Influence of inoculating white-rot fungi on organic matter transformations and mobility of heavy metals in sewage sludge based composting

•Sewage sludge composted with straw, bran and Phanerochaete chrysosporium.•The transformation of organics were associated to bioavailability of heavy metals.•Stepwise linear and quadratic curve indicated relationship between indexes.•The white-rot fungi passivate heavy metals by provoking the formation of humus. White-rot fungi, Phanerochaete chrysosporium was inoculated to sewage sludge composting. Its effect on transformation of organic matter and mobility of heavy metals (Zn, Pb, Cu, and Ni) was studied. Detailed sampling was performed to measure C contents in humic extracts (HE), humic acids (HAs), fulvic acids (FAs), humin and distribution of heavy metals, including acid exchangeable fraction (AE), reducible fraction (RED), oxidization fraction (OXI) and residual fraction (RES). In our study, it is evident that the HE, HAs increased obviously and hydrolyzed humin decreased markedly in inoculation. The stabilization rate ((OXI+RES)/(AE+RED)) of Zn, Pb, Cu, and Ni was 20.31%, 7%, 14.3% and 19.79% higher in inoculating reactor. Additionally, the changes of heavy metals fractions could be explained by the organic variables. The results of this study demonstrated that Phanerochaete chrysosporium passivates the heavy metal by provoking the formation of humus.