Biological method: Biological treatment is a new technology to treat electroplating wastewater. Some microbial metabolites can change the valence state of heavy metal ions in wastewater. At the same time, the microbial flora itself has strong biological flocculation and electrostatic adsorption, which can adsorb metal ions, make heavy metals enter the mud cake after solid-liquid separation, and thus make the wastewater discharge or reuse up to the standard.
Physical-chemical method: Physical-chemical method is to remove impurities contained in electroplating wastewater by ion exchange, membrane separation or adsorbent, which is widely used in industry and is usually used in combination with other methods.
Electrochemical method: electrolytic method is to treat or recover heavy metals by electrolysis, which is generally used for electroplating wastewater with high or single noble metal content. Electrolytic treatment of Cr(VI) uses iron as electrode. Ferrous ions produced by continuous dissolution of iron anode can reduce Cr (VI) to Cr (III) under acidic conditions, and Cr(VI) can be directly reduced to Cr (III) on cathode. Because hydrogen ions are consumed in the electrolysis process, the remaining hydroxyl ions in the water change the solution from acidic to alkaline, and generate hydroxide precipitation of chromium and iron, thus removing chromium. Electrolytic method can remove a variety of metal ions at the same time, which has the advantages of good purification effect, less sludge and small occupied area, but it consumes more electricity and steel, so it has been rarely used.