A Biophysicochemical Model for NO Removal by the Chemical Absorption–Biological Reduction Integrated Process

The chemical absorption-biological reduction (CABR) integrated process is regarded as a promising technology for NO_<i>x</i> removal from flue gas. To advance the scale-up of the CABR process, a mathematic model based on mass transfer with reaction in the gas, liquid, and biofilm was developed to simulate and predict the NO_<i>x</i> removal by the CABR system in a biotrickling filter. The developed model was validated by the experimental results and subsequently was used to predict the system performance under different operating conditions, such as NO and O₂ concentration and gas and liquid flow rate. NO distribution in the gas phase along the biotrickling filter was also modeled and predicted. On the basis of the modeling results, the liquid flow rate and total iron concentration were optimized to achieve >90% NO removal efficiency. Furthermore, sensitivity analysis of the model revealed that the performance of the CABR process was controlled by the bioreduction activity of Fe­(III)­EDTA. This work will provide the guideline for the design and operation of the CABR process in the industrial application

Partial physiochemical properties for HY12 strain.

<p>Partial physiochemical properties for HY12 strain.</p

<i>o</i>-Xylene removal using one- and two-phase partitioning biotrickling filters: steady/transient-state performance and microbial community

<p>In this study, one- and two-phase partitioning biotrickling filters (1P-BTF and 2P-BTF, respectively) inoculated with a pre-acclimated mixed culture were examined for the removal of hydrophobic and refractory <i>o</i>-xylene. A small fraction of silicone oil (5% v/v) was added as a non-aqueous phase. Due to the presence of silicone oil, the 2P-BTF exhibited superior performance and stability for <i>o</i>-xylene biodegradation at steady and transient operations. Higher macro-kinetic constants for <i>o</i>-xylene removal by the Michaelis–Menten model were obtained for the 2P-BTF with a saturation constant of 0.396 g m⁻³ and a maximum elimination capacity of 105.7 g m⁻³ h⁻¹. The enhancement of removal performance for the 2P-BTF was supported by dominant specialized microorganisms with <i>o</i>-xylene biodegradability. The diversity of microbial community was influenced by the presence of silicone oil. This study demonstrated that a BTF with 5% of silicone oil could be applied for the treatment of hydrophobic and refractory volatile organic compounds. It also provided valuable information for better understanding the relationship between microbial community and removal performance using two-phase partitioning bioreactors.</p

Unique amino acid mutations in the capsid proteins encoded by HY12 isolates.

<p>The amino acid sequence of HY12 isolates were deduced from the nucleotide sequence, and was aligned with 12 known BEV strains in the GenBank. Alignment analysis was performed using each HY12-encoded structural protein as a template. Results were shown respectively for VP1 (A), VP2 (B), VP3 (C), and VP4 (D). The identical amino acids were marked with symbol “·”, and different amino acids to HY12 were presented as individual amino acid symbol. The unique mutation for HY12 was highlighted with red color. Deletion of amino acids were marked as “-”.</p

Cytopathic effect of HY12 in cell culture and EM observation.

<p>HY12 caused a typical cytopathic effect in MDBK cells after 6–8 h inoculation. Cells became rounded with an increased refraction (B). 24∼48 h post infection, majority of the infected cells detached off the flask (C). The normal MDBK cells were used as negative controls (A). HY12 virus particles observed by electron microscopy to be about 22∼28 nm in diameter as indicated by arrow (D), the scale bar is 100 nm.</p

Two-Stage Chemical Absorption–Biological Reduction System for NO Removal: System Start-up and Optimal Operation Mode

A novel chemical absorption–biological reduction (CABR) integrated process, employing Fe­(II)­EDTA as an enhanced absorbent, is a promising technology for nitrogen oxides removal. In this work, we developed a new two-stage CABR system applying a mixed cultivation model of denitrifying bacteria and iron-reducing bacteria, which consists of a sieve-plate tower and a bioreduction tower to separate the absorption and reduction processes. The start-up period of the two-stage system was shortened to 19 days, while that of the one-stage CABR system was 46 days. In addition, the two-stage CABR system featured a better oxygen-resistance ability and a higher NO removal loading. In effort to optimize system operation, we compared different modes of system operation and found that (1) continuous addition of glucose was better than the batch-type addition and that (2) the NO removal efficiency could be maintained at >90% while the FeEDTA concentration was higher than 4 mmol/L; however, reducing the initial concentration of ferric iron complex could inhibit the loss rate of Na₂EDTA. Furthermore, the optimized operating mode parameters were 4 mmol/L initial Fe­(III)­EDTA, 0.6 mg/min Na₂EDTA, and 5 mg/min glucose with a 2 L/min gas flow rate under a 400 ppm of NO condition, while the NO removal efficiency was kept >90%; the corresponding operating cost in terms of glucose was 8.4 g of glucose/g of NO. The purpose of this work was to provide preliminary data to support future industrial application for NO_<i>x</i> removal, as well as sufficient technological insights on the process configuration and reactor operation of the two-stage CABR system

Phylogenetic analysis clustered HY12 strain to a new serotype/genotype within enterovirus E.

<p>Phylogenetic tree were generated by neighbor-joining methods by comparing the sequence regions of 5′-UTR, VP1, VP2, VP3, VP4, 3D, and the complete genome sequences for 15 enteroviruses. HY12 strain was placed to the cluster of enteroviruses E after phylogenetic analysis with the all nucleotide sequence regions except 5′-UTR (B–F). The HY12 strain was revealed as a new serotype/genotype (serotype/genotype 3) that only consists of D14/3/96 and HY12 strains in relation to serotype 1 (LC-R4, VG5-27,Vir 404/03) and serotype 2 (SL305, K2577,PS 42, PS 83) enterovirus strains (B–E). When nucleotide sequences for the non-structural proteins 3D and the complete genome sequence were employed, the HY12 were clustered to the same clade most close to SL305 and K2577 within enteroviruses E (F). However, HY12 strain was clustered to neither clade in enteroviruses E nor enterovirus F using the 5′-UTR sequence (A), suggesting an intraserotypic recombination during HY12 evolution. The position of HY12 was highlighted with a triangle.</p

Primers used for amplifying the complete genome sequence for HY12.

<p>S stands for sense; AS refers to antisense.</p

Primers used for differentiation of the potential agents.

<p>BPV: bovine parvovirus; FMDV: foot and mouth disease virus; BEV: bovine enterovirus; S: sense; AS: antisense.</p

Recombination revealed in the HY12 strain.

<p>Neighbor-joining trees of the structural proteins VP1-VP4, and the non-structural protein 3D of 15 enteroviruses were compared. When amino acid sequences for VP1, VP3, and VP4 were used to generate phylogenetic tree, similar patterns were observed as those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0097730#pone-0097730-g003" target="_blank">Fig 3B, 3D, and 3E</a>, indicating a interserotype recombination for the HY12 strain. Like the observation in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0097730#pone-0097730-g003" target="_blank">Fig 3A, F and G</a>, the HY12 was clustered closely to K2577, SL305, PS 42 and PS 83 strains, an indication of complex interserotypic and intraserotypic recombination in the evolution for HY12. The positions of HY12 were highlighted with a triangle.</p