants on the treatment process. The enhanced bacterial growth and accelerated treatment process attributed to the plants have collectively resulted in higher removal rates and improved water quality in a shorter timeframe. This reduction of BOD as organic compounds by plants is generally achieved through phytodegradation, which involves the release of enzymes from roots to the media and metabolic activity from the plant [20].

Based on Fig (5), the trend for COD started at 23.57% on the 5th day and increased to 27.08% on the 19th day. The increase in removal percentage continued to the 33rd and 70th day with readings of 41.10% and 70.95% each. It decreased to 49.08% and 31.90% on the 75th and 96th day. Increased removal reduction on the 107th day with a value of 70.93%. the lowest and maximum COD values are clearly visible. The lowest COD reading was recorded in Week 2, with a comparatively low value of 23.57%, while the greatest COD reading was found in Week 10, with a significant 70.95%. This very high COD level indicates that the water sample contained a substantial quantity of organic and inorganic contaminants during Week 10. In the context of this experiment, the focus is on the removal efficiencyof the phytoremediation system concerning COD. COD was a measure of the amount of oxygen required to chemically oxidize organic substances in water. Following the guidelines of the Environmental Quality (Sewage Effluent) Regulation 2009 stated that standard A of COD concentration was 120 mg/L.

All the effluent in the phytoremediation system showed a concentration COD lower than standard A. Most researchers proved that all four aquatic plants had successfully obtained high COD removal. In a recent article [21] Thypha angustifolia was used and managed to remove 77.3% of COD, from real wastewater. Another study [19] also showed the results that Lepironia articulata in Constructed Wetland showed high removal of COD with values up to 96.94%. A study [22] used Pistia stratiotes and Eichhornia crassipes and successfully reduced COD up to 99% after five weeks. Higher COD values indicate higher levels of organic pollutants in the water, which can be harmful to the environment if not treated. It was found that the sulfamethoxazole enriched the co-metabolizing bacteria resulting in higher removal rates of organics and antibiotics. It was not clear whether plants increased sulfamethoxazole removal through either uptake or microbial enrichment in the study by Qu et al. Similarly, COD found that in constructed wetlands, aerobic microbial degradation was responsible for the majority of sulfonamide removal. Biodegradation was found to be highest and closest to the plant roots [23].

Fig. (5). Removal performance of COD by phytoremediation system.

Fig. (6). Removal performance of TSS by phytoremediation system.

Fig. (6) provides data on the removal of TSS over the course of the experiment. The data shows that the concentrations of these suspended solids were reduced from their initial values as the wastewater flowed through the phytoremediation system. According to the figure, the percentage removal of TSS over a series of days reveals fluctuations in the efficiency of the remediation process. The results demonstrate a dynamic pattern in the reduction of TSS levels. On Day 5, there was a notable removal rate of 40.79%, which experienced a decline to 21.95% on Day 19. However, the efficiency rebounded on Day 33, achieving a removal rate of 43.75%, and remained relatively steady at around 43% on Day 47.

A substantial improvement was observed on Day 61, with a removal rate of 59.21%, yet this progress was followed by a decline on Day 75 to 42.67%. Over time, fluctuations persisted, with a decrease to 36.73% on Day 96, followed by an increase to 51.61% on Day 107. Overall, these results highlight the dynamic nature of TSS removal during the remediation period, emphasizing the need for careful monitoring and analysis to understand the underlying factors driving these fluctuations.

The combination of the 4 types of aquatic plants used in this phytoremediation system produced a high impact on the removal performance of TSS because almost all effluent samples were standard A. In the 4th week alone, the concentration of 64 mg/L remained constant but approached standard A. This is because microorganisms within the root zones of plants in phytoremediation systems can form biofilms.

These biofilms can help in the breakdown and entrapment of suspended solids. The microorganisms produce extracellular substances that can bind particles and improve their settling. Phytoremediation systems, such as constructed wetlands, incorporate plants with extensive root systems that create a matrix within the treatment system. This matrix helps slow down the flow of wastewater, allowing suspended solids to settle out of the water column and be trapped within the wetland sediment.

The plants themselves can also act as monitors by catching solid particles on their roots. Most of the species tried in this trial had a concentration of TSS that started to slowly go down or stayed the same.

This could be because it had already reached the highest concentration at which it could be removed [24]. Umar et al. stated that the charges on the roots of watery plants or macrophytes help them trap and attract particles like TSS in a medium. So, plants' ability to reduce TSS relies mostly on their root systems, and plants with woody roots can store more TSS than plants with taproots. In this study, the woody and long-rooted Pistia stratiotes sp lowered 98% of the TSS. Previous studies showed that Pistia stratiotes sp was able to make water clearer by catching floating solids in its roots [25].

Fig (7) shows the results of AN of phytoremediation system. The data reveals varying degrees of effectiveness in AN removal, showcasing both positive and negative trends. On Day 5, a modest initial removal rate of 3.75% was recorded. However, by Day 19, the system experienced an unexpected downturn, with a negative removal rate of -9.05%, indicating an increase rather than a decrease in AN level.

The system's efficiency slightly improved on Day 33, achieving a 1.17% removal rate, which remained consistent on Day 47. A notable upturn in AN removal was observed on Day 61, indicating a removal rate of 16.31%, suggesting improved performance. This positive momentum continued with a removal rate of 25% on Day 75, demonstrating a substantial improvement in AN removal. Nonetheless, the system encountered another setback on Day 96, with a negative removal rate of -3.77%. Rebounding from this decline, the system exhibited effective AN removal on Day 107, recording an 18.75% removal rate.

Pistia stratiotes is one that helps the removal of ammonia. During April observation, it was found that the Pistia stratiotes had been damaged by dragonfly larvae. Organic materials such as dead plant leaves increase ammonia and that decomposition produces high levels of ammonia. According to Gusti Wibowo et al. (2023), Pistia stratiotes and Eichhornia crassipes were used in this study and successfull reduced heavy metals i.e. Fe up to 89% and Mn up to 74%. Both plants also successfully reduce other pollutants such as BOD up to 98%, COD up to 99%, ammonia up to 70% after five weeks in a wetland system, plants play a significant role in removing AN content in wastewater through both direct (i.e. plant uptake) and indirect (microbial activity at rhizosphere) ways. For plant uptake, AN present in wastewater can be directly absorbed by roots, either accumulated in plants’ parts or assimilated by plants into transported amino acids (e.g. glutamine, glutamate, aspartate and arginine) to support biomass growth and development (Fig. 8) [26].

Hydraulic retention time (HRT) is the average amount of time that a compound or substance spends in a reactor or a system within a wastewater treatment plant. In the context of nitrification, which is the biological conversion of ammonia to nitrate via nitrite, HRT plays a crucial role in providing sufficient time for the nitrifying bacteria to carry out these conversions. The HRT for this study was regulated to 9 hours per cycle. In many wastewater treatment systems, biological processes are used to break down organic and nitrogenous compounds. HRT impacts the efficiency of these processes. A longer HRT typically allows more time for microorganisms to convert ammonium (NH₄⁺) to nitrate (NO₃^-) through nitrification and then to nitrogen gas (N2) through denitrification. This can lead to better removal of Ammoniacal Nitrogen. HRT indicates the mean residence time of the wastewater within a biological reactor, thus determining the contact time between the pollutant and the microorganisms. The HRT usually applied for conventional processes ranges from 5 to 24 hours [27].

Fig. (7). Removal performance of AN by phytoremediation system.

Fig. (8). A few thypha angustifolia condition on March dan pistia stratiotes on April.