## 3 Results and Discussion  
### Surface Water Quality  
Table 2 summarizes the chemical properties of the surface water in the ecologically engineered wetland, highlighting significant improvements in the water quality parameters from Site 1 (S1) to Site 3 (S3). The pH of the surface water, initially acidic at the inflow (3.9), rose to a neutral level (7.18) by the time it reached S3, indicating a more hospitable environment for aquatic organisms. The alkalinity also substantially increased, from 22 mg/L CaCO\({}_{3}\) at S1 to 143 mg/L CaCO\({}_{3}\) at S3, demonstrating a strengthened buffering capacity in the water. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Parameter** & **Unit** & **S1** & **S2** & **S3** & **Change (S1:S3)** & **\% Change (S1:S3)** \\ \hline \(\mathrm{pH}\) & – & 3.90 & 3.84 & 7.18 & +3.28 & 84.10 \\ \hline Alkanility & mg/L CaCO\({}_{3}\) & 22.00 & \textless{}5.00 & 143.00 & +121.00 & 550.00 \\ \hline Electrical conductivity (EC) & mS/m & 178.6 & 180.50 & 152.10 & \(-\)26.5 & 14.84 \\ \hline Total dissolved solids (TDSs) & mg/L & 1196.62 & 1209.35 & 1019.07 & \(-\)177.5 & 14.84 \\ \hline Dissolved organic carbon (DOC) & mg/L & 5.18 & 5.17 & 16.00 & +10.82 & 208.88 \\ \hline Aluminum (Al) & mg/L & 1.60 & 1.80 & \textless{}0.01 & \(-\)1.59 & 99.38 \\ \hline Iron (Fe) & mg/L & 0.33 & 0.58 & 0.26 & \(-\)0.07 & 21.21 \\ \hline Manganese (Mn) & mg/L & 10.80 & 10.90 & 37.10 & +26.30 & 243.52 \\ \hline Sulfate (SO\({}_{4}\)\({}^{2-}\)) & mg/L & 1310.00 & 579.00 & 774.00 & \(-\)536.00 & 40.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average physicochemical properties of the surface water at each site and the percentage change from the inflow (S1) to the far middle (S3) of the wetland. The electrical conductivity (EC), which measures the water's ability to conduct electrical current due to the presence of dissolved ions, remained fairly constant between S1 and S2. However, a slight decrease of around 15% was noted from S2 to S3. Changes in the EC are important as they reflect alterations in the concentration of dissolved salts and minerals in the water, which can impact aquatic life. According to the [39] a change greater than 15% in the TDS (total dissolved solid) concentrations, which are closely related to EC, is deemed significant in aquatic ecosystems. The dissolved organic carbon (DOC) exhibited a substantial increase from Site S2 to Site S3, rising by 208.88%, indicating a higher organic load in the surface water at Site S3. The metal concentrations typically associated with AMD--aluminum (Al), iron (Fe), and manganese (Mn)--showed varying trends: the Al and Fe concentrations were the highest at Site S2, decreasing from S1 to S3, while the Mn concentrations were the highest at Site S3, increasing significantly by 243.52% from S1 to S3. This increase in the Mn levels at Site S3 exceeded the South African Target Water Quality Range for aquatic ecosystems [39]. Conversely, the sulfate (SO4\({}^{2-}\)) concentrations decreased by approximately 40% from S1 to S3. A previous study by [8] assessed the impact of ecological infrastructure on the Zaalk-lapspruit wetland, focusing on water quality improvements before and after interventions. Their findings indicated a notable enhancement in the surface water quality, with the pH increasing from 5.3 to 7.6, and significant reductions in the Al and Fe concentrations from 0.89 to less than 0.01 mg/L and from 0.29 to less than 0.01 mg/L, respectively. The current study observed similar trends in the Al and Fe concentrations but noted a discrepancy in the manganese levels. Ref. [8] reported a 96% reduction in the Mn levels, whereas this study found an increase in the Mn concentrations from the inflow to the outflow. This elevated concentration of Mn at Site S3 can be attributed to several factors. The redox conditions at Site S3, being further from the inflow and experiencing longer water retention, may facilitate the release of manganese from sediments or enhance reduction processes that increase its concentration in the water.