Guidelines for Canadian Drinking Water Quality: Guideline Technical Document - Enteric Viruses - Figure 2

Treatment requirements to meet an acceptable level of risk of 10-6 DALY per person per year based on 1 L consumption

The level of treatment required to meet an acceptable level of risk based on 1 L consumption for enteric virus concentrations ranging from 0.0001 viruses per 100 litres to 10000 viruses per 100 litres in raw water is presented graphically. The x-axis of the graph is the raw water concentrations of enteric viruses per 100 litres using a log scale. The y-axis of the graph is the log removal using a linear scale. The relationship between the values on the x-axis and the values on the y-axis for the risk level of 10-6 DALY per person per year creates a diagonal line. Two examples of treatment requirements are illustrated on the graph using dotted lines. The first example draws a horizontal dotted line from the y-axis at approximately 4 log removal. This dotted line intersects the diagonal line at approximately 1 enteric virus per 100 litres of raw water. The second example draws a horizontal dotted line from the y-axis at approximately 7 log removal. This dotted line intersects the diagonal line at approximately 1000 enteric viruses per 100 litres of raw water.

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