AWWA QTC98251

The objectives of this study were to examine the impacts of water quality on the precipitation of calcium carbonate using lime and caustic for pH adjustment. This paper identifies ranges of the most important water quality parameters (pH, temperature, alkalinity, and calcium hardness), where conversion from lime to caustic soda will reduce the potential for calcium carbonate precipitation for finished water pH of 9.0 (without phosphate addition) and 7.5 (with phosphate addition). The AWWA Rothberg, Tamburini and Winsor model, a chemical equilibrium spreadsheet, was used to calculate the calcium carbonate precipitation potential for given water quality parameters. The model is used to evaluate calcium carbonate chemistry due to chemical addition. The water quality variables were: initial (post coagulated but pre-lime or pre-caustic addition) pH; initial alkalinity; initial hardness; temperature; and, desired finished water pH. For any given set of water quality conditions, lime or caustic was added incrementally until the desired finished water pH was reached, and the final calcium carbonate precipitation potential was calculated.

Product Details

Published:

01/01/1998

ISBN(s):

0898679796

Number of Pages:

8

File Size:

1 file , 89 KB