Supplementation of plant fermentation carbon sources significantly enhances the abundance of ammonia-oxidizing genes and increases nitrogen removal in a municipal wastewater treatment plant.

This paper deals with the effects of a cost-effective plant fermentation carbon source (PFCS) on nitrogen removal in a municipal wastewater treatment plant (WWTP). Carbon source and electron donor shortage remained one of the limiting factors for denitrification and nitrogen removal in the WWTPs of China. The PFCS was supplemented to increase the influent carbon/nitrogen (C/N) ratio from the original 9:1 to 82:1. The effluent ammonium (NH-N), total nitrogen (TN), and total phosphorus (TP) concentrations from the high C/N ratio group (group A) were significantly lower than those of the low C/N ratio control group (CK). Both Illumina sequencing and nitrogen metabolism gene copy number quantification demonstrated a notable increase in the abundance of aerobic denitrifying bacteria and functional denitrification genes at higher C/N ratios. Additionally, the optimal C/N ratios were investigated by using response surface methodology. Overall, high C/N ratios significantly improved the performance of municipal WWTPs in nitrogen and phosphorus removal. Moreover, inexpensive PFCS may provide a cost-effective strategy for improving wastewater treatment capacity, although excessive sludge increased. Utilization of PFCS could reuse and recycle the high-fiber solid waste of crops and timbers generated from agricultural, forestry, and wetland plants, which could contribute to global sustainable development and environment protection.