ANAEROBIC AND AEROBIC TREATMENT OF CHLORINATED ALIPHATIC-COMPOUNDS

Biological degradation of 12 chlorinated aliphatic compounds (CACs) was assessed in bench-top reactors and in serum bottle tests. Three continuously mixed daily batch-fed reactor systems were evaluated: anaerobic, aerobic, and sequential-anaerobic-aerobic (sequential). Glucose, acetate, benzoate, and phenol were fed as growth substrates to both the anaerobic and aerobic systems. Methane and toluene were also added to the aerobic systems to induce cometabolic degradation of the feed CACs. The anaerobic culture degraded seven of the feed CACs. The specialized aerobic cultures degraded all but three of the highly chlorinated CACs. The sequential system outperformed either of the other systems alone by degrading 10 of the feed CACs: chloroform, carbon tetrachloride, 1,1-dichloroethane, 1,1,1-trichloroethane, hexachloroethane, 1,1-dichloroethylene, trans-1,2-dichloroethylene, trichloroethylene, perchloroethylene, and 1,2,3-trichloropropane, plus the anaerobic metabolites: dichloromethane and cis-1,2-dichloroethylene. Sequential treatment did not show significant removal of 2-chloropropene, or 1,1-dichloropropene. Cultures from each of the reactors were used in bottle tests to determine relative CAC degradation rates. Maximum degradation rates observed for individual CACs ranged from 20 to 150 mug per gram volatile suspended solids per day.