Water discharged from households and industrial units is heavily contaminated with organic and inorganic matter. If released in the natural water bodies in the same form, this water may cause severe damage to marine life and result in high levels of water pollution. For the same reason this wastewater needs to be treated before it is released in a natural water body. Effluent Water Treatment Plants are designed and employed to make the sewage water safe for discharge. In that way, the Wastewater Treatment Plants make a significant contribution in maintaining a clean and unpolluted ecosystem.
What Happens In A Wastewater Treatment Plant?
A typical Wastewater Treatment Plant involves three stages of treatment namely primary, secondary and tertiary. These stages are preceded by a preliminary treatment in which wastewater undergoes screening and grit removal to get fit for the main treatment processes.
Primary Treatment
In the process, wastewater is directed into large tanks where heavier organic matter settles down. The remaining water is pumped to a storage tank where majority of solid contaminants are separated and concentrated into thick slurry. The slurry is removed and the liquid portion passes to the next section for further treatment.
Secondary Treatment
Secondary treatment is aimed at the elimination of dissolved organic material. There are two methods used for secondary treatment namely, biological filtration and treating with activated sludge. The second one is the more common. In both the methods the sewage is added with bacteria along with controlled supply of oxygen. This serves as a natural purifier as the bacteria grow by feeding on the organic pollutants present in the wastewater.
Tertiary Treatment
When there is a requirement of very high quality effluents, then tertiary treatment becomes very important. The stage involves the use of sand or gravel filters, and even fine membranes for the removal of bacteria and viruses, at times.
The stages mentioned above make the wastewater completely safe to be discharged in water bodies. As the calls for environmental awareness intensify, the role of Effluent Water Treatment Plants becomes more important.
