Wastewater Treatment Plant
In
Psyttalia
Athens, Greece
Orfanoudaki Evangelia
825323/21V1
1
Contents
1.Introduction……………………………………………………………………..…..3
2. Ecology…………………………………………………………………………..…3

Primary, secondary, tertiary………………………………………………....4

Delay……………………………………………………………………………4
3.Historical Overview – Sewage……………………………………….…………..4

Antiquity – Ottoman Period…………………………………….…………….4

1840 – 1930……………………………………………………..……………..5

1930 – 1950……………………………………………………..……………..6

1950 – 1980……………………………………………………..……………..6

1980 – The present……………………………………………..……………..7
4. Situation in greater Athens…………………………………………..…………….8
5. Psyttalia Waste Water Treatment Plant……………………………..…………….9
6. Sewage Network Operation……………………………………………………..10

Operations of the Pumping Stations………………………………………..10

Collectors……………………………………………………………………....11

-
Primary Collector mains………………………………………………11
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Secondary Collector mains…………………………………………..12
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Tertiary Waste Water Sewage systems……………………………..12
Sewage – Treatment stages………………………………………………..13
7. Network Maintenance………………………………………………………………14

Pipe inspection camera………………………………………………………..14

Upgrades during the construction…………………………………………….14
8. Psyttalia Waste Water Treatment – Phase B……………………………………..16

Primary effluent and return activated sludge mixing chamber…………….16

Bioreactor process units……………………………………………………….17

Final settlements Tanks……………………………………………………….18

Return activate sludge pumping station……………………………………..18
9.Legislation for Waste in Greece…………………………………………………….19
10. Results……………………………………………………………………………….20
11.Plans for future……………………………………………………………………….21
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1.Introduction
In Greek mythology, the citizens of Athens chose Athena, the goddess of war, over Poseidon
as their protector – in revenge, he flooded the Attica Plain, which surrounds Athens. In view
of the fact that the sewage from Athens has up to now been discharged almost without
filtration into the bay off Piraeus, it was high time to try to bring the god of the sea back into
a friendly mood. Greece therefore began the construction of Europe’s largest sewage
treatment plant, which will be the third largest in the world. Psyttalia Wastewater Treatment
Plant is the name of this ambitious project on the island of the same name in the Saronic
Gulf, the bay before Athens and its harbour area of Piraeus. Sewage will be pumped through
pipelines 1.5 km long from the mainland to the rocky island of Psyttalia. The technical data
underline the gigantic scale of the plant: The biological treatment stage will comprise 12
fermentation tanks with a capacity of almost 300,000 m³ and a daily throughput of 1,000,000
m³. Seven turbo compressors with a rating of 2.5 megawatts and a capacity of 80,000 m³/h
will fill the biological reactors with clarified sludge.
2.Ecology
Urban wastewater is responsible for one of the biggest problems of the aquatic environment:
the eutrophication of water. As well as bacteria and certain types of waste products, urban
wastewater carries mainly nitrates and phosphates along with it. Once they have spread into
the rivers, then into the sea, these substances encourage the growth of aquatic vegetation,
sometimes uncontrolled growth in the case of the now notorious green, red or brown
" slicks " (depending on the colour of the prevailing algae). This vegetation consumes the
oxygen in the water, in which all life becomes difficult or even impossible.
In 1999, a MAP (Mediterranean Action Plan) report identified the Gulf of Salonika
(Thessaloníki) and the Saronic Gulf (Athens) as hot spots of pollution in the Mediterranean.
The solution is simple: the waste water from all the cities concerned must undergo optimum
treatment.
3

Primary, secondary, tertiary
For a city, optimum treatment means applying three types of purification to waste water.
Firstly, a primary treatment that removes suspended solid matter, usually through a physical
process. Next, a secondary treatment, usually biological, which tackles the dissolved
pollutants. Finally, a tertiary treatment that tackles specific substances such as pathogenic
microbes or nutritive elements such as nitrates and phosphates. This type of treatment
requires considerable infrastructure.

