Metal processing industry wastewater is one of the factors that have the biggest role in the pollution of ecosystems because it contains toxic heavy metals such as arsenic, copper, chromium, cadmium, nickel, zinc, lead and mercury, which are very dangerous to be dissolved in water.

Galvanizing with zinc is a widely used method to increase the corrosion resistance of steel. Degreasing includes process steps such as pickling with hydrochloric acid to remove iron oxides such as rust or limescale, rinsing with water to chemically activate the surface and enriching the reaction with zinc, and dissolving. The wastewater resulting from this whole process is considered as special hazardous wastewater due to its high metal and acid concentration. The most commonly used method in this type of wastewater is heavy metal precipitation. By going beyond traditional methods, alternative ways are sought for water and raw material recovery. HCl and zinc recovery are costly techniques. The viability of the recovery investment depends on the amount of potentially recoverable zinc.