Characterization of Laboratory-scale Tidal Flow Constructed Wetlands in the Removal of Organic Carbon and Nitrogen from Sewage

Abstract

Tidal flow constructed wetlands (TFCWs) have been proposed as a new type of CW for enhanced wastewater treatment. However, the characterization of TFCWs in the removal of organic carbon and nitrogen remains unclear. This study investigated the efficiencies and characteristics of lab-scale TFCWs in removing organic carbon and nitrogen from sewage; in particular, the dynamics of dissolved total organic carbon (DOC), nitrogen, and dissolved oxygen (DO) were observed. Pumice- and zeolite-TFCWs were prepared, which treated sewage at 21 E fill and 3 E rest cycles. Sewage was rapidly oxidized in these TFCWs after inflow. The experimental results showed that DOC was efficiently decreased by aerobic biodegradation with DO consumption. Additionally, NH4+-N was oxidized to NO3∁EN by nitrification, the DO content decreased, and NO3∁EN was removed by denitrification in the TFCWs. The processes of aerobic-anaerobic switching, organic carbon biodegradation, and nitrification-denitrification were observed in the TFCWs. During 128-days of operation, the pumice- and zeolite-TFCWs exhibited the DOC removal capacities of 4.2 and 4.3 E-DOC/m2/d, respectively, and total dissolved inorganic nitrogen removal capacities of 3.1 and 5.1 E-N/m2/d, respectively. These results revealed the higher organic carbon and nitrogen removal capacities and mechanisms of pumice- and zeolite-TFCWs treating sewage.

Keywords

• nitrification-denitrification
• nitrogen removal
• organic carbon
• sewage treatment
• tidal flow constructed wetland