Now it is one of the most widespread and difficult to treat groundwater contaminants in the country. In addition to performing effectively, the bioremediation process lived up fully to the researchers' predictions, indicating that they understand the basic processes involved well enough to determine how the method will work in other areas contaminated with TCE, McCarty said. Groundwater is pumped to the surface, where air is blown through it to strip out volatile contaminants, which are then adsorbed onto activated charcoal filters. This approach wastes water, because the treated water is seldom reinjected into the aquifer. The contaminated charcoal also must be disposed.
Energy costs can be high for pumping contaminated water from deep aquifers.
The clean water that replaces the water pumped to the surface can become contaminated when it comes into contact with the tainted sands that remain. Then, when the operation is shut down, the bacterial populations will quickly return to normal. According to McCarty, the main advantages of bioremediation are water conservation and a substantial reduction in pumping costs. On the other side of the ledger, however, is the cost of the chemicals involved. In the case of TCE decontamination, the highest cost item in the process is hydrogen peroxide, which breaks down in the water to provide the oxygen that the bacteria need to attack the compound.