Application of Acidophilic Microorganism in the Metal Enrichment of Electroplating Sludge Use the Membrane Bioreactor

Abstract Background: Bioleaching is an important technology for treating electroplating sludge. Previous researches have focus on improving the leaching rate of metals in electroplating sludge by bioleaching. However, the concentration of heavy metals in the leachate after single leaching was lower, which is quite unfavorable for subsequent metal recovery. Additionally, membrane bioreactors (MBRs) have been widely used in the field of sewage treatment. Research on the application of bioleaching technology combined with MBRs to enrich metals in electroplating sludge has not been reported. Therefore, in this study, we first combined bioleaching technology and MBRs for metal enrichment in electroplating sludge to obtain the key technology of "acid production - electroplating sludge leaching - leachate regeneration -repeated electroplating sludge leaching - achievement of valuable metal enrichment".Results: In this research, through scaling up from the laboratory scale (shake flasks) to a factory-scale application (10 m³ membrane bioreactors), we mastered the key technology of acid production by acidophilic microorganism, and the acid solution can be repeatedly used for metal leaching. The results showed that the MBR maintained high-density cell growth (≈2.1×109/mL) and a stable sulfuric acid production rate (850 L/h) throughout the entire operational period. Under the above conditions, the maximum cycle number (10 times) for enrichment of the target metals in the electroplating sludge was obtained. Additionally, after the end of the cycle enrichment process, the concentrations of the target metals Ni+, Cu2+, and Zn2+ were 13.867 g/L, 18.118 g/L and 21.075 g/L, respectively, which were highly enriched.Conclusions: This study first solved the difficulties in the industrialization of bioleaching electroplating sludge through combining bioleaching technology and MBRs. Furthermore, this research can provide a demonstration project for the industrial application of MBR-bioleaching technology in electroplating sludge, with a view to applying this technology to the disposal of more types of hazardous waste.