Trichloroethylene (TCE) biodegradation and its effect on sulfate reducing activity in enriched sulfidogenic cultures prevenient from a UASB maintained at 20°C

Enriched sulfidogenic microorganisms sampled from a UASB reactor operated at room temperature were evaluated on their sulfate reducing activity (SRA) in the presence of trichloroethylene (TCE) (200, 500 and 900μM) in order to determine the degree of inhibition on the sulfidogenic microorganisms. The microcosms were incubated at initial sulfate (SO4-2) concentration of 6000mg/L with a mixture of volatile fatty acids (VFA's) as substrate (acetate, propionate and butyrate). SRA in the microcosms before TCE addition ranged from 400±258 to 8290±630mgCOD-H₂Sg^-1VSSd^-1, after TCE addition the SRA ranged from 5 to 1500mgCOD-H₂Sg^-1VSSd^-1. The lowest SRA observed was due to the highest TCE biodegradation (over 90%) yielding ethene as product of the TCE biodegradation within two weeks. The sulfide (H₂S) concentration in the microcosms was varied from 40 to 700mg/L, except for the transient interruption of sulfate reduction when TCE was biodegraded. The SRA in the microcosms was low but steadily observed in the enrichments after TCE biodegradation suggesting that it is possible to maintain a high biogenic sulfide production in the presence of the pollutant. Therefore the enrichments could be useful for further applications such as heavy metals precipitation along with biodegradation of moderate TCE concentrations.