The wastewater treatment follows following ends:
a)Making a healthy condition for people ‘s life
Urban sewage is always the source of a variety of microbes, some part of that makes up of disease-causing germs. Untreated wastewater entering the environment and natural water resources, either underground water or surface water, pollutes these sources with pathogenic microbes. In the event of human exposure to such sources, it will be a possible risk to spread disease among people.
 
b)Maintain a clean environment
Untreated wastewater entering the environment pollutes it which, in addition to direct threats to the human health, cause to other consequences such as ugly scenes, unpleasant odors and finally the accumulation of insects. Such insects are themselves the carrier of pathogenic microbes and contaminate the environment.
 
c)Wastewater recycling
Since the amount of mineral salts dissolved in water is far less than seawaters and wastewater is considered as the fresh ( but infected ) water, it is much cheaper to reuse wastewater instead of fresh water for irrigation, agriculture, etc. than desalination of seawater. It can save consumption of fresh water used in irrigation and farming especially in areas which encounters fresh water shortage. Besides saving freshwater, reusing treated wastewater for irritation can be a good source of food for plants and strengthen fields.
 
d)Natural fertilizer production
The sludge extracted by biological treatment of wastewater, contains a lot of chemicals such as nitrates, sulfates and phosphates which have the nutritional value for plant growth. To increase the absorptivity of sludge, it is mingled with plant fertilizers containing remaining tree leaves and stems or with organic fertilizers and then, it is used as a natural fertilizer.
 
e)Energy production
Methane forms nearly 70 percent of the gases produced in sludge digestion warehouses and its value as a fuel is approximately equal to the value of urban network gas, it is possible to supply the necessary heat for different units of the plant by burning Methane and warming boilers in treatment plants.