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Calcium Phosphate Precipitation at Slightly Alkaline pH Values

John F. Ferguson, David Jenkins and John Eastman
Journal (Water Pollution Control Federation)
Vol. 45, No. 4 (Apr., 1973), pp. 620-631
Stable URL: http://www.jstor.org/stable/25037801
Page Count: 12
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Calcium Phosphate Precipitation at Slightly Alkaline pH Values
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Abstract

A calcium phosphate precipitation process was found which could reduce chemical costs from one-half to one-sixth of the $20 to $50/mil gal ($5.30 to $13.20/1,000 cu m) projected for current methods using alum, lime, or iron salts. This process can be operated simultaneously with the activated sludge process because it is conducted in a reactor of similar dimensions and residence time distribution and at a pH between 7 and 9. The process is applicable and should be considered as a viable alternative in wastewater with alkalinity of less than 350 mg/l as ${\rm CaCO}_{3}$ and magnesium concentrations less than 24 mg/l as Mg. Laboratory scale, continuous-flow studies produced phosphate residuals ranging from 3.3 to 1.2 mg/l, representing removals from 63 to 87 percent of an initial 10 mg/l as P.

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