Nitrate Removal Characteristics of Nitrate-reducing Bacteria Pseudomonas sp. XS-18 at Low Carbon-to-nitrogen Ratio

L. L. Yan, M. Y. Yin, C. X. Wang, M. Y. Yang, L. T. Sun and Y. Jiao

Abstract
Low carbon-to-nitrogen (C/N) ratios are the main characteristic of domestic wastewater. In this study, we evaluated the nitrate removal characteristics of Pseudomonas sp. XS-18 at low C/N ratios (4.0 and 6.0) and pH 11.0. We also analyzed the causes of the nitrate removal at low C/N ratios in this strain. At pH 11.0 and a C/N ratio of 4.0, the strain was effective in removing nitrate. Additionally, the total organic carbon content decreased over time at low C/N ratios, requiring more energy to complete vital activities. Furthermore, low C/N conditions resulted in less strain secretion compared to high C/N settings, and the polysaccharide content degraded more quickly than protein over time. To provide a carbon source for the nitrate reduction process, strains with low C/N ratio and high pH secreted more soluble microbial by-products. This strain is able to metabolize its own secreted extracellular polymeric substances as a carbon source to enhance nitrate removal.

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Keywords
aerobic nitrate reduction, low C/N ratio, high pH, extracellular polymeric substances, nitrate assimilation process