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Reducing Aluminum Residuals in Finished Water
Author(s) -
Qureshi Naeem,
Malmberg Rickard H.
Publication year - 1985
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.1002/j.1551-8833.1985.tb05627.x
Subject(s) - alum , coagulation , ferric , chloride , lime , aluminium , turbidity , chemistry , water treatment , pulp and paper industry , environmental engineering , environmental science , metallurgy , materials science , inorganic chemistry , geology , engineering , psychology , oceanography , organic chemistry , psychiatry
Pilot‐ and plant‐scale tests were conducted in Minneapolis, Minn., in an attempt to reduce aluminum residuals in the finished water. At high pH, when the predominant mode of alum coagulation is sweep coagulation, increasing the intensity of chemical mixing reduced aluminum residuals only slightly. Reducing the pH with acid was effective in reducing the residuals, but posttreatment pH adjustment with lime to stabilize the water increased its hardness. It appears that the most promising means of reducing aluminum residuals is to replace part of the alum dosage with ferric chloride. At both Minneapolis and St. Paul water treatment plants, ferric chloride, at less than half the dosage of alum, reduced the residuals and resulted in longer filter runs.