Research on wastewater treatment through integrated constructed wetlands

This research examines the effects of a constructed wetland system in the treatment of wastewater of differing nutrient concentrations under outdoor natural conditions. We conducted the experiment by employing a three-series hybrid flow, cultivating plants in different seasons, and configuring the size and porosity of the substrate in different layers. The experiments consisted of two phases. In the first phase where eutrophic water was used as the inflow, results showed that water quality experienced two periods, instability and stability, stable after the 15th day. The average removal rates of chemical organic demand (COD), total phosphorus (TP), and total nitrogen (TN) were 71.62%, 60.00%, 91.44%, respectively. In the second phase, which the water concentration was increased (in order to simulate domestic waste water). In an operating cycle of 21 days, the system maintained relatively high impact resistance and stability, with average removal rates of COD, TP, TN reaching 80.59%, 92.60% and 97.71%, respectively; as a result, the effluent water quality met the Surface Water Environment Quality Standard Class and Urban Sewage Treatment Plant Emission Standards (an A class standard). This study demonstrates that this wetland treatment system can effectively remove organic matters, and N, P from the wastewater with different qualities, and still have treatment capability for sewage in a 1-year cycle. In addition, this system requires low investment, energy and management efficiency and therefore, it is likely an effective technology for the treatment of urban sewage and eutrophic water in small cities.