# Analysis of the Water Quality Improvement in Urban Stream Using MIKE 21 FM
## 6 Conclusions  
In this study, the water quality improvement and flow were compared on supplying the base flow after completing ozone treatment through the water quality measurement results and numerical modeling analysis, and the following conclusions were drawn. Based on the numerical analysis results of the MIKE 21 FM model, the water quality improvement of the ozone-treated water is significant in the Gulpocheon region. The DO was increased by 1.1 mg/L on the whole, while BOD concentration was reduced by 0.73 mg/L. If the water quality of the reclaimed water discharged is continuously managed \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \multirow{3}{*}{\begin{tabular}{c} **W.Q.** \\ **Parameters** \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} **Statistical** \\ **Parameters** \\ \end{tabular} } & \multicolumn{6}{c}{**Original Condition**} & \multicolumn{6}{c}{**After the Supply of the Ozone Treated**} \\  & & & & & & & & & **Reclaimed Wastewater** & & **Change** \\  & & & & & & & & & & **Ratio** \\ \hline \multirow{3}{*}{\begin{tabular}{c} BOD \\ (mg/L) \\ \end{tabular} } & Average & 4.07 & 3.71 & 1.58 & 2.62 & 3.00 & 4.12 & 1.92 & 1.82 & 1.30 & 2.29 & \(-\)30.8 \\  & Minimum & 1.75 & 1.63 & 0.84 & 2.00 & 1.55 & 1.75 & 1.05 & 1.35 & 1.02 & 1.29 & \(-\)20.3 \\  & Maximum & 9.53 & 8.21 & 2.80 & 3.56 & 6.03 & 9.53 & 3.60 & 3.13 & 2.81 & 4.77 & \(-\)26.3 \\  & S.D. & 1.88 & 1.56 & 0.27 & 0.36 & 1.02 & 1.86 & 0.56 & 0.32 & 0.20 & 0.73 & \(-\)38.7 \\ \hline \multirow{3}{*}{\begin{tabular}{c} DO \\ (mg/L) \\ \end{tabular} } & Average & 7.92 & 8.16 & 7.86 & 7.68 & 7.91 & 7.74 & 10.42 & 9.06 & 8.83 & 9.01 & 12.3 \\  & Minimum & 4.04 & 5.13 & 4.59 & 4.86 & 4.65 & 4.04 & 8.66 & 6.51 & 5.80 & 6.25 & 25.6 \\  & Maximum & 13.15 & 13.17 & 13.66 & 13.16 & 13.29 & 13.19 & 12.86 & 13.26 & 13.64 & 13.24 & \(-\)0.4 \\  & S.D. & 2.49 & 2.39 & 2.85 & 2.55 & 2.57 & 2.37 & 1.23 & 2.02 & 2.35 & 1.99 & \(-\)28.8 \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} TN \\ (mg/L) \\ \end{tabular} } & Average & 3.26 & 3.21 & 3.50 & 3.87 & 3.46 & 3.27 & 6.29 & 5.67 & 5.17 & 5.10 & 32.2 \\  & Minimum & 2.64 & 2.58 & 1.61 & 2.35 & 2.29 & 2.64 & 5.20 & 3.59 & 2.62 & 3.51 & 34.7 \\  & Maximum & 3.99 & 4.32 & 7.41 & 7.55 & 5.82 & 3.99 & 8.85 & 9.06 & 8.93 & 7.71 & 24.5 \\  & S.D. & 0.40 & 0.36 & 1.45 & 1.22 & 0.86 & 0.40 & 0.99 & 1.68 & 1.92 & 1.24 & 31.2 \\ \hline \multirow{3}{*}{
\begin{tabular}{c} TP \\ (mg/L) \\ \end{tabular} } & Average & 0.19 & 0.21 & 0.38 & 0.34 & 0.28 & 0.20 & 0.25 & 0.30 & 0.32 & 0.27 & \(-\)6.3 \\  & Minimum & 0.01 & 0.02 & 0.12 & 0.11 & 0.06 & 0.01 & 0.18 & 0.22 & 0.22 & 0.16 & 59.4 \\  & Maximum & 0.37 & 0.39 & 0.68 & 0.64 & 0.52 & 0.37 & 0.38 & 0.63 & 0.67 & 0.51 & \(-\)1.0 \\  & S.D. & 0.10 & 0.11 & 0.12 & 0.11 & 0.10 & 0.03 & 0.04 & 0.05 & 0.06 & \(-\)99.3 \\ \hline \end{tabular}
\end{table} 
Table 3: Statistical results of MIKE 21 FM simulation. and utilized as the base flow inside Gulpocheon, the stability preservation and water quality improvement of the stream can be expected. Compared with directly discharging the treated sewage water as the base flow of the stream, discharging it after passing through the ozone treatment process will lead to the immediate improvement of water quality, along with the dilution effect. Hence, it is expected to contribute to improving the accessibility to the residents around the urban stream. Future studies need to compare the water quality and concentrations with the stream environmental standards (Ministry of Environment), quantitatively analyze the base flow effect of the ozone treatment facility, and utilize it in the facility operation. Furthermore, the utilization effect of the ozone-treated water, monitored through the continuous water quality inside Gulpocheon, is expected to play a more critical role in water quality maintenance due to algal bloom in the summer season. This research was funded by Incheon National University Research Grant in 2020. Not applicable.