Delay
In principle, the cities of the European Union have been required to treat their waste water
since 1998. But this European regulation has been significantly delayed. Moreover, the
European Commission has taken systematic legal proceedings against Member States in
contravention of the regulation, and some cases, such as that of Athens, which we show in
this film, are handled by the European Court of Justice (? it is taken from a source word for word) .
The reason for this delayed implementation relates, above all, to a problem of funding.
The cost of the infrastructure for treating wastewater is high and requires towns to make
some difficult choices in terms of investments, public works, regional development and water
policy. This is because these works have raised issues relating to water pricing policy,
administrative reforms, the privatization of the water supply, local or regional taxes, etc. It
has taken time for these choices to take concrete shape. But there is real progress and all the
towns are now in the process of putting their project in place.
3.Historical Overview- Seweage

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.
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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 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
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 1983 (? 1893) 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
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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
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.
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
1950-1980
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
Up until 1980, water management in the greater area was carried out by the Greek Water
Company, and wastewater management was the responsibility of the so-called Wastewater
Organization of the Capital. In 1980, the government issued specific legislation for reforming
the water and sewage management sector in Greece.
7
According to the provisions of the above-mentioned legislation (law 1068), in the greater
area of Athens, the body responsible for water and sewage management is a legal entity of
private law but of public purpose, supervised by the Ministry for the Environment, called The
Athens Water Supply and Sewerage Company, abbreviated in Greek as 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 final stage of the sewerage administration cycle in Athens is constituted by the
Wastewater Treatment Plant in Psyttalia and Metamorphosis. 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
Psyttalia 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.
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4.Situation in greater Athens
The bodies of water from which water, which is to be supplied to the greater Athens area, is
extracted are situated at fairly long distances. The following are being used today :

The Marathon Reservoir, initially constructed in 1925 and expanded later by
damming Assopos river at the place of the ancient lake of Marathon, approximately
42 km away from the centre of Athens.

The Yliki Lake, connected to Athens by a closed gravity aqueduct; 143 km long,
constructed in 1957.

