Research on the feasibility of denitrifying phosphorus removing process by using nitrite as electron acceptor

This paper is to present the results of our study on the feasibility of denitrifying phosphorus removing process by using nitrite as electron receptor.For our research purpose,we have adopted the acclimation and enrichment method for denitrifying phosphorus accumulating bacteria(DPB) and the sediment pond sludge as inoculum.As is known,denitrifying phosphorus accumulating bacteria is a kind of traditional phosphorus accumulating bacteria.In order to investigate the feasibility of such bacteria,we have taken nitrite as electron receptor and used mensurate COD,NO-2-N and TP.In our paper,we have investigated the efficiency of nitrogen,phosphorus and COD removing in the steady operational conditions,and,then,discussed the influence of pH and NO-2-N concentration on the denitrifying phosphorus removal.The results of our investigations show that,after 126 cycles of anaerobic/aerobic and anaerobic/precipitation drainage/anoxic stage,it was possible to push the removing rates of nitrite,phosphate,and COD up to 91.78%,92.3%,94.7%,respectively.And,then,it was possible to domesticate the denitrifying phosphorus-removing bacteria successfully.When the system functions steadily during the anaerobic/anoxic stage,the concentration of COD and TP of the effluent tends to be 23.7 mg/L and 1.2 mg/L,whereas the removing rate of NO-2-N can be made to reach 94.2%,which implies up to theⅠ-B criteria stipulated in the Discharge Standard of Pollutants for Municipal Sewage Treatment Plants.In addition,we have verified the feasibility of denitrifying phosphorus removal by using nitrite as electron acceptor.Though we know that nitrite is a kind of electron receiver,too much nitrite is likely to lead to toxicity to denitrifying phosphorus accumulating bacteria.On the condition that the optimal nitrite concentration is 25 mg/L,phosphorus removing rate can be made as high as possible till up to 89.71%.And,beyond 25 mg/L,the phosphorus removing rate would begin to decline.The highest anaerobic phosphorus release volume proves to be up to 31.28 mg/L,when the value of pH is 7.5.Thus,it can be seen that the results of this study can serve as a reference to the practical application of denitrifying phosphorus accumulating bacteria with nitrite as electronic receptor.