The aim of this study was to evaluate the influence of rhamnolipid (RL) and ferric ions on the performance of a biotrickling filter (BTF) for the removal of gas-phase 1,2-dichlorobenzene (o-DCB). A comprehensive investigation of microbial growth, pollutant solubility, extracellular polymeric substances (EPS) and enzymatic activity in o-DCB degradation by an isolated strain Bacillus cereus DL-1 with/without RL and Fe3+ were carried out using batch microcosm experiments. In addition, o-DCB removal performance, biofilm morphology, and microbial community structures in two identical lab-scale biotrickling filters (named BTF1 and BTF2) inoculated with strain DL-1 were studied. The batch microcosm experiments demonstrated that 120 mg L-1 RL and 4 mg L-1 Fe3+ could enhance the biodegradation of o-DCB, which may be due to promotion on bacterial growth, o-DCB solubilization, C12O enzyme activity, and polysaccharide (PS) and protein (PN) in EPS. Fourier transform infrared (FTIR) spectra indicated that the addition of RL with Fe3+ had notable effects on the functional groups of PS and PN in EPS. The experimental results in BTFs indicate that the removal efficiency of o-DCB decreased from 100% to 56.4% for BTF1, which was not fed with RL and Fe3+, and from 100% to 80.3% for BTF2, which was fed with RL and Fe3+, when the inlet loading rate increased from 4.88 to 102 g m-3 h-1 at an empty bed residence time of 60 s. In addition, the microbial adhesive strength and the microbial community structure were different among both BTFs, highlighting the positive effects of RL and Fe3+.
Keywords: Biodegradation; Biotrickling filters; Fe(3+); Rhamnolipid; o-DCB.
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