Semestral Project Wastewater Treatment in Greece


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Semestral Project

Wastewater Treatment in Greece

Makris Ioannis

Papagiannis Nikolaos

Papadopoulou Konstantina

Saxonis Konstantinos

Souladaki Maria

Czech Technical University in Prague,

Faculty of Mechanical Engineering

Department of Process Engineering

December 2004


Wastewater treatment in Greece 1

Historical overview 1

The history of plumbing 6

Major wastewater treatment plants in Greece 10

Thesaloniki 10

Heraklion 24

Psyttalia 35

Small municipal wastewater treatment plants in Greece 38
Ammonia and phosphorus removal in municipal wastewater treatment 48

plants with extended aeration

Application of cost criteria for selection of municipal wastewater 57

treatment systems

Changes in wastewater treatment in regions of Europe between 77

1980s and late 1990s

Treatment and reuse of sewage and sludge in the South Mediterranean 84

and Middle East countries.

Development assistance programme in the field of environment
Computation intelligence in wastewater treatment 85
Freshwater country profile Greece 91

Wastewater Treatment in Greece

EYDAP (Athens Water Supply and Sewerage Company) is responsible for the monitoring of natural stream pollution and industrial unit sewage effluent, within its jurisdiction area. Discharging sewage effluent into the wastewater network is only allowed if the quality characteristics of the effluent are within the ranges pre-defined by Legislation, in order to ensure the smooth operation of the Wastewater Network and the Wastewater Treatment Plants.

EYDAP is obligated to monitor the industrial users of the sewerage network adherence to the guidelines issued in the respective operational licenses they have received. At the present, there are no installations for the treatment of toxic or radioactive waste.

EYDAP operates two Wastewater Treatment Plants (WWTP). The Wastewater Treatment Plant of Metamorfosi (WWTP-M), responsible for the treatment of cesspool waste for Attica and sewage from the northern suburbs and the Wastewater Treatment Plant of Psittalia (WWTP-P), where only phase A (primary sewage treatment - sludge treatment) operates for the moment, with phase B (secondary treatment) almost completed.

Historical overview

Antiquity - Ottoman Period

In the ancient times there was no distinct sewerage system in the city of Athens. However, there are some reports of combined sewerage networks, wastewater and storm water run-off, dating 500 BC, when Iridanos river together with the Central Sewer, were servicing the areas of Ancient Agora, Areios Pagos, and Pnyx.

In these open sewerage systems, stagnant water were often sources of serious diseases, like cholera, plague, etc. This practice continued for almost 15 centuries and was gradually phased out with the predominance of absorbing septic tanks. When septic tanks reached their saturation point, either a second tank was added or the waste was collected again and discharged into open streams or the sea. Naturally this technique did little to allay dangers to public health or to reduce pollution (from the contamination of the underground aquifer).

1840 - 1930 Period

Circa 1840, for the first time in the modern history of Athens, the first combined flow sewer system for collection and conveyance of wastewater and storm water runoff was constructed, along Kolokotroni, Ermou, and Aghios Markos streets, as well as along Hadrian street towards the Thisssion area. These sewers flowed to an open torrent in the Kerameikos area. A little later (1860), the existing Stadiou Street torrent, from Syntagma Square to Omonoia Square was covered.

Between 1880-1890 the first primary sewer network was completed with smaller diameter branches, mainly for local use, on various streets in the center of the city of Athens, with high population density. Until 1883 the total constructed combined network length was about 11,5 km while the urban development at that time required 90 km of sewer lines. The actual needs, in other words, were eight times more. Athens had only 12% coverage.

During the years 1893-1920, the Greek State successively invited different groups of experts from France, Germany and the USA to help finalize a strategy for solving the sewerage problem of Athens. One of the main issues considered was whether to proceed with the construction of a combined sewerage system or a separate one. The various proposals produced by the above experts, adopting the one or the other solution, only resulted in having the problem unsolved for many years.

In the meanwhile, due to the influx of refugees caused by the 1922 Minor Asia disaster, the need for the construction of wastewater projects became imperative. As the water supply distribution networks expanded, the total quantity of potable water consumption increased, resulting in the subsequent increase of sewage produced and conveyed to the existing wastewater network.

In 1929, the Italian Professor of Hydraulics Gaudecio Fantoli, was invited by the Greek Government to study the sewerage problem of Athens. Prof. Fantoli proposed the construction of a combined system for the Western part of the city (Kifissos River Catchment Basin) and a separate system for the Eastern part of the City (Ilissos River Catchment Basin), with outlet works of the Main Interceptor Sewer at Akrokeramos, the tip of the Piraeus Peninsula.

