Effect of long-term bioaugmentation on nitrogen removal and microbial ecology for an A²O pilot-scale plant operated in low SRT

Abstract

The effect of long-term bioaugmentation on nitrogen removal, nitrification activity, and microbial ecology for an anaerobic/anoxic/aerobic (A²O) pilot-scale plant operated in low sludge retention time (SRT) to treat municipal wastewater was investigated. Reject water from sludge treatment was used as a feed to cultivate the nitrifier contained in activated sludge for bioaugmentation. Under the conditions of 10 h hydraulic retention time, 8 d of SRT, and 14°C water temperature ammonia removal efficiency increased by 25%, and specific ammonia utilizing rate and specific nitrite utilizing rate increased by 1.86 and 1.90 times, respectively. The percentages of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the total number of bacteria increased from 2.4 and 2.1% to 6.8 and 7.8%, respectively. The dominant AOB and NOB were transformed from Nitrosospira and Nitrospira to Nitrosomonas europaea and Nitrobacter.

Keywords:

• Bioaugmentation
• Municipal wastewater
• Nitrogen removal
• Nitrification activity
• Nitrifier community structure
• Reject Water

Acknowledgment

This research was financially supported from a grant (No.: 2009ZX07317–009) of the State Key Project on Water Environmental Pollution Control, China.