A facility that receives wastewater (and sometimes runoff) from domestic and/or industrial sources, and by a combination of physical, chemical, and biological processes reduces (treats) the wastewater to less harmful byproducts; also known by the acronyms WWTP (Waste Water Treatment Plant), STP (sewage treatment plant), and POTW (publicly owned treatment works).


Such facilities are made up of buildings, tanks, electromechanical systems, devices and so on. Their size depends from mini compact systems capable to treat wastewater from a few inhabitants, to huge plants with a treatment capability of hundreds of thausands equivalent inhabitants.

Historical review

In many of the ancient cultures were known art of removing waste water by sewers. So in Mohenjorado, a city of the first flowering of Indian culture, which historically placed around 5000 BC found in excavations bricklayer who evacuated drains sewage from the houses. Babylon also found in sewage networks (Martz, 1970). Entries for drainage exist for the city Soumeriki Nippour (third millennium BC.). In the Minoan palace of Knossos (1950-1500 BC) were discovered sanitary facilities (bathrooms) and rainwater drainage and sewage. The network had visited wells for maintenance and came to the torrent Kairato, east of Knossos. The pipes were made of clay kanaleta open rectangular cross (height 12 cm) to cover the upper hand. To ensure the union, the kanaleta had trapezoidal layout (like Byzantine tiles but rectangular cross length about 60 cm, back 15/20 cm, see Markantonatos, 1986). The Acropolis in Athens found pieces of baked clay pipe. In ancient Rome, there were public toilets and sewage pipes to evacuate the sewage (Martz, 1970). Also there were pipes and rainwater, as the cloaca maxima (large sewer) that served the Roman market and operates until today (Markantonatos, 1986).

The art of sanitation neglected in the Middle Ages, why the full prevalence of religion in all areas of life, so the disappearance of science. After all, and the sanitary facilities were abandoned or deteriorated (eg toilets in erker over the moat Castles), while consumption of water for cleaning purposes was limited to a minimum. The result of this situation were the epidemics that have plagued medieval societies.

This situation continued in recent times, and even more exacerbated due to population concentration in cities. The development of the building that led to the construction of multi-storey buildings, was not accompanied by similar advances in hygiene habits and sanitation (eg palace of Versailles is not built sewers). So in many cities sewage left to run free in yards and streets. The construction of modern sewage systems, pipelines, with few exceptions, essentially begins in mid-19th century For example in Germany in the first sewage network was designed and constructed in 1842 in Hamburg (Martz 1970) after a fire which destroyed the city center. The design was made by the pioneering Anglo mechanical W. Lindley, on the basis of ideas and principles used in England today and the importance of drainage systems was recognized in 1855, after a cholera epidemic that began in 1848, and triggered the construction of adequate sewerage systems in London (Clare etc 1977) . It is interesting that the construction of sewerage works in recent times started to remove rainwater, in spite of domestic sewage. Indeed in several cities that had network rainwater for a long time prohibited the discharge of effluent in the ducts (Steel, 1960).

In Greece there was a general delay in the construction of modern sewage systems. In Athens, which has in the center of one of the oldest Greek pantorroiko drainage, and in the most modern separate system, a very high percentage of homes served yet with tanks. The construction of the pantorroikou system beginning in 1858, although individual drains were constructed earlier

At the beginning of the projects were no systematic studies. The first study, the French engineer Claye, which dates back to 1883, followed by disastrous floods. Systemic, however, studies began to be established by the beginning of our century, and have not yet been completed. The separation system was constructed in 1933. Once completed in 1959 the Central drain for (CCA) which resulted in Akrokeramo Keratsini, leading sewage into the sea without any treatment and surface (not underwater) disposal.

In other Greek cities until recently things were much worse For example, in Lefkada until the last decade a proportion of household waste water (without the dirty toilets discharged into surface ditches on the streets of the city. There are some exceptions. So the Naples Lassithi pantorroiko had an old network with vaulted lithoktistous pipelines for collectors, and rectangular lithoktistous secondary conductors (lagoumia). The network dates back to the Turks.

Today in Greece has generalized the use of modern sanitary facilities in almost all homes, urban and rural, and proceed with a relatively good pace - as long as the rates of funding - the construction or completion of a separate system of modern sanitation in all cities and towns, while in the smaller villages have widespread use tanks. In Athens has started in 1982 by a group of key projects for modernization of the sewage system, including the Additional Trunk Sewer (SKAA), the submarine-siphon Akrokeramou Psyttaleias, the submarine pipeline Estuary and the sewage treatment plants and the Psyttaleias of vothrolymaton Metamorphosis, while advancing and the extension of sewer networks.

After the construction of sanitation facilities in urban areas, the quality of life came to them but the pollution was moved outside the city, especially in waterways, lakes or seas where the disposal of wastewater. To address pollution problems developed technologies for cleaning and disposal of waste water, but require the construction of such facilities. So far each network for collecting and transporting waste water must be combined with effective compulsory treatment facilities and proper disposal iie them. In Greece the last decade have built such facilities in some cities and their use tends to generalize.

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