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Water Environ Res

Title:		Effect of bubble-induced surface turbulence on gas-liquid mass transfer in diffused aeration systems
Author(s):		Monteith HD; Bell JP; Parker WJ; Melcer H; Harvey RT;
Address:		"Hydromantis, Inc., Hamilton, Ontario, Canada. monteith@hydromantis.com"
Journal Title:		Water Environ Res
Year:		2005
Volume:		77
Issue:		2
Page Number:		128 - 137
DOI:		10.2175/106143005x41690
ISSN/ISBN:		1061-4303 (Print) 1061-4303 (Linking)
Abstract:		"Models that predict volatilization of organic compounds from wastewater treatment basins may underestimate emission rates if the surfaces are considered as quiescent. In reality, the water surface may be agitated by subsurface aeration, increasing mass transfer across the tank surface air-water interface. This study investigated the effect of turbulence, induced by diffused bubble aeration, on mass transfer at the water surface of a pilot aeration basin. The mass transfer of ammonia from an enclosed headspace over the basin to acidified water was measured when different diffuser types and airflow rates were applied. Oxygen-transfer tests were conducted immediately following each ammonia-transfer test. Increasing airflow rates through fine- and coarse-bubble diffusers had a significant effect on the ammonia mass-transfer rate. Experimental mass-transfer parameters (K(L)a's) for surface volatilization derived with aeration present were up to 48% higher than the K(L)a values for quiescent conditions over the range of conditions tested. No effect of diffuser type on ammonia transfer could be determined. The study results infer an effect on oxygen transfer into the water at the surface and potential transfer of volatile organic compounds, if present, from the water. The results of the ammonia mass-transfer experiments suggest that adjustments to the existing mass transfer correlations for surface volatilization from aeration basins may be in order. Such adjustments will have the greatest effect on predictions for the less volatile compounds, under conditions of low airflow rates"
Keywords:		"Air Movements Ammonia/*chemistry Diffusion Gases/chemistry Models, Theoretical Organic Chemicals/chemistry Oxygen/chemistry Sewage/chemistry Volatilization Waste Disposal, Fluid/*methods Water/chemistry;"
Notes:		"MedlineMonteith, H D Bell, J P Parker, W J Melcer, H Harvey, R T eng Research Support, Non-U.S. Gov't 2005/04/09 Water Environ Res. 2005 Mar-Apr; 77(2):128-37. doi: 10.2175/106143005x41690"