Abstract
The low carbon–nitrogen ratio (C/N) of influent wastewater results in the insufficient carbon source for the process of denitrification in urban wastewater treatment plants (WWTPs). A denitrifying bacterial strain, Pseudomonas sp. JMSTP, was isolated and demonstrated effective denitrification ability under a low C/N ratio of 1.5–4 (w/w) in anoxic conditions. Sequencing batch reactor (SBR) studies were conducted to test the bioaugmentation of JMSTP on total nitrogen (TN) removal under the influent COD/N ratio of 3/1. After the second bioaugmentation, the TN of effluent in the bioaugmented SBR was significantly lower than that in the control SBR. Redundancy analysis results showed that there was a positive correlation between Pseudomonas sp. abundance and TN removal in the bioaugmented SBR. Microbial community analysis showed that, especially after the second bioaugmentation, the abundance of Pseudomonas sp. decreased rapidly, but it was still much higher than that in the control SBR. Correlation network analysis showed that after the addition, Pseudomonas sp. had no significant co-occurrence relationship with other native bacteria, owing to the quick increase and decrease. Our results suggest that JMSTP shows the potential to enhance TN removal through bioaugmentation. Since the effect of bioaugmentation gradually diminishes, further research is still needed to investigate its long-lasting applications.
Highlights
Introduction iationsWith the rapid development of the economy and the continuous increase in urbanization, water pollution has been a severe problem in China
The effluent standard of total nitrogen (TN) discharged from wastewater treatment plants has been improved from 20 mg/L to 15 mg/L, or even 10 mg/L in certain areas, and a more effective strategy for TN removal will be required
The results show that when the COD/N ratio is 8, the effluent could meet the first class requirement of the National Municipal Wastewater Discharge Standards of China (TN ≤ 15 mg/L)
Summary
With the rapid development of the economy and the continuous increase in urbanization, water pollution has been a severe problem in China. The environmental standards implemented at existing wastewater treatment plants have become stricter [1]. The effluent standard of total nitrogen (TN) discharged from wastewater treatment plants has been improved from 20 mg/L to 15 mg/L, or even 10 mg/L in certain areas, and a more effective strategy for TN removal will be required. Bioaugmentation, which enhances the removal of pollutants in original systems by adding functional strains or populations [2,3,4,5], has shown the potential to improve nitrogen removal in wastewater treatment systems [6,7].
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