The constructed root channel technology and its application in constructed wetlands
人工湿地生态根孔技术及其应用

Clogging problem of subsurface layer media has increasingly been an obstacle to the long-term effective operation of constructed wetlands, which greatly limits their practical application and sustainability. In the field experimental study in Baiyangdian Lake, we found that the aquatic macrophytes could form root channels network with various sizes. Based on that, an innovative subsurface structure modification method of constructed wetlands, named as constructed root channel technology (CRCT), was developed. This technology utilized artificially buried straws as substrate media, aiming to emulate the structure and functions of natural root channel systems. Self-renewal of wetland substrates were effectively achieved by the transition between constructed root channels and natural root channels and the continual renewal of wetlands root channels. This mechanism overcame the shortcoming that the substrates of common subsurface flow constructed wetlands tended to be clogged with a period of operation. Constructed root channels would fill the gap before a great number of natural root channels were developed during the initial operation period of constructed wetlands. The CRCT had been successfully applied in the pilot constructed wetlands. Corn straws and Kochia straws were used as the subsurface media in this pilot study, whose volumetric amount accounted for 2%~4% of the soil mass. The experimental cells with constructed root channels could stimulate hydraulic conductivity and nutrient removal efficiency with comparison to the matrix soil cells without buried straws. Results showed that the lateral hydraulic infiltration rates of the constructed root channels formed by decayed straws were about 20 times that of matrix soil. Under the low to moderate inflow nutrient loads, the cells with buried straws could increase the removal efficiency of dissolved total nitrogen (DTN) and dissolved total phosphorus (DTP) by 4.5%~27.1% and 7.0%~20.4% in average, respectively.