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Bench, pilot and full-scale testing showed that the addition of phosphate during alumcoagulation reduces soluble (dissolved) aluminum (Al) concentrations in filtered water. Duringpilot testing, a dose of approximately 0.5 milligrams per liter (mg/L) as PO4, orthophosphatedecreased aluminum residuals by 25 percent, a blended phosphate (60 percent poly, 40 percentortho) decreased Al by 31 percent, and polyphosphate decreased Al by 17 percent compared tono phosphate addition. While all three forms of phosphate decreased aluminum residuals, visualobservations made during pilot testing showed that floc particles were smaller and didn't settle aswell when the blended or polyphosphate was added. Turbidity readings on pilot plant filteredwater confirmed that polyphosphate and blended phosphate addition slightly increased filteredwater turbidity levels. Due to the smaller floc particles observed with blended andpolyphosphate, only orthophosphate addition was investigated full-scale. Follow-up full-scaletesting confirmed that orthophosphate addition decreased aluminum residuals without affectingfinished water turbidity levels. Includes reference, tables, figures.

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Edition: Vol. - No. Published: 06/15/2003 Number of Pages: 9File Size: 1 file , 280 KB