Operation and unit processes of water treatment

After the water has been used, both in households and in industry, it cannot be discarded in any way into the environment. It is important that this used water, also known as wastewater, goes through a treatment process. The last step of this whole process is the operation at the water treatment plant, but until it is time for this step many other things must have been done. During its circulation over the Earth's surface, water can be contaminated by humans and animals. This happens especially in cities, where sewage from homes, hospitals, and factories is discharged untreated into rivers, lakes, and seas.