Performance and microbial community structure of BC/FeC2O4/SB modified carriers on the nitrogen removal from mariculture wastewater

The recent development in mariculture production has led to the global need to find an eco-friendly treatment that could mitigate the detrimental effects of nitrogenous compounds on aquatic species, the environment, and public health. The potential application of corn straw biochar (BC) combined with nano-ferrous oxalate (FeC 2 O 4 ), integrated into a sponge (BC/FeC 2 O 4 /SB) as a cost-effective and sustainable novel carrier for the removal of nitrogenous compounds, was explored in this study. The modified carriers were filled into a moving bed bioreactor (MBBR) to treat simulated saline aquaculture wastewater for the first time. Scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) spectroscopy analyses characterized the carrier biofilm morphology and functional group compositions. Findings showed that the modified carrier achieved the highest reduction percentages of 99.49 ± 0.29% for ammonium and 81.3 ± 2.1% for nitrate, with lower nitrite accumulation by day 136. The microbial sequencing analysis revealed that the coexistence of nitrogen removal and salt-tolerant microbes from the genera Aquimonas (25.15%), Woodsholea (20.44%), Hydrogenophaga (14.73%), Nitrosomonas (4.01%), Rhodococcus (2.70%), and Nitrospira (1.97%) resulted in the enhanced treatment performance observed in the modified BC/FeC 2 O 4 /SB carrier-filled MBBR as compared to the control MBBR. The data obtained in this study provide a comprehensive understanding of the role of modified BC/FeC 2 O 4 /SB carriers for the efficient treatment of saline RAS wastewater using MBBR.