JINXiao,WUYun-sheng,YINZheng-yi,et al.Heavy Metal Speciation Transformation and Ecological Risk Assessment in a Sludge Pyrolysis and Carbonization Project[J].China Water & Wastewater,2025,41(19):60-65.
Heavy Metal Speciation Transformation and Ecological Risk Assessment in a Sludge Pyrolysis and Carbonization Project
China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU]
volume:
第41卷
Number:
第19期
Page:
60-65
Column:
Date of publication:
2025-10-01
- Keywords:
- sludge pyrolysis and carbonization; heavy metal; speciation transformation; ecological risk assessment
- Abstract:
- This study analyzed the migration and transformation characteristics of eight heavy metals (Cd, Cr, Pb, Ni, Zn, Cu, As, and Hg) from the dewatered sludge and its derived carbonized products during the carbonization process of a municipal sludge pyrolysis and carbonization project, with a focus on both their total contents and chemical forms (weak acid extractable fraction F1, reducible fraction F2, oxidizable fraction F3, and residual fraction F4). The risk assessment code (RAC) method was employed to evaluate the ecological risks associated with these heavy metals. The total contents of eight heavy metals in dewatered sludge and sludge-based biochar (SBB) did not exceed the permissible limits specified by the current national standards. The pyrolysis and carbonization process resulted in varying degrees of enrichment of the heavy metals Cr, Pb, Ni, Zn, Cu, and As present in the sludge. This project employed medium-and high-temperature pyrolysis and carbonization (550-650 ℃), which facilitated the migration and transformation of heavy metals from high bioavailable fractions (F1 and F2) into relatively stable forms (F3 and F4). The decreasing order of the proportion of F3 and F4 forms of heavy metals in SBB was as follows: Cr, Pb, Ni, Cu, Zn, As/Cd, and Hg. Specifically, the proportions of F3 and F4 forms for Cr, Pb, Ni, and Cu exceeded 94%, while that of Zn increased significantly to 87.09%. The proportions of F3 and F4 forms for As and Cd were approximately 84%. The results of RAC indicated that the heavy metals Zn and Cd in dewatered sludge exhibited relatively high potential ecological risk levels, whereas the heavy metals present in SBB were predominantly categorized as low?risk or non?risk, with the exception of As and Hg. Therefore, the legal and compliant utilization of SBB is unlikely to pose significant environmental risks.
Last Update:
2025-10-01