BACKGROUND: Besides acting as power sources, sediment microbial fuel cells (SMFC) could be explored to remove organic matter in sediments and then maintain the water quality in aquatic environments. Until now, the role of the external resistance in the removal of organic matter by SMFC has received only limited attention. In this work, the removal of organic matters in sediments by lab-scale SMFCs at five different external resistances from 10 to 1000 Omega was investigated. RESLUTS: The external resistance in SMFCs had a strong influence on the working potentials of anodes. Application of a 100 Omega external resistance corresponded to the lowest internal resistance and highest removal efficiency of organic matter in sediment. The removal efficiency of readily oxidizable organic matter in a layer of sediment with a distance of 0-1 cm to the anode reached 28.3 +/- 1.9% at 100 Omega external resistance after 2 months of operation. In addition, there existed a linear relationship between current production from the SMFCs and removal efficiency of organic matter from sediments. CONCLUSIONS: The performance of SMFCs for the removal of organic matter in sediments could be enhanced through the selection of optimal external resistance. The SMFC real-time removal process could be monitored remotely using current generated. Thus, SMFCs offer an attractive alternative for the environmentally-friendly removal of organic matter in sediments. (C) 2010 Society of Chemical Industry