Dichloromethane (DCM) is a recalcitrant volatile organic compound that exhibits biological toxicity and bioaccumulation. In this study, gaseous DCM was removed using an electroactive bacterial biofilter (EBB) with graphite rod as the anode and carbon felt as the cathode. The highest removal efficiency (97.09%) was achieved at a cathodic potential of −600 mV (vs. Ag/AgCl). The EBB had a maximum elimination capacity of 79.29 g m −3 h −1 when the inlet load was 96.48 g m −3 h −1 . There was no substrate inhibition phenomenon observed in the EBB, and the Michaelis–Menten model was used to describe the kinetics of the EBB. High-throughput sequencing indicated that electroactive genera such as Rhodanobacter sp., Sphingomonas sp., Pseudomonas sp., Chryseobacterium sp . , Pseudochrobactrum sp., and Mycobacterium sp. dominated the EBB. The microbial communities were stable and were slightly affected by the DCM inlet concentration. The results can be applied for the effective treatment of recalcitrant volatile organic compounds (VOCs).
Jiajie Wang,Yu Wu,Caiyun Zhang,Anqi Geng,Zhuqiu Sun,Jiawei Yang,Jinying Xi,Liping Wang,Bairen Yang
The microbial electrolysis cell coupled with the biotrickling filters (MEC-BTF) was developed for enhancing the biodegradation of gaseous m -dichlorobenzene ( m -DCB) through weak electrical stimulation. The maximum removal efficiency and elimination capacity in MEC-BTF were 1.48 and 1.65 times higher than those in open-circuit BTF (OC-BTF), respectively. Weak electrical stimulation had a positive impact on the characteristics of the biofilm. Additionally, microbial community analysis revealed that weak electrical stimulation increased the abundance of key functional genera ( e . g ., Rhodanobacter and Bacillus ) and genes ( e . g ., catA/E and E1.3.1.32), thereby accelerating reductive dechlorination and ring-opening of m -DCB. Macrogenomic sequencing further revealed that electron transfer pathway in MEC-BTF might be mediated through extracellular electroactive mediators and cytochromes.
Peng Wang,Chen Zhu,Yingji Gao,Zhonghua Cai,Ye ye,Yi Tao
Nitrate-driven sulfide oxidation has been proven to be a cost-effective approach for controlling sediment odor. However, injecting liquid nitrate (LN) directly into sediment carries ecological risks of nitrate escape and release of pollutants into overlying water. In this study, slow-release nitrate granules (GN) were prepared and applied in a continuous flow reactor to assess the differences between GN and LN in sediment remediation and control of this ecological risk. The results showed that the GN slowly released calcium nitrate, resulting in a decrease in acid volatile sulfide (AVS) from an initial 1328 ± 42.7 mg/kg to 490 ± 341 and 212 ± 32.8 mg/kg in the upper (U) and deeper (D) layers of the sediment, respectively. No significant decrease in AVS concentrations was observed in the LN treatments. Compared with LN-D and -U, the NH 4 + -N production and PO 4 3- -P release doses were reduced by 29.5% and 52.0% for GN-D and 41.2% and 37.8% for GN-U, respectively. Taxonomic analysis showed that sulfide-driven denitrifiers such as Thiobacillus , Rhodanobacter , Sulfurimonas , and Pseudomonas became dominant in the GN treatments, which were 2.8–6.7, 27.0–201.8, 1.5–3.0, and 3.0–496 times that of the LN treatments, respectively. The abundance of sulfur oxidation genes (e.g., sat and aprB ) and denitrifying genes (e.g., nirS and nosZ ) were also upregulated to higher levels by GN. Moreover, the genes (e.g., nrfA ) responsible for the isomerization of nitrate into ammonium were down-regulated by GN. The results showed that the slow-released calcium nitrate should be a promising way for in-situ remediation of sulfide-rich sediment.
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