Improving aeration systems in saline water: measurement of local bubble size and volumetric mass transfer coefficient of conventional membrane diffusers

• Published in: Water science and technology Vol. 78; no. 3-4; pp. 860 - 867
• Main Authors: Behnisch, J, Ganzauge, A, Sander, S, Herrling, M P, Wagner, M
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01.09.2018
• Subjects: Aeration; Air flow; Ascent; Bubbles; Chemical engineering; Coalescence; Coalescing; Diffusers; Drinking water; Electrolytes; Investigations; Mass transfer; Oxygen; Publishing; Resource recovery; Saline water; Saline Waters; Salt; Science; Sodium Chloride; Water; Water treatment; United Kingdom > UK; United States > US; Germany
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2018.358

In this study, for the first time, the influence of the design of conventional membrane diffusers on the volumetric mass transfer coefficient (k a) and bubble size in tap water (TW) and saline water (SW) was investigated (up to 15 g/L NaCl). By using a new analytical approach, k a and the bubble size along the ascent of the bubble swarm were measured simultaneously and in real time. The results show that in TW, after collision bubbles merge into larger bubbles by coalescence. In SW, coalescence is inhibited by salt. Due to the smaller bubble size, k a increases to more than double compared to TW. The results show that in SW, membrane diffusers with dense slit patterns and smaller slit lengths are to be recommended in order to enable improved utilization of oxygen in saline water.