[Strengthening Effect of Different Cattail Pretreatment Methods on the Denitrification of Horizontal Subsurface Flow in a Constructed Wetland]

Nitrogen removal in constructed wetlands (CWs) is highly affected by the supply of organic carbon. Thus, to enhance nitrogen removal in the horizontal subsurface flow of CWs, plant carbon sources were added during the downstream portion of the wetland. Moreover, the characteristics of static release and the denitrification potential of Typha were evaluated using three different pretreatment methods (i.e., minced, acid-heated, and alkali-heated). The average concentrations of COD released and the nitrate removal rate with the alkali-heated, acid-heated, and minced Typha were 89.57 mg·L^-1 and 75.2%, 67.27 mg·L^-1 and 67.2%, and 54.45 mg·L^-1 and 23.5%, respectively. The results showed that different pretreatment methods resulted in the release of different amounts of acetic acid, and the alkali-heated Typha performed much better than the other pretreatments. Therefore, the alkali-heated Typha was selected and added to the middle of the horizontal subsurface flow CW, which improved the nitrogen-removal rate significantly; the average removal rate of TN and TP was higher than that of a control CW by 30.3% and 33.9%, respectively. However, the COD concentration of the CW with the alkali-heated Typha was not significantly increased.