Nitrogen removal in polluted water with low carbon source by a membrane bioreactor-attapulgite clay integrated system was investigated, and the contribution of membrane and microorganisms to organic pollutant removal was evaluated and discussed. The result confirmed that the two MBR treatments can be effective for the removal of trace organic matters, which CODMn and UV254 were higher than 80% and 78%, respectively. Moreover, it can be also highlighted that there is a limitation of MBR in removing nitrogen (e.g. ammonia, nitrite, and nitrate) and that attapulgite clay could complement MBR well as a biological carrier. The MBR-attapulgite clay system obviously showed higher nitrogen removal efficiency; the ammonia nitrogen and total nitrogen efficiencies improved by 8% and 40% than that of MBR. Furthermore, the membrane fouling in MBR-attapulgite clay system remarkably reduced as well, which provided a longer operation time (more than 35 days) before backwashing with chemical solution. (C) 2013 Elsevier B.V. All rights reserved.