Distribution of Heavy Metals and Their Corresponding Nanoparticles in Different Treatment Unit Processes in the Sewage Treatment Plant

Abstract

Total heavy metal concentration, heavy metal nanoparticle concentration, particle size, and the removal effect of different treatment unit processes on heavy metals and heavy metal nanoparticles were analyzed in this study. Inductively coupled plasma mass spectrometry (ICP-MS) and single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) were applied in nine treatment units performing continuous wastewater treatment processes in the Chengdu Shuangliu International Airport sewage treatment plant. Results showed that different treatment unit processes had different effects on the removal of different total heavy metal elements, with the effects on Fe being the most significant; Fe was mainly removed in the secondary sedimentation tank at a rate of 98.53%. The removal effects of different heavy metal nanoparticles varied in different treatment unit processes, with the effects of Ni, Pd, and Fe being the most significant. Heavy metal nanoparticles removal varied by treatment unit processes (aeration grit tank, secondary sedimentation tank, and high-efficiency sedimentation tank). The particle size distribution of heavy metal nanoparticles in different treatment unit processes was 23.28-147.83 nm, and different treatment unit processes did not have a significant impact on the particle size of each heavy metal nanoparticle. In addition, pH exhibited a significant negative correlation with Fe and Fe nanoparticles. Excluding Fe and Fe nanoparticles, other heavy metals and their nanoparticles were not significantly related; thus, different processing unit processes exhibited different removal mechanisms for heavy metals and their corresponding nanoparticles.