Microbiological evaluation of fecal bacterial composition from surface water through aquifer sand material.

When bacterial pathogens from livestock contaminate drinking water supplies, they can cause different forms of gastroenteritis. The objective of this study was to enumerate the concentrations of fecal indicator (Escherichia coli and enterococci) in surface water in order to determine removal efficiency by sand filtration. The concentrations of different indicator bacterial species were determined after running tertiary treated water through two tanks containing aquifer material. Enterococcus faecalis primers targeting the ddl gene and primers for Enterococcus faecium were used to identify the two species in the samples. A PCR assay based on the partial sequence of the 13-D-glucoronidase gene (uidA) for specific detection and differentiation of E. coli populations was used to confirm the presence of E. coli after a biochemical test. The biochemical test overestimated the percentage of E. faecium in our samples, but the PCR assay with the ddl gene produced 100% specificity with Enterococcus faecalis. The biochemical test was 91.5% specific in identifying E. coli. The composition of indicator bacteria in Santa Ana River was dominated by intestinal microflora of humans and animals; filtration by aquifer sand material may reduce the transport of indicator bacteria from surface water to groundwater.

Characterization of microbial communities and composition in constructed dairy wetland wastewater effluent.

Constructed wetlands have been recognized as a removal treatment option for high concentrations of contaminants in agricultural waste before land application. The goal of this study was to characterize microbial composition in two constructed wetlands designed to remove contaminants from dairy washwater. Water samples were collected weekly for 11 months from two wetlands to determine the efficiency of the treatment system in removal of chemical contaminants and total and fecal coliforms. The reduction by the treatment was greatest for biological oxygen demand, suspended solids, chemical oxygen demand, nitrate, and coliforms. There was only moderate removal of total nitrogen and phosphorus. Changes in the total bacterial community and ammonia-oxidizing bacterial composition were examined by using denaturing gradient gel electrophoresis (DGGE) and sequencing of PCR-amplified fragments of the gene carrying the alpha subunit of the ammonia monooxygenase gene (amoA) recovered from soil samples and DGGE bands. DGGE analysis of wetlands and manure samples revealed that the total bacterial community composition was dominated by bacteria from phylogenetic clusters related to Bacillus, Clostridium, Mycoplasma, Eubacterium, and Proteobacteria originally retrieved from the gastrointestinal tracts of mammals. The population of ammonia-oxidizing bacteria showed a higher percentage of Nitrosospira-like sequences from the wetland samples, while a higher percentage of Nitrosomonas-like sequences from manure, feces, raw washwater, and facultative pond was found. These results show that the wetland system is a natural process dependent upon the development of healthy microbial communities for optimal wastewater treatment.