Effect of water-surface desorption on volatile compound removal under bubble aeration

Two mechanisms of desorption of volatile compounds (VCs) can occur when a tank undergoes bubble aeration: desorption to the bubble and desorption at the free-water surface. A quantification method for prediction of bubble transfer is presented and experimentally verified. Experimental results show that desorption from the surface can be a major fraction of the total desorption rate for VCs. For field conditions, surface transfer accounts for 17 to 60% of the transfer of four chlorinated solvents, even though it accounts for only approximately 6% of the oxygen transfer. Thus, ignoring surface desorption in bubble-aeration systems can cause a major underestimation of the stripping rate of VCs.