AWWA ACE63144

In most water treatment plants, coagulation involves precipitation, i.e., the formation of newsolids from added chemicals. These plants add iron or aluminum salts in the "sweep floc" regimeto form solid hydroxides, or they employ precipitative softening to form calcium carbonate (and,perhaps, magnesium hydroxide). This precipitation is vital to the removal of dissolvedconstituents (e.g., arsenic and natural organic matter by adsorption) and particles (includingmicroorganisms). Ultimate removal of these constituents relies primarily on the resultant particlesize distribution (PSD) fed to downstream particle removal processes (i.e., sedimentation orflotation and granular media or membrane filtration). The current understanding of howprecipitation changes the PSD is only qualitative. The goal of this work is to create andexperimentally verify a mathematical model capable of quantitatively predicting how PSDschange due to simultaneous precipitation and flocculation. Experiments are being performedwith calcium carbonate to emulate softening and aluminum hydroxide to emulate alum sweepfloccoagulation. Includes 13 references, figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2006

Number of Pages:

9

File Size:

1 file , 460 KB