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Two process changes were proposed at the Dalecarlia and McMillan water treatmentplants operated by Washington Aqueduct, a United States Army Corps of Engineersorganization. It was proposed at both plants to switch from alum to polyaluminumchloride (PACl) and from chlorine gas to sodium hypochlorite for coagulation anddisinfection, respectively. However, throughout the proposed process changes, bothplants must maintain a finished water pH of 7.70.1 to meet their optimal corrosioncontrol treatment (OCCT) targets.This paper addresses the analysis conducted to determine the changes that will beneeded at both plants' corrosion control processes to maintain the OCCT target pH of7.70.1. The analysis includes computer modeling work, which was evaluated withbench-scale testing.Projections show that, following the switch to hypochlorite, it was necessary to addacid feed capabilities at McMillan to stay within the target range. While acid was notneeded at Dalecarlia, significantly lower doses of lime was needed. Lime, causticsoda, and acid dose projections were made for each plant. Includes tables, figures.

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Edition: Vol. - No. Published: 11/01/2007 Number of Pages: 9File Size: 1 file , 95 KB