Recycling of rural abandoned constructed wetlands: mariculture wastewater treatment

This study aimed to investigate the behavioral shifts of constructed wetland (CW) when the treated water was changed from domestic wastewater to mariculture wastewater. The results showed that the average removal efficiencies of ammonium nitrogen (NH4 -N), total nitrogen and chemical oxygen demand (COD) were 29.54, 46.07 and 57.15% in mariculture wastewater, respectively, which were significantly lower than those in domestic wastewater (71.35, 66.34 and 74.98%, respectively). While there was no significant difference in the removal efficiency of nitrate and phosphate (P> 0.05) between the two systems. Based on the analysis of bacterial community and adsorption properties, the results further indicated that the removal mechanism of NH4 -N between both systems was mainly due to substrate adsorption: the maximum adsorption capacity of NH4 -N on the substrate in mariculture wastewater was 5,432 mg kg , whereas that in domestic wastewater was 18,033 mg kg . In terms of bacterial communities, the dominant bacteria at the family level were Victivallaceae (18.63%) in domestic wastewater and Porphyromonadaceae (18.37%) in mariculture wastewater, which showed the significant alteration to the bacterial community. In conclusion, this study showed that conventional CW could be used for treating wastewater from land-based marine aquaculture, while the operating conditions needed to be optimized in the process of application.