## 3 Results
### Phosphate Reduction Analysis  
The results of the phosphate analysis obtained during the phytoremediation of domestic wastewater using three selected aquatic weed plants for two weeks with varying retention times of 6, 12, and 24 h are represented in Figures 6-8. Figure 6: Bar plot of the average phosphate vs. the sampling period with a 6 h retention time. Figure 7: Bar plot of the average phosphate vs. the sampling period with a 12 h retention time. From Figure 6, the phosphate concentration of the influent wastewater samples obtained from the STP varied throughout the sampling period and ranged from 4.21-6.8 mg/L. The initial average phosphate concentration of the influent samples gradually decreased across the 14-day sampling period, except for the _P-stratites_- and _S-molesta_-treated water samples on the 10 th day of the sampling period. Similarly, on the second day of the sampling period, the phosphate level of the influent wastewater samples was decreased from 6.8 \(\pm\) 0 mg/L to 5.40 \(\pm\) 0.02 mg/L, 5.55 \(\pm\) 0.01 mg/L, and 5.44 \(\pm\) 0 mg/L by the _P. stratites_, _S. molesta_, and _E. crassipes_ plants, respectively. This reduction led to a change of 20.58%, 18.67%, and 20% phosphate removal efficiency for the _P. stratites_, _S. molesta_ and _E. crassipes_ treatment systems, respectively. Furthermore, on the sixth day, the influent phosphate values were lowered from 4.26 \(\pm\) 0 mg/L to 3.38 \(\pm\) 0 mg/L, 3.89 \(\pm\) 0 mg/L, and 2.75 \(\pm\) 0 mg/L by _P. stratites_, _S. molesta_, and _E. crassipes_, respectively. However, the maximum phosphate removal efficiencies of _P. stratites_ (34.28%), _S. molesta_ (32.04%), and _E. crassipes_ (48.7%) were achieved on the 14 th day of the sampling period. Furthermore, a significant change (_p_ < 0.05) was detected between the influent and the effluent wastewater samples. Finally, a slow reduction performance by the three test plants in reducing the phosphate concentration of the domestic wastewater samples was observed as a removal efficiency of below 50% was obtained in the 14-day treatment period with a 6 h retention time. From Figure 7, it can be seen that the phosphate concentration of the influent wastewater samples from the STP varied throughout the sampling period. However, on the second day of the sampling period, the three test plants reduced the influent phosphate concentration from 3.6 \(\pm\) 0.04 mg/L to 3.3 \(\pm\) 0.04 mg/L, 3.3 \(\pm\) 0 mg/L, and 1.2 \(\pm\) 0.04 mg/L for _P. stratites_, _S. molesta_, and _E. crassipes_, respectively. On the eighth day, the test plants lowered the influent phosphate concentration from 5.56 \(\pm\) 0.05 mg/L to 5.36 \(\pm\) 0.04 mg/L (_P. stratites_), 5.44 \(\pm\) 0 mg/L (_S. molesta_), and 3.84 \(\pm\) 0 mg/L (_E. crassipes_). Furthermore, the maximum phosphate removal percentage was noted for _E. crassipes_ (70.45%) on the 2 nd day, followed by _S. molesta_ (46.96%) on the 12 th day, and _P. stratites_ (32.36%) on the 10 th day of the sampling period. Therefore, in this present study, _E. crassipes_ exhibited the highest phosphate removal percentage, trailed by _S. molesta_ and _P. stratites_ aquatic weed plants, for a 12 h retention time. A below-average reduction performance was observed in the _S.-molesta_- and _P.-stratites_-treated wastewater samples. This can be attributed to the 12 h retention time, as up to an 82% phosphate reduction was achieved in the 24 h treatment system of the two plants. Furthermore, a significant reduction (_p_ < 0.05) was observed between the influent samples' phosphates values and the treated wastewater samples. From Figure 8, the phosphate values of the influent wastewater samples from the STP were observed to be inconsistent throughout the sampling period and fell within the 4-20.1 mg/L range. A steady decrease was observed in the results throughout the sampling days, with slight inconsistencies observed in the pattern of phosphate level reduction of the effluent samples.