Acorus calamus recycled as an additional carbon source in a microbial fuel cell-constructed wetland for enhanced nitrogen removal

Abstract

Acorus calamus was recycled as an additional carbon source in microbial fuel cell-constructed wetlands (MFC-CWs), for efficient nitrogen removal of low carbon wastewater. The pretreatment methods, adding positions, and nitrogen transformations were investigated. Results indicated that alkali-pretreatment cleaved the benzene rings in dominant released organics, producing chemical oxygen demand of 164.5 mg from per gram of A. calamus. Pretreated biomass addition in the anode of MFC-CW attained the maximum total nitrogen removal of 97.6% and power generation of 12.5 mW/m2, which were higher than those with biomass in the cathode (97.6% and 1.6 mW/m2, respectively). However, the duration of a cycle with biomass in the cathode (20–25 days) was longer than that in the anode (10–15 days). Microbial metabolisms related to organics degradation, nitrification, denitrification, and anammox were intensified after biomass recycling. This study provides a promising method to improve nitrogen removal and energy recovery in MFC-CWs.