Gas- and liquid-phase mass transfer resistances of organic compounds during mechanical surface aeration
Gas- and liquid-phase mass transfer resistances of organic compounds during mechanical surface aeration
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机械表面曝气过程中有机化合物的气相和液相传质阻力
DOI：
10.1016/0043-1354(89)90026-2
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发表时间：
1989
期刊：
影响因子：
12.8
通讯作者：
P. Roberts
中科院分区：
文献类型：
--
作者：
C. Munz;P. Roberts
在实验室规模的机械表面曝气反应器中研究了一套六种挥发性卤代有机物和氧气在活性污泥处理过程中的传质行为。有机物的传质速率与氧的传质速率之间存在比例因子ε。在液相控制传质的假设下，观察到挥发性最小的溶质与预期的恒定值的最小值的显著偏差。数据分析和解释，根据两个电阻传质模型与适当的校正分子扩散系数的微小变化表明，气相阻力传质比以前假设的更重要。基于这项工作和对另外两项研究的数据分析，建议使用kG/kL = 40的值来估计在高比功率输入条件下机械表面曝气中气相和液相传质阻力的相对重要性。因此，只有无因次亨利常数≥ 0.55的化合物才能被认为表现出完全（≥ 95%）的液相控制传质行为。根据渗透和表面更新理论，液相传质速率常数kLa与扩散系数的平方根成正比。存在于经处理的废水中的溶解成分以成比例的方式降低有机溶质和氧气的传质速率。由于在这项工作中的操作条件和观察到的氧气传质速率是类似的，在该领域遇到的，有理由相信，这些研究结果也是有效的水和废水处理的典型条件下。
The mass transfer behavior of a suite of six volatile halogenated organic compounds and oxygen was investigated in a laboratory scale reactor representative of mechanical surface aeration during activated sludge treatment. The rate of mass transfer of the organics was related to that of oxygen by a proportionality factor Ψ. Significant deviations were observed for the least volatile solute from the expected constant value of Ψ under the assumption of liquid phase controlled mass transfer. Data analysis and interpretation according to two-resistance mass transfer models with appropriate correction for the slight variation in molecular diffusivities indicates that the gas phase resistance to mass transfer is more important than previously assumed. Based on this work and on the data analysis of two other studies it is recommended that a value ofkG/kL≈ 40 be used to estimate the relative importance of gas and liquid phase mass transfer resistances in mechanical surface aeration under conditions of high specific power input. Consequently, only compounds with a dimensionless Henry's constant ⩾0.55 can be considered to exhibit complete (⩾95%) liquid phase controlled mass transfer behavior. It appears that the liquid phase mass transfer rate constant,kLais proportional to the square root of the diffusivity in accordance with the penetration and surface renewal theories. The dissolved constituents present in treated wastewater reduce the rate of mass transfer of organic solutes and oxygen in a proportional fashion. Since the conditions of operation and the observed rates of oxygen mass transfer in this work are similar to those encountered in the field, there is reason to believe that these findings are also valid under conditions typical of water and wastewater treatment.