Investigating the Potential of Biobinder for Bottom Ash Solidification/Stabilization: Leaching Behaviour and pH Dependence

Abstract

Nowadays, a large amount of municipal solid waste incineration bottom ash (IBA) is produced from waste incineration plants; therefore, it is still a challenge for IBA management. To investigate the potential of microbially-induced carbonate precipitation (MICP) for IBA treatment, a harmless biobinder was prepared by using biosolutions with different bacterial concentrations. A series of tests were carried out on the sample of the IBA treated with different biosolutions, such as leaching behavior, sequential extraction, pH dependence, pore distribution, and microscopic morphology. The results showed that Zn, Cu, and Pb in the IBA after biotreatment were all below the standard limitation. In the sample with 108 cells/mL bacterial concentration, the leaching concentrations of Zn, Cu, Pb, and Cr were 0.39 mg/L, 0.12 mg/L, 0.025 mg/L, and 0.021 mg/L, respectively, and the average immobilization ratio reached 76.4%. The results of the characterization and microscopic morphology showed that biomineralization generated a large number of bioprecipitates and biogels, which formed a compact structure to reduce the pore size of samples, thus immobilizing the heavy metals. The bacteria could change the chemical speciation and bonds of the heavy metals by induction, which turned the heavy metals into stable compounds. Additionally, the lowest leaching concentration of Zn, Cu, Pb, and Cr appeared at pH of 8–10.5. This study analyzed the feasibility of bacterial concentration for IBA solidification/stabilization and provides a new biotechnology idea for IBA management.