THE DYNAMIC EFFECTS OF POTASSIUM LIMITATION ON BIOLOGICAL PHOSPHORUS REMOVAL

A full-scale sewage treatment plant designed for biological phosphorus removal may experience short- or long-term shortage in potassium of t he influent. In this study, using an anaerobic-aerobic sequenced batch reactor system, inoculation sludge from laboratory-, pilot- and full- scale phosphorus removal plants was exposed to different potassium-pho sphorus ratios in the influent. By simulating the conditions which may occur in practice, it was shown that potassium is an essential factor in biological phosphorus removal processes. When the system was expos ed to severe shortage of potassium in the influent: (a) phosphorus rem oval was absent, (b) polyphosphate concentration in the biomass decrea sed exponentially due to sludge wasting and (c) the anaerobic phosphor us release and the related acetate uptake was only affected after seve ral days of potassium absence, likely due to insufficient content of p olyphosphate in the biomass to allow full acetate uptake under anaerob ic conditions. In contrast, the system achieved complete phosphorus re moval when potassium was present in excess amounts. Copyright (C) 1996 Elsevier Science Ltd