PROCESS ANALYSIS OF POINT SOURCE LEAKAGE, MIGRATION AND IN SITU AIR SPARGING OF NAPLS

The numerical simulation technique of three-phase non-isothermal flow in heterogeneous porous media was adopted to analyze the point source leakage, migration, and in situ air sparging(AS)process of Light Non-Aqueous Phase Liquids(LNAPLs) and Dense Non-Aqueous Phase Liquids(DNAPLs).The mass fraction distribution and removal rate of the contaminants were studied. The effects of sparging flow rate, well distance, and sparging depth on the contaminant removal rate were discussed. Theoretical analysis indicates that both the mass fraction distribution scope and concentration of dissolved benzene are larger than that of dissolved trichloroethylene(TCE).There exist peak concentration regions around 1～2m above the underground water level for both benzene and TCE.In addition, benzene mainly concentrates in the upper part of the aquifer as well as the vadose zone, while obvious distribution of the TCE can be found in the lower part of the aquifer. The largest migration depth of TCE is 5 times as much as that of benzene. The ratio of contaminant removal after a short period(1 day) of continuous AS remediation increases a little with the increase of sparging depth, decreases quickly with the increase of well spacing, but increases a lot with the air flow rate. To reach the required remediation standard given by standards, the operation periods for air sparging of benzene and TCE contaminated underground water need 60 and 30 days respectively, indicating a shorter period for TCE.In addition, experimental research achievements from different literature were referenced to verify the reasonability of above theoretical analysis.