Treatment of Trichloroethene (tce) with a Fluidized-bed Bioreactor

Fluidized-bed bioreactors (FBBR’s) offer a promising alternative to existing treatment technologies for the treatment of water contaminated with chlorinated solvents. The objective of this research was to test a laboratory-scale FBBR for removal of trichloroethene (TCE) from groundwater and to study the FBBR kinetic behavior so that field-scale treatment systems could be designed. Phenol was selected as the growth substrate for biofilm-forming microorganisms enriched from activated-sludge because phenol induces enzymes capable of cometabolizing TCE and lesser chlorinated ethenes. The biofilm forming microorganisms were identified as Pseudomonas putida, a common soil bacterium. Experiments with a conventional, single-pass FBBR addressed TCE removal as effected by changes in TCE loading, phenol loading, and media type. In this study, TCE removal using quartz filter sand (25/30 mesh) and garnet filter sand (30/35 mesh) as the biofilm attachment media was measured. Removal ranged from 20 to 60% and was not affected by the media type. Also, removal was not affected by inlet TCE concentration over the range of 100 to 500 μg/L provided the phenol loading was decreased with increasing TCE loading. The FBBR was capable of complete phenol removal at an inlet concentration of 20 to 25 mg/L and an empty-bed contact time of 2.7 minutes. However, the empty-bed contact time was insufficient to sustain greater than 40 to 50% removal of TCE in a nutrient-amended groundwater.