Method for integrated treatment of electroplating wasterwater

A method for integrated treatment of electroplating wastewater, comprising:

• (1a) adjusting the electroplating wastewater with lime milk to pH of 10.5-12 under mechanical stirring, and adding an oxidant for an oxidation for 90-240 minutes by controlling an ORP value to precipitate pyrophosphate, phosphate, heavy metal ions and fluoride ions;
• (2a) adding a ferrous chloride solution into the electroplating wastewater treated in step (1a) under mechanical stirring and adjusting the electroplating wastewater with lime milk to pH of 10.5-12;
• wherein a synergistic effect of ferrous ions and calcium ions allows a complete precipitation of carboxyl-containing organic acid complexants;
• metal ions released from complexes react with hydroxyl ions to form hydroxide precipitate;
• and ferrous ions reduce hexavalent chromium to trivalent chromium to form chromium hydroxide precipitate;
• (3a) flocculating the precipitate in the electroplating wastewater treated in step (2a) with a flocculant into particles of large size to settle ;
• (4a) filtering the electroplating wastewater treated in step (3a) to remove the precipitate;
• (5a) adjusting and maintaining pH of the electroplating wastewater treated in step (4a) at 4.5-5.5 with dilute hydrochloric acid, and introducing a heavy metal capturing agent to precipitate heavy metal ions;
• (6a) adding activated carbon to the electroplating wastewater treated in step (5a) to absorb the resulting precipitate and the remaining heavy metal capturing agent so as to settle the precipitate;
• (7a) filtering the electroplating wastewater treated in step (6a) to remove the precipitate;
• and
• (8a) adjusting the electroplating wastewater treated in step (7a) to pH of 6-8 with a sodium hydroxide solution, and further processing the resulting electroplating wastewater using a biochemical method.