A methanogenic-methanotrophic system has been established to assess the capability of sequential treatment to transform the chlorinated aliphatics perchloroethylene (PCE), carbon tetrachloride (CT) and 1,1,1-trichloroethane (1, 1,1-TCA). Experiments compared the transformation of PCE alone and in a mixture of the target compounds. A comparison of acetate and iron as electron donors was also made. Data from the anaerobic systems have shown that PCE transformation is inhibited when in a mixture with CT and 1,1,1-TCA compared to when it is fed alone. When iron is the electron donor, PCE and 1,1,1-TCA are transformed without an acclimation period. CT was completely transformed regardless of the electron donor used. The acetate-fed system required approximately 60 days to acclimate to 1,1,1-TCA and 70 days for acclimation to PCE. Although the sequential system has been constructed, sampling from the aerobic column was not done before the thesis project ended. More investigation is required to determine the ability of the sequential system to degrade PCE, CT, and 1,1,1- TCA.