CZECH TECHNICAL UNIVERSITY
IN PRAGUE
FACULTY OF MECHANICAL ENGINEERING
DEPARTMENT OF PROCESS ENGINEERING
Semestral Project:
WASTE WATER TREATMENT
IN THESSALONIKI
(Thermaikos Gulf)
Sintosi Vasiliki
January 2006
Index:
General Information about Thessaloniki.................................3
Information about Thermaikos Gulf…………………………4
The origins of water masses and the rivers that discharge in
Thermaikos Gulf……………………………………………..6
E.Y.A.Th……………………………………………………..9
[Thessaloniki Water Supply & Sewage Company]
The development of the drainage works more detailed….…10
Interventions before the full operation of the biological
treatment ……………………………………………..……..12
Waste water control of the Industries…………………..…...13
Wastewater treatment plant-Detailed description of the
treatment process……………………………………………16
Septage waste reception & pre-treatment……………….….17
Supplementary works and works upgrading energy usage
Outfall discharge pipe………………………………………18
Conclusion……………………………………………..……19
Literature……………….……………………………………20
2
GENERAL INFORMATION ABOUT THESSALONIKI:
Thessaloniki is the second largest city in Greece with a population
of 1,050,000 inhabitants, is one of the oldest cities in Europe. It is also the
capital of the Greek region of Macedonia, the capital of the Thessaloniki
prefecture and the capital of the EU region (or, synonymously, Greek
periphery) of Central Macedonia. It stretches over 12 km in a bowl
formed by low hills facing a bay that opens into the Gulf Thermaikos.
Today Thessaloniki is a thriving city and one of the most important
trade and communications centres in the Mediterranean. This is evident
from its financial and commercial activities, its port with its special Free
Zone, which provides facilities to the other Balkan countries, its
international airport, its important industrial complex, its annual
International Trade Fair, etc.
3
INFORMATION ABOUT THERMAIKOS GULF:
Thermaikos Gulf is a semi-closed shallow sea basin, with a
southern opening to the Aegean Sea approximately 19 km wide, situated
in the northwest Aegean Sea. The Gulf is bordered to the east by the
Kassandra peninsula, to the west by the coast of Pieria and to the north by
the coastline of the city of Thessaloniki. The northern part of the
Thermaikos Gulf constitutes the Gulf of Thessaloniki.
Due to the dense population and the concentration of industrial and
other activities, the atmosphere, the soil, and the Thermaikos Gulf have
been degraded. Environmental systems are overloaded with pollutants,
and there is a lack of infrastructure with which to create and control the
limitation of emissions, and the reduction of pollutants discharged into
the Gulf.
The urban complex of Thessaloniki is considered as the second
industrial area of the country, with large units like oil refinery, unit for
the production of chemical fertilizers, steelworks, breweries, etc. There
are also food-stuff industries, dye-houses, tanneries, medium-size
chemical industries, while there also are many other activities like nickel
plating units, pesticide units, gas stations etc. that are described as being
of small capacity but nevertheless, they are not allowed to have heavy
wastes.
4
According to measurements conducted by the Chemical Laboratory
of the Department of the Environment, Ministry of Macedonia-Thrace,
the water of the Gulf is alkaline with stable conductivity values.
Pollutant categories that contribute to pollution of the Thermaikos
are urban sewage, industrial waste, cultivation draining, petroleum-based
products and toxic substances. Pollution of the Gulf affects all human
activity, which is directly or indirectly related to the waters, such as
recreation, swimming, sports, living along the coast, fishing, shellfish
cultivation, and so on.
Until 2000, the 75% of the municipal and industrial wastewaters of
the city of Thessaloniki were channeled into the sea without any
treatment at all and resulting in the pollution of Thermaikos Gulf.
5
THE ORIGINS OF WATER MASSES AND THE RIVERS
THAT DISCHARGE IN THERMAIKOS GULF:
More precisely, Thermaikos gulf receives about 150,000 m3 per
day of sewage from the city of Thessaloniki and approximately 43,500m3
per day of industrial discharges from the industrial zone. In addition, four
rivers: Gallikos, Axios, Loudias and Aliakmon, flow into Thermaikos
gulf after the drainage of 935 km2 of agricultural land. Previous pollution
studies in the area have shown elevated values for heavy metals in
sediments in the vicinity of the pollution sources, mainly the industrial
zone, the port of Thessaloniki and the sewage outfall.
The western coast of the Inner Thermaikos Gulf (depth: 0-50 m) is
influenced by the four river estuaries (Gallikos, 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.
