铬渣堆场重污染土壤微生物修复及Cr（Ⅵ）污染阻隔研究

【作者】 王兵；

【导师】 杨志辉；

【作者基本信息】 中南大学 ， 环境工程， 2010， 硕士

【摘要】 我国是一个铬盐生产大国,排放的铬渣对堆存场地和周围环境造成严重的污染。目前传统的土壤铬污染修复方法均存在处理成本高、易引起二次污染等原因,不能彻底解决铬渣污染土壤的污染问题。近年来,生物法修复法因其投资小、运行费用低、无二次污染等优点,引起广泛关注并获得了较快的发展。论文在课题组前期从铬渣堆场分离筛选出一株高效六价铬还原菌(Pannonibacter phragmitetus BB)的基础上,提出了铬渣污染土壤“破碎-筑堆-喷淋修复-回收铬”的新工艺；利用柱浸实验优化铬渣污染土壤微生物修复的各工艺参数；在此基础上进行了铬渣污染土壤修复的半工业化试验。并通过吸附实验初步确定铬污染阻隔技术,试图优化工艺用于铬渣污染土壤的原位修复。通过以上研究,获得如下研究成果：1)柱浸试验研究结果表明：营养物的加入,能刺激土著微生物修复土壤中水溶性Cr(Ⅵ)、交换态Cr(Ⅵ)和碳酸盐结合态Cr(Ⅵ)。粒径、喷淋强度、初始Cr(Ⅵ)浓度、修复工艺制度是土著微生物修复铬渣污染土壤过程中的重要工艺影响参数。当粒径为O-2cm,喷淋强度为29.6-59.2 ml/min时,能取得较好的细菌修复效果；土著微生物修复铬渣污染土壤所需的时间随初始Cr(Ⅵ)浓度的提高而增加；选择多次喷淋循环的修复效果要优于一次喷淋循环。柱浸实验的结果表明土著微生物修复铬渣污染土壤的可行性,并为中试试验提供了技术参数。2)中试试验优化了铬渣污染土壤堆的现场工艺条件,并运行了25吨／批规模的铬渣污染土壤细菌修复并选择性回收金属铬的示范工程,经过7-10天的微生物修复,土壤中Cr(Ⅵ)浸出毒性浓度由53.8 mg/L降低至0.41 mg/L (HJ/T299-2007),达到《铬渣污染治理环境技术规范》(HJ／T301-2007)中用作路基材料和混凝土骨料的标准限值。中试实验结果表明铬渣污染土壤微生物修复工业化的可行性,为铬渣污染土壤的修复开辟了新的途径。3)糖渣对Cr(Ⅲ)和Cr(Ⅵ)的吸附以及载Fe(Ⅱ)生物炭对Cr(Ⅵ)的吸附等温线与Langmuir等温吸附模型相拟合,而生物炭对Cr(Ⅲ)的吸附与Freundlich等温吸附模型相拟合。生物炭对Cr(Ⅲ)的最大吸附容量为21.57 mg/L,远高于糖渣吸附Cr(Ⅲ)的最大吸附容量(3.38mg／L)；载Fe(Ⅱ)生物炭对Cr(Ⅵ)的最大吸附量为22.92mg/L,远高于糖渣吸附Cr(Ⅵ)的最大吸附容量(0.57mg/L)。以载Fe(Ⅱ)生物炭作为阻隔材料用于铬渣污染土壤修复生化回灌修复,阻隔材料对铬的吸附容量最大可达到860mg/g。更多还原

【Abstract】 China is one of major country to produce chromate. The discharge of chromium(Cr)-containing salg resulted in serious pollution for the deposition site and ambient environment. Nowadays, the traditional treatment methods for the remediating the Cr-contaminated soils all have the disadvantages, such as high cost and secondary pollution. The biological remediation was paid more attentions in recent years due to the low investment and low function fees.In our previous researches, one indigenous microbial strain with high Cr(Ⅵ) reduction efficiency was isolated and screened from the soils contaminated by chromium containing slag. Based on the previous research, a novel technique "crashing-heaping-leaching-chromium recovery" for the remediation of soils contaminated by chromium-containing slag was proposed. The optimal parameters of technique was obtained using column leaching experiment. A pilot scale experiment was further carried out. Moreover, the obstrauct technology was preminary studied using absorption experiment and attended to further optimize technique for in-situ microbial remediation of chromium-contaminated soils. The results were obtained as follows:1) The result of the column experiment showed the addition of culture medium could stimulate the remediation of water soluble Cr(Ⅵ), exchangeable Cr(Ⅵ) and carbonate-bonded Cr(Ⅵ) in soils contaminated by chromium-containing slag. Particle size, spray intensity, initial Cr(Ⅵ) concentration and process systems were crucial parameters. The preferable result was obtained when the partical size was less than 20mm and the spray intensity was in the range of 29.6-59.2 ml/min. With the increasing of initial Cr(Ⅵ) concentration, the time for Cr(Ⅵ) remediation in soils increased. The cyclic spray revealed better efficiency of Cr(Ⅵ) remediation than a single spray cycle. The column experiment verified that it is feasible to remedate chromium contaminated soils using indigenous microorgainism. The result can provide the technique parameters for pilot experiment.2) A pilot experiment was further explored to optimize condition and a demonstration project of 25 tons/batch was run. The result revealed that the soils contaminated by chromium containing slag is completely remediated after 7-10 days run. The Cr(Ⅵ) leacing concentration declined from 53.8 mg/L of the initial concentration to 0.41 mg/L (HJ/T299-2007) at 10 days, which was lower than the Cr(Ⅵ) limited value of chromium-containing slag used as roadbed material and concrete according to the Environmental Protection Technical Specifications for Pollution Treatment of the Chromium Residue ((HJ/T301-2007). It was verified that the microbial remediation of the soils contaminated by chromium-containing slag was feasible in pilot experiment. The result provides an innovative way for the remediation of chromium contaminated soils.3) Langmuir adsorption isotherm can well describe the adsorption of Cr(Ⅵ) and Cr(Ⅲ) by sugarcane pulp residue and Cr(Ⅵ) by Fe(Ⅱ)-loaded biochar, while the adsorption of Cr(Ⅲ) by biochar fitted to Freundlich adsorption isotherm. The maximum adsorption capacity of Cr(Ⅲ) by biochar was 21.57mg/L, which was much higher than that of sugarcane pulp residue (3.38 mg/L); The maximum adsorption capacity of Cr(Ⅵ) by Fe(Ⅱ)-loaded biochar was 22.92mg/L, which was much higher than that of sugarcane pulp residue (0.57 mg/L). Therefore, Fe(Ⅱ)-loaded biochar was used as obstacle material of pollutants and applied to the micrpbial remediation technique of chromium contaminated soils. The revealed that the maximum adsorption capacity of Cr(Ⅵ) by Fe(Ⅱ)-loaded biochar can reach up to 860mg/g.更多还原