Comparing Spatial and Temporal Diversity of Bacteria in a Chlorinated Drinking Water Distribution System

Abstract

Temporal and spatial drinking water bacterial diversity was evaluated through bulk water sampling from three locations, at varying distances from the treatment plant, in a chlorinated distribution system serving 250,000 people. Most bacteria were identified as alpha-, beta-, and gamma-Proteobacteria based on quantitative polymerase chain reaction assays targeting these bacterial classes as well as bacteria. Temporal variability is correlated with seasonal changes in the chlorine concentration as shown by the positive relationship between the hypochlorite dose and alpha-Proteobacteria. Analysis of variance of alpha-, beta-, and gamma-Proteobacteria and bacteria quantities for all sites and months suggests that temporal patterns are stronger than spatial patterns in this system population. Band patterns from PCR-based denaturing gradient gel electrophoresis using bacterial primers also reveal the importance of temporal variability as samples clustered by months more than by locations. These results demonstrate the consistent presence of alpha-, beta-, and gamma-Proteobacteria at different locations within a particular distribution system and suggest these bacterial classes may be useful indicators of system conditions.