Application of Riverbed Quiferous System to Indoor Simulation of Decontamination of Aromatic Hydrocarbons

In the five-month indoor earth-column experiment, three representative kinds of natural sand are analyzed, and the refluxes of domestic sewage are used to simulate the contaminated river flow. This indoor experiment aims at both the simulation of the migration and transfer law of aromatic hydrocarbons in the surface water-underground water system in a long-term drainage river and that of the impacts of different aquiferous media and hydrodynamic conditions on the decontamination of aromatic hydrocarbons. Aromatic hydrocarbons in column decrease gradually with the flow direction, where the natural decontamination occurs at 0.4 m of the surface layer. Total decontamination ratios of benzene, toluene and total aromatic hydrocarbons (TBETX) in the coarse sand is 32.06%, 21.39% and 27.13%, respectively; in the first kind of the medium sand is 76.26%, 81.40% and 87.99%, respectively; in the second kind of the medium sand is 68.94%, 74.41% and 81.69%, respectively. All these results indicate that the hydrous medium in the riverbed is perfectly saturated in the early period of the contamination of the river, where the greater the size of the hydrous medium, the lower the decontamination rate of the aromatic hydrocarbons. In this case, the aromatic hydrocarbons migrate easily into the underground water system. As times went by, the silt seams in the riverbed became thicker and thicker till unsaturated flow moves into the sand. However, when the decontamination rate of aromatic hydrocarbons in the silt seams and hydrous medium system is greater than that in the saturated water flow, the aromatic hydrocarbons will not easily migrate into the corresponding underground water system.