Biodegradation Of M-xylene By Mixed Bacteria In The Presence Of Surfactant

M-xylene, as an important member of the single ring aromatic hydrocarbon organic compounds—BTEX, is difficult to dissolve and biodegrade. Irregular releases of m-xylene can pose threats to human health and ecological environment. In order to realize the highly stable and efficient degradation of m-xylene, mixed degrading bacteria were screened from activated sludge by progressive domestication process and further identified. Then the growth conditions of the bacteria were optimized. The solubilization and carbon-competitive effects of m-xylene by adding Tween 80 were also researched in this paper. Based on the above research, the enhancement purification performance of m-xylene in biotrickling filter in the presence of Tween 80 was further researched. The main research results were described below.Activated sludge, which from coking wastewater treatment plant of Xuzhou Huayu Gas Company, was selected as bacteria source. Mixed degrading bacteria were screened by the progressive domestication process of “Inducer(Toluene)-Intermediate(Catechol)- Target pollutants(M-xylene)”. And the bacteria were identified by high-throughput sequencing technology. The mainly bacteria included: Rhodanobacter sp., Mycobacterium sp., Agrobacterium sp., Bosea sp., Bacillus sp., Sphingomonas sp., Hyphomicrobiaceae and so on.The degradation characteristics of mixed degrading bacteria were further researched. The results showed that the optimal growth conditions for mixed bacteria and degradation of m-xylene were 30~35 ℃ and the vavle of pH from 6.5 to 7.0. Under optimal culture conditions, while the initial concentrations of m-xylene were 25 mg / L, 50 mg / L and 100 mg / L, m-xylene could be almost completely degraded after 16 hours, 48 hours, and 72 hours culturing, the degradation efficiency of m-xylene were 99.54%, 99.76% and 98.26%, respectively. The results demostrated that the adaptation period of degrading bacteria would be gradually extended with the increase of m-xylene concentration.Owing to the high volatility and low solubility of m-xylene, ionic surfactant Tween 80 was added to enhance solubilization effect. The results showed that the effective critical micelle concentration(CMCeff) of Tween 80 was 50 mg / L, and Tween 80 could be utilized by mixed degrading bacteria as a carbon source. There was no significant growth inhibition on mixed degrading bacteria as the concentration of Tween 80 within 1200 mg/L. However, during degradation process, when Tween 80 concentration was higher than 100mg/L, the mixed degrading bacteria would give priority to the use of Tween 80 as carbon source, thus inhibiting the degradation of m-xylene. At the same time, the degradation rate of m-xylene was the highest when 100mg/L of Tween 80 was added 12 hours in advance. The results indicated that the abovementioned method of adding Tween 80 was the most favorable to bacteria growth and m-xylene degradation.Based on the abovementined research, mixed degrading bacteria were inoculated into biofiltration filter(BTF) in order to further understand the enhancement effect of Tween 80 on m-xylene gas degradtion. The system of BTF1 with the addition of 100 mg / L Tween 80 and BTF2 without the addition of Tween 80 completed start-up after 16 days and 21 days respectively, and then both systems run continuously for 52 days. Results showed that BTF1 system were more efficient and stable for the removal of m-xylene compared with BTF2 system.