TREATMENT OF TETRACHLOROETHYLENE WITH ANAEROBIC ATTACHED FILM PROCESS

A laboratory-scale continuously fed anaerobic attached film expanded b ed (AAFEB) reactor is utilized to examine the feasibility of tetrachlo roethylene/ trichloroethylene (PCE/TCE) dechlorination under methanoge nic conditions at 35 degrees C. Sucrose is used as the electron donor. After a short acclimation period (two weeks), the system shows excell ent dechlorination capability for treating PCE and TCE. Influent PCE c oncentrations of 8.2-26 mg/L are reduced to less than 0.2 mg/L (greate r than 98% removal) in most cases, even though efforts are made to ach ieve intermediate removal efficiencies to support kinetic analysis. TC E and cis-1,2-dichloroethylene (cis-1,2-DCE) remain at low concentrati ons, which indicates that they were not the rate-limiting intermediate s throughout much of the test program. Preliminary estimates of the ha lf-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, respectivel y. Most of the PCE and TCE appear to be converted to vinyl chloride. T he cometabolism-like reactions require a minimum of about eight mass u nits 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 eff icient and rapid enough to appear to be a feasible bioremediation proc ess for PCE and TCE treatment, but further treatment of vinyl chloride is necessary.