Combined reduction/precipitation, chemical oxidation and biological aerated filter processes for treatment of electroplating wastewater

In this work, a combination process was developed in lab-scale for the purpose of removing pollutants in electroplating wastewater with high cyanide and metal loadings. Most of heavy metal ions were removed by Fe2+ reduction (for Cr6+) and subsequent precipitation (for Cr3+, Cu2+, and Ni2+ ions), and cyanide was efficiently removed by the formation of insoluble complex compounds with Fe2+ ions. During the following chemical oxidation process, the residual cyanide was mainly transformed to low-toxic cyanate, and Cu2+ and Ni2+ ions were released due to degradation of organic compounds and then removed by precipitation.