| Chromium slag is a kind of the poisonous solid waste that is generated from chromate industry. Which increased at the speed of several dozen tons every year, and pile the stock was up to 6 million tons over the years. Harmfulness of the Cr(Ⅵ) in the chromium slag to the environment and human beings has become a urgent problem for our society to solve. Two serious pollute accident occurred by chromium slag in 2003 had attended much attention. The necessity of treating chromium slag had become the common knowledge. But, up to now, methods of dry-detoxification and wet-detoxification can still not solve the pollution problem of the chromium slag because of the high cost, low slag using amount and causing secondary pollution.For these years, Biological technology was used more and more in the environmental protection field and was paid wide attention to for its costless, high-effective, free secondly polluted characteristics. But, Microorganisms for treating Cr(Ⅵ)-containing wastewater were limited in acidic and neutral system at home and abroad, by which the concentration of treated was only about 200 mg/L The method, therefore, was difficult to be applied at industrial scale, especially, to alkaline wastewater containing Cr(Ⅵ) from chromium slag and the slag itself..For the physicochemical state of the slag and on the basis of many investigator's studied, novel idea of bio-detoxification chromium slag was firstly put forward. In this study, anthor isolated a strain with reducing high concentration Cr(Ⅵ) in alkaline solution from nature. And cultrure conditions, physiology characteristic , factors of affecting Cr(Ⅵ) reduction in alkline filter solution of chromium slag by bacteria and feasibility of detoxificating chromium slag by bacteria were studied. The innovated achievement obtained in this research were showed:The strain with reducing high concentration Cr(Ⅵ) in alkaline solution was isolated. Through identified, the strain is belonging to achromobacter sp., and named as Ch-1. which the suitable growth conditions are: pH 8.0-11.0, 25-35℃ and aerobic. The strain can useorganic-carbon and organic-nitrogen as nutrition sourceThe isolate can tolerate high salinity, reach 20g/L. The ability of effectively reducting Cr(VI) was up to 1.5g/L, especially, With being treated for 16 hours treatment by the isolate, the concentration of Cr(VI) in alkline filter solution of chromium slag was reduced from 1570 mg/L to 0.6 mg/L. Furthermore, the strain can also tolerate 4g/L Cr(VI). The ability of reduction and toleration Cr(VI) are beyond of level reported at home and broad, and the area of treating wasterwater containing Cr(VI) was enlarged to alkline condition.There are 32.8% Cr(OH)3 in the sediment produced by bacteria treating wasterwater containing Cr(VI). And Cr(VI) was hardly detected when ieaching-toxification of sediment was studied. The results showed the isolate can completely reduce Cr(VI) in alkline solution, and the sediment in process has great value of resource reclamation.Leaching experiment of chromium slag by strain showed bio-detoxification chromium slag and reclaiming chrome in the slag were feasible. On the basis of optimizing process conditions , we are looking forward to detoxifying completely chromium slag by microorganism. In the end, we can put forward to a feasible , simple, new method with rational economy for treating alkaline wastewater containing chromium and chromium slag. |
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