The Mornos River Reservoir, which involved the construction of an earth dam 150
km northwest of Athens. The Mornos Reservoir will be further expanded thanks to
water transferred from the Evinos river dam, currently under construction.
Serious water shortage problems due to low rainfall occurred between 1992-94. Special
measures taken by EYDAP, such as price increases, penalties for excessive consumption, and
awareness campaigns proved quite effective in controlling consumption.
There are four water purification plants, approximately seventy pumping stations, and the
estimated length of the distribution network is 7,000 km. The latter has been constructed in
many stages, and without a master plan, and is in some cases very old and in urgent need of
replacement. The mains in some cases belonged to private bodies and in other case to
municipalities, and they have been poorly maintained. Leakages are estimated to exceed 20
% on average, but there is currently a great effort to diminish them. In other cases, the mains
still belong to the municipalities, which are usually not very prompt in paying their debts to
EYDAP. The sewer system construction began in 1858 in the greater Athens area.
Nowadays, municipalities construct the secondary drains and EYDAP constructs main sewers
of the separate sewage. The total length of the network is 6,500 km and the number of
pumping stations is forty-one. Wastewater treatment takes place in two plants, namely
Psyttalia and Metamorfossis.
The Metamorfossis plant was inaugurated in 1986. It is a rather small plant, treating 8,000
m³/day of septic tank waste and 13,000 m³/day of sewage. Septage is delivered to the plant by
trucks and their organic load is approximately four times that of sewage.
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5.Psyttalia WasteWater Treatment Plant
The construction of the plant began in 1983, when it was decided to transfer and treat all the
sewage of the greater Athens area on the island of Psyttalia. The island location was chosen
because Athens, a city of almost 4 million people, is so densely populated that there was
simply no room on the mainland.
The treatment plant occupies almost the whole of the island of Psyttalia in the Saronic Gulf,
just outside Athens’ harbor area of Piraeus. The plant handles the majority of Athens’
wastewater – amounting to about 1 million cubic meters a day, or 12 cubic meters a second –
which is transferred to the island via nine huge Archimedes screw pumps (what is their head ?).
After treatment and dewatering, the waste sludge, amounting to about 800 tonnes per day, is
shipped back to the mainland for disposal in landfill sites.
The treatment installations on the island ensure the treatment of a peak discharge of 27 m3/s
during phase A and B. They include primary treatment, disinfection and disposal of treated
wastewater into the sea at about 50 m depth. A complete biological treatment plant (here is
probably absent an end of the sentence). Sludge treatment includes pre-thickening, anaerobic
digestion, post-thickening, sludge dehydration after thickening with belt-presses, etc.
Methane is collected, stored and used for heating the digester and electricity production.
The Psyttalia Wastewater Treatment Plant treats daily with 750.000 m3 of sewage and has a
nominal daily capacity of 1.000.000 m3 (11,6 m3/s).
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6.Sewerage Network Operation
Fig.: ? Construction of Psyttalia WWTP
Athens’ sewage is initially pre-treated (screening, degridding ? de-gritting) at the Akrokeramos
facilities, and is subsequently directed, via an inverted siphon (underwater), to the facilities
on the island of Psyttalia, where it undergoes primary treatment. The sewerage consists of
both storm water runoff and sewage pipes. The storm water runoff flows reach, via gravity
flow, the sea (Saronic Gulf) and the sewage pipes discharge at the Psyttalia island sea region
after undergoing wastewater treatment at the Psyttalia Wastewater Treatment Plant. The total
length of the network is 5.800 km and covers 92% of the wastewater needs of the area. The
large diameter sewers run through areas where the slopes permit the conveyance of the
wastewater by gravity (gravity sewers) with only exception the Saronic Gulf Coastal
Collector, which operates with the assistance of 42 pumping stations. After the treatment the
water is carried through an underwater disposal pipeline at a satisfactory depth and diffused
into the Saronicos bay with an organic load reduced by 35-40%.

Operation of the Pumping Stations
The Coastal Collector system consists of a series of pumping stations and two pressure mains
that are constructed to ensure the continuous wastewater flow - even if one of the pipes has a
problem. The construction of the pumping stations faced difficulties due to:
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a) the high level of the aquifer (water table)
b) the necessary water-proofing of the pumping stations tanks to avoid pumping of
underground water.
The coastal system involved the construction of 42 pumping stations from Varkiza to Perama
that started in the 1950’s and is continuing until today. In 1958, the first pumping station,
pumping station No 17 at Neon Phaliron, started its operation conveying the area’s sewage to
the Main Interceptor Sewer. The pumping stations’ network is continuously being expanded
and construction of new pumping stations is planned for other locations having as discharged
point the Psyttalia Wastewater Treatment Plant.
These pumping stations operate either in groups (parallel operation) or in a chain formation.
In the first case, the wastewater of some local pumping stations is conveyed to a bigger one,
which then forwards it to the Main Interceptor Sewer. In the second case, the wastewater is
pumped consecutively from the one pumping station to the next one, with twin force mains,
discharging finally to the Main Interceptor Sewer (the Coastal pumping stations from Varkiza
to Amphithea and from Perama to Moschato).
The installed power of the pumping stations above is ~11.500 kW. These pumping stations
operate automatically through start and stop electronic level sensors, according to specified
limits. Their operation is monitored by a modern Supervisory Control and Data Acquisition
System (SCADA) installed at the Neon Phaliron Control Center. This Modern System
operates with Programmed Logical Controllers (PLCs) at the local stations of the pumping
stations. Through leased telephone lines, the PLCs are monitored on a 24hr basis from the
Neon Phaliron Control Center.
All the wastewater is pumped to the Main Interceptor Sewer, and finally it reaches the
Psyttalia Wastewater Treatment Plant. Along this system, there are scheduled operational
monitoring events, maintenance work, repairs, construction, as well as unscheduled work
when necessary, on a 24hr basis. The works are accomplished by maintenance groups based
at Neon Phaliron, in order to secure uninterrupted service. For the proper maintenance of the
pumping stations, periodic clean-ups take place.
12