1930 - 1950 Period

twin sewage system

   In 1931, the "Societe Anonyme for the Construction of Sewers in Athens and the Suburbs" was established, and despite the outbreak of World War II final designs for the construction of the basic sewerage network infrastructure, based on the preliminary studies by Fandoli, proceeded. One project was the design study for the Main Interceptor Sewer. Construction for this project began in 1954 and ended in 1959. Rainwater run-off and raw sewage collected by the combined system, was channeled to the Main Interceptor Sewer, running from the end of Patission Avenue to Akrokeramos, where the wastewater was finally discharge into the sea.  During this period (the 1950s and the beginning of 1960s), the Construction Company called HYDREX undertook a large portion of the design and construction of the local sewerage network.

1950 - 1980  Period

   In the 1950s, Athens population began to expand exponentially. It was evident that the existing networks were insufficient. At the same time it became necessary to revise existing design studies because new areas were continuously being added to the city, and each new area included within the city zones required adequate network infrastructure.

The severe need for the planning and construction of large wastewater projects resulted in the establishment of the Athens Sewerage Organization with the enactment of Law 1475/50. The Athens Sewerage Organization was the first company who undertook the design, construction, maintenance, operation and exploitation of the City’s wastewater and storm water drainage networks and managed successfully to set up strong and long-term foundations for the infrastructure of the Athens sewerage system 

Besides the operation and maintenance of the networks, the Athens Sewerage Organization established the fundamental standards for the short term and the long term planning of Athens future needs in wastewater and storm water drainage networks. Thus, in 1950, the preliminary design of the Athens Sewerage System began covering an area of 20.000 hectares.  This study was finalized in 1963. The preliminary design was used as a basis for development of the city’s networks during the 1960s’ and 1970s.  In 1977 the Ministry of Public Works commissioned the English firm, "Watson Company", to investigate an alternative proposal for the disposal of Athens liquid wastes.

In the 1980s, the Supplementary Main Interceptor Sewer, another large diameter main collector, was added to the existing sewerage network of Athens. This collector main was constructed by the Ministry of Environment, Urban Planning and Public Works and begins at a junction with the Main Interceptor Sewage Main, running through the Rendis Area, to discharge at the Akrokeramos location.

1980 - the Present

   In 1980, the responsibilities of Athens Sewerage Organization were transferred to a new company established for the handling of water supply and sewerage needs of the greater Athens area, called EYDAP. In the sewage sector, this new organization undertook the collection and discharge of urban wastewater and industrial waste, as well as the expansion of the existing sewerage networks in co-operation with the local Municipalities. Its duty was also to monitor the wastewater treatment procedure and the final disposal of treated effluent into the sea.

   In the years that followed, EYDAP expanded the primary sewerage collector network of Athens. The Municipalities, in turn, undertook the construction of the secondary sewer network, consisting of the smaller diameter pipes. The Municipalities also carried out the construction of the house connections to the local network (branches).

   The local secondary networks constructed by the Municipalities become part of the network owned and controlled by EYDAP, after an official asset transfer procedure.

Apart from constructing the primary network, EYDAP also deals with the thorough and efficient operation of the overall sewerage system, providing regular maintenance and immediate repair in cases of failures. EYDAP uses state-of-the-art monitoring and control systems, such as CCTV cameras for the monitoring of the sewage pipes.  With the use of advanced technology, EYDAP administers an aggressive preventive maintenance program that quickly traces areas of future damage and efficiently implements repairs.

The Wastewater Treatment Plants in Psyttalia and Metamorphosis constitute the final stage of the sewerage administration cycle in Athens. For decades, wastewater from the Athens Basin flowed to Akrokeramos, into Saronikos Gulf, without any treatment, thus polluting the Gulf and degrading its ecological balance.  Since 1994, the first phase in Psittalia Waste Water Treatment Center has been in operation. This means that Athens wastewater is initially collected, pretreated in large sedimentation tanks, where 40% of its polluting load is removed, and then it is conveyed, through three underwater pipelines, it is discharged into the Gulf of Saronikos.   

Another Wastewater Treatment Plant that has been operating since 1985 is the Metamorphosis Plant. Biological treatment wastewater is carried out at this facility, producing treated water 90-95% clean. This water after chlorination is discharged into the Kifissos River.   

The future planning for the sewerage sector encompasses the expansion of the water supply and sewerage networks in the northern suburbs of the City as well as expansion of the wastewater collectors in the southern areas of Attica. At the same time, for the environment protection of the coastal areas surrounding Attica, there is a master plan for the design and construction of new Wastewater Treatment Plants in different locations around Attica.  Already the construction of the Thriassion Pedion Wastewater Treatment Plant is in the tender phase.

In the following paragraphs we will shortly describe the history of water treatment and plumbing in general in some significant periods in greek history, Ancient Greece, the Macedonian and Minoan Empire.

