System for treating polluted groundwater

System for in-situ treatment of contaminated groundwater in an aquifer, wherein:

• the system is of the kind in which the contaminated groundwater moves through the aquifer due to in-ground pressure-head gradients;
• the system includes a barrier or wall that extends down into the ground, the wall being placed in the path of the in-ground movement of the contaminated groundwater, the wall dividing an upstream portion of the aquifer from a downstream portion of the aquifer;
• the wall is watertight, in the sense of being effective to substantially prevent the passage of groundwater through the wall;
• the system includes at least one gap or gate in the wall;
• the system includes a body of treatment material;
• the body of treatment material is porous and permeable to the extent that groundwater can pass through the treatment material;
• the treatment material is of such a chemical composition, in relation to the nature of the contaminant, that the contaminant in the water undergoes a chemical change, upon the water being passed through the treatment material;
• the body is located in the ground, in the gate, and is so arranged that groundwater can pass from the upstream portion of the aquifer to the downstream portion of the aquifer through the treatment material;
• the system includes a gate sealing means which is effective to prevent the passage of groundwater between the wall and the body of treatment material in the gate, whereby groundwater cannot pass from the upstream portion of the aquifer to the downstream portion of the aquifer except through the treatment material;
• the arrangement and dimensions of the gate, the body of treatment material, and the sealing means are such, in relation to the velocity of flow of the groundwater, that even the shortest path through the treatment material from the upstream portion of the aquifer to the downstream portion of the aquifer is long enough to ensure a residence period of the contaminated water within the body of treatment material of sufficient time as to ensure the effective treatment of the contaminant.