## 3 Results and Discussion  
### Nitrogen Removal Effect of Reed Carbon Source Constructed Wetland  
#### 3.1.1 Removal Effect of NH\({}_{4}\)+-N  
As shown in Figure 2, the NH\({}_{4}\)+-N concentration of the influent from RW, CW and N-RW was 3.95-4.90 mg/L and the NH\({}_{4}\)+-N concentration of the effluent was 0.17-0.35, 0.14-0.39 and 0.30-0.52 mg/L, respectively. The corresponding average removal rates of NH\({}_{4}\)+-N were 93.84 \(\pm\) 1.22%, 94.01 \(\pm\) 1.57% and 90.70 \(\pm\) 1.38%, respectively. It was seen that the concentration of NH\({}_{4}\)+-N in the effluent of the three groups of wetlands was low, and the removing effect of NH\({}_{4}\)+-N was good and stable. The comparison between RW and CW showed that the addition of the reed carbon source had no significant impact on NH\({}_{4}\)+-N removal in constructed wetlands (\(p>0.05\)). Wetland nitrification mainly occurred in the top layer of the substrate and reeds were planted in both RW and CW, which increased the dissolved oxygen content in the top layer of the substrate and promoted the nitrification reaction [22]. The reed carbon source in RW was added to the middle layer of the substrate, which had little impact on the nitrification of the top layer of the substrate, so the NH\({}_{4}\)+-N removal rates of RW and CW were almost the same.  
The comparison between RW and N-RW showed that the NH\({}_{4}\)+-N removal rate of RW was 3.14% higher than that of N-RW wetlands, and reed planting could improve the NH\({}_{4}\)+-N removal effect of constructed wetlands. The oxygen secretion function of reed roots could create an alternating aerobic/anoxic environment in the wetland, increase the number and activity of denitfying microorganisms, and help synchronize the occurrence of nitrification and denitrification. Some rhizosphere microorganisms in the wetland could promote the growth of reeds and improve the absorption of nitrogen in the sewage by reeds. At the same time, plant absorption could also restore adsorption capacity of wetland substrates and promote adsorption of NH\({}_{4}\)+-N in wastewater by wetland substrates. The three synergistically enhanced the removal of NH\({}_{4}\)+-N from wetlands [23]. However, the removal rate of 3.14% is comparatively lower, but the phenomenon still works for constructed wetlands. Perhaps the plants would not have grown enough to ensure greater uptake of NH\({}_{4}\)+-N in addition to nitrification. Similar behavior was reported by [PERSON] et al. where plant growth is one of the main issues with constructed wetland startup [24].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Targeting Gene** & **Primer** & **Sequence (5\({}^{\prime}\)-3\({}^{\prime}\))** & **Reference** \\ \hline \multirow{2}{*}{_amoA_} & amoA-1F & GGGGTTTCACTGGTGGT & [PERSON] et al., 1997 [16] \\  & amoA-2R & CCCCTCKGSAAAGCCTTCTTC & \\ \hline \multirow{2}{*}{_nxrB_} & nxrB-169F & TACATGTGATCACA & \\  & nxrB-638R & CGGTTCTGCTRATCA & \\ \hline \multirow{2}{*}{_hzo_} & hzocl1F1 & TGYAAGACYTGCYAYTGTG & \\  & hzocl1R2 & ACTCCGAGATRTGCTGACC & \\ \hline \multirow{2}{*}{_nirK_} & nirK-1 aCuf & ATCATGCTSCTGCCG & \\  & nirK-3 Cur & GCCCTGATCAGRTTTGGT & \\ \hline \multirow{2}{*}{_nirS_} & cd3 af & GTSAACGTSAAGGARACSG & \\  & r3 cd & GASTTCGGGTCTTTGA & \\ \hline \multirow{2}{*}{_nrfA_} & nrfAF2 aw & CARTGYCAYGTBGARTA & \\  & nrfARI & TWNGGCATRTGCRCARTC & \\ \hline \hline \end{tabular}
\end{table}
Table 3: List of the primers for qPCR.