TABLE 24.5.

Pathogen Removal during Sewage Treatment

	Enteric viruses	Salmonella	Giardia	Cryptosporidium
Concentration in raw sewage (per liter)	10 5–106	5,000–80,000	9,000–200,000	1–3,960
Primary treatmenta% removal	50–98.3	95.8–99.8	27–64	0.7
Number remaining (per liter)	1,700–500,000	160–3,360	72,000–146,000
Secondary treatmentb% removal	53–99.92	98.65–99.996	45–96.7
Number remaining (per liter)	80–470,000	3–1075	6,480–109,500
Secondary treatmentc% removal	99.983–99.9999998	99.99–99.999999995	98.5–99.99995	2.7d
Number remaining (per liter)	0.007–170	0.000004–7	0.099–2,951

^aPrimary sedimentation and disinfection.

^bPrimary sedimentation, trickling filter or activated sludge, and disinfection.

^cPrimary sedimentation, trickling filter or activated sludge, disinfection, coagulation, filtration, and disinfection.

^dFiltration only.