Iron (Fe) Fraction Analysis

1. Total Fe: Analyze raw or finished water sample using Ferrover #8008 for total Iron.

2. Soluble Fe: Analyze raw or finished water sample using the 1,10 Phenanthroline Method #8146 to determine soluble iron. Soluble unbound (ferrous) iron can be sequestered with polyphosphate to prevent water discoloration, or to minimize iron color when corrosion occurs in the system. Sequestering iron at the water supply or in the system reduces chlorine demand and improves disinfection efficiency in the system, so as to control microbial regrowth and corrosion byproducts.

3. Oxidized Fe: Oxidized iron (ferric or bound) can be calculated by subtracting the soluble ferrous iron from the total iron result, (#1 – #2) = #3 (Oxidized Fe). Ferric iron forms an orange-red color in water and when it precipitates it settles out in the distribution system. If ferric iron is present in water supplies it can be filtered and removed before it passes into the system. Low levels of ferric iron may break through filters into the system during regular flow and it should be flushed regularly from fire hydrants. No flow/stagnant water conditions or corrosion reactions, may allow ferric iron to be reduced back into ferrous iron which directly demands more of the chlorine residual, re-generating rusty water further along in the system. System ‘dead-end’ conditions and unflushed fire hydrants can create oxygen-starved (anaerobic) zones that allow microbial iron to ‘migrate’ back into the flowing oxygen- rich water environment, creating additional dirty water throughout the system. Iron and color can be chemically controlled by maintaining a free polyphosphate residual in the distribution system and by flushing fire hydrants.

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