The Marathon Dam is a gravity dam on the Charadros River  located 8 km west of Marathon and 45 km northeast of Athens; it was constructed between 1926 and 1931 being until 1959 the sole supplier of water to Athens.

The Dam is 54 m tall, 285 m long, while its crest and base width are equal to 4.5 m and 28.0, respectively; it creates the lake (reservoir) Marathon that has a maximum capacity equal to 41 million m3. It is the only dam in the world covered by Pentelikon marble, the same marble used to construct the Parthenon.

The Marathon Dam is a major symbol of modernization in Greece signifying the victory of modern Athenians against drought. At the base of the dam, a replica of the Athenian Treasury temple at Delphi was constructed to commemorate the victory of Athenians at the battle of Marathon (490 BC).

For more information on the water supply system of Attica and its history click here and here.

Marathon dam: Life at the settlement

The Psyttalia Athens Wastewater Treatment Plant (WWTP) is the main wastewater treatment plant in the greater Athens area, receiving an average wastewater flow of approximately 730,000 m3/d; its capacity is 5.600.000 p.e., being one of the biggest WWTPs in Europe and worldwide.
The Psyttalia WWTP facilities include wastewater pretreatment at Akrokeramos (on the Attica mainland), comprising debris removal, screening, grit removal and odour control units, as well as a smaller pretreatment unit at Kynosoura, on Salamina Island.
Pretreated wastewater is piped to Psyttalia Island, by means of submerged pipes, to undergo primary treatment, producing primary sludge.
Primarily treated wastewater further undergoes advanced secondary biological treatment, using activated sludge processes, achieving both organic load removal and a considerable reduction of nitrogen load in the biological stage, which comprises bioreactors and final settling tanks, where biological sludge sedimentation clarifies the treated wastewater.
The Psyttalia WWTP final effluent is discharged to the Saronic Gulf through gradual deep disposal by means of a system of submerged outfall pipes. By then, wastewater treatment has achieved suspended solids and organic load reduction by about 93% and total nitrogen reduction by about 80% in comparison with influent loads.
Part of the effluent undergoes filtration (through sand-filters) and disinfection (by means of UV devices) to be reused as process water for the facilities on Psyttalia Island.
Primary sludge and surplus activated sludge constitute the organic residue of urban wastewater sludge treatment that can be beneficially utilized. At Psyttalia WWTP sludge treatment includes thickening, followed by digestion of the thickened sludge mixture, digested sludge dewatering in centrifugal decanters and eventually dewatered sludge thermal drying in rotating drums.
The sludge drying unit final product (120 – 150 t/d with approximately 92% dry matter) is a renewable source of energy and it is being utilized as secondary fuel in cement factories and power stations.

For more information on the sewerage and wastewater treatment of Athens click here.