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Water: Drinking Water Standards

Table 1: Microbial Monitoring under GWDR: possible indicators

Organism Density in raw sewage Occurrence in human stools Survival in environment Lab Availability Association with fresh fecal contamination
Bacterial indicators

total coliforms >109/L 100% Weeks to years Excellent Indirect
E. coli 109/L 100% Weeks to months Excellent Good
Enterococci 107/L 100% Weeks to months Excellent Good

perfringens spores

106/L 100% Months to years Potential good Fair
Viral indicators

Somatic coliphage1 106/L 50% Weeks to months Potential good Good?
Male-specific coliphage1 106/L <5% Weeks Potential good Good
Viral pathogens


by PCR2

50-250+ PFU/L in U.S. --- Weeks to months Potential fair Good

1Coliphage are viruses that infect the bacterium, E. coli.

2Enteroviruses include polioviruses, coxsackieviruses, and echoviruses. PCR (polymerase chain reaction) is a process to multiply the number of a specific DNA or RNA strands, allowing easier detection by a variety of methods. PCR must be combined with other processes, such as sample filtration, filter elution, sample purification, perhaps tissue cultures, and assay procedures (e.g., genetic probes).

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