A strain, Brevibacillus agri DH-1, isolated from dry lands was used to remove m -dichlorobenzene. After 48 h culturing, the concentrations of m -dichlorobenzene decreased from 26–130 to 7.87–28.87 mg/L and dry cell weight for bacterial growth reached 52.43–75.05 mg/L. The growth and degradation kinetics were analyzed by the fitting of Haldane-Andrews model and pseudo first-order model. A degradation pathway was proposed according to major intermediates (phenol), chloride ion variation, ring-opening enzyme activity, and high mineralization (0.47 g Cl- /g m -dichlorobenzene , 0.65 g co2 /g m -dichlorobenzene , 0.15 g DCW /g m -dichlorobenzene ). In addition, the performance in a biotrickling filter (BTF) was evaluated through removal efficiency and pressure drop values with increasing inlet loading rate from 4.10 to 122.57 g/m 3 /h at three empty bed residence time points (30 s, 60 s, and 90 s). The results demonstrated that strain DH-1 possessed high removal efficiency and stable operation in a BTF.
This study aimed to investigate the performance of biotrickling filters (BTFs) in the microbial degradation of m -dichlorobenzene ( m -DCB) to construct an enhanced treatment of removing m -dichlorobenzene ( m -DCB) at different concentrations of rhamnolipids (RLs) and lanthanum (La 3+ ) or neodymium (Nd 3+ ) ions. We found a significantly enhanced removal of m -DCB when 110 mg/L of RLs and 0.2 mg/L La 3+ or 0.4 mg/L Nd 3+ ions were added. The addition of RLs and La 3+ or Nd 3+ ions increased the m -DCB average removal efficiency (101–110 days) by 19.7% and 22.7%, respectively, when the inlet m -DCB concentration was 800 mg/m 3 and the empty bed residence time (EBRT) was 60 s. Further, the mechanisms that strengthened the mass transfer were the decrease of contact angle, surface tension, and Henry’s constant after the addition of RLs and La 3+ or Nd 3+ ions in the nutrient solution; further, we noticed a significant increase in the dissolved oxygen levels. Improvements in the performance of BTFs were associated with enhanced microbial community and an increased abundance of functional genes. In conclusion, the addition of RLs and La 3+ or Nd 3+ ions can enhance the performance of BTFs in degrading m -DCB by improving mass transfer and microbial activity simultaneously.
Caiyun Zhang,Jin Qian,Jiajie Wang,Xinyan Zhang,Zhuqiu Sun,Bairen Yang
Herein, a microbial consortia directed domestication approach based on degradation pathways was proposed. This approach employs intermediates capable of promoting ring-opening and dechlorination of m -dichlorobenzene ( m -DCB), in conjunction with m -DCB itself, as substrates for stepwise domestication, with the aim of overcoming the limitation of microbial activity due to the high toxicity of m -DCB. The microbial community analysis for the directed domestication of consortia domesticated that microorganisms responsible for ring-opening and dechlorination were predominant. Meanwhile, the removal efficiency (RE) of m -DCB by directed domestication microbial consortia was significantly higher than the original microbial consortia and abiotic control. To further improve the ring-opening and dechlorination performance of m -DCB, electrical stimulation was introduced as a means of enhancing the directed domestication. Performance tests showed that the highest RE and elimination capacity (EC) of m -DCB were 95.23 % and 23.77 mg/m 3 /h, at an electrical stimulation of 0.7 V, respectively. The microbial community analyses revealed that electrical stimulation led to an increase in the relative abundance of key functional genera (e.g., Rhodanobacter and Pseudomonas ) and functional genes (e.g., catE and dhaA), thereby facilitating the oxidation ring-opening and reductive dechlorination of m -DCB. Metagenomic sequencing further revealed the potential and mechanisms for enhanced biodegradation of m -DCB by the coupled approach of electrical stimulation and directed domestication. The study demonstrates that the biodegradation potential of m -DCB can be enhanced through electrical stimulation based on directed domestication, providing a strategic pathway for microbial construction and improved m -DCB removal from exhaust gases.
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