Nitrate Removal in Horizontal Subsurface Constructed Wetland with Cattail Litter Addition

Denitrification is the main removal process for nitrate, but the low concentration of dissolved organic carbon in horizontal subsurface constructed wetland limit the nitrate removal rate. Effect of vegetation (cattail) and carbon addition (100g dried cattail litters per month) on the nitrate removal rate were examined in three horizontal subsurface constructed wetland microcosms fed with nitrate-contaminated water (20 mg N/L, 1mg P/L). Results showed that nitrate removal rate was 63% greater in the microcosms with litter addition than in that without litter, and vegetation also enhanced the removal of nitrate by about 18%. Temperature is another factor influencing nitrate removal efficiency. Vegetation and addition of cattail litter can enhance nitrate removal in horizontal wetlands receiving nitrate-contaminated water with low concentration of organic carbon.