In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites. The surfactant present in flushing solutions is bound to affect the aeration efficiency. The purpose of this study is to evaluate the effect of surfactant frequently used in soil flushing on the oxygen mass transfer in micro-nano-bubble (MNB) aeration system. Firstly

bio-surfactants and chemical surfactants were used to investigate their effects on Sauter mean diameter of bubble (

d

BS

)

gas holdup (

ε

)

volumetric mass-transfer coefficient (

k

L

a

) and liquid-side mass-transfer coefficient (

k

L

) in the MNB aeration system. Then

based upon the experimental results

the Sardeing's and Frössling's models were modified to describe the effect of surfactant on

k

L

in the MNB aeration. The results showed that

for the twenty aqueous surfactant solutions

with the increase in surfactant concentration

the value of

d

BS

k

L

a

and

k

L

decreased

while the value of

ε

and gas-liquid interfacial area (

a

) increased. These phenomena were mainly attributed to the synergistic effects of immobile bubble surface and the suppression of coalescence in the surfactant solutions. In addition

with the presence of electric charge

MNBs in anionic surfactant solutions were smaller and higher in number than in non-ionic surfactant solutio

ns. Furthermore

the accumulation of surfactant on the gas-liquid interface was more conspicuous for small MNB

so the reduction of

k

L

in anionic surfactant solutions was larger than that in non-ionic surfactant solutions. Besides

the modified Frössling's model predicted the effect of surfactant on

k

L

in MNB aeration system with reasonable accuracy.