The bio-diatomite dynamic membrane (BDDM) reactor is an emerging micro-polluted surface water treatment technology that combines diatomite (the microorganism carrier) and a stainless steel mesh (the dynamic membrane support module). A constant water head of 20 cm was designed to drive the BDDM filtration. The BDDM with sintered diatomite had good water penetration capacity, a filtration flux as high as 92 L/m(2) h after a filtration time of 15,780 min, and an effluent turbidity in the range of 0.15 NTU-0.20 NTU. The BDDM reactor effectively removed organic matter and ammonium nitrogen. The diatomite adsorption and the BDDM interception did not have high pollutant removal efficiencies. The dehydrogenase activity (DNA) of the bio-diatomite was in the range of 2.27-3.20 (mg TF)/(gVSS) h, indicating good microorganism activity for organic matter removal. The PCR-DGGE analysis showed that the microbial community was very abundant. Bacteroidetes, Firmicutes, Proteobacteria (e.g. alpha-, beta-, -gamma-proteobacteria), Verrucomicrobia, and Nitrospirae were dominant in the bio-diatomite mixed liquor and removed organic matter and ammonium nitrogen. The microbial degradation of pollutants by the bio-diatomite mixed liquor was primarily responsible for the pollutant removal in the BDDM reactor. (c) 2012 Elsevier B.V. All rights reserved.