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The treatment of wastewater from the areas under EYDAP’s competence that currently have a sewerage network is carried out at the three Wastewater Treatment Plants on the island of Psyttaleia (WWTPPS), Metamorphosis (WWTPM) and Thriasio Pedio (WWTPTH). The Wastewater Treatment Plants are basic environment protection infrastructures. The efficiency of the operation of the WWTPs and the quality analyses of the treated wastewater quality related to the effluents of the WWTPs are derived from laboratory analyses accessible to all interested parties through the National Database for the Monitoring of the Operation of Wastewater Treatment Plants of the Ministry of Environment http://astikalimata.ypeka.gr/.




95% or more for certain pollutants is the efficiency of the installation in terms of removal of the total pollutant load

One of the largest WWTPs in Europe and internationally.  It has been operating since 1994. The opening of the WWTPs has been a milestone in improving the status of the marine ecosystem of the Saronic Gulf.

1.000.000m3/day (bold)wastewater treatment capacity  

694.575 m3/day (bold)average incoming wastewater flow

Municipal wastewater and pre-treated industrial wastewater are discharged into the WWTPs:

  •  The wider area of the Attica basin ( Metropolitan Capital Region), except for certain areas whose wastewater is treated at the Metamorphosis Wastewater Treatment Plant
  •  The island of Salamina


In the WWTPPS, biological treatment and drying of the produced dehydrated sludge is carried out.



From 2014 to 2021, through the installation of new equipment and operational adjustments, a 23% reduction in the energy consumption of WWTPPS was achieved, with a subsequent reduction in greenhouse gas emissions and carbon footprint.


The sludge treatment process produces biogas, which is also used for the production of electricity and thermal energy. The dried sludge produced is used as an alternative fuel in cement industries.




Above 99% is the removal rate of the pollutant load, in terms of organic load.

It is the oldest wastewater treatment plant, operating since 1986, and is a receiving and co-treatment facility  


  • urban wastewater, through a network of sewage collectors and
  • domestic sewage from areas of Attica lacking a sewerage network


44,000 m3/daywastewater treatment capacity (20,000 m3/day of urban wastewater and 24,000 m3/day of urban sewage).

24 000 m3/day average incoming wastewater flow


The WWTP co-treats urban wastewater and sewage, with chlorination of the treated effluent and treatment and dehydration of the sludge.



The dehydrated sludge is transported to the WWTP of Psyttaleia for drying. The use of the produced biogas as a fuel instead of fossil fuels contributes to the reduction of EYDAP's carbon footprint.


Above 95% is the removal rate of the pollutant load.

It is the most modern WWTP, operating since 2012 and is a comprehensive solution to the chronic problem of the residents of the Thriasio area.

21,000 m3/daywastewater treatment capacity

6,089.43 m3/dayaverage flow of incoming wastewater



The operation of the WWTPTH contributes to the restoration of the sensitive receiving area of the Gulf of Elefsina’s ecosystem balance.

Planning of the New WWTPs in Eastern Attica 


EYDAP has included in its operational plan the implementation of sewerage projects in Eastern Attica, amounting of 700 million euros, so as to provide solution to the area’s longstanding wastewater disposal, ensuring the protection of the environment, sustainable development and public health.

In the coming years, 1,250 km of new sewerage networks will be constructed, extending from Marathon to Pallini and Saronikos area.

EYDAP's objective for these significant sewerage projects is the area’s integrated wastewater management by reusing the treated effluents so to ensure maximum environmental benefit.

In this direction, the about to-be built Wastewater Treatment Plants (WWTP) of Rafina-Pikermi-Spata-Artemida and Marathonas counties are designed to operate with state of the art technology, ensuring the ability of reusing the treated effluents, in full harmonization with the current institutional reuse framework.

In addition, in the facilities of  WWTP of Rafina-Pikermi-Spata-Artemida, a Center of Environmental Awareness and Information will operate, as an integral part of it, covering an area of approximately 23 acres. Its design philosophy aims at upgrading the aesthetic and quality of the WWTP and - in combination with the provision of educational and cultural activities - highlighting it as a landmark in the area. Specifically, a variety of initiatives will be implemented, such as pilot application programs regarding the optimal utilization of the reused water, informative and educational environmental actions as well as environmental activities.



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