The phosphate removal by the blast furnace slag was applied to a practical secondary effluent. An automatic calcium ion controller was supplied using the process described in the previous paper(1), and the necessary calcium ion for phosphate removal was supplied by using a calcium feeder column packed with converter slag. The concentration of calcium ion and pH were adjusted at 90 mgl#x2010;1and pH 7#x2013;9 after decarbonation, and the phosphate removal was carried out. The regeneration of the blast furnace slag was investigated by two methods, i.e., back washing using the treated water and standstill by halting the influent.
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