Study on Nitrogen Removal Process of Treatments for Slightly Contaminated Water on Hybrid Constructed Wetlands

In order to study nitrogen removal process of treatments for the slightly contaminated water on hybrid constructed wetlands,three indicators including nitrogen concentration,bacteria quantity and intensity of nitrification/denitrification were analyzed in the Dengbeiqiao wetland system.Meanwhile,the process of nitrogen variation and the removal rate were discussed.The results showed that the concentration of NH3-N and TN stepwisely decreased in this hrbrid system of oxidation pond-surface flow-subsurface flow-surface flow wetland.Removal rates of NH3-N and TN reached for 53.24% and 48.21% in average respectively.Intensity of nitrification in the oxidation pond and in the surface flow wetland were much higher than those in the subsurface flow wetland;The final surface flow wetland owns the greatest amount of nitrate bacteria(93.00×105 g-1) and the highest intensity of nitrification(8.42×102 mg/(m3·h) in the surface soil);while DO on the subsurface flow wetland is the lowest,and intensity of denitrification in the surface and the deep soil reached for 32.70×102 and 32.09×102 mg/(m3·h),respectively.The primary unit of denitrification on hybrid constructed wetlands is the subsurface flow wetland.