Mechanism of nitrogen removal by a hybrid membrane bioreactor in municipal wastewater treatment

Abstract

A pilot scale experiment was conducted to evaluate the characteristics of nitrogen removal in a hybrid membrane bioreactor (HMBR) which was developed by introducing biofilm carriers into a conventional membrane bioreactor (CMBR) in municipal wastewater treatment for more than three months. During the experimental period, the HMBR performed well on organic matter and nitrogen removal. The COD, -N, and TN removal rate in the HMBR was enhanced by 3.8, 5.4, and 12.7%, respectively, compared to the CMBR. The effluent TN in the CMBR ranged from 21 to 33 mg L⁻¹, while it dropped to 15–24 mg L⁻¹ in the HMBR. Further investigation was conducted on the property of activated sludge such as biomass quantity, sludge volume index, particle size distribution, and sludge particle structure. Results showed that the activated sludge particle size in HMBR was increased by nearly 100% comparing with that in CMBR, and the sludge in HMBR was more compact, which means that the effect of simultaneous nitrification and denitrification (SND) can occur in the HMBR sludge more easily. Like in the sludge, SND can also occur in the thick biofilm. According to the experiment, the contribution of activated sludge and biofilm in HMBR to the enhancement of TN removal rate was 7.7 and 5%, respectively.

Keywords:

• Hybrid membrane bioreactor
• Nitrogen
• Simultaneous nitrification and denitrification
• Activated sludge
• Biofilm

Acknowledgments

This study was supported by the National Sparking Plan Project of China (Grant No. 2012GA690325) and the Key Laboratory Open Project of Jiangsu Food Resources Development and Quality Safety of China (Grant No. SPKF201320).

Notes

Presented at the Conference on Water Resources and Urbanization Development, 26–27 September 2012, Tianjin, China