Page 179 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

WATER TREATMENT AND PURIFICATION

WATER TREATMENT AND PURIFICATION 4.15

FIGURE 4.2 pH of saturation for water.

AGGRESSIVENESS INDEX (AI)

Developed by the EPA, the aggressiveness index is used rarely as a guideline to find the
corrosive tendency of potable water. AI is calculated as follows:
AI = pH + log (alkalinity × hardness) (4.5)
10
Values less than 10 indicate aggressive water, values between 10 and 12 indicate moder-
ately aggressive water, and values more than 12 indicate nonaggressive water.

TABLE 4.6 Prediction of Water Tendencies by the
Ryznar Index
Ryznar index Tendency of water
4.0–5.0 Heavy scale
5.0–6.0 Light scale
6.0–7.0 Little scale or corrosion
7.0–7.5 Significant corrosion
7.5–9.0 Heavy corrosion
9.0 and higher Intolerable corrosion

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