Aromatic acids affect the performances of constructed rapid infiltration systems based on red mud and coke: Removal efficiency, electron transport, and metabolism

This study investigated the effect of coke and red mud as fillers in a constructed rapid infiltration system on the removal of three aromatic acids in wastewater. In addition, a combination of X-ray photoelectron spectroscopy (XPS) and metagenomics sequencing was used to explore the microbial communities and metabolic mechanisms. Results showed that the removal rates of chemical oxygen demand of the three columns containing phthalic acid (PA), benzoic acid (BA), and 1-naphthoic acid (1NA) were 83.59%, 92.52%, and 88.72%, and the removal rates of ammonia nitrogen were 37.33%, 40.83%, and 38.38% of, respectively. Meanwhile, the removal efficiency of three aromatic acids by the systems was BA > PA > 1NA. Proteobacteria and Actinobacteria were among the dominant bacterial groups in the columns. The highest relative abundance of Sphingopyxis was found in the column with 1NA, which provided a certain guarantee for the degradation of 1-naphthoic acid by this column. Compared to PA and 1NA, BA upregulated the abundance of the norB gene. The relative abundance of phoBR, a regulator of the. phosphoryl regulator response, was significantly down-regulated in the PA column, leading to a decrease in total phosphorus removal at the later stage. This study provides an economical and simple process for the treatment of wastewater containing aromatic acid. These promising results also indicate that red mud can be used as a resource in wastewater treatment.