Theory and Practices of Water Pollution Control by Wetland - a Case Study of Reed Wetland in Baiyangdian Lake

Wetland is an important eco-system on the earth and can effectively control agricultural non-point source pollution. Reed is a typical wetland plant for land/inland water ecotone in north China. The studies indicated that reed had a underground rooted-stem, which formed a 'high speeded-connecting vessels' i.e. reed root channel (RRC) in Baiyangdian lake of Hebei province. It spread predominantly along horizontal direction underground and are mainly distributed at 18-75 cm. The results of field work from healthy reed-wetland (HRW) and regarded reed-wetland (RRW) showed that the reed, averagely, in HRW is 4.2 m height, 1 cm diameter, 65/m2 density; in RRW is 2.4 m height, 3 mm diameter, 86/m2 density. These results indicated the regradation of the function of RRC in RRW. The results of laboratory work of sewage purification from reed soil column (RSC) $(0\~100cm)$ and wheat soil column (WSC) showed that the efficiency of purification to sewage, in RSC, is high than in WSC, especially for phosphorus. The efficiency of purification, in RSC, is $92.6\%$ for total phosphorus, $43.5\%$ for total nitrogen, $54.1\%$ fur COD, respectively; in WSC, is $86.0\%$ for total phosphorus, $241.3\%$ for total nitrogen, $29.8\%$ for COD, respectively.