The History of Plumbing – Greece

Until Philip of Macedon, father of Alexander the Great, rampaged through and destroyed the city in 432 B.C., Olynthus was a rich and flourishing metropolis, its people enjoying the luxury of the latest plumbing innovation - bathtubs. Excavations at Olynthus, in northern Greece, attest to tiled bathrooms and self-draining tubs. Several of the tubs have survived intact, shaped like present-day models though with one sloping end cut off. It is assumed that underground piping was made of since-deteriorated clay, as there was no lead piping found.

At this stage the early plumbers were still toying with a new metal -- lead. Indeed one tub uncovered in a tiled bathroom was repaired with lead clamps. (Archaeologists also found the skeletal remains of a woman near the tub, her jewelry evidently overlooked by Philip's soldiers as they plundered the town.)

From the shapes of the ancient tubs uncovered, the bathers apparently sat upright and rested their feet on a depression formed at the bottom. No doubt they were influenced by Hippocrates, the "father of medicine," who said that sitting in a tub was more healthy than reclining. Hippocrates also advocated cold water baths as a cure for almost any ills. The Greeks followed his advice very carefully.

The ancient Greeks set a high standard for themselves in promoting bodily and mental fitness. This was a concept reflected in their approach to exercise and cleanliness - having created the Olympic Games in 776 B.C. In any large city from the 7th Century B.C. onwards, one could find a gymnasium that featured hot and cold shower baths. As using hot water was considered effeminate, a man's bath typically was a quick douse of cold water over the head. On average, his "tub" typically was a 30" high, polished marble bowl. He probably stood beside it.

Private bathrooms, on the other hand, usually contained portable earthenware tubs for milady, whose taste no doubt demanded warm water for a more relaxing soak.

A Traveler's Treat: More ritual than hygienic, it was considered good manners for a host to offer his guest the services of his bathroom after a dusty and arduous journey. Ah, the joys of being treated by a winsome slave girl as she scraped his skin of perspiration and dirt with an iron utensil! Ah, the shock when she completed her work with a good dousing of cold water from an urn setting on a stand nearby! (As a rule, the Greeks much preferred sponges, oils, scrapers and rinses over the type of soap available at that time. Perhaps it was no wonder, for Grecian soap was manufactured from a combination of goat fat and ashes.)

Many houses in ancient Greece were equipped with closets or latrines that drained into a sewer beneath the street. They seemed to have been flushed by waste water. Some of the sewers were fitted with ventilating shafts.

The Greeks gave special protection to their water supplies to ward off severance by enemy attack. Aqueducts were generally laid underground, sometimes to a depth of 60 feet. Some were broad enough to accommodate two men waltzing abreast; the deeper ones connected with the surface through large wells.

The city of Athens required many aqueducts to bring water from the mountains. The people also depended upon deep wells which they laboriously had to dig through layers of rock to secure. The water supplies were directed to storage cisterns which in turn fed a multitude of street fountains, some of which are still in use today. Water porters carried a supply to homes of the well-to-do.

Heavenly Water: To the people of ancient Greece, everything in nature possessed religious significance. Water especially played a key role in the development of their culture. For instance, fountains and springs were held to have certain mystical and medicinal powers which were imbued in a pantheon of gods and goddesses that the people worshipped.

A free citizen would bathe at three significant times in his life: at birth, marriage and after death. To assure a long and happy life, for example, a bride would bathe in water taken from a fountain with nine pipes, called Calirrhoe. In Athens, the Calirrhoe fountain was also the principal source of water supply, for the most part conveyed by a conduit which brought the water in from the river Illisius.

The Greeks made strong headway in the development of water systems, especially cold water systems. But it would still remain for others to expand upon their achievements. In 201 B.C., Carthage would fall to the relentless Roman legions, and then Macedonia four years later. The ancient Greeks would lose their hold on themselves and soon their Near East conquests, including Assyria, Judea and Egypt.

The History of Plumbing - CRETE

Across the Mediterranean Sea from Mesopotamia, the ancient people of Crete and their Minoan sea-kings were leaving their mark on the early annals of history. Between 3000-1500 B.C., their early plumbers had laid elaborate systems of sewage disposal and drainage that resemble one of today. In fact, archaeologists have discovered underground channels that remained virtually unchanged for several centuries, except for extensions to include structures built over the original ones. Some vestiges of the pipes still carry off the heavy rains.

Unlike hot and dry Mesopotamia, Crete suffered from extremes of variable climate and geography. Some say those forces provided the catalyst to design systems for the inhabitants' comfort. Likewise, the sharp and jagged slopes of the country provided an early understanding into the principles of hydraulics.

The Palace: It was originally surmised that the Minoan civilization had been an offshoot of the ancient civilization of Greece. When the fabled palace of King Minos at Knossos came to light, however, it proved there was a separate and earlier civilization, and King Minos was no ordinary monarch.

