Effect of saline aquaculture wastewater treatment by constructed mangrove wetland

To explore the feasibility and operating characteristics of the treatment of saline aquaculture wastewater by constructed wetland, mangrove plants Kandelia candel were used to construct salt-tolerant wetland to treat saline aquaculture wastewater. Three unplanted units were also set as a control. The planted units showed better capability of COD and NH4+-N removal than unplanted units obviously. Treatment performances of the planted units were found to be 66.4%-73.8% for COD and 64.3%-72.4% for NH4+-N. For the unplanted units, the reduction in COD and NH4+-N was in the range of 56.7%-62.4%, 51.2%-57.5%, respectively. However, for the removal of TP, there was no significant different between the planted units and unplanted units. The TP removal efficiency varied between 55.7%-61.7% for the planted units and between 54.3%-60.4% for the unplanted units. The enzyme activity of urease and phosphatase in the substrate of planted units was obviously higher than that of unplanted units. And the region with the highest enzyme activity was in 0-5 cm surface area in the substrate, where roots system distributed most broadly. So the roots of mangrove could be considered to have a significant role for the biological activity and contaminants removal of the constructed wetland. The effect of HLR on the treatment performance of the constructed mangrove wetland was studied, and the result indicated that the removal of organic matter and nitrogen of the wetland was obviously influenced by the HLR of the system. The effluents discharge from the constructed mangrove wetland could meet the water quality standards of the National Fisheries when the HLR of the wetland below 0.1 m3/ (m2·d). The findings of this article can provide a way for the biological treatment of saline aquaculture wastewater.