6
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.
Gallikos, Loudias and Aliakmon River spring from the inner part
of Greece, only Axios River is a transboundary river and traverses
FYROM, thus its load of pollution is greater and less easy to be
controlled. It caries the biggest mass of water than the other three in
Thermaikos Gulf and also, great amounts of nutrients (P and N), 82% of
which caused by human activity (urban, agriculture and industrial
pollution).
Loads of dissolved nutrients from Axios River in Thermaikos Gulf:
Flow km/year
4.90
Nitrate (N-NO3 ) mg/mL
1.584
+
Ammonium (N-NH4 ) mg/mL
0.065
-3
Phosphate (P-PO4 ) mg/mL
0.48
Many times exaggerating values of BOD, NO3, and toxic
substances from pesticides were detected in the ground water that spring
from Axios.
 30% of the water samples was not potable [ΝΟ3-Ν > 11.3 mg/l]
 60% of the samples the concentration of toxic substances>0.1 μg/l
[0.1 μg/l is the maximum allowed concentration].
 High concentrations of pesticides:
Alachlor (μg/L)
<0.05-1.30
Atrazine (μg/L)
<0.05-0.7
Metolachlor (μg/L)
<0.10-0.50
Molinate (μg/L)
<0.001-0.90
Simazine (μg/L)
<0.06-0.30
* The annual mean concentrations of some important pesticides analysed
in marine waters in the Adriatic Sea are lower than 0.1 µg/l in contrast
the annual mean concentration for some pesticides in the Gulf of
Thermaikos is higher than 0.1 µg/l.
7
Some statistics for Axios River and measures that must be taken:
1. Axios river is the main contributor for Nitrogen (N) and Phosphorus
(P) to the Thermaikos Gulf, supplying 43% of N and 56% of P.
2. The most important N-emission pathways are: groundwater -45%,
wastewater -29%, point sources -12%. The most important P-emission
pathways are: point sources -64%, wastewater -20%.
3. P-emissions can be reduced by as much as 85%, if certain measures are
undertaken (management of point sources and use of P-free detergents).
4. Improvement of the Thermaikos Gulf by managing solely the Axios
River nutrient emissions is not feasible. Other sources (minor rivers and
point sources) should be managed as well.
5. Reduction of P-emissions from the Axios River will have a positive
effect on the N/P ratio, which at present is <6, with positive influence on
the biology.
The situation in Thermaikos Gulf 20 years before was completely
different from nowadays. Till 1992 all the waste water was channelled
directly into the sea in front of the city of Thessaloniki without any
treatment, resulting in significant pollution with excessive amounts of
nitrogen and phosphorus salts and litters.
From 1992 started the function of the first phase of the waste water
project in Sindos, but it wasn’t enough effective. At the beginning of
1997 started function of the WW plant in Michaniona for the treatment of
the nearby Summer Resort areas and at 2000 completed the second phase
of the plant of the Biological treatment of Thessaloniki (urban waste
water) and started its full operation.
At the begging of 2003 started the function of the waste water treatment
plant that was designed for the Industrial Area of Thessaloniki, and the
special treatment of all the industries under the responsibility of
E.Y.A.Th.
8
E.Y.A.Th:
The Thessaloniki Water Supply and Sewerage
Co. [E.Y.A.Th] S.A. is responsible for the
water supply of the Thessaloniki urban
complex and the collection and the convey of
the urban waste waters to the Waste Waters
Treatment Installations.
It originates from the merging, in 1998, of the
Thessaloniki Water Supply Co. (OYTh) and
the Thessaloniki Sewerage Co. (OATh).
E.Y.A.Th. S.A. aims at a friendly and quick servicing of its consumers,
providing better services and increased credibility, and aims at playing a
leading role in South-Eastern Europe in the sectors of water supply and
sewerage, taking into consideration the needs of both citizens and
environment.
E.Y.A.Th. S.A. has
- A daily average water supply of 250 000 m3
- A daily average waste waters treatment of 170 000 m3 (but also has a
maximum capacity of 296 000 m3)
- The length of the Water Supply pipes is 1800 km without the
connection to the Aliakmon River. The length of the Sewerage Network
ducts is 1600 km.
E.Y.A.Th. S.A. has the exclusive right to provide Water Supply and
Sewerage services in the geographic areas extending of its activity, which
are
α) As for the water supply : The urban complex of Thessaloniki with the
Panorama Municipality and the Industrial Region.
