Commensal fecal bacteria: Population biology, diversity, and usefulness as indicator organsims in reclaimed water.

摘要

Water treatment facilities have been relying on indicator bacteria to assess the quality of water for decades. The purpose of this group of studies is to investigate the predictive capabilities of conventional and alternative indicators for pathogenic microorganisms in disinfection processes and treated wastewater effluents. In addition, the possibility that diversity of indicator bacteria, as well as overall bacterial diversity, correlate with fecal contamination in water bodies has been investigated. Indicator organisms (total coliforms, fecal coliforms, enterococci, C. perfringens, and coliphages) as well as pathogens (enteroviruses, Giardia, and Cryptosporidium) were enumerated from six wastewater treatment facilities at various stages of treatment. Statistical analyses were conducted to determine if the indicator organisms (individually or as a set) could predict the presence or absence of pathogens. Single indicator organism analysis failed to correlate with the occurrence pathogens, thus monitoring a suite of indicator organisms may be a better measure to predict the presence of pathogens. The product of chlorine residual concentration and contact time (CT) was identified as a factor for determining the log 10 reduction of enteric viruses in wastewater treatment facilities that used chloramines for disinfection.; Samples were also collected from river waters and sediments in watersheds with different human population densities to identify the impact of anthropogenic activities on bacterial diversity. 16S rRNA restriction fragment length polymorphism (RFLP), ribotyping, and denaturing gradient gel electrophoresis (DGGE) were used to determine total coliform, Escherichia coli, and bacterial community population structures, respectively. The concentrations of indicator organisms were significantly different among the river sites in sediments, but not in water column. The population diversity measurements were not significantly different among the river sites; while the indicator population and bacterial community structures were dissimilar in water column vs. associated sediment samples. Accumulation curves demonstrated that greater than 20 isolates must be sampled at most of the sites to represent the dominant populations. A better understanding of the relationship between the indicator organisms and pathogens as well as knowledge of the ecology of indicator organisms in pristine and anthropogenically impacted waters may contribute to water quality restoration and public health protection.