Treatment methods are completely different depending on the toxic ingredients. In a common, continuous wastewater treatment system, hexavalent- chromium wastewater and cyanide wastewater may mix, allowing cyanides or chromium to be discharged without being treated. The two substances are also not treated if they enter acid wastewater or alkaline wastewater. They are detected in effluent from the plant. Even if wastewater treatment equipment is complete and is operated and controlled correctly, wastewater treatment may be imperfect due to imperfect water classification.
Many problems related to wastewater treatment occur due to imperfectly classified wastewater.
Plating wastewater can be classified into washing wastewater, which is thin and occupies most of the plating wastewater in volume, and highly concentrated wastewater, which is low in volume and produced intermittently as a plating bath or collection bath is refreshed. Continuous wastewater treatment equipment is designed and used based on the average wastewater volume and concentration. Therefore, if a good amount of highly concentrated wastewater enters equipment, the equipment is overloaded and wastewater may be discharged without being treated completely. For perfect wastewater treatment, it is necessary to control wastewater inflows to the equipment to classify wastewater correctly and to keep wastewater concentration constant.