Investigation of Cu, Zn, Mn, Cr, Hg and As migration in domestic wastewater treatment plant

A series of urban wastewater in one WWTP of Xi´an, China was picked to investigate the mechanism of representative heavy metals removal by the wastewater treatment plant (WWTP). Under determine the six different heavy metals(Cu, Zn, Mn, Cr, Hg, As) and SS concentrations of the effluent of the fine screen, sand chamber, oxidation ditch and secondary sedimentation settler, it is wished to find the kinetics and partition aspects of the heavy metal transportation. The result is that heavy metal pollution was not very serious in such biological wastewater treatment plant, and the oxidation ditch was effective to remove most of Cu, Hg and As, with removal efficiency of 77.1%, 90.2% and 99.9%, respectively. But it has less effect on the Mn, Zn, and Cr, with removal efficiency of 40.0%, 33.3%, and 30.8%. Cu, Zn, Cr and As mostly go from the water phase to the solid phase. Hg was more stable than others. Cu, Hg and As were mostly transferred to the solid phase, and Zn, Mn and Cr were mostly in the water phase in the effluent.