β) As for the Sewerage : The area extending from the Axios river, the
hillocks of the Thessaloniki urban complex (limits of forestry
department) up to the Tourist Areas.
9
THE DEVELOPMENT OF THE DRAINAGE WORKS
MORE DETAILED:

The first stage started to be built in 1985 followed by the second
stage in 1997, for the second degree sewage waters treatment, that
is the main Thessaloniki Sewage Treatment Installation as we
could call it. At the same time started the construction of the
central drainage duct of the city.

The construction of Central Drainage Duct, of 15.800 meters
length was completed in 1990, and was connected to the existing
universal flow and separative sewerage networks of Thessaloniki.

The Tourist Regions Sewage Treatment Installation in Michaniona
started to be constructed in 1995 and decisively affects the antipollution at the eastern part of the Thermaikos Gulf.

In 1992 the Stage I of the Sindos Sewage Treatment Installation
started operating.
10

In 1997 was inaugurated in Michaniona the operation of the
Tourist Regions Sewage Treatment Installation, under the name of
AENEIAS. The same year started the construction of Stage II of
the Sindos Sewage Treatment Installation, with a perspective of
increasing the quantity of treated sewages to 300 thousands cubic
meters per day. It has to be noted that today, the sewages of
Thessaloniki amount to 150 thousands cubic meters per day. So,
the Installation has the possibility to cover the needs of the city and
its extensions for many years.

The construction of Stage II was completed in 2000 and in May of
the same year started the collection and treatment of the
Thessaloniki sewages, providing a full anti-pollution protection to
the western part of the Thermaikos Gulf. At the same time the
central drainage duct of the tourist regions was built and the
construction of the duct connecting the central installation with the
industrial area of Sindos advances, and the extension of the central
drainage duct to Kalamaria and Thermi was completed.

In 2003, E.Y.A.Th. S.A. assumed the operation and maintenance of
the Sewage Treatment Unit at the Industrial Area.
The results of the water treatment were prominent, the presence of
dolphins in the inner part of Thermaikos and the witness of the fishermen
regarding the increase of the fish catches were an indisputable proof.
Still, the total purification of the gulf also depends on additional
anthropogenic activities, such as the pollution caused by passing ships
and the incoming pollutants through the rivers flowing into the gulf.
11
INTERVENTIONS BEFORE THE FULL OPERATION
OF THE BIOLOGICAL TREATMENT:
But, already some time after the operation of the Stage I of the Sindos
installation, in 1992, there was a possibility for the treatment of small
sewage quantities, starting from
40 thousands cubic meters, up
to 50 and 60 thousands in
continuation and till the
completion of installation in
2000.
At the Thessaloniki Drainage
Co. that was then responsible,
and merged with the Water
Supply Co., E.Y.A.Th. S.A.
was established in 1998, it was
decided for a better exploitation of this opportunity and aiming at the as
much as possible better results, as concerns the cleaning of the sea, to
stop the flow of urban sewages at the sea-front. From the White Tower to
the position of the actual Music Palace, there was a sewage flow at 16
points, from the seawall to the sea.
With a series of interventions, this same sewerage was collected
and led through the Central Drainage Dust to the partially operating
Sewerage Treatment Installation. The result was to note a sensible
improvement.
Nevertheless, the spectacular progress that was noted today at the
seafront, after the definitive stoppage of the sewage outflow to the
Thermaikos Gulf, is mainly due to the fact that the aggravation of the
situation at that point has stopped during the last years.
12
WASTE WATER CONTROL OF THE INDUSTRIES:
Based on the present legislation, the industries are obliged to build
and operate treatment units for their liquid wastes, so that their quality to
be in correspondence with the in force, prescriptions of the legislated
European Union specifications, for the outflow of liquid wastes.
In their totality, the units treat their liquid wastes, before they dispose
them to the sewage network. For the granting of an operation license, the
industrial units are required to have an approved study, and also, a
definitive license for the disposal of their wastes. This part of the license
granting has been assigned by the Thessaloniki Prefecture to E.Y.A.Th ,
S.A. , for the case these wastes end at the
Waste Treatment installations.
The treated wastes of the industries
established in the Industrial Area of
Thessaloniki, are conveyed to Waste
Treatment Unit, operating under the
E.Y.A.Th. responsibility, which receives
about 10.000 m3 /d for further treatment.
In continuation, after their treatment,
they as well end, just like the E.E.L.Th. discharges at their final recipient,
that is the sea.
