The use of simultaneous chemical precipitation in modified activated sludge systems exhibiting biological excess phosphate removal Part 3: Experimental periods using alum

Abstract

An investigation was conducted into the effect of simultaneous alum dosing on biological phosphorus (P) removal in an activated sludge system at pilot scale. Two continuous flow (36 l/d) activated sludge pilot plants were used to develop “semi-enhanced” biological excess phosphorus removal (BEPR) organism cultures of activated sludge by means of acetate supplementation of the feed. BEPR was strongly exhibited in these systems. One was used as a test system (to which alum was dosed), while the other served as control (no chemical addition). Additional removal due to chemical precipitation was measured as the difference in system P removal between the two systems. The extent of Prelease in the anaerobic reactors of the two systems was compared by mass balance, as one indicator of the “magnitude” of BEPR in the test system. Phosphorus fractionation of the mixed liquor suspended solids also served as an indicator of the respective biological and chemical mechanisms.

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