MIOX RIO Series Operators Manual
P/N: 102-00076-G Page 73
Oxidant Demand Determination
After 90 minutes, determine which sample has the FAC residual nearest to the desired
residual specified by the water system operator. If a desired residual is unknown, look for a
FAC slightly greater than 0.2 ppm, which is usually the standard required by the state.
Subtract the selected FAC reading from the initial FAC dose for the corresponding sample.
This signifies how much of the oxidants were consumed by the water and thus how much of
an oxidant demand there is in the sample water.
Example:
Determine the oxidant demand of the water. In this case, let’s assume the operator wants a
1.0 FAC residual in the water system. Looking at the bottom row (t + 90 minutes) of the
chart filled out above, note that Sample B at 1.8 ppm is closest to the desired residual. The
initial FAC dose in this case was 3 ppm, so the oxidant demand of this water is 1.2 ppm (3.0
- 1.8 = 1.2). (This means that the operator must dose at 2.2 ppm (1.2 + 1.0 = 2.2) to
achieve his desired residual of 1.0 ppm.
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