| In recent years, with the development of urbanization and the improvement of human quality of life and living environment, lots of artificial scenic water bodies have been built in central cities and rural towns in order to satisfy people’s growing material and cultural needs. With the frequent occurrence of eutrophication and serious pollution, the paper investigated the effects of micro-nanometer aeration on repairing urban landscape water and studied its volumetric oxygen transfer as well as influence factors. The results showed that:(1) We find that volumetric oxygen transfer coefficient(KLa) is in positive correlation with air flow, at the same time,negative correlation with standard oxygen transfer efficiency(SOTE) in air flow condition of 1～6L/min. In temperature from 20℃ to 35℃, and SOTE in Micro-nanometer aeration group were both increased with temperature rise. of micro-nanometer aeration was the minimum at pH 7.2, and it increased firstly and then decreased with the pH increased. Ku, was affected by NH4Cl and turbidity of water, and that was a positive correlation with turbidity, and a negative correlation with NH4Cl. But SOTE increased with temperature rise, microporous aeration group had the same trend, but the value was smaller than micro-nano aeration group. SOTE and K.La of micro-nanometer aeration were more sensitive to air flow rate than other influence factors.(2) The simulation experience of aeration was operated on the actual landscape water. In the polluted water, the oxygen transferring of micro-nanometer aeration performs was much better than microporous aeration. But due to the pollution, KLa of both groups declined when compared with the performance in the clean water test. After 21 days’observation, DO in the micro-nanometer aeration group reached 6 mg/L in the fourth day while the number in the micro-nanometer aeration group reached the same level in the seventh day, which indicated that the micro-nanometer aeration can effectively improve the aquatic environment. The average air holdup in 21 days was 1.09%.(3) In the simulation experiment, for the water treatment effect of the landscape water, the operating conditions of the micro-nanometer aeration group were set to be:ventilation volume as 2L/min and the water temperature as 25℃. After 21 days’experiment, the final removal efficiency of CODcr, TP, NH4+-N and TN in the micro-nanometer aeration group were 67.59%,17.30%,70.20% and 66.75%, respectively. Chl-a increased 14.03%. While in the microporous aeration group, the final removal efficiency of CODcr, TP, NH4+-N and TN were respectively 56%,13.46%,54.36% and 55.6%.The Chl-a increased 15.69%.(4) By recording the variation of water DO under different aeration durations, an empirical model was established to deal with the relation between DO, different influence factors and time. This model took all factors of water conditions into account and calculates the needed aeration duration to reach the saturated DO, which can provide quantitative basis for the aeration control in the real application of micro-nanometer aeration. Moreover, the research method adopted had guiding significance to study on the rules of the aeration dissolved oxygen. Meanwhile, with the back calculating the water DO empirical equation, a prediction model of aeration’s KLa can be obtained and this model laid the foundation for the research on oxygen transferring. |
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