The effect of salinity on trichloroethylene co-metabolism by mixed cultures enriched on phenol

Abstract

This work examines the effects of salinity on the biodegradation of trichloroethylene (TCE) by four chemostat-cultivated cultures: LHPO-3, LHPO-6, HHPO-3 and HHPO-6, all of which had been enriched on phenol but grown under different conditions. Cultures LHPO-3 (with hydraulic retention time [HRT] of 3.1 days) and LHPO-6 (6.5-day HRT) were cultivated with fresh water, whereas cultures HHPO-3 (3.3-day HRT) and HHPO-6 (6.1-day HRT) were cultivated with seawater. Batch tests of TCE degradation by the four bacterial consortia in the absence of phenol were undertaken in solutions with salinities in the range 0–3.28% (w/v). Moreover, the effect of adding phenol on TCE degradation by LHPO-3 in 1.64% salinity solution was investigated. The results showed that the observed bacterial yields for the cultures LHPO-3, LHPO-6, HHPO-3 and HHPO-6 were 0.66, 0.47, 0.58 and 0.33 mg volatile suspended solids/mg phenol, respectively. In the absence of phenol, the extents of TCE degradation by cultures LHPO-3 and LHPO-6 increased with salinity stress, reaching 0.052 mg TCE/mg VSS for LHPO-3 and 0.033 mg TCE/mg VSS for LHPO-6, and then declined as salinity increased further. The tolerance of TCE degradation to salinity for culture LHPO-3 was around 3.28% and that for LHPO-6 was 1.64–2.33%. In the presence of phenol, the rate and extent of TCE degradation by LHPO-3 were enhanced when an optimal dosage of phenol of 10 mg phenol/mg TCE was applied. Degradation of TCE by cultures HHPO-3 and HHPO-6 was not observed.