The effects of pH and Fluoride on the soluble fraction of aluminium in water coagulated with alum.

Abstract
Various waters were coagulated with alum to remove color. For alum dosages of .apprx. 20-90 mg l-1 (as Al2(SO4)3 .cntdot. 14 H2O) and an operating pH of 5.5-7.5, colloidal and particulate aluminum hydroxide exist. The soluble fraction of Al as determined by 0.1 .mu.m membrane filtration follows a simple function of pH and the presence of fluoride at the l mg l-1 level was shown to significantly increase the total soluble fraction of aluminum when pH < 7. [The toxic effects of Al are discussed.].