[Clogging characteristics of the subsurface flow wetland]

In order to resolve clogging problem of constructed wetlands caused by improper design or imperfect management and reveal the clogging mechanism, clogging characteristics of the horizontal flow reed wetland and vertical flow reed wetland were studied. Operation stabilities of two types of wetlands were compared. It shows that organic matter accumulates in medium and the concentration is 1.5% - 5%. It mostly occurs in the fore section of top layer in wetland and the concentration is 4% - 5%. The negative correlation between the organic matter content and the subsurface depth was demonstrated. The clogging mechanisms in the horizontal flow wetland and the vertical flow wetland are different. The hydraulic retention time of the horizontal flow wetland is 3.5154 d which is shortened by 21.88%. While the hydraulic retention time of the vertical flow wetland is 5.4648 d and extended by 21.44%. The results indicate that clogging decreases the treatment capacity and running stability conspicuously. The clogging phenomenon of the vertical flow wetland is worse comparatively.