Oxygen absorption into moving water and tenside solutions

Oxygen absorption into water and waste water is an important process taking place with both natural and technical means, and a tool for a theoretical determination of the oxygen transfer coefficient, K-L, is desirable. The objective of this investigation was to study the environment at and nea r the liquid side of a gas-liquid interface in order to present a model for a theoretical determination of K-L. The gas was pure oxygen and the liquid s were clean tap water and various concentrations of two types of tenside s olutions. Various sized hemispherical oxygen bubbles were impressed by vari ous liquid how velocities while measuring the liquid how velocity and the f ilm thickness using a Laser Doppler Anemometer (LDA). The LDA was also used to determine K-L Furthermore, the surface tension and the bulk kinematic v iscosity for various liquids were measured. For clean tap water it was Found that the Two Film Theory by Lewis and Whit mann [(1924) Industrial and Engineering Chemistry, 16(12), 1215-1220] had t o be modified, and that K-L can be calculated from a correspondingly modifi ed version of an equation presented by Dobbins [(1956) Biological Treatment of Sewage and Industrial Wastes, Section 2, eds B. J. McCabe and W. W. Eck enfelder Jr, pp. 141-148. Reinhold publishing Corp., New York]. The calcula tion is based on a theoretical determination of the liquid film thickness w ith respect to normal Row which is also presented in this paper. For tenside solutions it was found that ICL is a function of the relative f low velocity (nu(r)) (K-L increases with increasing nu(r) until a certain l imit), the bubble size (K-L decreases with increasing bubble size), and the surface tension (K-L decreases with decreasing surface tension) but not th e kinematic viscosity of the bulk, However, it was not possible to present a thorough calculation model. A more detailed description of the investigation is given in Pedersen [(199 8) A study of liquid film, liquid motion, and oxygen absorption from hemisp herical air/oxygen bubbles. Ph.D. thesis, Brunel University, London]. (C) 2 000 Elsevier Science Ltd. All rights reserved.