Composite Thiobacillus Applications And Study On Changes Of Dissovled Organic Matter In The Bioleaching Process

In this paper,with complementary strengths of A.ferrooxidans and A.thiooxidans,the experiment directly enriched composite thiobacillus from the activated sludge,and compared with single、mixed thiobacillus.The results showed that:compared to single and mixed thiobacillus,composite thiobacillus had obvious advantages on reducing bioleaching time and improving the efficiency of bioleaching heavy metals.Under the condition of30℃, the sludge concentration of8%,dosing substrate of Sulfur and Ferrous sulfate heptahydrate,the study used composite thiobacillus to the bioleaching shake flask experiments,and researched on the ratio of the best nutrition.The results showed that:the inceasing dosage Sulfur gradient did not result in significant impact.In contrast,the increasing of dosage of Ferrous sulfate heptahydrate had great advantages on increaseing in redox capacity and reducing leahing cycle. At the same time,periodic dosing ferrous sulfate heptahydrate to the bioleaching system needed.And finally the nutrient substrate dosage was4g/L of Sulfur+6g/L Ferrous suifate heptahydrate.In the reactor experimental,the excessive heavy metals Cu、Zn’s morphological changes were studied to determine the releasing ability of each form. Cu,Carbonate fraction> Residual fraction> Fe-Mn oxides> Organic bound matter,Zn, Fe-Mn oxides> Residual fraction> Carbonate fraction> Organic bound matter.Through analysising the sludge of three wastewater treatment plants in Taiyuan and utilizing composite thiobacillus to the bioleaching,the conclusion was that high levels of organic matter had slow leaching process,and pH and ORP changed significantly in the low organic content sludge.It was said that the higer organic matter content,the slower system process and the lower efficiency. At the same time,it was noted that the content of organic matter in the sludge was an important factor which limited the leaching process.Studied on the changes of DOM in different systems, the amount of DOM decreased with the leaching process without adding substrate,and pH and ORP were positively correlated with the amount of DOM.In adding substrate systems,the amount of organic matter increased with the different dosage of substrates,and pH and ORP were negatively correlated with DOM.Possible reasons for the increasing amount of DOM were that organic material which coated by sludge released with composite thiobacillus proliferated, pH reduction and resulting in the sustained growth of DOM.At the same time,it explored to enrich heterotrophic bacteria from the original sludge and applicated to the bioleaching experiments.Heterotrophic bacteria could reduce the content of soluble organic matter, disinhibite the composite ferrooxidans and improve the efficiency of bioleaching.