[Application of two stage subsurface constructed wetland technology in cold area of northeast China]

Base on the two stage subsurface constructed wetland system running at the suburb of Siping city in Jilin province, the applicability and characteristics of the two stage system which had especial active media and measurements of isolation for temperature protection were studied and the advantages of the two stage system in the pollution removal were analyzed. The results showed that, the choice of especial active media and the measurements of isolation for temperature protection of the system made the two stage subsurface constructed wetland run efficiently in cold area and the system had very stable effects of the COD, BOD5, SS, NH4(+) -N and TP removal. In the whole process, the concentration of COD, BOD5 and SS in the outflow was about 16.01, 4.27 and 4.01 mg/L respectively and the concentration of NH4(+) -N and TP in the outflow was below 9.72 and 0.45 mg/L respectively. The subsurface wetland with two stages can overcome the disadvantage of the single system and improve the pollution removal efficiency.