Effect Underlying Bone Meal Additives on the Passivation of Zinc, Chromium and Lead During Sewage Sludge Aerobic Composting

To explore heavy metal passivators with environmentally friendly, economical and effective properties is crucial for improving the security of sewage sludge for the land application. In this paper, the bone meal was selected as heavy metal passivator and added in different proportions for sewage sludge aerobic composting with a period of 40 d to investigate its passivation effect on zinc, chromium and lead, in which to reveal the mechanism. The results showed that the bone meal efficiently promoted the conversion of heavy metal speciation from effective form to stable form. When the proportion of bone meal was added at 10%, the proportion of zinc in residual form, chromium in residual form and lead in residual form respectively increased from 4.71 to 13.65%, 57.53–68.77% and 45.49–88.91%, the best heavy metal passivation was obtained for the composting. The residual samples were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffractometer and Fourier transform infrared spectroscopy, it was found that zinc, chromium and lead in sewage sludge was transformed into phosphate minerals with high stability. In addition, the redundancy analysis between physicochemical parameters and heavy metal speciation indicated that phosphorus minerals formation in composting was positively related to the available phosphorus content, and the main influencing factor affecting the speciation conversion of heavy metals was organic matter. Graphical Abstract