All above industries are systematically controlled by the
department of Drainage Laboratory Controls and Environment, with
about 14.000 analyses annually, for both the controlling of the treatment
units operation they dispose, and for the allocation of the Waste
Treatment Unit expenses to the different industries of the Thessaloniki
Industrial Zone.
The number of the controlled units has been sensibly increased,
although the connection of all the industries and handicrafts established in
the Thessaloniki Industrial Zone, Kalokhori, Thermi, the Diavata
industrial complex, the tanneries, etc. has not yet been completed with the
Thessaloniki Waste Treatment Installation.
The quality control of the Sewage Water Treatment Installations
outflows as to the physical & chemical, toxic, and microbiological
parameters is being conducted scrupulously and consistently by the
department of Drainage Laboratory Controls and Environment, in
conformity to the in effect legislation for the required special conditions
for the discharge of wastes and liquid rejects.
13
The discharge limits for the Waste Water of Industries:
COD
150 mg/l
Sulphurous
2mg/l
BOD
40mg/l
Ammoniac
15mg/l
SS
40mg/l
Phenol
0.5mg/l
HC
10 mg/l
Cyanide
0.5mg/l
6+
T
<35ºC
Cr
0.2mg/l
pH
6-9
Pb
0.1mg/l
Additionally, E.Y.A.Th, monitors since many years the quality
state of the recipient Thermaikos Gulf, aiming at optimizing its protection
and the proper administration of the marine environment. This monitoring
is carried out both by the department of Drainage Laboratory Controls
and Environment and the Hellenic Marine Research Center, with which
E.Y.A.Th, has been signing successive contracts, since many years.
According to its last technical report the Hellenic Marine Research
Center, the operation of the Sewerage Treatment Installations has already
brought about positive reactions to the marine ecosystem.
Also, the Water Supply and Sewerage Company of Thessaloniki
obtained the permission to install a unit for electrical energy production
form the biogas station, with a capability of 2.5 MW. For the whole
period of the year the plant removes:
1. More than 95% of the organic load.
2. More than 95% of the total nitrogen.
3. The 60 to 70% approx. of the total phosphorous.
14
Besides, the project for the construction of the facilities for the
Reception and Pretreatment of the septage waste, the testing operation of
which is being competed in September 2003, The Thessaloniki
Wastewater Treatment Plants will be able to take in for treatment
processing up to 1,200 cubic meters per day of septage, which
uncontrollably polluted the underground aquifers and the surface
receiving water bodies.
The following information table comes from a research that was
made in 1999 on the quality of water of Mediterranean Sea and the loads
of pollution that are being discharged from several countries and specific
cities. In that year the WWT plant was treating only 30% of the waste
water. The information is about the mixed pollution that discharges in
Thermaikos Gulf (domestic and industrial together).
BOD (t/year)
COD (t/year)
Total N (t/year)
Total P (t/year)
TSS (t/year)
Oil (t/year)
297
1043
(no info
found)
15
142
38
15
WASTEWATER TREATMENT PLANT – DETAILED
DESCRIPTION OF THE TREATMENT PROCESS:
The incoming wastewater is received in the inlet pumping station.
With three screw pumps, the sewage
is raised and after been led through
bar screens, it is collected into two
aerated grit removal tanks, where
grit and grease are removed. The
sewage is then subjected to various
treatment steps, as follows:
* Primary sedimentation takes place
in five circular tanks, where a 50%
removal of suspended solids and a reduction of 30% at least of the
organic load are attained.
* Through the primary sedimentation effluent channel and then through
the booster pumping station, the sewage is directed to the "activated
sludge" process, consisting of eight biological reactors and of eight final
sedimentation tanks.
* The removal of organic load as well as of nitrogen is attained in the
biological reactors. The final sedimentation and clarification of sewage is
then carried out in the final sedimentation tanks.
* The clarified sewage is disinfected and then directed to the outlet
pumping station, from where it is
discharged into the outlet gulf of
Thermaikos through the new
Twin Discharge Pipe.
*
The produced primary sludge is
directed into four thickening
tanks and then it is transferred
into the anaerobic digesters
through a pumping station.
*
Following digestion, the sludge is collected in six storage and postthickening tanks and then through a pumping station it is led to the
homogenization unit.
* The produced biogas, resulting from the anaerobic digestion, is stored
in two gas-holders and is utilized for energy production.
16
SEPTAGE WASTE RECEPTION & PRE-TREATMENT:
The septage waste reception and pre-treatment unit consists of:
* Equipments for the reception and pre-treatment of the municipal
septage waste, with a capacity of 1200 cubic meters per day.
