Importance of Natural Pyrite in Treating Carbon-Constraint Wastewater by Constructed Wetland-Microbial Fuel Cells

Abstract

Pyrite is regarded as a natural electron donor and has the potential to enhance autotrophic nitrogen removal and electricity generation. In this study, two constructed wetland-microbial fuel cells (CW-MFCs) with pyrite as anodic filling materials were constructed to treat wastewater with low-carbon sources (e-PCW1) and without carbon sources (e-PCW2). In e-PCW2, the removal efficiency of nitrogen and phosphorus was 11.44%–15.79% and 79.79%–84.35%, respectively. The e-PCW1 system removed up to 63.56% nitrogen and 86.37% phosphorus at 0.2 L/min aeration rate and 180 mg/L COD loading. The highest electricity generation was also achieved in the stage. The e-PCW1 exhibited a greater nitrogen removal ability due to the higher abundance of Thauera, which can act as denitrifying bacteria and sulfate-reducing bacteria. The phosphorus removal relied on chemical precipitation and contributions of Candidatus_Competibacter and norank_o__Run-SP154. In sum, pyrite can play its advantages in CW-MFCs to treat carbon-constraint wastewater.

Keywords: Constructed wetland-microbial fuel cell, Carbon-constraint wastewater, Pyrite autotrophic denitrification, Electricity generation