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The removals of particles and total organic carbon (TOC) or natural organic matter (NOM) by clarification andfiltration processes depend highly on coagulation. Dissolved NOM is coveted into particles bycoagulation either by direct precipitation or by adsorption onto flocs. Favorable coagulationchemistry of dose and pH affects this phase change of NOM, and affects subsequent particleflocculation and separation of the flocs by clarification and by granular media filters.The conventional view of coagulation is that coagulant dosing is controlled largely by theraw water turbidity (Stumm and O'Melia, 1968) or by color for highly colored waters (Black etal, 1963). One can say that these water cases represent certain water supply types; however, mostwater supplies contain both turbidity and NOM. So the questions are, under what circumstancesdoes turbidity control, and under what circumstances does NOM control, coagulant dosing?Edzwald (1993) showed that the raw water specific UV absorbance (SUVA) can be used toanswer these questions. This is explored in detail in this paper, but basically for waters withintermediate to high SUVA the NOM controls, while turbidity controls for low SUVA waters.The objective of this study was to present a framework and confirming data from full-scaleplants showing that water plants can set their alum dosage in response to the raw water UV (254nm) level. Several full-scale plants of Aquarion have operated with this strategy for many years.This paper presents data for a plate settling plant (Easton Water Treatment Plant (WTP)).The oral presentation presents additional data for a dissolved air flotation plant and aconventional settling plant. Includes 6 references, figures.

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Edition: Vol. - No. Published: 11/01/2007 Number of Pages: 6File Size: 1 file , 290 KB