In the post-9/11 environment, the anthrax attacks of 18 September 2001 re-energized several aspects of water security research. In the private sector, there was a resurgence of interest in transportable water treatment devices and in developing sensor technology to identify contaminants in water. Government scientists and engineers became interested in improving the current understanding of fate and transport of contaminants in water distribution systems and in developing water treatment and cleanup technology that did not generate hazardous waste. The U.S. Environmental Protection Agency (USEPA), ECBC, and ERDC stakeholders concluded that the pre-existing fate and transport models should be updated to include results from meso-scale testing. The Water Security Research Test Loop (WSRTL) is designed to help update these models with meso-scale testing of fate and transport of chemical and biological (CB) agents. The WSRTL would also serve as a test-bed to facilitate new generations of sensor technology and water treatment technology. This paper presents basic discussions about likely attack scenarios, remaining problems with current models of fate and transport of contaminants in a distribution system, and areas of current research. Includes 14 references, figures.