Construction of an ecological ditch based on periphyton reactor

To make the effluent of constructed wetlands in a pond recirculating aquaculture system satisfy aquaculture requirent, a 150m in length, 0.5m in width and 0.6m in depth ecological ditch was constructed on the basis of the periphyton reactor theory. The reoxygenation and deep purification effect of the ditch on the effluent of constructed wetlands was explored in this study. The results showed that the level of dissolved oxygen (DO) in the effluent of constructed wetlands increased to a range of 4.41-7.91 mg/L and pH value increased significantly by flowing though the ecological ditch (P <0.05). DO level in the water of ecological ditch increased linearly with the length of the ditch within the range of 150 m (P <0.05). The ecological ditch deeply purified NH4+-N, IMn and PO43--P in the effluent of the constructed wetlands with removal rate of 19.46%, 13.38% and 31.09%, respectively. The total coliform group was also eliminated with removal rate fluctuating between 12.5% and 78.13%. These results indicated that the ecological ditch based on periphyton reactor could increase DO level and further reduce N、P content of the effluent from the constructed wetlands . The ecological ditch can be used as a matching water reuse system of constructed wetlands.