Study On Operation Performance And Nitrogen Removal Pattern In Hybrid Oxidation Ditch

Since the issued and written of Water pollution control action plan and Five Development Concept in 2015, low-Carbon, environmental protection and green sustainable development have already become essential questions in our economic development. As is well-known, water eutrophication, caused by excessive emission of nitrogen and phosphorus, is a global water environmental problem urgently to be solved all the time. Of which, accumulation of nitrogen in the global cycle will be harmful to atmosphere, waterbody even our human health. With the development of social economy, our domestic wastewater treatment industry has taken shape and various wastewater treatment processes have a certain scale. Considering the high energy consumption of wastewater treatment industry, it still has a very important practical significance to research on the fields of reasonable energy configuration, optimization technological parameters, alternation new and old technologies and so on.As a traditional active sludge technology, the Oxidation Ditch?OD? has its own characteristics and advantages. In this paper, a hybrid OD which is based on the theory of Integrated Fixed-film Activated Sludge?IFAS? was used to investigate the processing property and operation performance under different control factors, and to analyze the mechanism of contaminants degradation and Simultaneous Nitrification and Denitrification?SND?, which was aimed at offering theoretical reference to correlative processes. Following which, a batch assay was carried to explore the biological denitrification mechanism and offer a different thinking direction to innovation and practice about new biological denitrification technology.The hybrid OD of independent research development was Successfully started after about 30 th day starting tests. Then aeration rate?G?, return ratio?R? and hydraulic loading?Q? were controded as factors to investigate its influence on reactor running performance. Finally, aeration rate?G?, return ratio?R? and hydraulic loading?Q? were controded at 0.4m3/h?100% and 0.55m3/m3·h respectivly as the optimized parameter values. The hybrid OD obtain a relatively well operation effect when the aeration rate?G? was 0.4 m3/h, bottom aeration was 50L/min, rotate speed was 100 r/min, and its concentration effluent of CODcr and NH₄⁺-N were 35.8mg/L, 1.04mg/L, the averageThe degradation alongway and removal pathways of N element was analyzed optimally during the hybrid OD which was used to treat domestic wastewater. It was necessary maintainning suitable C/N ratio,which was 2.12 to 5.56 in these tests, to ensure nitrification and denitrification carried out completely during the process of biological nitrogen removal. The removal pathways of N element included assimilation, traditional nitrification and denitrification, effluent liquor, SND and so on in this experiment. The optimal SND% was achieved with a percent of 42.7% by controlling critical DO value optimally. And the TN removal rate was 71.7% at that point.A 2k factorial experimental design was used whereby to explore and analyze the SND phenomenon and denitrification mechanism in the two-phase mixed liquids zone. And also statistical analysis methods were used to discuss the results of factorial experimental about heterotrophic nitrification /aerobic denitrification and autotrophic denitrification. The results indicated that novel microorganisms made a very limited contribution, which could be neglected, to the N loss during the SND process. The endogenous respiration and endogenous denitrification caused by traditional bacteria decay were applied to explain the statistical significance?P<0.05? of volumetric NH₄⁺-N and TIN reaction rates in the batch assays. The analysis and elucidation about substance transformation mechanism in the process of nitrogen removal could be extended by stoichiometry and cell decay kinetics. Meanwhile, the correctness of analysis results could be verified.In conclusion, with the research and discussion through all pilot-scale tests and batch factorial assays, we could use a macroscopic or microscopic physics phenomenon to explain the SND process in the hybrid OD. How to realize partial SND and partial endogenous denitrification, and then achieve its attractive advantages in improving denitrification efficiency and reducing sludge yield,which offering thinking deeply on innovation and practice in the field of wastewater treatment new technologies.