WASTE WATER TREATMENT

IN WALLONIE

3,400,000 inhabitants

Guillaume PIROTTE January, 12th

Contents

First part: General information on waste water treatment in Belgium

Second part: Description of a future waste water treatment plant in Sclessin

General information

Description of a WWTP

General information

Description of a WWTP

History

Purification in BelgiumIndividual waste water

treatment

History

Purification in BelgiumIndividual waste water treatment

First part: General information

General information

Description of a WWTP

History

• Until 1999:

After French revolution of 1789, new laws

-> First sewer

Until 1700, no pipes, no treatments

Sewer in Liège

1971: First national law

1999: Creation of a Public Company for Water Control History

Purification in Belgium

Individual waste water treatment

General information

Description of a WWTP

• Between 1999 and 2004:

Wallon government adopted an investment program

-> 898 M€ (~25 billion CZ) between 2000 and 2004July 2000: Belgium was sanctionned by European Court of Justice

• Nowadays:

A lot of construction sites have been opened

Location of waste water treatment plants in Wallonie

History

Purification in Belgium

Individual waste water treatment

General information

Description of a WWTP

Purification in Belgium

• Context:

Everyday, 120 l per capita

Only one third is treated… Very far from European goals

• Treatment:Classical way

Individual approach

History

Purification in Belgium

Individual waste water treatment

General information

Description of a WWTP

• Legal situation, three zones:

With a network of sewers

-> Customers have to connectWithout a network of sewers but it is planned to build it

-> Local authority has to decideNo network of sewers is planned to be built

-> Customers have to construct an individual

waste water system before December 2009 History

Purification in Belgium

Individual waste water treatment

General information

Description of a WWTP

Individual waste water treatment

• The classical system:Pretreatment: Septic tank

Treatment: Aerobic bacteria

Final evacuation: To a pipe or directly to the soil

• The lagoon’s system:Waste water flows different basins with special

aquatic plantsAfterwards, water can filtrate to the ground

Septic tank

History

Purification in Belgium

Individual waste water treatment

General information

Description of a WWTP

• Dry toilets:

Make compost with faeces instead of evacuating them by water

-> Quite unusual and ask a lot of efforts

• Economic standpoint:

Classical system: 3,000 to 5,000 € (84,000 to 140,000 CZ)Lagoon system: 5,000 to 8,000 € (140,000 to 225,000 CZ)Dry toilets: 1,000 to 1,500 € (28,000 to 42,000 CZ)

History

Purification in Belgium

Individual waste water treatment

General information

Description of a WWTP

Context

Technical features

Water treatment

Context

Technical featuresWater treatment

Sludge treatment

Sludge treatment

Second part: Description of a WWTP

General information

Description of a WWTP

Context

• Place: Sclessin• Construction: From Mey 2006 to January 2009• Cost: 51.5 M€ (1.4 billion CZ)

Context

Technical features

Water treatment

Sludge treatment

Sclessin

General information

Description of a WWTP

Technical features• Maximum inlet:

Nominal loading: 200,000 EI

Day-to-day volume: 40,712 m³/d

Maximum flow: 6.463 m³/s

Day-to-day BOD loading: 10,800 kgO2/dDay-to-day COD loading: 22,610 kgO2/dDay-to-day azote loading: 2,084 kg/dDay-to-day phosphore loading: 402 kg/d

Context

Technical features

Water treatment

Sludge treatment

General information

Description of a WWTP

• Outlet demand:

Maximum BOD: 25 mgO2/l

Maximum COD: 125 mgO2/l

Maximum waterborne particles: 35 mg/lMaximum sedimentation matter concentration: 0,5 ml/lMaximum fat and oil concentration: 3 mg/lMaximum azote concentration: 10 mg/lMaximum phosphore concentration: 1 mg/lMaximum detergent concentration: 3 mg/l

Context

Technical features

Water treatment

Sludge treatment

General information

Description of a WWTP

Water treatment• Mechanical treatment:

Pump station with three bar screens (40 mm gap)Six other bar screens (10 mm gap)

Inlet flow measure

Six longitudinal basins which remove sand, oil and fatsThree circular covered settlers

-> Solid matters decay in an anaerobic way

-> Primary sludge

Context

Technical features

Water treatment

Sludge treatmentBar screensVenturi

systemLongitudinal basin

General information

Description of a WWTP

Context

Technical features

Water treatment

Sludge treatment

• Biological treatment:

Three big rectangular aerated and mixed basins

-> Flocs are formedThree secondary clarifiers

-> Clean water is separated

Activation tanksSecondary clarifier

Sludge treatment

General information

Description of a WWTP

Context

Technical features

Water treatment

Sludge treatment

Sludge is purged

Sludge is obtained thicker

Sludge is dewatered

-> Reducing transport cost

-> Dry enough for final storage

Global view of the future WWTP

Conclusion

• Total capacity:

Evolved from 1,800,000 in 2000 to 2,600,000 EI in 2004660,000 EI are planned to be added in the future

• People do just begin to understand…

THANk YOU FOR

YOUR ATTENTION

Guillaume PIROTTE January, 12th