Heat Preservation of Subsurface Flow Constructed Wetland in Cold Area in Winter and Its Operation Effect

To solve the heat straying problem of constructed wetland in north China, a series of measures was adopted in an engineering application case. The operation results showed that, after using the heat preservation measures, vertical current constructed wetland in the north went through the winter safely, and the gas exchanged with the air by water into and out efficiently, remitting oxygen inadequacy in the bed, greatly improving the pollution removal. In terms of the effect, the removal efficiency in winter was similar to that in summer, with little variation. The average removal rates of COD, NH4+-N and TP were 90.85%, 98.38% and 89.68% respectively, and the quality of effluent achieved the national emission standard.