Study On Application Of Subsurface Constructed Wetland Treating Polluted River Water

With the development of economy, many rivers in china are polluted severely. The characteristics of the rivers in northern China, such as large flux changes in different seasons, large pollutant concentration changes and large water temperature changes, make it more difficult to control river pollution. The constructed wetland is one of the best techniques for the northern China river water treatment, because of its low investment, and operation cost, easy maintenance and low energy cost.The study used constructed wetland to treat polluted river water of Xiaofu River in Zi Bo. The construction and technique characteristics of system, the constant operation of wetland and the biological characteristics in wetland were studied systematically.This study selected waste bricks, waste potters, air brick and mixed media(waste bricks and potters mixed with the same volume scale) as the media of constructed wetland. Reed, Calamus and Canna were selected as the plants of constructed wetland. The results showed that with the hydraulic loading of 15cm/d, in higher pollutant concentration influent (COD_Cr and the ammonia nitrogen concentration were 40～70mg/L and 10³5mg/L respectively) and lower pollutant concentration influent (COD_Cr and the ammonia nitrogen concentration are 15～30mg/L and 0.3～3mg/L respectively), the best pollutant removal performance was aimed in the wetlandwith mixed media, the COD_Cr and ammonia nitrogen removal rates were 40%, 56% respectively and 25%, 70% respectively. The wetland plants was fixed as Reed and Calamus because that the Canna couldn't overwinter.Season changes influenced ammonia nitrogen removal rates greatly. Ammonia nitrogen removal rate was 70% in summer, while when the water temperature fell down below 15℃, ammonia nitrogen removal rate was decreased to below 30%. Season changes had a little influence on the COD_Cr removal rate. The 2 years pollutants removal rates of the constructed wetland were compared. The results showed that ammonia nitrogen removal rate fell down in the second year, while the COD_Cr removal rate rose.