Bioremediation System for Heavy Metal -Contaminated Soils Using Bacteria Associated with the Sulfur Cycle

本文介绍了一种重金属污染土壤的生物修复系统，该系统利用与硫循环相关的几种细菌人工构建硫循环（金属硫化物→硫酸盐→硫化氢→元素硫），并利用微生物硫转化对污染土壤中的重金属进行浸出和对浸出残渣进行后处理。在污染土壤的淋溶过程中，硫的氧化。发现布氏酸杆菌（Acidianus brierleyi）从土壤中所含的硫化物（黄铁矿和闪锌矿）中溶解重金属。在生物下游处理中，通过使用硫酸盐还原细菌金色素脱硫肠状菌（Desulfotomaculum auripigmentum）将浸出溶液中积累的硫酸盐离子生物还原为硫化氢。之后，使用化学自养细菌硫杆菌将生物源硫化氢氧化成元素硫，并将形成的元素硫作为沉淀物回收。进行批试验以获得速率数据并优化各个生物过程的各种工艺参数，例如金属硫化物的生物浸出和硫酸盐通过硫化氢生物转化为元素硫。速率数据表明，生物沥滤过程是速率决定步骤（最慢的步骤），在拟议的生物处理系统。在确定的最佳浸矿条件下，用A. Brierleyi，花了一周时间才从污染土壤中的闪锌矿和黄铁矿中实现重金属的高提取（大于80%的浸出）。

In this report we describes a bioremediation system of soils contaminated with heavy metals, in which the sulfur cycle (metal sulfide → sulfate → hydrogen sulfide → elemental sulfur) is artificially constructed using several bacteria associated with the sulfur cycle, and the microbial sulfur transformations are utilized for the leaching of heavy metals from contaminated soils and for the post-treatments of the bioleaching residue. In the leaching of contaminated soils, the sulfur-oxidizing. bacterium Acidianus brierleyi was found to solubilize heavy metals from sulfides (pyrite and sphalerite) contained in soils. In the biological downstream processing, sulfate ions accumulated in the leach solution were biologically reduced to hydrogen sulfide through the use of the sulfate-reducing bacterium Desulfotomaculum auripigmentum. After that, the biogenic hydrogen sulfide was oxidized to elemenal sulfur using the chemoautotrophic bacterium Thiobacillus denitrificans, and the formed elemental sulfur was recovered as a precipitate. Batch tests were performed to obtain rate data and optimize various process parameters for the individual bioprocesses such as the bioleaching of metal sulfides and the bioconversion of sulfate to elemental sulfur via hydrogen sulfide. The rate data indicated that the bioleaching process was the rate-determining step (the slowest step) in the proposed biotreatment system. Under the conditions determined as optimum for the bioleaching with A. brierleyi, it took a week to achieve high extractions (greater than 80 % leaching) of heavy metals from sphalerite and pyrite in contaminated soils.