STC has a wide experience in the waste-water neutralization process. The plants can be a compact unit, modular for smaller flow rate or specifically designed in case of large volumes to be treated.
The simplest process uses a double-stage neutralization with milk of lime followed by flocculation, coagulation, lamella settling, sludge filtration.
The neutralization can be achieved by using several chemicals (lime, caustic soda, soda ash, etc.) depending on the local availability and may be accompanied by specific sections for the removal of Sulphates and heavy metals. When using lime, the oxy-carbonation process has demonstrated higher efficiency.
In case of a complete treatment, the process may foresee the use of PAC or Iron compounds, calcium alluminate and others depending on the characteristics of the water and the required purification level.
After the neutralization stage, it is possible to add additional steps to allow an almost zero-liquid discharge process with reuse of water. In battery recycling industry, this process is not necessary when the electrolyte is processed together with the paste in the desulphurization unit as, in this case, all the sulphuric acid contained in the electrolyte is converted into pure sodium or ammonium sulphate salts.