Collectors
As it has already mentioned the total length of the sewerage network exceeds 5.800 km, of
which, only 17 km is the old combined system (collection of waste and storm water drainage
pipes) covering the center of Athens.
The sewerage system of the greater Athens region is composed of:
Primary collector mains
The primary collector mains of the sewerage network are a major part of the wastewater and
storm water system.
There are ten combined wastewater and storm water collector mains, which converge at the
Central Sewer Pipeline. Under dry conditions, these collectors operate as part of the sewerage
network, conveying all wastewater to the Central Sewer Pipeline. Under wet conditions, the
collector mains also accommodate storm water, though in this case only portion of the
wastewater is directed to the Central Sewer Pipeline. Wastewater generated by the Athens
basin drains towards the Psitallia Wastewater Treatment Plant via the Central Sewer Pipeline
and the Auxiliary Central Sewer Pipeline. The primary collector mains that direct the
wastewater to the Central collector are the following: Parakifissios - gathering wastewater
from the western municipalities - and Parailissios - gathering wastewater from eastern
Athens. The Central Coastal Collector gathers wastewater from the southeastern regions of
Athens.
EYDAP is responsible for the construction of the primary sewerage network.
Secondary Collector Mains
The secondary collectors direct wastewater towards the primary collectors and are also
constructed by EYDAP.
Tertiary Wastewater Sewerage System
The tertiary system consists of pipelines with maximum diameter of 30 cm, which are
constructed by local authorities. According to article 25 of Law 1068/1980, the local
authorities are obliged to construct the network according to the design studies performed by
13
EYDAP to ensure proper operation of the secondary wastewater collector mains.
Unfortunately, when the completed networks are handed over to EYDAP - as the Law
specifies - EYDAP frequently discovers that the works have not been constructed as per
specification. The networks constructed by the local authorities often exhibit operational
problems, such as defective pipeline construction, defective pipeline- chamber interface
works, frequent blockages, network misalignments, etc., that significantly increase EYDAP’s
operational costs.
With the enactment of Law 2576/1998 (article 9), the responsibilities of the local
municipalities were extended to include the following:
• The construction of the local storm water drainage network (of diameter smaller than or
equal to 80 cm) within their jurisdiction areas
• The standard maintenance (cleaning) of the storm water catchment’s chambers (except
those located on main streets and avenues)
• The standard maintenance (cleaning) of storm water collector mains, (excluding natural
streams).
The planning and implementation of projects concerning the general flood protection of
Attica, after the enactment of Law 2744/99, was assigned to the Ministry of Environment,
Physical Planning and Public Works. This includes the responsibility for the design,
construction and operation of the flood protection works.
Approximately 92% of the sewerage system of the Athens Basin has been constructed.
Practically all of the primary and secondary collector mains in this area have been
constructed and have sufficient capacity to satisfy demand at least the next decade. However,
the sewerage and storm water drainage networks of the Thriasio Pedio and eastern Attica are
practically non-existent. The majority of the inhabitants of these regions are served by septic
tanks.

