Study On The Impact Of DO Concentration On The Denitrification Effect Of Completely Autotrophic Nitrogen Removal Granular Sludge

As a low energy consumed, sustainable and novel denitrification process, completely autotrophic nitrogen over nitrite process exhibits wide application prospect in nitrigon removal area of wastewater. Nowadays, the eutrophication situation of water has become more and more severely. In this study, based on the successful cultivation of completely autotrophic nitrogen removal granule sludge, the influcence of dissolve oxygen(DO) concentration on the denitrification effect of the sludge was investigated, which was used to obtain new research progess in some aspects, for example the connection between the succession of microbial community and its nitrogen removal efficiency, so it could provide theoretical basis and technical support for the high efficiency, stabilization treatment of nitrogen-containing wastewater.Under the condition of micro-aerobic aeration, by taking DO as the single variable, this paper took the strategy of raising the level of DO step-by-step to investigate the trans-formation on denitrification efficiency along with the autotrophic nitrogen removal efficiency of the completely autotrophic nitrogen removal granule sludge. The comparision and analysis on the influence of DO concentration towards the sludge were performed and the optimum range of DO was explored to maintain the stable denitrification effect. Furthermore, the microorganism change of the sludge was observed by molecular biological method and the distribution regulation of ammonia oxidizing bacteria(AOB) and anaerobic ammonium oxidation(ANAMMOX) bacteria inside the sludge was presented in mircoscale.The result indicated that, under the condition of micro-aerobic aeration, the symbiotic system consisted by AOB, ANAMMOX inside the sludge was established in appropriate range of hydraulic retention time(HRT), DO and p H. The completely autotrophic nitrogen removal granule sludge was successfully cultivated in 58 days. The results also found that the DO concentration shows significant impact on the denitrification effect and completely autotrophic nitrogen removal effect of the sludge. The optimum concentration range of DO for the autotrophic nitrogen process of the sludge was found to be 0.1-0.2 mg/L. In this stage, the average removal rate of NH4+-N and total nitrogen(TN) reached 90.6% and 72.3%, respectively; the average nitrogen loading removal rate reach to 1.216 kg?N/(m3?d). The average chemometrics relationship in denitrification process was 0.85, 0.12 which is nearly identical to the theoretical relationship of autotrophic nitrogen removal process 0.86, 0.11. In addition, the variation of DO concentration was found to alter the composition and distribution of the surface morphology and the interior microorganism community of the sludge. SEM result showed that the particle size were all between 0.9~1.0 mm with smooth, neat and regular shape. The interior microorganism composition was distributed compactly which was aggregated by globular, rhabditiform and heliciform flora; The FISH result alos proves that the microorganism inside the sludge was composed by two kinds of flora in which AOB was distributed intensively in the exterior area of the granule, ANAMMOX in the interior area of the granule and NOB in the exterior area of the granule.