TREATMENT OF TETRACHLOROETHYLENE WITH ANAEROBIC ATTACHED FILM PROCESS

A laboratory-scale continuously fed anaerobic attached film expanded bed (AAFEB) reactor is utilized to examine the feasibility of tetrachloroethylene/ trichloroethylene (PCE/TCE) dechlorination under methanogenic conditions at 35 degrees C. Sucrose is used as the electron donor. After a short acclimation period (two weeks), the system shows excellent dechlorination capability for treating PCE and TCE. Influent PCE concentrations of 8.2-26 mg/L are reduced to less than 0.2 mg/L (greater than 98% removal) in most cases, even though efforts are made to achieve intermediate removal efficiencies to support kinetic analysis. TCE and cis-1,2-dichloroethylene (cis-1,2-DCE) remain at low concentrations, which indicates that they were not the rate-limiting intermediates throughout much of the test program. Preliminary estimates of the half-velocity coefficient (K,) and maximum PCE uptake rate (q(max)) are 0.25-mg PCE per liter and 22.9-mg PCE per gram VS-per day, respectively. Most of the PCE and TCE appear to be converted to vinyl chloride. The cometabolism-like reactions require a minimum of about eight mass units of COD reduction for each mass of PCE dechlorinated with a range of less than five to greater than 10. The results of the study suggest that the AAFEB system with sucrose as carbon and energy source is efficient and rapid enough to appear to be a feasible bioremediation process for PCE and TCE treatment, but further treatment of vinyl chloride is necessary.