Abstract:

In order to obtain a better insight into the metabolic behavior of denitrifying phosphorus-removing bacteria, the effects of various types of electron acceptors on the denitrifying anoxic phosphorus uptake were investigated.Then , batch experimental tests were carried out using the activated sludge cultivated in a sequencing batch reactor ( SRA) in anaerobic/ aerobic condition. The results indicate that (1) anoxic phosphorus uptake occurs when there exists an electron acceptor , be it nitrate or nitrite; (2) as compared with nitrate , nitrite results in a relatively small amount of anoxic phosphorus uptake; (3) the initial mass concentration of the electron acceptor has great effect on the reaction; (4) the amount and rate of phosphorus uptake reach their maximum values when the mass concentrations of NO₃^- -N and NO₂^- -N are respectively 30 and 20 mg/L; (5) with the increase in the initial mass concentration of electron acceptor below or more than the optimal value , the amount and rate of anoxic phosphorus uptake increase or decrease accordingly; (6) the nitrite with a content of 80 mg/L has no inhibition to the phosphorus removal process; and (7) the denitrifying phosphorus-removing bacteria may rapidly lose their ability of phosphorus release and uptake in continuous anaerobic/ anoxic condition.

Key words: denitrifying phosphorus removal, electron acceptor, sequencing batch reactor, denitrifying phosphorus-removing bacterium, biological phosphorus removal