AWWA WQTC58859

The wide variety of possible threat agents or contaminants that could be introduced to the nation's drinking water supplies preclude testing for every possible agent. This forces us to rely on screening methods capable of detecting a diversity of analytes in a single test. Toxicity assays are one possibility. What is needed is a low cost easy to use system that can be widely deployed The Hach ToxTrak£ method makes use of resazurin reduction to measure respiration, a critical pathway for cell viability. Resazurin is a redox-active dye which, when reduced, changes color from blue to pink. Substances that are toxic to bacteria can inhibit their metabolism and thus inhibit the rate of resazurin reduction. This inhibition of resazurin reduction is taken as an indication of toxicity in the test. The method makes use of an accelerant (gluteraldehyde: U.S. patent 5,413,916) in the method to reduce the reaction time thus preventing oxygen interference and also, allowing the use of a lower level of inoculum to reduce the dye. The use of gluteraldehyde allows measurement on a low cost instrument such as a spectrophotometer or colorimeter. Even lower cost visual measurement with a color wheel has also been shown to work. Any type of bacterial culture may be used. This method has been evaluated and found to be effective in detecting contamination by a wide variety of threat agents in drinking water including heavy metals, herbicides, pesticides, rodenticides, radionuclides, industrial chemicals including cyanide, commercial products, biotoxins and chemical warfare agent surrogates. The method was found to be effective in detecting almost all compounds tested at levels of interest to human health. This system represents a cost effective and wide scope sentinel method for use by drinking water utilities. The low cost, wide range of effectiveness and ease of use entailed in this system make it ideal for the development of citizen based water monitoring groups that could be used as an early warning system in the event of a contamination incident. The method could also find use by first responders and in forensic investigations in tracing contaminant plumes or verifying system incursions. Includes 7 references, tables, figure.