AWWA ACE68863

This powerpoint presentation begins by providing a brief historical overview of the study, including the following:"classical" equilibrium model for carbonate +orthophosphate system suggests best resultsbetween about pH 7.2 and 7.8 based on solubilitypredictions;reports of difficulties achieving LCR Action Levelwith DS pH > 8; and, wide variation in tabulated and published equilibriumconstants for key lead solids and aqueous complexes,which can affect predictions and treatment choices. The experimental setup of test systems is presented, along with pipe preparation, chemical analyses performed, data analysis approach, and integration with scale mineralogy. Presentation conclusions indicate the following: confirmed prior prediction of best lead solubility reduction byorthophosphate between pH 7 and 8;confirmed problem with orthophosphate performance at pHin low- to mid-8's;mechanism is not clear but near several phase boundaries;not simple charge, colloid stability or particle size issue; and,Saturation Index approach promising, but more complicatedthan expected because ofdisequilibrium, even after 1 year,important role of metastable phases (like Cu(II)),multiple phases simultaneously present, andsome unidentified solid phases present.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

41

File Size:

1 file , 1.5 MB