AWWA ACE63026

AWWA ACE63026 Preparing Old Man River for Modern Treatment: Softening and Coagulation of the Mississippi River for a 70MGD Ultrafiltration Plant
Conference Proceeding by American Water Works Association, 06/01/2006

Bankston, Annika; Cooke, Trevor H.; Rezania, Shahin; Pressdee, Jonathan; Hill, Chad

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Minneapolis Water Works (MWW) has been treating Mississippi River water for over100 years. Two water treatment facilities operated by MWW provide water toMinneapolis, Minnesota and adjacent cities. The treatment process has remained thesame since the 1940s and employs lime softening, powdered activated carbon (PAC) andferric-based coagulation and settling prior to filtration. MWW has embarked on aprogram to ultrafiltration membrane filtration at both sites.The raw water characteristics reviewed in this paper include variable temperature,alkalinity and turbidity, although the pH remains fairly consistent. The temperaturevariation of the raw water affects plant operations in many ways including reducedtreatment capacity at lower temperatures and occasional freezing of the lime softeningsolids. Methods have been incorporated by the Minneapolis Water Works to handle theraw water temperature variations, including operating at reduced capacity in the low rawwater conditions and feeding whiting (fine calcium carbonate solids). Includes figures.