Sewage-treatment stages
The plant’s sewage-treatment stages are as follows:
• Sewage screening and degridding (a procedure carried out at the Akrokeramos facilities).
14
• Primary sewage settlement (with an average removal rate of 63% for suspended solids and
38% for the organic load), sludge removal, pre-consolidation, as well as anaerobic sludge
digestion, post-consolidation and dehydration (a procedure carried out on the island of
Psyttalia).
• Disposal of treated sewage into the sea via an underwater pipeline.
• Disposal of the dehydrated sludge at the Sanitary Land Fill of Ano Liosia.
In July 2001, on the island Psyttalia, a Power Production Plant to utilize the biogas produced
during treatment, began operation. This 7,4 MW - electrical power plant has benefited
EYDAP in two ways: the wastewater treatment plant’s energy needs are completely covered,
and any excessive energy is sold to the Hellenic Public Power Corporation.
Moreover, the increase of the electric and thermal output of the Psyttalia WWTP’s power unit
by the burning of biogas producing an additional 4 MW, is currently under review.
Furthermore, the construction of a new natural-gas power unit to generate 14 MW of electric
and thermal energy is also being considered. This additional power would cover the thermal
needs of the sludge dehydration unit.
7.Network Maintenance

Pipe Inspection Camera
In order for EYDAP to locate and repair damages in the sewerage network in a precise and
direct way, it uses cutting-edge technology Mobile Units that inspect the network
telescopically. These mobile units contain:
The Control Chamber containing all the electronic systems necessary to move and control the
unit and the camera. This chamber also contains the recording, photographic, and videorecording systems that convey all the data that the camera collects from inside the pipe (such
as the exact location and kind of the damage) to a computer.
The mechanical gear chamber, that contains three small vehicles on which 2 cameras, are
adjusted. These cameras are used to inspect pipes ranging in diameter from 200 mm to 1500
mm, as well as for the inspection of individual building connections. For pipe sections of
15
larger diameter, which can accommodate direct inspection by technical personnel, the
cameras can be adjusted to a portable system.
EYDAP uses this technology on a daily basis, in sections of the network that present
operational problems or for the inspection of municipal networks to be handed over to
EYDAP. EYDAP also uses this technology to inspect pipe networks on behalf of third
parties, providing consulting services based on EYDAP’s know-how and experience. With
the use of cutting-edge technology EYDAP achieves lower maintenance costs and quicker
repair time, while minimizing social adversity from unnecessary digging.
The Preventive Maintenance Service Department functions under the Division of the
Sewerage Network and is located at the Psytalia Wastewater Treatment Plant.

Upgrades during the construction
The Psyttalia Wastewater Treatment Plant, Europe’s largest sewage treatment facility, makes
extensive use of Festo pneumatic valve actuators to provide intrinsically safe and
maintenance-free operation. The plant originally discharged effluent to sea, but was upgraded
to meet the EU’s Urban Wastewater Treatment Directive, in time for the Olympic Games last
year. The upgrade involved the addition of a large-scale biological treatment plant,
comprising 12 fermentation tanks with a capacity of almost 300,000 cubic metres.
To ensure that the plant will operate reliably for many years, the construction companies in
this joint venture (Themeliodomi, Aktor and Athena from Greece, Giovanni Putignano &
Figli from Italy and Passavant Roediger Products from Germany), chose pneumatic
automation technology.
According to George Lousis, the consortium’s mechanical engineer responsible for the
construction of the plant, “It is vital that the actuators used to open and close the shut-off
valves offer explosion protection, particularly in the area of the fermentation tanks, where the
high-temperature sludge fermentation process generates gases such as methane and carbon
dioxide. It is laborious and costly to configure electrical drives for operation in potentially
explosive atmospheres.”
Nicholaos Zaminos, a system planner for the project, also points out that the long service life
and overload tolerance of pneumatic drive technology are important factors. “Pneumatic
16
drives are maintenance-free, and with a service life of more than a million operating cycles,
will outlive any process valve. In this application, accumulated or dried material on the
valves may make their breakaway torque much higher than normal. Pneumatic drives are
’overload-tolerant’, while electrical drives run up against torque limiters if required to deliver
exceptionally high torque or force. With pneumatic drives, it is easy to increase the operating
pressure and thus the force and torque generated.”
As most process valves in sewage plants are operated in a simple open/close mode or
manually, the use of pneumatic technology has made it possible to achieve a significant
rationalization effect. With electrical drives, in contrast, it is necessary for control system
planners to include monitoring functions for values such as overtemperature, torque,
switching frequency and servicing and maintenance intervals, which means a vast number of
inputs and outputs to wire up.
The flow of sludge into the fermentation tanks is controlled by a total of 50 Copac DLP
pneumatic linear actuators supplied by Festo. These actuators are ideal for the control of gate
valves as they act directly on the gates, making it possible to position them precisely.
The flow control system for the biogas generated in the fermentation tanks employs 40
quarter-turn Copar DRD/DRE actuators from Festo. These actuators are used for open/close
functions, and in conjunction with standard position controllers to achieve precise positioning
of ball valves, stopcocks, shut-off and flow control valves.
The biogas produced during the fermentation process in the tanks is used as an energy supply
for the sewage treatment plant. The Copar actuators also control the distribution of hot water
for the heat exchangers, which are used to maintain a temperature of 33 ˚C in the
fermentation tanks to dry the sludge.
17
8.Psyttalia wastewater treatment Phase B
? Air photo of Psyttalia WWTP
We have advertised details for the process of the development of the Wastewater Treatment
in Psyttalia only for certain modules in Phase B. These are:

