Water that arrives in WTPs is raw. It contains several solids (twigs, dirt, mud) that has drifted in its passage, as well as germs and microorganisms that are not visible to the naked eye.

The process for the water treatment is the following:

1st stage: addition of chlorine (disinfection)
With the prechlorination process the germs in the water are killed and the subsequent treatment becomes more easy.

2nd stage: addition of aluminum sulfate (flocculation)
The addition of aluminum sulfate helps solid particles present in the water to unite among themselves and settle down. The whole process is called flocculation.

3rd stage: Sedimentation
After the flocculation, accumulated solids settle to the bottom of the sedimentation tank. In this way the water is cleaned at a rate of 80%.

4th stage: Filtration
The very light particles and the colloids (20%) which cannot settle are withheld on special sand filters from which water comes out clean enough to be potable.

5th stage: Postchlorination
If prechlorination is not satisfactory, additional chlorine is added in the water at its exit from the closed water reservoirs and before it enters the water distribution network.

 

The Galatsi WTP began operating in December 1931 with two modern methods : water disinfection with chlorine and using aluminum sulfate to accelerate water clarification. The facility production capacity was expanded with the construction of two plant extensions in 1952 and 1964. The Galatsi WTP supplies the portion of the distribution network that serves the city center of Athens and Piraeus with a daily total water treatment capacity of 540, 000 m³.

 

The 1968 decision to supply Athens with water from Mornos River in combination with the densely populated areas of Athens with its many hills at high altitudes meant that the new Water Treatment Plant had to be built in Acharnes. The installation supplied the water network for the first time in 1978 and it’s located at an altitude of 232 m. Its daily total water treatment capacity is 850.000 m³. The Aharnon WTP supplies the 60 % of Attica Region and primarily the areas with higher altitudes .

 

Polydendri WTP has been in operation since 1986. The plant’s total daily water treatment capacity is 200,000 m³, reaching 300, 000 m³ during peak periods. It has an altitude of approximately 237 m. It supplies with water the eastern and northern suburbs of Athens.

 

Aspropyrgos Water Treatment Plant began operating in 1997. It is located directly below the Mornos aqueduct, and its total nominal daily water treatment capacity is 200.000 m³. It has an altitude of approximately 232m. It primarily supplies the portion of the distribution network that services the area of the Thriassio Pedio, Salamina and the western suburbs of Athens.