What is the unit area of surface flow constructed wetland?

The typical structure of surface flow constructed wetland is shown in the figure, also known as free water surface constructed wetland system, which is widely used in North America. Wetlands usually consist of one or several ponds, with partition walls between them, and anti-seepage measures are taken at the bottom and pond walls to prevent sewage from spreading.

Ponds are usually filled with soil, sand or other suitable substrates for the growth and fixation of aquatic plant roots. The flowing water level of this kind of wetland is shallow, mostly at (0. 1~0.6)m, and the sewage flows slowly and horizontally in the wetland unit. Most of the organic matter in the sewage is removed by the biofilm growing on the underwater stems of plants, which is closest to the natural wetland.

Its advantages are simple construction and low investment. Disadvantages are low load and large area; The temperature is high, mosquitoes and flies are easy to breed, and the sanitary conditions are poor. When the temperature is low, surface icing will occur, which will greatly reduce the treatment effect of the system. Fillers and rich plant roots can not be fully utilized and are rarely used in practical projects.