The researchers tested a method to clean up a harmful chemical called trichloroethylene using a special filter filled with fungi. They added another chemical, methanol, to help break down the trichloroethylene. They found that methanol initially helped remove the trichloroethylene, but at higher levels, it actually slowed down the process. However, the trichloroethylene did not affect the removal of methanol. One filter performed better than the other because it was better at handling the competition from methanol.