INDUCTION METHOD OF EXCESS PHOSPHATE ACCUMULATION FOR PHOSPHATE REMOVING BACTERIA ISOLATED FROM ANAEROBIC AEROBIC ACTIVATED-SLUDGE/

Many bacteria considered to be phosphate removing bacteria (PRE) have previously been isolated from phosphate removing activated sludge (PRA S). However, these bacteria have never exhibited the typical function of PRE which take up excessive phosphate (P) in aerobic conditions and release P with a concomitant uptake of organic substrates in anaerobi c conditions. We hypothesized that the enzyme system responsible for e xcess P accumulation (EPA) should be inducible, because PRE can take u p organic substrates anaerobically in spite of being obligate aerobes. Therefore, PRE cells grown aerobically have to be additionally treate d with alternating anaerobic incubation with organic substrates and ae robic incubation without organic substrates to exhibit the above typic al function. We succeeded in the first isolation of a strain of true P RE by this induction method. The isolate is a Gram-positive coccus and its generation time is approximately 12 hours. The anaerobic/aerobic incubation cycle was required at least two times (2 days) to induce th e ability of EPA for PRE. The velocity of P removal in the aerobic pha se was decreased to approximately half by the existence of organic sub strates. Therefore, it is recommended that organic compounds be remove d during the anaerobic phase in PRAS systems.