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Speaker: Mrs Gina StefanakouDeputy Director WWTP Division &Head of Psyttalia WWTP DepartmentEYDAP S.A., www.eydap.gr

GREEN ENERGY PRODUCTION

THROUGH BIOGAS UTILIZATION

IN PSYTTALIA WWTP, ATHENS, GREECE

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EYDAP S.A.

Athens Water-Supply and Sewerage Company S.A.

• Formed in 1980 through merging of the Greek Water Company (utility) and the Athens Sewerage Organization (state-owned)

• Athens Stock Exchange entry in 1999

• Current Shares:

61 % Greek State

10 % Agricultural Bank of Greece (state-owned)

29 % Private shareholders

• Personnel: 29002

Athens Water Supply and Sewerage CompanyServes the population of Athens metropolitan area with

Water services4 Water treatment plants (Galatsi, Menidi, Kiourka, Aspropyrgos)8.400 km of water distribution network

Wastewater collection 6.000 km of sewer network

Wastewater treatment2 plants in operation (Psyttalia, Metamorphosis) 1 plant in test operation (Thriassio WWTP - West Attica)5 plants in design phase (Peania-Kropia WWTP, N. Makri-Marathon WWTP, North Mesogaea WWTP, Lavreotiki WWTP & Fokea WWTP -East Attica)

EYDAP S.A.

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Akrokeramosinstallations

Psyttalia island

Salaminainstallations

Port of Piraeus

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Psyttalia Wastewater Treatment Plant

Psyttalia WWTP installations were constructed by the Greek Ministry for the Environment, Physical Planning and Public Works, with European Union co-funding, in three phases:

1994 Phase A’ works completion, including wastewater pretreatment and primary treatment installations, primary sludge treatment installations, inverted siphon system for pretreated wastewater transport to Psyttalia and submerged outfall system for treated wastewater dispersion to the Saronic Gulf.

2004 Phase B’ works completion, including wastewater biological treatment installations and surplus activated sludge treatment installations.

2007 Phase C’ completion – construction of sludge thermal drying unit.

Construction Phases

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Additionally, the following works have been constructed at Psyttalia WWTP by EYDAP S.A. with European Union co-funding:

Wastewater pretreatment unit on Salamina Island and submerged pipes for wastewater transport from Salamina to Psyttalia (2002)

Two cogeneration plants for heat and power (CHP) utilizing biogas (2001 & 2009) and

One CHP plant utilizing natural gas (2009)


Construction Phases

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Population equivalent (design, peak): 5 600 000

Design flow-rate (mean): 1 000 000 m3/d

Peak flow-rate : 27m3/s (Phase A)

16 m3/s (Phase B)

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Psyttalia WWTP Flow - diagram

ELECTRIC ENERGY

BIOGAS THERMAL ENERGY

NATURAL GAS

ELECTRIC ENERGY THERMAL ENERGY

DRIED SLUDGE UTILIZATION

EFFLUENT

SLUDGE

PUMPING

GRAVITY THICKENING

(TANKS)DIGESTION

WASTEWATER INFLOW PUMPING

COGENERATION (BIOGAS)

DRYING

SCREENING

GRIT REMOVAL

PRIMARY

SEDIMENTATION

DEWATERING

MECHANICAL

THICKENING (BELTS)

FINAL SETTLING TANKS BIOREACTORS

COGENERATION

(NATURAL GAS)


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AkrokeramosInstallations

Wastewater PretreatmentDebris

Removal

Screening

Grit Removal

Odor Control

Twin inverted

siphon9

Psyttalia Wastewater Treatment PlantWastewater treatment processes

Akrokeramos (mainland)Inlet Pumping Station

9 Archimedes Screw Pumps capacity 3m3/sec each, total capacity 27 m3/sec

Pretreatment

Screening6 pairs of screens (30 / 10 mm)

Grit removal 6 aerated spiral-flow channels

Odor control (sodium hydroxide and sodium hypochlorite solutions, air treatment capacity 140 000 m3/h)

Wastewater transport to Psyttalia through twin inverted siphon system10

Psyttalia Wastewater Treatment PlantWastewater pretreatment (Salamina island)

Population served7 000 (start of operation), 32 000 (full service)

Flow-rate Peak 700 l/sAverage (full service) 7000 m3/day

PretreatmentScreening: Screen (20 mm)Grit removal: Aerated spiral-flow channel (retention time 3 min)

Wastewater transport to Psyttalia through twin pipe system

Current status of operation: Limited flow, pending further service connections

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Wastewater Inlet Channel

Primary Treatment

Biological Treatment

Final SettlingFiltration

C.H.P.

