Comparison of Escherichia coli, Total Coliform, and Fecal Coliform Populations as Indicators of Wastewater Treatment Efficiency

Escherichia coli, total coliform, and fecal coliform population data were collected from two wastewater treatment facilities, a subsurface flow artificial wetlands, and a receiving stream. Results are presented from individual wastewater treatment process streams, final effluent, and river sites upstream and downstream of the treatment facilities. The QuantiTray technique with 4-methylumbelliferyl-β-glucuronide-based Colilert media was an effective method for quantifying E. coli and total coliform populations in these waters. Thermotolerant Klebsiella pneumoniae present in the effluent from one treatment facility interfered with recovery of fecal coliforms on m-FC media using the delayed-incubation membrane filtration technique; Klebsiella interference was not observed in the enumeration of E. coli by the QuantiTray technique. Both stream standards and discharge permits can be revised to apply E. coli as the indicator of fecal contamination. The results support development of E. coli-based effluent and stream standards to protect public health.