| The removal of nutrients such nitrogen and phosphrous have become a big headeachein in treating urban malodorous rivers. After the effective blockage of exogenous pollution, the endogenous-nitrogen and -phosphorus from sediment will become the main pollution sources of nutrients. As an important technology to treat the malodorous water, the artifical aeration can change the DO level and distribution of hypoxic microzones to control the nitrification-denitrification and the coupling of "anaerobic phosphorus release" and "aerobic phosphorus uptake". Previous studies by Our research group had been done to explore the relatively optimized aeration disturbance intensiy and depths. Based on the above-mentioned studies, this thesis systematically discusses the reponses of endogenous-nutrients behaviors and nitrogen-transforming bacteria to different aeration disturbance modes in black-odorous river sediment. Amongst them, the optimized aeration disturbance mode was determined and the microbial mechanism of nitrogen-transforming with different aeration disturbance modes was discussed. This research is of great significance for providing scientific basis for treating the excessive nitrogen and phosphorus as well as the technical references for the optimization design and operation of aeration engineering. The main results are as follows:(1) Different aeration disturbance models in overlying water can control the release of endogenous nitrogen in the sediment to a variable extent. The reduction rate of NH4+-N and DTN are 22.2%-94.9% and 35.9%-79.9% in the overlying water, respectively. While the aeration time is 12.00 h, and the DO concentration is at a low conditions (1.00 mg·L-1), then the DO is raised up to 4.00 mg·L-1, there is significant role in improving the reduction rate of NH4+-N and DTN. When the aeration is 12.00 h, and the DO concentration is 4.00 mg·L-1, then the DO is raised up to 7.00 mg·L-1, there is no significant role in improving the reduction rate of NH4+-N and DTN. Under a low DO concentration (about 2.50 mg·L-1), the extension of aeration time can effectively increase the reduction rate of NH4+-N and DTN in the overlying water. But the DO concentration is up to 5.50 mg·L-1, the extension of aeration time has no significant effect on the reduction rate of NH4+-N and DTN. Regarding the reduction rate of DTN in the overlying water as the ultimate control indicator, and aeration operation condition is optimized by using response surface methodology. Under the mode of water aeration disturbance, the best operation conditions can be concluded as follows:under the condition of aeration, the aeration time is 24.00 h, DO concentration is 4.76 mg·L-1, at this point the response value of the reduction rate of DTN in overlying water is 77.0%.(2) Different aeration disturbance models in overlying water can control the release of endogenous phosphorus in the sediment to a variable extent(except the run 7). At the same time of intermittent aeration(12.00 h), raising the DO level can can effectively cut down the content of DTP in the overlying water. When the DO level is low(2.50 mg·L-1), and the aeration time is 6.00 h, the extension of aeration time(to 18.00 h) can effectively increase the reduction rate of DTP. When the DO level is raised to 5.50 mg·L-1), the extension of aeration time(to 18.00 h) isn’t beneficial for the removal of DTP. Regarding the reduction rate of DTP in the overlying water as the control indicator, and the aeration disturbance mode is analyzed by using response surface methodology, then the best operation conditions can be concluded as followed: the aeration time is 6.00 h, DO concentration is 5.72 mg·L-1, and the response value of the reduction rate of DTP is 72.4% in overlying water.(3) Different aeration disturbance models to sediment can control the release of endogenous nitrogen in the sediment to a variable extent. The reduction rate of NH4+-N and DTN in the overlying water are 92.5%-97.6% and 54.9%-89.4%, respectively. Under the same aeration time (12.00 h), and the turbulence intensity is up to 354.33 s-1, the enhancement of turbulence intensity goes against the reduction of DTN in the overlying water, and under the same disturbance intensity (404.82 s-1) when the aeration time is 6.00 h, the extension of aeration time isn’t beneficial for the removal of DTN. Under the mode of sediment aeration disturbance, the best operation conditions can be concluded as followed:the aeration time is 21.39 h, the aeration flow is 0.10 L·min-1, and the response value of the reduction rate is 96.1%. Therefore, regarding the reduction rate of DTN in the overlying water as the control indicators, the effect of sediment aeration is better than that of water aeration, meanwhile the optimal aeration conditions is considered as the operation conditions of the sediment aeration by optimization.(4) In the aeration disturbance models to sediment, the run 9(354.33 s-1,12.00 h) has the highest reduction rate of TP, and it shows that the intermittent aeration of low turbulence intensity has higher reduction rate of TP. The increase of SS casued by aerating disturbance increases the content of particulate phosphorus, and the cut rule of TP isn’t obvious under different mode of sediment aeration disturbance, so we can’t analysis to obtain the optimal condition.(5) The CFD simulation results show that the flow rate is centrosymmtric in the overlying water of experimental device. And it reduces from the center to the surrounding until 0. The size of aeration flow rate is as follows:u9>u8=u12>u5=u11> u3=u7>u6, and it indicates that the flow rate and aeration disturbance intensity increase with the aeration flow.(6) qPCR results show that AOA is the predominant ammonia bacteria, and Anammox is the predominant Nitrogen-transforming bacteria. The different aeration disturbance models can promote the increase of bacteria and nirK-type denitrifying bacteria in urban black-odorous river sediment, but it doesn’t significantly reduce the quantity of Anammox, maybe the Anammox is in a resting state with high concentration of DO. |
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