* Equipments for the reception and
treatment of the high organic load
nontoxic industrial waste with a
capacity of 250 cubic meters per day.
* Line for the reception and treatment
of the waste with high content of
coarse inorganic solids.
* Equipment for the treatment of grid residues.
* Equipment for sampling and quality checking of the incoming septage
waste, as well a fully equipped modern lab for the 24 hour monitoring of
the operation of the overall wastewater treatment plant of Thessaloniki
The septage is pre-treated, depending on case, and then directed in the
Wastewater Treatment Plant (E.E.L.Th.), where it is treated.
SUPPLEMENTARY WORKS AND WORKS UPGRATING
ENERGY USAGE:
The project includes the
repairing or the replacement of the
electromechanical equipment and also
repairing works in parts of the
facilities initially built, with the target
of operational safety and step-up, as
well as the target of operational cost
reduction.
The above works are carried out in the following units of the plant:
inlet pumping station, screening - grit removal, primary sedimentation
tanks, primary sludge and froth pumps, sludge pre-thickening tanks,
pump of the excess sludge, sludge dewatering unit, gas-holders, final
sedimentation tanks, outlet pumping station, lightning arrester,
automation, area for the temporary deposition of the final sludge.
The project is under construction and it is expected to finish in the end of
2004.
17
OUTFALL DISCHARGE PIPE:
The work of Twin Outfall Discharge Pipeline of the Treated
Effluent includes a 7.9 km long land section and a 2.6 km long sea
outfall. It consists of 10 m pipe sections, constructed of reinforced
concrete with 1.6 m internal diameter. The twin sea outfall is constructed
for the first 1,000 m of its length to a depth of 14 m. Two diverging
branches each 1,600 m long, are then laid to depths reaching 23 m. Both
branches are laid outside the navigation channels.
To achieve better diffusion of treated
effluent, the last 400 m consist of
diffusers of various diameters, with 50 risers. For the sake of
environmental protection and safety, the sea outfall is protected with
stone armouring and concrete mattresses.
18
CONCLUSION:
The construction of the WWT Plant of Thessaloniki was completed
in two phases, the first in the period 1982-1992 and the second in 19952003, the cost for the whole construction was 103,609,083€.
Because the plant was so expensive and huge there were done
many researches about its effectiveness and if the citizens were willing to
pay an extra amount of money in the water bill of EYATh (but the plant
was still partially operational). After its completeness, the results were
prominent. A significant amelioration of the quality if water was
mentioned, less bacterial, nutritient and chemical loads were mesured.The
bad smells in Thessaloniki port went away and the water of many beaches
is now suitable for bathing.
19
LITERATURE:
1. http://www.globaloceans.org/country/greece.html
2. http://www.biat.uni-flensburg.de/biat.www/projekte/RecyOccupation/Sector_Study_Greece.doc
3. http://www.uea.ac.uk/env/cserge/pub/wp/gec/gec_2001_04.pdf
4. http://www.born-ermel.de/english_site/greece.htm
5. http://www.cs.iia.cnr.it/EUROCAT/publications/EuroCatSummary
.pdf
6. http://tovima.dolnet.gr/print_article.php?e=B&f=12885&m=A42&
aa=1
7. http://portal.tee.gr/pls/portal/PORTAL92.wwv_media.show?p_id=
5377722&p_settingssetid=19&p_settingssiteid=0&p_siteid=159&
p_type=basetext&p_textid=5377723
8. http://tanea.dolnet.gr/print_article.php?e=A&f=17885&m=N52&aa=1
9. http://www.eydeael.gr
10.http://www.geocities.com/e_telescope/Greek/Greece/greece_gr_01
0804.htm
11.http://www.eyath.gr
12.http://www.minagric.gr/greek/2.9.3_summary.html
13.http://data.ecology.su.se/MNODE/Europe/Med_Aegean_BlackSea/
Greece/InnerThermaikos/thermaikosbud.htm
14.http://www.iahr.org/elibrary/beijing_proceedings/Theme_F/numerical%20studies%20O
F%20ThE%20Matter%20transfer.html
15.http://intranet.bell.ac.uk/sites/courses/BSc3ESEMPE/Eutrophication%20docs/Topic_Report_7_2001.pdf
16.http://195.97.36.231/acrobatfiles/MTSAcrobatfiles/mts142.pdf
17.http://195.97.36.231/acrobatfiles/MTSAcrobatfiles/mts124Eng.pdf
20