Effect of nitrite on strengthening the biophosphorus removal system

This paper takes it as its focus to investigate the effects of nitrite on the metabolic behavior of Phosphorus Accumulating Organisms( PAOs) under the anaerobic,aerobic and anoxic conditions,respectively. For the said purpose,we have laid out a series of batch tests to study the changes that take place in the anaerobic phosphorus release and aerobic phosphorus adsorption when adding nitrite at the beginning of anaerobic time and aerobic time, respectively. And, then, the anaerobic / anoxic / aerobic SBR has been used to cultivate the Denitrifying Phosphors Removal Organisms( DNPAOs) with nitrite as a kind of electron acceptor. Furthermore,we have analyzed the relation between the removal amount of phosphorus and the nitrite uptake in the anoxic time and that between the amount of phosphorus removal and PHB uptake in the anoxic time. The experiment results have shown that the anaerobic phosphorus release tends to speed up with the addition of nitrite volume,whereas the net uptake of phosphorus tends to occur with the depletion of carbon source in the anaerobic process. However,nitrite is likely to inhibit its phosphorus uptake rate and denitrifying rate when the concentration of nitrite nitrogen comes over 10 mg / L. What is more,nitrite tends to restrain the aerobic uptake rate when it is added at the beginning of the aerobic time. Moreover, when its nitrogen concentration keeps at a level of less than 10 mg / L,the aerobic phosphorus uptake rate may well tend to drop quickly,though the inhibition of nitrite on phosphorus uptake may not be as strong as it was before when the concentration of the nitrite nitrogen was over 10 mg / L.Furthermore,it has also been found that the DNPAOs has been enriched in the anaerobic / anoxic / aerobic SBR in the process of63 days. To be more accurate,when the concentration of PO3-4-P in the effluent is reduced to less than 1 mg / L,the removal proponent of the anoxic phosphorus tends to reach 36 mg / L,that is,by82. 36% in the total phosphorus removal. All in all,the two linear relations can be found in the whole reaction process: one is taking place between the anoxic phosphorus uptake and the nitrite consumption,the other—between the anoxic phosphorus uptake and the PHB consumption.