铬渣的细菌解毒工艺研究

【作者】 李雄；

【导师】 柴立元；

【作者基本信息】 中南大学 ， 环境工程， 2006， 硕士

【摘要】 随着国民经济的快速增长，我国铬化合物生产有了较快的发展，目前我国铬化合物的生产和消费量已成为世界上第一，但其生产过程中所排放的有毒废渣——铬渣毒性很大，严重污染生态环境和危害人体健康。全国每年新排放铬渣约60万t，历年累计堆存量近600万t，经过解毒处理或综合利用的不足17％。严重污染土壤1250多万t。而目前的主要治理方法均存在处理成本高、吃渣量小、引起二次污染等原因，不能彻底解决铬渣污染问题。近年来，生物法治理含铬废水因其投资小、运行费用低、无二次污染等优点，引起广泛注意并获得了较快的发展。但生物法治理铬渣的报道还甚为少见。针对此现状，课题组通过前期的研究，在铬渣堆埋场附近的淤泥中己获得一株耐高碱度、高Cr(Ⅵ)浓度的高效还原Cr(Ⅵ)的有效菌株Ch—1菌。该菌适应强碱性环境，能耐受pH为12的高碱度，其Cr(Ⅵ)耐受能力可达4 g／L以上，且能在高碱度高Cr(Ⅵ)浓度的情况下有效还原Cr(Ⅵ)。在此基础上，本文提出了铬渣生物解毒新思路：通过摇瓶实验初步确定铬渣细菌解毒的可行性，利用柱浸实验优化各工艺参数，最后进行了铬渣细菌解毒的半工业化试验。通过以上研究，获得如下研究成果：1．铬渣原渣中六价铬含量7.394 g／kg，其中水溶性六价铬含量为1.756g／kg，浸出毒性22.133ppm,均远超国家标准。铬渣细菌解毒能有效解决浸出液pH值、Cr(Ⅵ)浓度较高的问题。在解毒周期内由于细菌的还原作用，浸出液pH值能降低到9以下，浸出液Cr(Ⅵ)浓度解毒为0ppm。2．柱浸实验研究结果表明：温度、粒径、初始pH值均是细菌解毒铬渣过程重要的工艺影响因素，当温度为28℃，粒径为4～8mm，初始pH为10.0时，能取得较好的细菌解毒效果，渣中六价铬全量由最初的7.394 mg／kg降低到最终的0.585mg／kg,浸出率达到92.088％。3．中试实验研究结果证明了铬渣细菌解毒工业化的可行性，为铬渣的解毒开辟了新的途径。采用“铬渣造粒-细菌堆浸”工艺进行了铬渣堆的现场工艺条件优化试验，并运行了10吨／批规模的细菌解毒铬渣并选择性回收渣中金属铬的示范工程。经过7～10天的细菌解毒，铬渣解毒彻底，完全达到国家危险废物浸出毒性鉴别标准(GB5085-1996)。折合吨渣处理成本为200元。更多还原

【Abstract】 Along with the rapid growth of the national economy, chromium compound in our country is developed rapid. At present, the production and consumption of chromium compound in our country is the highest inthe world. But the poisonous waste residue -chromium-containingslag which is discharged during the production of chromium compound is toxic . It contaminated the environment seriously and harm to the human health . Every year, about 600,000 tons chromium-containing slag is discharged in our country. The accumulative total of the last is 6,000,000 ton, but the quality which is deal with detoxification and comprehensive utilization is less than 17%. There are 12,500,000 tons soil is contaminated severely. Now the main processing method of the chromium-containing slag are all have the problem of high cost, low disposal amount and secondary pollution.The biological method deal with the chromium-containing waste water is attentioned broadly and developed rapidly in recent years due to the low investment and low function fees. But the report of the biological treatment of chromium-containing slag is scarcely.In the face of the research state, our research group obtained effective bacteria named Ch-1 which is isolated from sludge nearby the chromium slag site through several years work. The bacteria Ch -1 is suited to alkaline condition and the tolerance ability can reach pH=12 , the Cr( VI) tolerance concentration is above 4 g/L. At the same time, the Cr (VI) can be detoxificated under the high pH and high Cr (VI) concentration.On the basis of research, the new way to chromium-containing slag detoxification by microbe is coming into being: feasibility study is conducted through bottle experiment; then optimize the technical condition by column experiment; finally technical grade experiment is conducted.On the basis of above research, the innovative conclusions were obtained as follows. 1. The Cr(VI) content in the chromium-containing slag is 7.394 g/kg , the water-solubility Cr(VI) content is 1.756 g/kg ,and the leaching toxicity is 22.133ppm which is all far beyond the national level. However, the problem of the leaching water can be solved out when the bio-detoxification is conducted. During the detoxification period, the pH of the leaching water can be reduced to 8-9 and the Cr(VI) concentration reduced to 0ppm.2. The result of the column experiment showed: temperature partical size and initial pH are important technical impact factor. The preferable result can be obtained when the temperature is 28℃, the partical size is in the scale of 4mm to 8mm and the initial pH value is 10.0. The Cr(VI) content is reduced from initial 7.394 mg/kg to 0.585mg/kg in the end,the leaching percent is 92.088%.3. The pilot plant research verified the bio-detoxification of the chromium-containing slag is feasible in industrialization. It is a innovate way to the detoxification of the chromium-containing slag. Condition optimization experiments is conducted by "granulating-bacterial heap leaching". The demonstration project of 10 tons/ batch is functioned and the result demonstrate that the chromium containing slag is detoxification completely after 7-10 bio-leaching and reached the leaching toxicity discriminate national standard of hazardous waste (GB5085-1996) .The treatment cost for every ton chromium containing slag is 200 yuan.更多还原