AWWA WQTC52888

Bacillus is a genus of aerobic, gram-positive, spore-forming bacteriathat are ubiquitous in nature and are common in soil, water, and airborne dust. These microorganisms have the ability to exist either as metabolically active vegetative cells (favorable conditions) or as highly resistant metabolically inactive cell types (unfavorable conditions) called spores. Due to their ubiquitous nature and the resistance of the spores to chlorine, Bacillus can often be isolated from drinking water. Most species of Bacillus are harmless and pose no public health threat, however, it has been suggested that aerobic spore-forming bacteria may be used as a microbial surrogate for evaluating drinking water treatment plant performance. There is presently no standard method for the enumeration of Bacillus in water samples. The objectives of this study were to compare two approaches for the detection of Bacillus in water and to develop a simple, reliable method of detecting Bacillus in finished water. Centrifugation and membrane filtration methods of water sample concentration were evaluated. The centrifugation method was previously used in our laboratory for the evaluation of highly turbid raw water and other environmental samples not amenable to filtration. In contrast, finished water samples can be easily filtered. Includes 2 references, table, figure.