Log Reduction

Water Security Corporation's purification technology can provide extremely large reductions of viruses and bacteria to produce healthful drinking water. The design of the water purifier using WSC's technology determines the amount of pathogen reduction achieved. The US EPA suggests a reduction by 6 Log of bacteria, 4 Log of viruses, and 3 Log of cysts should be achieved for water purifiers to deliver healthful drinking water. Typically cysts are most cost-effectively removed with standard, off-the-shelf Cyst Rated Absolute filters. The specifications for the Log reduction level of pathogens for healthful drinking water may vary in accordance with different organization’s perspectives; however, WSC’s technology effectively scales and can meet a wide range of requirements. The following may help to place into perspective the meaning of the numeric value of Log reduction.

1 log reduction = 90% eradication of pathogens
2 log reduction = 99% eradication of pathogens
6 log reduction = 99.9999 eradication of pathogens

Occurrence of Pathogens in Natural Water:

	Lakes and Rivers	Impacted Rivers
E Coli	10,000-1,000,000/liter	30,000-1,000,000/liter
Viruses	1-10 PFU/liter	30-60 PFU/liter

Guidelines for Drinking-water Quality, First Addendum, Vol. 1, Recommendations.-3rd ed., Chapter 7, WHO 2006

Infectivity

–Healthy Adult Consuming 1 liter of water per day

E Coli – 1-100 organisms (CFU's, colony forming unit)
Virus – 0.01-1.0 particles (PFU's, plaque forming unit)

Bacteria concentration required to be less than 1cfu/l

–10⁶ to 1, reduction by 1,000,000 or 6 Log

Virus concentration required to be less than 0.01pfu/l

–60 to 0.01, reduction by 6,000 or 3.77 Log