The objectives of this project were to evaluate the recoverability of coliforms from waters which have: (1) High populations of non-coliform organisms, and (2) high levels of turbidity due to natural mineral turbidity, hydrated oxides and organic debris. After initial isolation and identification of coliforms and non-coliforms from raw and distribution water interactions between these two groups of organisms were studied. The outcome of the interaction was found to be dependent upon numerous factors. These included: the specific non-coliform, the number of each type of organism, the nutrient environment in which the interaction occurred, the physiological status of the interacting organisms and the type of media used to recover the coliforms. Turbidity augmentation and reduction experiments were done to distinguish non-bacterial turbidity inhibition of coliforms from the inhibition caused by other bacteria. The more serious inhibition to coliform detection seemed to be caused by the large populations of non-coliforms which exceeded the resident coliforms in water mains by factors of 100 to 100,000. Turbidity per se was not an impediment to coliform growth, but it did make it more difficult to recognize coliforms on membrane filters. These results will be of interest to individuals concerned with water quality and interpretation of microbiological data.

Includes bibliographical references (pages 64-65). Prepared for U.S. Environmental Protection Agency, Office of Research and Development, Municipal Environmental Research Laboratory, Cincinnati, Ohio, submitted by the University of Delaware and Wilmington Water Department, Willmington, Delaware, under grant no. Contract Number: R805102.