Bench, pilot and full-scale testing showed that the addition of phosphate during alum
coagulation reduces soluble (dissolved) aluminum (Al) concentrations in filtered water. During
pilot testing, a dose of approximately 0.5 milligrams per liter (mg/L) as PO4, orthophosphate
decreased aluminum residuals by 25 percent, a blended phosphate (60 percent poly, 40 percent
ortho) decreased Al by 31 percent, and polyphosphate decreased Al by 17 percent compared to
no phosphate addition. While all three forms of phosphate decreased aluminum residuals, visual
observations made during pilot testing showed that floc particles were smaller and didn't settle as
well when the blended or polyphosphate was added. Turbidity readings on pilot plant filtered
water confirmed that polyphosphate and blended phosphate addition slightly increased filtered
water turbidity levels. Due to the smaller floc particles observed with blended and
polyphosphate, only orthophosphate addition was investigated full-scale. Follow-up full-scale
testing confirmed that orthophosphate addition decreased aluminum residuals without affecting
finished water turbidity levels. Includes reference, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 280 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 9 |
| Published : | 06/15/2003 |
