|dc.description.abstract||This study was aimed to develop a novel fibrous-bed bioreactor (FBR) for removing toluene and trichloroethylene (TCE). The attached specificity of Pseudomonas putida F1 was investigated for the fibrous-bed when toluene was the carbon source. In addition, the FBR were operated at the biofiltration processes to evaluate the performance of removing toluene vapor. The FBR was also used as the co-metabolism bioreactor to study the co-metabolic degradation of TCE in contaminated solution.
Results indicated that the culture of cells with the supply of toluene vapor was an acceptable way to obtain high specific-growth rate because the carbon source was supplied continuously without toxic inhibition of high concentration toluene. Moreover, the study proposed that the attached site of biomass was primarily on the surface of cloth fiber. The biomass could attach into the fibrous-bed by means of the entrapment of cloth fiber, hydrogen bonds between the biomass and fibrous matrix, and generation of extracellular polymeric substance (EPS) matrix. Additionally, the fibrous-bed exhibited superior ability for cells attachment. The attached biomass approached 95000 g VSS/m3, and over 80% of biomass was the EPS.
The removal of toluene vapor was over 90% when FBR was operated at a trickling filter and the inlet loading was below 70 g/m3/h. However, when FBR was operated in the mode of submerged biofilter, the removal of toluene was greater than 90% when inlet loading was below 150 g/m3/h. Also, the operation of submerged biofilter avoided the problem of clogging.
Furthermore, the FBR was operated in the mode of the sequential batch. Attached biomass of fibrous-bed utilized toluene to induce toluene dioxygenase (TDO) and co-metabolized TCE. Because the FBR has attached great amount of biomass, the degradation of TCE followed the first order rate equation even the TCE concentrations was as high as between 2.4 mg/l and 47.6 mg/l. This rate constant also increase with the increase of dissolved oxygen in the range of 1.0 and 10 mg/l. Adding 0.005%(w/v) of hydrogen peroxide per 30 min was an efficient way to sustain 8-9 mg/l of dissolved oxygen in this reactor. The removal of TCE was 98% within 4 h of operation period. Moreover, the transformation capacity of TCE co-metabolism was 0.26 mg/mg by P. putida F1 biofilm. The inhibition of toxic metabolite was neglected within 18 h of operation period because the removal of TCE decreased somewhat from 98% to 93%. Also, the competitive inhibition of toluene degradation was limited on co-metabolism of TCE. The removal of TCE was still over 90% within 4 h of operation period when the initial toluene concentration was below 95 mg/l.||en_US|