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To enhance the biological degradation of volatile organic sulfur compounds, a microbial fuel cell (MFC) system with superior activity is developed for dimethyl disulfide (DMDS) degradation. The MFC achieves a removal efficiency near 100% within 6 h (initial concentration: 90 mg L

Desulfurization of organic sulfur in the fuel oil is essential to cut down the emission of sulfur dioxide, which is a major precursor of the acid rain and PM2.5. Currently, hydrodesulfurization is regarded as a state-of-art technology for the desulfurization of fuel oil. However, due to the stringent legislation of the fuel oil, the deep desulfurization technology is urgent to be developed. Adsorptive desulfurization method is promising due to the high selectivity and easy operation. The development of efficient adsorbent is important to advance this technology into industrial application. In this work, the five types of metal-organic frameworks (MOFs), including Cu-BTC, UMCM-150, MIL-101(Cr), UIO-66, and Cu-ABTC were synthesized for the adsorption of dibenzothiophene (DBT), a typical organic sulfur compound in the fuel oil. The experimental results revealed that the adsorption capacity of the five MOFs followed the order of Cu-ABTC, UMCM-150, Cu-BTC, MIL-101(Cr), and UIO-66, which adsorption capacities were 46.2, 34.2, 28.3, 26.3, and 22.0 mgS/g, respectively. The three types of Cu-based MOFs such as Cu-ABTC, UMCM-150, and Cu-BTC outperformed the Cr-based MOFs, MIL-101, and Zr-based MOFs, UIO-66. Since the surface area and pore volumes of the Cu-based MOFs were not the greatest among the tested five MOFs, the physical properties of the MOFs were not the only limited factor for the DBT adsorption. The π-complexation between DBT and linkers/metal in the MOFs was also important. Kinetic analysis showed that the DBT adsorption onto the five tested MOFs follows the pseudo-second-order kinetics, confirming that the chemical π-complexation was also contributed to the DBT adsorption. Furthermore, the operation parameters such as oil-adsorbent ratio, initial sulfur concentration and adsorption temperature for the DBT adsorption onto Cu-ABTC were optimized to be 100:1 g/g, 1000 mgS/L and 30 °C, respectively. This work can provide some insights into the development of efficient adsorbent for the organic sulfur adsorption.

A new strain, Pseudomonas sp. SJ-1, which was able to remove model odorous organics methanethiol (MT) has been isolated from the wastewater treatment plant and identified via 16S rRNA analysis. Initial MT concentration, temperature and pH played an important role in MT removal, and up to 100% of 260 mg L

Microbial electrolysis cell (MEC) with a biocathode could provide extra reaction driving force for gaseous chlorobenzene (CB) removal. In this work, external potentials (−0.1 to −0.7 V vs. SHE) were applied to regulate the biocathodic activity. Results showed −0.3 V was the optimum potential, while the removal efficiency, dechlorination efficiency and Coulombic efficiency achieved 94%, 65%, and 89%, respectively. Electrochemical stimulation enriched dechlorination microorganisms (Achromobacter and Gordonia), and significantly improved CB mineralization efficiency, which was twice higher than that without additional potential at 300 mg m−3 inlet concentration. Furthermore, electron transfer between biocathode and microorganisms was mainly through direct electron transfer (DET). A new integrated redox pathway for CB anaerobic degradation was proposed, in which CB was sequentially converted into 2-chlorophenol and 3-chlorocatechol, then dechlorinated to catechol, and finally mineralized into CO2. Overall, this work provided an insight into gaseous CB bioelectrochemical degradation through the potential regulation.

