基于生物淋滤的城市污泥重金属溶出及形态迁移

利用生物淋滤法处理城市污泥，以生物淋滤过程中pH、ORP（氧化还原电位）变化以及重金属（Zn、Cu、Cd）溶出率为指标，考察淋滤菌接种比例、初始pH、淋滤时间对生物淋滤的影响，并分析了生物淋滤前后，重金属形态变化以及重金属的生物有效性和迁移性。结果表明富集筛选的嗜酸性氧化亚铁硫杆菌（A. f）可有效溶出污泥中的重金属。生物淋滤最佳条件为：初始pH=4.00，淋滤菌接种比例30%，重金属Zn，Cu，Cd在第10天的整体处理效果最优，溶出率分别达到75.30%、50.40%和74.44%。BCR形态分析表明：原污泥中Zn，Cu，Cd主要以弱酸提取态、可还原态和氧化态存在，残渣态较少；生物淋滤之后，3种重金属弱酸提取态、可还原态和氧化态含量有不同程度降低，其中，可还原态含量降低最为显著，残渣态基本无变化，并且淋滤后污泥中重金属氧化态及残渣态所占比例较淋滤前高，污泥稳定性得到提升。生物淋滤可以通过减少污泥中重金属含量和改变重金属形态降低其生物有效性和迁移性。

Dissolution and transformation of heavy metals in sewage sludge based on bioleaching

Bioleaching was applied to treat municipal sludge, the pH, ORP (oxidation-reduction potential) and heavy metals (Zn, Cu, Cd) dissolution rate were analyzed to investigate the effects of leaching bacteria inoculation ratio, initial pH and leaching time on the bioleaching. Meanwhile, the transformation, bioavailability and migration of heavy metals were also analyzed before and after bioleaching. The results showed that the enriched Acidithiobacillus ferrooxidans (A. f) can effectively dissolve out heavy metals from sludge, the optimum conditions of bioleaching were as follows：the initial pH of 4.00, leaching bacteria inoculation ratio of 30% and leaching time of 10 days. The dissolution rate of Zn, Cu, Cd could reach 75.30%, 50.40% and 74.44%, respectively. Fractions of heavy metals analysis showed that Zn, Cu, and Cd existed mainly in acid extractable state, reducible state and oxidized state with less in residual state. After bioleaching, heavy metals of the acid extractable state, reducible state and oxidized state were decreased in different degrees, among them, heavy metals of the reducible state decreased significantly with constant content of the residual state. Besides, the proportion of the oxidation and residual state of heavy metals after leaching was higher than that before leaching, the stability of sludge was improved. Bioleaching could reduce the bioavailability and migration of heavy metals by decreasing the content and altering the form of heavy metals.