Treatment of trichloroethene-contaminated water with a fluidized-bed bioreactor

Biological systems are a potentially attractive means of treatment for groundwater contaminated with chlorinated solvents. In this research, a bench-scale fluidized-bed biological reactor (FBBR) was used to treat water contaminated by trichloroethene (TCE). The bed volume was 2.4 L and the flow rate was 0.8 L/min. Applications of the reactor are primarily for treatment of groundwater extracted during aquifer remediation. Reactor feed water was amended with phenol and nutrients to stimulate the growth of bioparticles with the ability to cometabolize TCE. The FBBR was operated in a bed growth mode for two weeks followed by a TCE removal period of two weeks during which TCE and phenol were fed simultaneously. Experiments were conducted to determine the removal of 0.1 mg/L TCE for phenol loading rates ranging from 3 to 9 mg/min. Higher phenol loading inhibited TCE degradation and resulted in phenol not being completely removed by the reactor. Phenol was not detected in the reactor effluent at loadings below 6 mg/min (3.6 g/L/d). A phenol to TCE mass ratio of 75:1 provided an average 60% removal of 0.1 mg/L TCE at an empty bed contact time of 3 minutes. Higher removal of TCE may be possible in field-scale reactors where the FBBR height (bed-depth) may be extended.