An integrated gravity-driven ecological bed for wastewater treatment in subtropical regions: Process design, performance analysis, and greenhouse gas emissions assessment

This study focused on the development of an integrated gravity-driven ecological bed (IGEB) for treating wastewater from agritainment activities in subtropical region. An integrated treatment process including multiple modules was designed. A filed scale treatment system was built and operated at an agritainment farm in Xiamen, China. Although the developed system had no requirement for electric power, it presented the good performances in pollutant removal and shock resistance. The effluent concentrations of COD, NH3-N, and TP reached 50.4, 10.4, and 0.9 mg/L, with removal rates of 78.0%, 72.7%, and 69.6%, respectively. The IGEB modules of anaerobic tank, multiple soil layer system and subsurface flow constructed wetland functioned as preliminary, secondary, and polishing treatments, respectively. The total greenhouse gas (GHG) emissions of IGEB system were about 21.3 kg CO2-eq/d. IGEB system had a significant advantage in terms of mitigation of GHG emissions over centralized wastewater treatment. In addition, the total cost of IGEB system was about 0.3 RMB Yuan to treat 1 tonne wastewater. As a sound decentralized wastewater treatment technique, it provides a sustainable solution for the environmental pollution issues related to agritainment activities.