Ohkawa A, Kusabiraki D, Shiokawa Y, Sakai N, Fujii M
Department of Chemical Engineering, Faculty of Engineering, Niigata University, 8050, Ikarashi Ni-no-cho, Niigata City 950-21, Japan.
Biotechnol Bioeng. 1986 Dec;28(12):1845-56. doi: 10.1002/bit.260281212.
For the plunging water jet system using inclined short nozzles, the flow characteristics such as the bubble penetration depth and the gas entrainment rate, which changed depending on the jet velocity, the nozzle diameter, the jet length, and the jet angle were first evaluated in an air-water system. A comparable investigation between our results and those of existing studies used the long nozzles on those characteristics revealed that both the bubble penetration depth and the gas entrainment rate differed depending on the nozzle length; that is, the nozzle-length-to-diameter ratio L(N)/D(N) and that of these characteristics the gas entrainment rate affected considerably by its magnitude and tended to be high when the nozzle of a large L(N)/D(N) ratio was used. It was also confirmed from the oxygen transfer experiments that the transfer efficiency at low jet velocities in the present water jet system was not inferior to the ones of other types of existing aeration systems; that is, the utilization of this jet aeration system to a high rate reactor for wastewater treatment or fermentation was sufficiently possible. The applicability of the plunging jet aeration method to microbial processes was then examined. As a typical example of microbial processes to be tested, the continuous treatment of an organic wastewater using activated sludge microorganisms was carried out, and the performance and related problem when this type of aeration system was applied to such a microbial process were investigated. Experimental results showed that, when viewed from the removal ability of dissolved organic matters, the plunging jet aeration system was capable of treating a wastewater of considerable high loading without the rate of oxygen transfer becoming the biooxydation-rate-limiting factor. Special attention was necessary for the choice of the liquid pump to be employed, however, due to the increased amount of fine suspended solids in the treated water caused by the shearing action between sludge flocks and pump blades.
对于使用倾斜短喷嘴的淹没式水射流系统，首先在气 - 水系统中评估了诸如气泡穿透深度和气体夹带率等流动特性，这些特性会根据射流速度、喷嘴直径、射流长度和射流角度而变化。将我们的结果与现有研究中使用长喷嘴对这些特性进行的比较研究表明，气泡穿透深度和气体夹带率均因喷嘴长度而异；也就是说，喷嘴长径比L(N)/D(N)以及这些特性中的气体夹带率受其大小的影响很大，当使用L(N)/D(N)比值较大的喷嘴时，气体夹带率往往较高。从氧传递实验中还证实，在当前水射流系统中低射流速度下的传递效率不低于其他类型现有曝气系统的效率；也就是说，将这种射流曝气系统应用于废水处理或发酵的高负荷反应器是完全可行的。然后研究了淹没式射流曝气法在微生物过程中的适用性。作为要测试的微生物过程的一个典型例子，使用活性污泥微生物对有机废水进行连续处理，并研究了将这种曝气系统应用于此类微生物过程时的性能及相关问题。实验结果表明，从溶解有机物的去除能力来看，淹没式射流曝气系统能够处理相当高负荷的废水，而不会使氧传递速率成为生物氧化速率的限制因素。然而，由于污泥絮体与泵叶片之间的剪切作用导致处理水中细悬浮固体量增加，因此在选择使用的液体泵时需要特别注意。
