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

AbstractA 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 de...