The characteristics of Microlunatus phosphovorus and Tetrasphaera elongata, which were reported to be polyphosphate accumulating bacteria, were investigated with respect to phosphate uptake rate, effect of organic substance, substrate utilization, denitrifying ability and mixture effect with activated sludge. Phosphorus removal experiments were performed in 3 cycles of anaerobic/aerobic phases, alternating anaerobic incubation followed by aerobic incubation. The specific phosphorus removal rate of M. phosphovorus reached 1.4〜12.2 (mgP/g cell/hr) and that of T. elongata was 0.96〜3.89 (mgP/g cell/hr). M. phosphovorus could not exercise phosphate accumulating activity in the absence of organic substance in the anaerobic phase. On the contrary, T. elongata could remove phosphate without organic substance. The addition of glucose, casamino acids, glutamate in the anaerobic phase led to phosphate removal, but the addition of acetate and leucine had little effect in phosphate removal. Each of two microorganisms didn't show phosphate accumulating ability in the anoxic phase containing nitrate. When two microorganisms were mixed with activated sludge, M. phosphovorus and T. elongata could accumulate phosphate in activated sludge. Especially, M. phosphovorus exhibited an excellent phosphate removal activity. Mixing M. phosphovorus into activated sludge in biological phosphate treatment processes may improve phosphate removal ability.
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