Study of enhanced nitrogen removal efficiency and microbial characteristics of an improved two-stage A/O process

ABSTRACT

During the cold winter in northern China, the temperature is generally below 8°C, and low water temperature significantly inhibits biological treatment processes, especially the biological denitrification process. To solve this problem, this study proposed an improved two-stage A/O process with built-in submerged biofilm modules. Experimental water was acquired from the Sanbaotun Wastewater Treatment Plant, which is situated in the city of Fushun, Liaoning Province. After one year of experimental research, the improved two-stage A/O process proved to be significantly better than the traditional two-stage A/O process, especially in winter. In the one-year experiment, the average removal rates of COD, TN, and NH₄⁺-N in the improved two-stage A/O process were 85.2%, 77.6%, and 96.9%, respectively. Microbial properties of the process were studied by means of high-throughput sequencing. High-throughput sequencing was conducted on the biofilm of the improved two-stage A/O terminal aerobic tank and the activated sludge of the conventional two-stage A/O aerobic tank. The result showed that the microbial diversity and abundance of the biofilms were considerably higher than those of the activated sludge during stable operation in winter. Under low-temperature conditions, the main denitrifying bacteria of the improved two-stage A/O process was Terrimonas, belonging to the sphingolipid class of Bacteroides, and the main genus of nitrifying bacteria was Nitrospira, belonging to the nitrite oxidizing bacteria.

GRAPHICAL ABSTRACT

KEYWORDS:

• Improved two-stage A/O
• severe cold region
• enhanced nitrogen removal
• microbial characteristics
• high-throughput sequencing

Acknowledgments

This research was supported by the National Key Research and Development Program of China (2017YFB0602804), the Major Projects of Science and Technology (No. 2014ZX07202-011) in China, the National Natural Science Foundation (No. 51878278), and the Shanghai Pujiang Programme (No. 13PJD009).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation: [Grant Number No. 51378207]; National Key Research and Development Program of China: [Grant Number 2017YFB0602804]; the Major Projects of Science and Technology: [Grant Number No. 2014ZX07202-011]; the Shanghai Pujiang Programme: [Grant Number No. 13PJD009].