Composite Sampling for Detection of Coliform Bacteria in Water Supply

摘要

Low densities of coliform bacteria introduced into distribution systems may survive in protected habitats. These organisms may interfere with and cause confusion in the use of the coliforms as indicators of sewage contamination of drinking water. Methods of increasing the probability of coliform detection include examination of (1) larger volume samples, (2) a larger number of samples, and (3) composite samples. The first two methods can be achieved by increasing the amount of sampling and will increase the probability of detecting coliform bacteria. Project objectives were to mathematically model the detection of very low densities of coliform bacteria, develop and test equipment for composite sampling of potable water, verify the mathematical models in laboratory and field studies, and determine if composite sampling increases the actual probability of finding coliforms. Field sampling was conducted in two water distribution systems, West Chester and Downington, PA, to test the use of the composite sampler.