Re-oxygenation Technology For Prevention And Control Of Black Water In Eutrophic Lakes

Localized outbreaks of black smelly water in shallow lakes seriously threaded to the safety of drinking water and lake ecosystems, and that preventing and rapidly controling of this phenomenon must master controling mechanism and development efficient equipment which applicable to shallow lakes. In this study took the artificial oxygen technical mechanism to prevent and control shallow lakes water from black-odor pollution as the base;and took the development and test and simulation, verification, analog studies of the up-flow oxygen device as the core; and took the eventual establishment of the local black smelly water emergency plan as the purpose, we established initially shallow lakes local black smelly water prevention and control system.First we eatablished a simulation test as Taihu Lake,which algae concentration was 1.0×109 cells/L, and the water temperature was about 28℃ when the water was kept static,the CODMn, Fe, Mn, DMTS of water would continuesly rose, and after 6days the black smelly phenomenon of water would occurred. When we made artificial reoxygenation maintain 1.0mg /L or more dissolved oxygen levels, smelly black water phenomenon could be prevented, and the water black-odor would return to the normal appearance; So by reoxygenation to control the dissolved oxygen concentration above 1.0mg /L counld as a effective technical to prevent and rapidly control from becoming black smelly water .By small scale experimental we developed three types apparatus that suitable for emergency reoxygenation to black smelly water of shallow lakes which name was up-flowing cycle reoxygenation (UFCR). The type Ⅲ was tested to be the optimal. By test we improved the effect of reoxygenation from optimizing the discharge head and increasing the height of the aeration zone; using multi-faceted hollow ball packing; provided aeration tube according to 1.0m3/m.h; increasing the exposure to the extent appropriate gas and other means to; and improved the effect of lifting water by increasing the number of water holes or taking cross-stitch. We established the oxygen mass transfer model and verificated the reliability of the model by experiment.Based on the results of small scale experiment, we completed the pilot scale design and manufacturing, including Pall ring type I ,pall ringllH type, multi-faceted hollow ballⅢ-type .Pilot site was located in a algae pool(20m × 10m × 1.8m), the pilot experiments showed the pilot type Ⅲ multi-faceted spherical packing device could restore dissolved oxygen from O.OOmgL/L to 1.69 mg/L in 28 h, the device oxygen efficiency was 26%, and the degradation of water CODCr, ammonia nitrogen was satisfactory. The device could be used for emergency management of black water group outbreak such as in Taihu lake.The pilot Ⅲ multi-faceted hollow ball-type UFCR and other forms reoxygenation pilot-plant were carried out in the oxygen transfer experiments, the research shows that:The oxygen transfer law of UFCR was that along the radial directionr from center to edge and from water surface to bottom the DO decreased by DO tranfer; and other law was that he surface DO was close to middle, and near bottom DO increased very difficulty. The actual oxygen transfer ability of UFCR which air was 25 m3/h was 2.57 kgO2/h, and its oxygen utilization rate was 34%, which 84.09% of them was used to participate in the degradation of CODCr, 15.91% of them was ascent the DO.By the Fluent model soft we simulated the UFCR reoxygenating test in pilot site which length and width was 100m and its depth was 1.8 m.The simulation results showed that at the beginning of the aerobic zone only reoxygenation near the outlet, but with time past aerobic circle gradually expanded, the oxygen concentration in the aerobic circle also gradually increase from the device, and simulations result showed after 48 h UFCR DO influence radius was 72.00 m, it could reflect the UFCR DO transfer characteristics, and could evaluate the performance of it. algae-induced odorous black water agglomerate and contributed to the construction of a prevention system.