Removal of perchloroethylene in two methanogenic-denitrifying continuous systems

The performance of two laboratory-scale, mesophilic complete mix reactors (CM1 and CM2) and an anaerobic fluidized-bed reactor (AFBBR) for the removal of perchloroethylene when fed a moderate concentration of organic co-substrate 1000 mg COD-methanol/L in the influent in two states: methanogenic and methanogenic-denitrifying, were evaluated. The experimental design consisted of three periods of operation with 1000 mg/L methanol as carbon source and 40 mg/L PCE in AFBBR and CM1 and 20 mg/L PCE in CM2. In Period 1, methanogenic regime, AFBBR showed the best performance with higher values of both organic matter removal and PCE, compared to CM reactors, in spite that volumetric loadings on AFBBR were 15-fold higher and some process stress would have been expected. During Period 2, simultaneous M-D regime at λ = 18 g COD/g N-NO₃^-, an improvement in performance for CM2 was observed. In Period 3, simultaneous M-D regime at λ = 9 gCOD/gN-NO₃^-, and concerning the two reactors fed with the highest PCE concentration 40 mg/L (AFBBR and CM2), the AFBBR outperformed CM2 in almost all the performance parameters and its metabolite profile was better than both of CM2 and CM1 (lower trichloroethylene, dichloroethylene, and vinyl chloride in the effluent). This is an abstract of a paper presented at the proceedings of the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).