Gas-holders

Sludge Thermal Drying

Sludge Digesters

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Wastewater treatment processes Psyttalia island

Primary sedimentation6 tanks (combined area 12 000 m2)

Biological treatment12 bioreactors (combined volume 300 000 m3)Organic load removal and nitrogen reduction

Final settling64 rectangular tanks (combined area 52 000 m2)

Filtration - Disinfection3 sand-filters (one spare; com. capacity 1500 m3/h) and mechanical filters 2 UV disinfection unitsProduction of process water, for use in facilities on Psyttalia

Outfall systemTwo main pipes (1870 m long each, depth 65m) Receiving waters: Inner Saronikos Gulf


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Effluent Disposal Requirements

Based on Approved Environmental Terms according to Directive 91/271/EEC :

Treated Effluent Concentration (mg/l)

BOD5 25

COD 125

Suspended Solids 35

Total Nitrogen Removal (%) >70


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Typical wastewater inflow characteristics (mg/l)

COD: 720, BOD5: 320, TSS: 350

Operation efficiency

Load reduction (%) exceeding

COD 93

BOD5 93

TSS 93

Total Nitrogen 75


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Sludge Treatment Processes - Biosolids

ThickeningPrimary sludge gravity thickening Surplus activated sludge thickening

Sludge mixing

Digestion

Dewatering

Thermal drying

Biosolids : Organic products of municipal wastewater treatment that can be

beneficially used.

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Sludge Τhickening

Primary sludge:Fine screening

Six screens (5 mm gaps) Gravity thickening facilitated / aided by use of

polyelectrolyte solution 3 tanks (combined area 1500 m2)Odor control unit (2 lines)

Waste activated sludge:Mechanical thickening aided by polyelectrolyte

14 belt thickeners (comb. capacity: 1750 m3/h)

Sludge in-pipe mixing prior to digestion


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Sludge Digestion

Method: anaerobic, mesophilic, high-rate

Installations: 8 digesters (combined volume 80 000 m3)

Type: Cylindrical, conical bottom, fixed-cover (dome-like)

Mode of operation: parallel

Biogas production from partly destruction of sludge organic content

Mixing medium: Compressed biogas

Heating medium: Water

Heating source: Cooling water from CHP plant using Biogas


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CH4

CO2

Carbohydrates

Proteins

Lipids

Phosphorylated

Organics

Glucose

Amino-acids

Fatty Acids

Phosphates (PO4-3)

Acetic Acid

Propionic Acid

Lactic Acid

Cells (Biomass)

Cells (Biomass)

Stabilized Organic

Compounds

Extracellular

enzymes

Acid-producing

microorganisms

Methane-producing

microorganisms

Complex Organic Compounds

Hydrolysis Soluble Organic Compounds

Acids Formation

Organic Acids

Methane Formation

Anaerobic Digestion


Sludge Digestion

Phase A digesters: 4Heating and mixing:

6 heat-a-mix units in each tank

Phase B digesters: 4Heating: external heat exchangersMixing: top-mounted hanging lances

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Biogas temporary storage

Biogas produced at the anaerobic digestion plant is temporarily stored in the gas-holders (two tanks with 5600 m3 capacity each) and it is utilized as a fuel at the sludge thermal drying unit and at the gas-engines of the CHP plant.

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Dewatering plant

Decanter characteristics

• Number: 6

• Type: Centrifugal

• Capacity: 70 m3/h each

• Bowl diameter / length (mm): 725 / 2911


Dewatering Plant (foreground)

2222

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Cogeneration plant for Heat and Power

production (CHP)

utilizing natural gas (gas-turbine)




Unit

Hot gases

Granular sludge

Dried granulesand water-vapor carrying gases

Thermal drying plant evaporating capacity: 40 t water / h (4 parallel units)

Hot gases temperature: 400 o C


Rotating Drum Method


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Utilization of Biogas produced at Psyttalia WWTP


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The need for sustainable development combines environmental protection with

meeting energy needs and in this framework the full utilization of available renewable

energy sources including biogas, is a continuous necessity and one of the major

goals for Psyttalia WWTP.

