Bioremediation Of Combined Pollution Of BDE-209/Pb By Bacillus Thuringiensis J-1 Enhanced By Biosurfactants

The combined pollution caused by persistent organics and heavy metals in the e-waste recycling area and its remediation have attracted extensive attention in recent years. This dissertation conducted research on the characteristics and mechanism of remediation of BDE-209/Pb combined pollution by Bacillus thuringiensis J-1 and biosurfactants. The main works included:investigating the effect and mechanism of temperature, pH and pollutants concentration on J-1 degradating BDE-209 and adsorbing Pb; exploring the degradation products of BDE-209; observing the effects of three kinds of biosurfactant on BDE-209 degradation by J-1 in a single BDE-209 pollution system; researching on the effects of three kinds of biosurfactant on BDE-209 degradation and Pb adsorption, screening out the suitable biosurfactant and determining its best concentration and studying its mechanism in BDE-209/Pb combined pollution system. The results were showed as follows:The optimal temperature and pH were 30℃and 7 respectively for the bioremediation of combined pollution of BDE-209/Pb by J-1.In the combined pollution, Pb significantly inhibited the degradation of BDE-209 by J-1, and the removal amount of Br- declined significantly with the increase of Pb concentration. Low concentration BDE-209(0.1-2 mg/L) could enhance the adsorption of Pb by J-1, in which 1 mg/L of BDE-209 showed the best effect and increased the adsorption efficiencies of Pb(1 mg/L) by 10.16%. High concentration BDE-209(5mg/L) inhibited Pb adsorption. The coordinate repression that BDE-209 and Pb acted on the degradation of BDE-209 and adsorption of Pb by J-1 was especially apparent at higher concentration.No low bromination biphenyl ethers were detected in the degradation of BDE-209. According to the analysis of the derivative products, the intermediate products of BDE-209 were probably hydroxylated or carboxylated.The solubilization of BDE-209 by the three surfactants was in the following order: rhamnolipid> sucrose fatty acid ester>tea saponin. The low concentration rhamnolipid (<100 mg/L), sucrose fatty acid ester (<50 mg/L) and tea saponin (<50 mg/L) could enhance the degradation of BDE-209 by J-1 due to their solubilization and synergic metabolism with J-1, and the highest efficiencies were increased by 23.18%,16.47% and 12.64%, respectively. The medium concentration sucrose fatty acid ester (200-700mg/L) and tea saponin (100-200mg/L) inhibited the degradation of BDE-209, owing to that they were preferentially utilized by J-1 or/and at this concentration BDE-209 being wrapped inside the surfactant micelle made it unaccessible to the microorganism. The high concentration surfactants reducing the degradation of BDE-209 were caused by their toxicity to J-1.Three kinds of biosurfactant, ranged from 20 to 100 mg/L, could enhance the degradation of BDE-209 and the adsorption of Pb by J-1. In combined pollution of BDE-209/Pb (lmg/L/lmg/L),50 mg/L of rhamnolipid increased the degradation efficiencies of BDE-209 and adsorption efficiencies of Pb by 38.37%,16.46% respectively. Compared with the sucrose fatty acid ester and the tea saponin, the rhamnolipid showed best application advantages because of its low consumption and good effect in bioremediation of the combined pollution.Rhamnolipid combined with Pb in the form of single molecule or micelle, to enhance adsorption of Pb and alleviate the toxicity of Pb to J-1, thus facilitating BDE-209 biodegradation. The high level rhamnolipid (>200mg/L) caused J-1 shrink and die.