Effects of Contaminants on Oxygen Transfer in Microbubble Aeration

Contaminants in wastewater influenced oxygen transfer in aeration process greatly. The effects of different typical contaminants on oxygen transfer in microbubble aeration were investigated and compared with traditional bubble aeration, including surfactant SDBS, soybean oil, phenol and nitrobenzene as well as kaolin. The results indicated that these contaminants showed different effect on oxygen transfer in microbubble aeration, compared with traditional bubble aeration. The negative effect of both soluble organic contaminants and suspended solid in traditional bubble aeration seemed to be counteracted in microbubble aeration. The range of K
_L
a values were 7.44~11.56 h
^-1
and the range of α-factors were 0.77~1.20 under all test conditions, larger than these in traditional bubble aeration. In addition, both K
_L
a values and α-factors increased along with an increasing of concentration for soluble organic contaminants, whereas the maximum K
_L
a value and α-factor existed for suspended solid kaolin with concentration of 100 mg/L. The gas holdup and average bubble retention time in microbubble aeration containing these contaminants increased, compared with these in clean water. So the improvement of microbubble generation and stability in presence of these contaminants should be responsible for oxygen transfer enhancement probably.