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Sludge Digestion Biogas

Composition of biogas produced from the sludge anaerobic digestion process

• Methane CH4 61 - 65 %

• Carbon Dioxide CO2 34 - 38 %

• Nitrogen Ν2 0.05 %

• Oxygen Ο2 0.0001 %

• Hydrogen Sulfide H2S 1000 - 2000 ppm


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PSYTTALIA

WWTP

NATIONAL

GRID

MANAGER

SLUDGE THERMAL DRYING

CHP

PLANTS

BIOGAS

GAS-HOLDERGAS-HOLDER

BURNERS

BOILER

DIGESTER

HEATING

HEAT

EXCHANGER

ELECTRIC

ENERGY

ON-SITE CONSUMPTION

ENERGY SALE

DIGESTER

HEATING

CLOSED

CIRCUIT

HEAT

SLUDGE

D I G E S T E R

BIOGAS PRODUCTION IN DIGESTERS BIOGAS STORAGE IN GAS HOLDERS U T I L I S Α T I O N

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Dried sludge silos

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Psyttalia Wastewater Treatment PlantBiogas Utilisation as Fuel in Sludge Thermal Drying

THERMAL DRYING Psyttalia WWTP - Rotating Drum Method

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Thermal Drying - Dried product characteristics

• Satisfying US EPA 503 Class A specifications for hygienized sludge

• Particle size 1 – 5 mm

• Maximum temperature 45oC

• Dried solids content (%) 90 – 95, mean 92

• Maximum dust (<75 μm) content < 1% w/w


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CHP Plants utilizing Biogas

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GAS - HOLDERS

ELECTRIC

ENERGY

THERMAL

ENERGY

THERMAL

ENERGY

DIGESTERS

CONSUMPTION

ON-SITE

SALE TO

NATIONAL GRID

ELECTRIC

ENERGY

SALE TO

NATIONAL GRID

BIOGAS UTILIZATION AS FUEL IN CHP PLANTS

FOR ELECTRIC POWER AND HEAT PRODUCTION

CHP PLANT

7,14 ΜWe

Phase A’

Power gridPhase B’Power grid

Power supply to

Phase B’

installations at

Psyttalia WWTP

Commisioning

2001Commisioning

2009

Power supply to

Phase A’

installations at

Psyttalia WWTP

Electric energy

surplusElectric energy

surplus

CHP PLANT

4,25 ΜWe

33CONSUMPTION

ON-SITE33

TECHNICAL CHARACTERISTICS OF 7.14 MWe CHP PLANT

Number of Gas-Engines 3 Mechanical Power 2 521 kW Electrical Power Capacity 7.14 MWe Heat Capacity 10.35 MWth Number of Pistons 12V Frequency 1 000 rpm Peak Biogas Consumption 3 x 1 000 m3/h Biogas Inflow Pressure 14 mbar Fuel Pressure (Biogas after compression) 3.2 bar Generators Capacity 2 900 KVA Generators Output Voltage 3 300 V Electric Current Frequency 50 Hz Voltage to Grid 20 KV

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7.14 MWe CHP PLANT FLOW DIAGRAM

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Biogas

Psyttalia WWTP Psyttalia WWTP

Power

Mechanical Electrical Grid

Energy Energy

Heat

Flue Gases

Gas Engine Generator

CombustionPower

Production

CompressionDigestionDehumidi-

fication

Psyttalia

Substation

Akrokeramos

Substation

Storage Cleaning

TECHNICAL CHARACTERISTICS OF 4.25 MWe CHP PLANT

Number of Gas-Engines 2 Mechanical Power 2 495 kW Electrical Power Capacity 4.25 MWe Heat Capacity 6.8 MWth Number of Pistons 20V Frequency 1 500 rpm Peak Biogas Consumption 2 x 925 m3/h Biogas Inflow Pressure 14 mbar Fuel Pressure (Biogas after compression) 40 mbar Generators Capacity 3 400 KVA Generators Output Voltage 3 300 V Electric Current Frequency 50 Hz Voltage to Grid 20 KV

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Internal

Combustion

Engine

GBiological

stage for

Hydrogen

Sulfide

removal

Chemical

Stage

Biogas

Ο2

Nutrients

Ο2

NaOH

Replenishment

Η2S

Activated Carbon Filter

Gas-engine Feed

Gas-holders

Biogas

Measurement

Biological

Stage Control

Measurement

Chemical

Stage Control

Biological

Desulphurization

Unit

Process WaterGenerator

Biological Desulphurization Unit

4,25 MWe CHP Plant

Nitrates

Nitrogenous

substances

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Production and Utilisation of Biogas

Biogas Thermal Energy: 6.4 kWhth / m3

Biogas Production (mean) : 65 000 m3 / day 24 x 106 m3 / year

70% - 90% to CHP & Thermal Drying PlantsBiogas Utilization

10% - 30% for Digester heating

Electricity Production from CHP Plants (mean): 35 000 MWhe/year


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Environmental , Economic and other Benefits

from Biogas Utilization

Fuel savings

Considerable reduction of power purchasing cost

Income from sale of surplus power

Reduced emissions of pollutants to the atmosphere

Gain of know-how

New jobs creation


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