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 Fe 3+ 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 Fe 3+ could enhance the biodegradation of o -DCB, which may be due to promotion on bacterial growth, o -DCB solubilization , C 12 O enzyme activity , and polysaccharide (PS) and protein (PN) in EPS. Fourier transform infrared (FTIR) spectra indicated that the addition of RL with Fe 3+ 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 Fe 3+ , and from 100% to 80.3% for BTF2, which was fed with RL and Fe 3+ , 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 Fe 3+ .
Na Li,Jie Cheng,Xin Xing,Yonggang Sun,Zhengping Hao
Clarifying the oxidative products and their formation mechanisms in the catalytic oxidation of chlorinated volatile organic compounds is important to provide detailed understanding of the degradation of pollutants with the simultaneous removal of secondary pollutants. In this study, catalytic oxidation of 1,2-dichlorobenzene (1,2-DCB) using commonly commercial catalysts (Pd/γ-Al 2 O 3 , Pd/ZSM-5, and Pd/SiO 2 ) was investigated. During the oxidation processes, substantial amounts of polychlorinated organic by-products, such as trichlorobenzene, tetrachlorobenzene and pentachlorobenzene, were detected. The reaction temperature and types of supports played a vital role in the formation of chlorinated organic by-products. With an increase of the reaction temperature, the degree of chlorination of the organic by-products increased gradually, and the concentration of polychlorinated organic by-products was increased sharply at low temperatures and then decreased when the reaction temperature was above 450 °C. Meanwhile, the amounts of polychlorinated organic by-products increased with an increasing silicate-to-aluminium ratio. Furthermore, based on the distribution of chlorinated organic by-products and characterization results of pyridine from FTIR, XPS, UV–vis-DRs, and in situ FTIR, the formation mechanisms of the polychlorinated organic compounds were proposed.
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