A microbial fuel cell (MFC) was used to evaluate its performance of the gaseous toluene removal in this work. The experimental results revealed that the MFC exhibited a removal efficiency as high as 88% with a toluene concentration of 300 mg m−3. Moreover, the closed-circuit MFC exhibited 1.4–3.5 times higher toluene removal efficiency compared with the open-circuit MFC, indicating that the interaction between the electrodes and microorganisms accelerates the electron transfer rate and thus enhances the microbial degradation rate. The microbial community analysis indicated that, in the toluene-powered MFC, the growth of the exoelectrogens such as Arcobacter and Geobacter were inhibited and the toluene degraders such as Chryseobacterium and Zoogloea prevailed in the MFC. For example, Arcobacter was almost disappeared and Geobacter was decreased by 40% as the fuel in the MFC switched from the acetate to toluene. Moreover, compared with Chryseobacterium, Zoogloea exhibited a high activity in the toluene removal as evidenced by the relationship between microbial community and its performance. Furthermore, the cyclic voltammetry analysis showed that an oxidation peak at −0.31 V vs Ag/AgCl and an apparent redox-area at −0.1 to +0.2 V vs Ag/AgCl was observed compared to the abiotic control, which are typical to the menaquinone and the outer membrane cytochromes (OMC) such as OmcZ, OmcS, a-type, and d-type. Therefore, a direct electron transfer pathway involving the menaquinone and OMC were proposed in the toluene-powered MFC. This work will provide some insight into development of gaseous VOCs-powered MFC and a novel technology for the VOCs removal.

A new isolate identified as Rhodococcus sp. ZJUT312 via taxonomic and 16S rRNA analysis was used for the efficient degradation of benzene, toluene, ethylbenzene, and xylene (BTEX). The strain ZJUT312 was able to degrade all the BTEX. Their average biodegradation rates followed the order o-xylene > ethylbenzene > toluene > benzene > m-xylene > p-xylene. The degradation rate of o-xylene reached as high as 0.117 mmol L−1 h−1, which was one to two orders of magnitude higher than that of all other reported o-xylene degrading bacteria. GC-MS analysis revealed that o-xylene degradation pathway mainly proceeded with 2-methylbenzylalcohol as an intermediate and CO2 as a final product. Mass balance analysis of the carbon element indicated that approximately 59% the o-xylene carbons were transferred to cell biomass and about 20% were mineralized into CO2. Furthermore, the o-xylene degradation kinetics fitted well with Haldane's model. The maximum specific degradation rate (0.953 h−1) was approximately 2.25 times higher than the reported data in the literature.

The volatile organic compounds (VOCs) impose severe environmental issues such as haze, photochemical smog, ozone depletion, and global warming. The degradation of VOCs in the gas phase is determined by the gas-liquid mass transfer and/or the microbial activity depending on the properties of the VOCs such as solubility, bioavailability, and toxicity. Bioelectrochemical systems (BESs), integrating microbial–electro-chemical removal mechanisms, have been intensively investigated for the organic compound removal in wastewater. In BESs, the interaction between the microbes and electrodes facilitates the electron transfer rate during the organic compound degradation and hence have a great potential to enhance the microbial activity. Currently, BESs are also under development for the refractory VOCs removal both in the liquid phase and gas phase. This review summarizes the current advances of the VOCs removal by BESs in terms of the mechanisms, pathway, removal efficiency, and coulombic efficiency. Furthermore, the challenges and future perspectives on the development of the efficient BESs for VOCs removal with a high coulombic efficiency are briefly discussed. It is believed that this review provides a new insight into the biological removal of VOCs.

Biotrickling filter could be used for the abatement of volatile inorganic compounds (VICs) and volatile organic compounds (VOCs) simultaneously, a multi-layer biotrickling filter (MLBTF) system was constructed to lift the contradiction of pH between VICs degrader and VOCs degrader. The pH levels of the bottom, middle, and top layers of the MLBTF were controlled at 4.5, 6.0, and 7.5, respectively. Biological removal of ternary mixed hydrogen sulfide (H2S), tetrahydrofuran (THF), and dichloromethane (DCM) was conducted for 120 days. The result indicated that H2S was mainly removed in the bottom layer, the THF and DCM were mainly removed in the middle layer. The removal efficiency of 200 mg/L H2S, 100 mg/L THF, and 100 mg/L DCM were all exceeded 95% with an empty bed residence time of 35 s. The maximum elimination capabilities of H2S, THF, and DCM were 52.5, 26.7, and 17.2 g/(m3·h) respectively. Results from polymerase chain reaction denaturing gradient gel electrophoresis revealed that the dominant microorganisms in the bottom layer of MLBTF were Methylosinus sp. and Acidithiobacillus sp. The Pseudomonas sp., Achromobacter sp., and Methylobacterium sp. remained dominant throughout the operation in the middle and top layers. These findings demonstrated that the proposed method can effectively enhance the performance of VICs and VOCs removal by controlling pH and microbial community in each layer of the MLBTF. It is believed that this work provides a new insight into the biological removal of VOCs by the MLBTF.

