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THE INFLUENCE OF OXIDANT TYPE ON THE PROPERTIES OF IRON COLLOIDS AND SUSPENSIONS FORMED FROM FERROUS IRON
Citation:
Lytle*, D A. AND V. L. Snoeyink. THE INFLUENCE OF OXIDANT TYPE ON THE PROPERTIES OF IRON COLLOIDS AND SUSPENSIONS FORMED FROM FERROUS IRON. Presented at AWWA WQTC, Seattle, WA, November 10 - 14, 2002.
Impact/Purpose:
To inform the public.
Description:
"Red water" describes the appearance of drinking water that contains suspended particulate iron although the actual suspension color may be light yellow to brown depending on water chemistry and particle properties. Iron can originate from the source water and from distribution system materials. The relatively soluble +II oxidation state is the dominant form of iron in anoxic environments including some groundwaters, the hypolimnion of eutrophic reservoirs, drinking water distribution system dead ends, and beneath thick iron corrosion scales. Upon exposure to oxygen or disinfectant during water treatment and distribution, Fe(II) is oxidized to the insoluble Fe(III) form, which readily precipitates and is responsible for colored water. The oxidtion of Fe(II) is the basis for iron removal treatment of iron-containing groundwaters, and an important step in iron corrosion by-product development and red water formation in drinking water distribution systems. The relationships between redox potential, and aqueous iron chemistry and iron mineralogy are well known1 . No research, however, has considered the effect of oxidant type on the properties of Fe(III) particle suspensions formed following the oxidation of Fe(II). The objective of this research was to study the effect of oxidant (oxygen and free chlorine) on the properties of iron particles and suspensions formed from the oxidate of Fe(II) over a broad pH range. Particle properties including size, electrophoretic mobility, and suspension properties including turbidity and color were studied.