Primary effluent and return activated sludge mixing chamber
As part of the treatment process, Primary Effluent (up to 16m3/s) and Activated Sludge (up
to 18m3/s) will be combined with a mixing chamber to form a mixed liquor. Downstream of
the mixing chamber the flow will be equally divided between two outlet channels and the
flow in the outlet channels will be measured using venturi flumes.
A 1:12 scale physical model was used to investigate the performance of the mixing
arrangement and the performance of the outlet channels / venturi flumes.
18
Fig.: ???? What is it? (? a model of the bioreactor?) – describe it more detailed

Bioreactor process units
As part of the treatment process a total of 12 Bioreactor Units will be constructed, each some
27 cm wide, 80 m long and 8 m deep.
HR Wallingford made use of a 1:12 scale physical model of a single Bioreactor unit in order
to investigate the performance of the Bioreactor arrangement. The tests carried out for the
initial arrangements indicated that the overall dimensions of the Bioreactor unit were
satisfactory and the inlet and outlet arrangements were shown to perform adequately.
19
?? The same fig. ? error during copying?

Final settlements Tanks
As part of the treatment process at total of 104 Final Settlement Tasks (? Tanks) (FSTs) will
be constructed, each 50 m long, 8.5 m wide and 4 m deep (as a minimum).
HR Wallingford made use of a 1:8 scale physical model of a single FST unit in order to
investigate the performance of the inlet and outlet arrangements associated with the FSTs.
Tests demonstrated that the initial design of the inlet baffle arrangement did not perform
satisfactorily and flow patterns were produced that were non- uniform and considered likely
to cause scouring and re- suspension of settled sludge. The model was therefore used in order
to develop an inlet baffle arrangement that produced uniform flow distribution at the entry to
the settling zone (thereby promoting good settling performance within the FST) and reduced
scouring potential. Flow conditions at the FST outlet were shown to be satisfactory in that
there was no evidence of any eddy formations or vertical currents that were likely to cause
scouring or re- suspension of settled sludge.
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
Return activate sludge pumping station
As part of the treatment process, Activated Sludge will be withdrawn from hoppers within the
Final Settlement Tanks and returned to the head of the treatment system via the RAS
Pumping Station. The pumping station will comprise twin inlet channels, a common forebay
area and seven pump units positioned within individual pump chambers. Up to six pump
units will operate at any one time, providing a total pumped flow of 18m3/s.
A 1:9 scale model was used to investigate the performance of the inlet channel, forebay and
pump chamber arrangement associated with the station. The model tests confirmed that the
overall plan dimensions of the pumping stations were satisfactory. However, tests
demonstrated the need to effect modifications within the pump chambers in order to inhibit
the formation of air- entraining vortices and strong pre- rotation in the flow entering the
pump suctions. A modified pump chamber arrangement was developed incorporating a
curtain wall at the upstream end of the pump chamber, a flow splitter beneath the pump and
ribs at the sidewalls of the pump chambers. The modified pump chamber performed
satisfactorily in that vortex activity and swirl angles at the pump suctions were within
acceptable limits for a full range of operating scenarios.
ditto
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9.Legislation for Waste in Greece
The National law 1650/86 is the main legal framework for the protection of the environment.
Law 1739/87 established the institutional framework for the management of water resources.
The Common Ministerial Decisions A5/2280/83 and A5/5180/88 refer to the protection of
water resources that are used for water supply in the Athens area. In accordance with relevant
EU directives, the Common Ministerial Decision 46399/1352/86, concerning the quality of