A newly isolated strain was identified as Ochrobactrum sp. by 16S rRNA sequence analysis and named as ZJUTCB-1. The strain was able to degrade mono-chlorobenzene (CB) as the sole carbon and energy source under aerobic conditions. This study is the first to report the degradation of CB by the genus Ochrobactrum. The degradation rate of CB reached 170.9 μmol L−1 h−1, which is at least 6 times higher than the previously reported data. The strain can efficiently degrade CB under a rang of temperatures (30–40 °C) and pH (6.0–7.0) with optimum at 40 °C and pH 7.0. Salt concentration higher than 0.05 mol L−1 remarkably reduced the biodegradation capability. Moreover, true oxic condition was not an essential element for biodegradation given that the CB degradation rate of 210.4 μmol L−1 h−1 was obtained under microaerobic condition. Based on the Haldane kinetic model, the maximum specific growth rate was 0.895 h−1, which is the highest in ever described CB-degrading strains. According to GC-MS analysis and enzymatic assay, CB was degraded via the meta-cleavage pathway by using 2,3-dioxygenase and 2-chlorophenol as the main intermediates, producing CO2 and Cl− as the final products. The great performance of CB degradation by Ochrobactrum sp. ZJUTCB-1 provided an alternative for development of more effective and reliable biotreatment process.

Microbial fuel cell (MFC) is an innovative technology to stimulate the anaerobic degradation of hydrocarbons and recover their chemical energy. Typically, for the hydrocarbon oxidation, its performance depends upon the activity of the bioanode. In this work, four anodic potentials pertained to the redox of four different membrane proteins of the microbes, namely -0.52, -0.35, -0.16, and 0.17 V vs. Ag/AgCl, were applied to tune the bioanode. Experimental results revealed that, the more negative the bioanode potential was, the more obvious the enhancement became. The biofilm tuned at -0.35 V exhibited a highest toluene removal efficiency of 99% (800 mg/m3), and a maximum power density of 8.97 mW/m2 with the Coulomb efficiency of 2.06%. The microbial community analysis indicated that the dominant microbes in the bioanode were Comamonas sp., Petrimonas sp., Sedimentibacter sp., Ignavibacterium sp. and Parachlamydia sp., which was almost unaffected by the applied anodic potentials. The cyclic voltammetry analysis showed that the bioanode tuned at 0.17, -0.16 and -0.35 V exhibited three completely different electron transfer pathways. Furthermore, three metabolic pathways with o-cresol as an intermediate were proposed under the four applied anodic potentials. These results demonstrated that the anodic potential acclimation offers an effective enhancement method for the gaseous toluene removal combined with power generation.

Microbial fuel cells (MFCs) are regarded as promising alternatives to anaerobic benzene, toluene, ethylbenzene, and xylene (BTEX) mineralization due to the enhancement of microbial degradation rate caused by bioanodes. In this research, a dual-chambered MFC was employed to evaluate the removal efficiency and power generation of single TE(o-X) or of dual or ternary TE(o-X) mixtures. Individually, TE(o-X) was readily biodegradable with a removal efficiency of 94.8%, 86.3%, and 71.6%, respectively, but the presence of toluene and o-xylene exhibited an adverse influence on the degradation of other mixed components. The o-xylene has the greatest inhibitory effect on microbial activity, as evidenced by laser scanning confocal microscope images. Microbial community analysis revealed that exoelectrogens prevailed in the absence of the o-xylene. Shifting the feeding gas from toluene to another individual gas or mixture caused the quantities of the exoelectrogens to gradually decrease. Moreover, the o-xylene degrader of Alicycliphilus sp. were prevailed from ~17.7% to ~60.3% in presence of the o-xylene. In addition, the observation of the nanowire/pili using scanning electron microscope images and cyclic voltammetry analysis revealed that the electrons produced were transferred to the anode directly.