Knossos was the Minoan capital and home to a population of about 100,000, crowded into an area of about 22 acres. The multi-storied houses of sun-dried brick or dressed stone encircled on different levels the king's intricate, four-story palace. There was a public inn too, located near the palace. It featured a convivial foot-bath with grandiose dimensions of 65' x 4'6" x 18" deep. Surrounding slabs which formed seats for the foot-bathers jutted over the bath.

The palace of the king had been built up over the centuries, and already experienced one earthquake and ruin in its history. But by 1500 B.C., it had become four stories high, with endless winding passages, innumerable halls and corridors and rooms of state and storerooms. The entire floor space comprising 1,500 rooms spanned five acres. Its huge rectangular central court faced north and south.

The palace exemplifies a labyrinth construction; indeed, the word labyrs is derived from the Greek meaning "double ax". To the Greeks, the Place of Minos was truly a labyrinth, the house of the double ax, and the double ax design appears on its decoration.

The early plumbing engineers took advantage of the steep grade of the land to devise a drainage system with lavatories, sinks and manholes. Archaeologists have found pipe laid in depths from just below the surface in one area, to almost 11 feet deep in others.

They constructed a main sewer of masonry, which linked four large stone shafts emanating from the upper stories of the palace. Evidently the shafts acted as ventilators and chutes for household refuse. The shafts and conduit were formed by cement-lined limestone flags, but earthenware or burnt clay pipes were used in the remainder of the system. These were laid out under passages, not under the living rooms.

The drainage system consisted of terra cotta pipes, from 4"-6" in diameter. The rain water from the roofs and the courts and the overflows from the cisterns carried the water down into buried drains of pottery pipe. The pipes had perfect socket joints, so tapered that the narrow end of one pipe fixed tightly into the broad end of the next one. The tapering sections allowed a jetting action to prevent accumulation of sediment.

The queen's bathroom featured decorated walls covered with monochrome frescoes and decorated friezes, and plaster stands which held ewers and washing basins. At the heart was a five-foot long, tapered bathtub. The tub was painted terra cotta, and decorated in a bas relief of a watery motif of reeds. Evidently filled and emptied by hand, the tub had no outlet. The used water was discarded into a cavity in the floor and connected directly with the main drain. The drain discharged into the river Kairatos.

A terra cotta tub from the Palace of King Minos, circa 1700 B.C.

Not too far away was the world's earliest "flushing" water closet, screened off by gypsum partitions on either side. It was flushed by rain water or by water held in cisterns. Two conduits were built into the wall. There were several other closets found in the palace too.

The Minoan religion is elaborately bound up with the image of the bull. Periodic "roarings" far underground in the earthquake-prone region were attributed to the bellowing of the huge mythical bull, the Minotaur, as he thrashed about in the labyrinth caves below. Undoubtedly he portended the future. In 1400 B.C. the Minoan kingdom at Knossos was leveled, devastated and lost for centuries by a cataclysmic earthquake.

Major Wastewater Treatment Plants in Greece

  • Thessaloniki population since 1950 (in thousands)



























Study area description

The Thermaikos Gulf forms the north-west Aegean continental shelf and it is a typical deltaic platform. Four rivers (Axios, Loudias, Aliakmon, Pinios) constitute the major sources of material input into the marine system of the Thermaikos Gulf. The drainage basin covers an area of ~72,000 km2. Measurements carried out during the METRO-MED project showed a mean annual water discharge of the river system of about 207 m3 sec-1 or 18x106 m3 d-1 (Karamanos et al. 2000).

Thessaloniki Bay, the northern part of the Inner Thermaikos Gulf, receives domestic, agricultural and industrial effluents not only through the rivers but also in sewage from the city of Thessaloniki. Fishing activities and extensive aquaculture farming also occurs, along with water recreational activities. This northern part of the study area is characterized by eutrophic conditions due mostly to the intense nutrient supply through the sewage. The western coast of the Inner Thermaikos Gulf (depth: 0-50 m) is influenced by the three major river estuaries (Axios, Loudias, Aliakmon) and the prevailing eutrophic conditions are also related to this freshwater inflow, whereas the eastern coast is influenced by the oligotrophic Aegean Sea. However, depending to the seasonal variability, eutrophic conditions due to the rivers can be recorded in the whole Inner Gulf area.

Two different water masses have been detected seasonally: the freshwater from the rivers in the surface layer and the saline Aegean waters in greater depths. Dissolved oxygen and nutrient concentrations are dependent not only on the water masses circulation and stratification, but also on the freshwater discharge, especially during the rainy period, when there are high levels of dissolved nutrients and oxygen. On the other hand, low oxygen and high nutrient concentrations were recorded in Thessaloniki Bay, especially during summer, due to anthropogenic inputs combined with minimal water exchange.

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