ABSTRACT
183A full-scale sewage treatment plant designed for BPR may experience short or long-term shortage of potassium in the influent. In this chapter, using an anaerobic-aerobic SBR system, inoculation sludge from laboratory, pilot and full-scale P-removal plants was exposed to different potassium-phosphorus ratios in the influent. By simulating the conditions which may occur in practice, it was shown that potassium is an essential factor in BPR processes. When the system was exposed to severe shortage of potassium in the influent (a) phosphorus removal was nil, (b) poly-P concentration in the biomass decreased exponentially due to sludge wasting, and (c) the anaerobic P release and the related acetate uptake were only affected after several days of potassium absence, likely due to insufficient content of poly-P in the biomass to allow full acetate uptake under anaerobic conditions. In contrast, the system achieved complete P removal when potassium was present in excess amounts in the feed (in this case 1.25 and 2.5 g K/g P).
