The type, content and existing form of heavy metals in wastewater vary with different manufacturers. Since heavy metals cannot be decomposed and destroyed, they can only transfer their location and change their physical and chemical forms.
For example, after chemical precipitation treatment, the heavy metals in the wastewater are transformed from dissolved ions into insoluble compounds and precipitated and transferred from the water to the sludge: After ion exchange treatment, the heavy metal ions in the wastewater are transferred to ions The exchange resin is transferred from the ion exchange resin to the regeneration waste liquid after regeneration. Therefore, the principles of heavy metal wastewater treatment are: first, the most fundamental thing is to reform the production process, avoid or use less toxic heavy metals, and secondly adopt reasonable process, scientific management and operation to reduce the amount of heavy metals and the amount of waste water lost. Minimize the amount of wastewater discharged outside.
Heavy metal wastewater should be treated on-site at the place where it is produced, and mixed with other wastewater to avoid complicating the treatment. Moreover, it should not be discharged directly into urban sewers without treatment, so as not to expand heavy metal pollution.
The treatment of heavy metal wastewater can generally be divided into two categories: First, the heavy metals in the dissolved state of the wastewater are converted into insoluble metal compounds or elements, which are removed from the wastewater by precipitation and floating. Applicable methods such as neutralization precipitation, Sulfide precipitation method, floating separation method, electrolytic precipitation (or floating) method, diaphragm electrolysis method, etc.: the second is to concentrate and separate heavy metals in wastewater without changing their chemical form. The applicable methods include reverse osmosis , Electrodialysis, evaporation and ion exchange, etc. These methods should be used alone or in combination according to the wastewater quality and water volume.