Effects of flow velocity changes on nitrogen transport and conversion in an open channel flow
Effects of flow velocity changes on nitrogen transport and conversion in an open channel flow
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流速变化对明渠流中氮传输和转化的影响
DOI：
10.1016/0043-1354(96)00308-9
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发表时间：
1996
期刊：
影响因子：
12.8
通讯作者：
Jau
中科院分区：
文献类型：
--
作者：
H. Leu;C. Ouyang;Jau
研究表明，流速的短期变化会影响含氮化合物在浅缓流河道中的迁移和转化。两种不同的流动条件控制的不同的流速，包括层流和湍流，提出了描述可溶性和颗粒状含氮化合物之间的水柱和生物膜。提出了利用初始湍流来设计高硝化率、低再悬浮率的流道。通过一系列可控的间歇试验研究了含氮化合物在不同流速下在人工河道中的转化规律。批量试验的结果表明，一种特定类型的水运动将控制氮的命运，而有机物浓度在水柱中是低的。当流道内发生层流时，总凯氏氮（TKN）去除率基本保持不变;氧化态氮的生成率随流速的增大而增大;硝酸盐氮和铵态氮转化缓慢;有机氮和总氮浓度随试验时间的延长而逐渐降低。而当水流条件由层流转为湍流时，TKN去除率随流速的增加而降低，氧化态氮的生成速率比层流时增加得更多，且随流速的增加而保持恒定，硝酸盐浓度增加，氨氮浓度迅速下降;总氮和有机氮含量先降低后升高。在已知有机物浓度和水流条件的情况下，可以识别含氮化合物转化和运移的主要途径。
This study demonstrates that short-term changes in flow velocity affect nitrogenous compounds' transport and conversion in a shallow, slow-flowing channel. Two different flow conditions controlled by varied flow velocities, including laminar and turbulent flow, are proposed to describe soluble and particulate nitrogenous compounds transported between the water column and biofilms. The incipient turbulent flow was suggested to design a flowing channel which will induce a high rate of nitrification and a low rate of resuspension. A series of well-controlled batch tests were carried out to investigate nitrogenous compound transformations in an artificial channel at varied flow velocities. The results of the batch tests show that a particular type of water motion will control the fate of nitrogen, while organic matter concentration is low in the water column. When laminar flow occurs in the flowing channel, total kjeldahl nitrogen (TKN) removal rate is held approximately constant; oxidized nitrogen generation rate increased when flow velocity increased; nitrate and ammonium nitrogen converted slowly; organic nitrogen and total nitrogen concentration gradually decreased with the test time. In contrast, when the flow condition transferred from laminar flow to turbulent flow, the TKN removal rate decreased when flow velocity increased; the oxidized nitrogen generation rate increased more than it did during the laminar flow, and it maintained a constant rate when flow velocity became higher; nitrate concentration increased and ammonium nitrogen concentration decreased quickly; total nitrogen and organic nitrogen concentration gradually decreased and later increased. The primary pathways of nitrogenous compounds' conversion and transport can be recognized when organic substance concentrations and flow conditions are known.