| Summary: | 碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程所 === 96 === In an attempt to remove heavy metals from contaminated soils, chemical methods such as soil washing, solvent extraction and solidification have been generally employed. However, some disadvantages of physico-chemical treatment methods, for example, high cost, operational difficulty, high energy requirements and unsatisfactory efficiency of metal solubilization. The microbial method has been considered as an efficient and cost-effective alternative to physico-chemical treatment methods of treating pollutants in the environment because of low energy demand and less generation of waste by-products. Recently, bioleaching is one of the microbial methods employed for the treatment of metal-contaminated solids, e.g. sludges, sediments, and soils.
The bioleaching of heavy metal form contaminated soils is a complex process. Various physico-chemical and biological parameters such as nature of contaminated particles, sulfur concentration, temperature, oxygen, pH, oxidation-reduction potential (ORP), composition of the medium and bacterial strain affect the bioleaching process. The objectives of this study were to examine the effects of solid concentration and sulfur concentration on the performance of suspension bioleaching process and to investigate the feasibility of bioleaching process for metal-contaminated soils in a solid-bed reactor.
In the suspension bioleaching process, it was found that the rate of pH reduction increased with decreasing solid concentration and increasing sulfur concentration. The results reveal that the maximum removal efficiency of heavy metal was greater than 80%, except Pb. The optimum operation conditions for this suspension bioleaching process were 1-3 % for soil solid concentration and 0.1-0.3 % for sulfur concentration. In solid-bed bioleaching process, it was found that washing flowrate affected the rates of pH reduction, ORP increase, sulfate production and metal solubilization. Higher efficiency of metal solubilization was found when the medium with chlorides salts used in the solid-bed bioleaching process.
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