Enrichment Of Denitrifying Phosphate Accumulating Organisms In Sequencing Batch Membrane Bioreactors

It is significant to control the emission concentration of nitrogen and phosphorus to prevent eutrophication in close water systems, and the design of municipal wastewater treatment processes must take nitrogen and phosphorus removal into account. A mass of energe, region and poor water quality are disadvantages of nitrogen and phosphorus removal in conventional biological nitrogen and phosphorus removal processes. Denitrifying dephosphatation process utilizes a special kind of bacteria named Denitrifying Phosphate Accumulating Organisms (DPAO) which have the characteristics of utilizing nitrate as electron acceptor to realize simultaneous nitrogen and phosphorus removal in anoxic condition. In this way, the competition between PAO and denitrifiy heterotrophs organisms is avoided and the amount of energe consuming, surplus sludge and exhaust of CO₂ is reduced largely. Denitrifying dephosphatation is the advanced biological phosphorus removal mechanism which accord with the conception of continuable development.The enrichment of DPAO was investigated in a laboratory-scale Sequencing Batch Membrane Bioreactors (SBMBR). The alternant anaerobic(anoxic)/aerobic condition was necessary both nitrogen removal and phosphorus removal. SBR mode not noly afforded the growing condition for PAO but also settled for the nitrogen removal, moreover it was able to alleviate membrane fouling. As a result it was possible to realize organic pollutants, nitrogen and phosphorus removal simultaneously in a single reactor. On the other hand, membrane filtration replaced two setting tank to go along abruption of solid and liquid, which not only operation was simple also effluent was safety. Furthermore, SBMBR is able to intercept microorganism in the sludge to improve their activity and ensure the good effluent effect.The paper included three parts as follows:1.Studied and compared the kinds and amount of PAO and the performance of nitrogen and phosphorus removal in SBMBR, which operated in anaerobic/aerobic and anaerobic/anoxic/aerobic mode, in order to offer the base of the experiment for next DPAO enrichment. The result indicated that the sludge which included PAO took up 44.5% and 35.9% in AO MBR and A²O MBR when the system operated steadily. The value of DPAO/PAO was only 7.5% in AO MBR, the value of DPAO/PAO increased from 17.8% to 48.8%. Average total phosphor removal efficiency were 83.7% and 80.3%. Nitrate was added in anoxic phase which could effectively enrich and induce DPAO in A²O MBR, but the cumulation of nitrate restrained the growing of PAO. Therefore, it is key to improve the...