surface waters for: water supply, swimming, and the survival of fish, was issued, defining
measurement methods, sample frequency, and drinking water analysis. A series of decrees
was also established for the protection of water quality. The Common Ministerial Decision
5673/400/97 defines the measures and terms for the management of wastewater treatment.
YPEHODE (in Greek: Ministry of the Enviroment & Public Works), in collaboration with
other competent authorities, drew up a National Solid Waste Management Plan, which was
incorporated into the Greek legislation in year 2000. This National Plan is based on the
Community principles as well as on national needs and priorities. The National Solid Waste
Management Plan was completed by the issuing of Joint Ministerial Decisions containing
general guidelines, technical specifications and specific programs. For the implementation of
this Plan, which lies with the regional and perfectural/local authorities, YPEHODE has drawn
up respective Master Plans for each Perfecture in order to facilitate the process of the drawing
up of their own solid waste management plans and projects.
Regarding hazardous waste, YPEHODE is currently elaborating the National Plan
and the Technical Specifications on Hazardous Waste Management, which will soon
be incorporated into the national legislation.
Regarding packaging waste and recycling, a new Law on measures and for the
alternative management of packaging material and other used products will soon be
issued after approval by the Hellenic Parliament. This Law contains general 3
guidelines for the alternative management of packaging material and used products,
including debris, electrical devices, catalysts, batteries etc. It is based on the
principles of the aquis communautaire, namely prevention of waste generation, reuse,
recycling and recovery. For its implementation, a National Organization for the
Alternative Management of Packaging and other Products will be established,
consisting of representatives from all society’s stakeholders (public and private
sectors, local authorities, NGOs, consumers’ groups etc).
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EYDAP 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 predefined 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.
10.Results
Summarizing the institutional arrangements in the water sector in Attica, the following
statements can be made:

The Ministry of Environment Physical Planning and Public Works is responsible for
the policy making.

The Athens Water Supply and Sewage Company (EYDAP) is responsible for water
and wastewater services and is supervised by the Ministry of Environment Physical
Planning and Public Works.
The considerably positive results from the operation of the Metamorfossis WWT plant
encouraged the administration of many local authorities of certain small towns and/or tourist
villages to start constructing their own treatment plants. Furthermore, the contribution of the
EC funds resulted in a full promotion of the infrastructure in the field of environmental
protection.
In addition, public awareness of and sensitivity to the need for better living conditions and
governmental policy for wastewater treatment in any municipality throughout the continental
and island territory of Greece mobilized a national effort to eliminate the sources of water
pollution. EC Directive 91/271 is now a milestone and an official guide for the future
environmental trends in all EC countries.
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11. Plans for the future
After the above, the Saronicos bay will gradually return to being a safe place for fishing and
recreational activities for Attica residents. Various economic parameters that were adversely
affected in the past by the uncontrolled disposal of sewage, will thus, gradually improve.
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.
? Add a flow sheet of the Psyttalia WWTP.
? What are WW parameters = inlet and outlet (e.g. BOD and insoluble or if you know it
nitrogen and phosphorus too).
? For your presentation add some photos.
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