TABLE 8. 1 SwTR Assumed log removals and turbidity requirements Log removals Filtration process giardia Virus Turbidity requirement Conventional 2.5 2.0 =or <0.5 ntu in 95% of samples each month and never >5 ntu Direct 2.0 or<0.5 ntu in 95% of samples each month and never >5 ntu Slow sand 2.0 =or< l ntu in 95% of samples each month "s and never>. n Diatomaceous earth 2.0 1.0 =or< 1 ntu in 95% of samples each month and never >5 ntu s From Table IV-2 in Supplementary Information, p. 27511 sw Special provision was made for slow sand filters to exceed 1 ntu in some cases, providing effective dis infection was maintained Filtration processes that do not function on the principles of the processes defined in the SWTR are called alternative filtration processes, and the log removal for Giardia cysts or ruses that can be allowed for alternative processes must be determined for each alternative processFiltration processes that do not function on the principles of the processes defined in the SWTR are called alternative filtration processes, and the log removal for Giardia cysts or viruses that can be allowed for alternative processes must be determined for each alternative process