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Sewage treatment plant

The Hotton sewage treatment plant was inaugurated on Friday June 20th 2008 in presence of the Walloon Minister of Agriculture, Rural Matters, Environment and Tourism and the Walloon Minister of Home Affairs and Public Service.
This plant has a capacitance of 200 EH and will be treating wastewater in Hottton, Melreux and Hampteau while contributing to protect the Hotton and Noiseux bathing zones.



1. General information:

Work financing authority S.P.G.E. à 100%
Contracting authority A.I.V.E.
Annual operation costs (per inhabitant) +/- 12,50 €
Address: Rue de NAIVE, HOTTON

Technical features of the sewage treatment plant :

Nominal capacity 4.000 EH
Daily rate of flow 720 m3/days
Maximum daily rate of flow for biological treatments 120 m3/hour
DBO5 daily intake 216 kg/day
MES daily intake 360 kg/day

Discharge standards :

DBO5:   15 mg O2/l DCO:   75 mg O2/ MES:   20 mg/l

2. Water circuit:

Water are driven to the sewage treatment plant through drains. A pumping tank raises the flow of flow to create a gravitational flowing through the whole biological treatment process.
A first treatment consists of a grit classifying process phase that remove any solid waste exceeding 6mm. Clarified waste are compacted, dumped and stocked into a container.
This process is followed by a sand washing phase. A sand catcher system remove non-organic compounds from the influent thanks to double-drain equipment, which dispose of 90 percent of sand
Then the flow is divided into biological rate of flow and thunder rate of flow by a flow separator equipped with an inox discharge spout. In case of continuous rain or thunder, a part of the flow is deflected to the thunder basin where water is clarified from sediment compounds.
The biologic flow is driven to a setting tank (770 m3) that is preceded by a contact tank or channel selector which mixes the influent and the reused sludge effectively.
Purifying micro-organisms grow in air tank tanks to oxygen and biodegradable pollution contained in wastewater. This is called the “active sludge "system. Three superchargers provide micro-organisms with necessary oxygen needs estimated at +/- 700 m3/hour.
The last phase of the biologic treatment process consists in separating wastewater from water that has been clarified from micro-organic sludge. This separation phase is carried out in the classifier system (+/- 410 m3)
Before being discharged into the NAIVE brook, clarified water is disinfected by ultraviolet rays to dispose of all the micro-organisms still contained in water.
This treatment process is scheduled between May 15th and September 15th.

3. Sludge circuit:

Clarified sludge is called « secondary sludge ».
It is pumped and driven back into the contact tank to seed fresh sludge in the influent. A part of this sludge is extracted from the system and constitutes “exceeding sludge” resulting from the excessive multiplication of micro-organisms.

« Exceeding sludge » is removed from the clarifier and stocked in a sludge tank (+/- 600 m3) where they get thickened thanks to drains.
Exceeding sludge production is estimated at +/- 200 kg of dry compounds per day.
The sludge tank allows to stock exceeding sludge over a more or less 90 day period.

4. Integration of the plant into the environment:

All measures have been taken as regards construction, technology and landscape in order to cut down sound and smell pollution and to integrate the plant in the selected site at best.

All the equipment that could generate noise is soundproof. All the zones that could be exposed as regards smells, are automatically covered with either concrete slabs or teardrop steel sheets ( sludge moots, sludge tanks).

Concrete treatment buildings are maximum 0.75 m higher than ground level  (air tank plus clarifier system and sludge tank).
Seule, la zone de tamisage fin émerge de +/- 1,80 m, ainsi bien sûr que le bâtiment de service.

Some long stalks remind people of the background with quite high trees as ground surface and planted slopes are covered with lawn and shrubs matching the surrounding pastureland. Some flower beds hide a part of the work building.

5. Telecommunication:

The plant is equipped with IT and telecommunication tools that allow telemanagement and telesurveillance of the building. That equipment provides remote control so that plant doesn’t require any permanent human attendance.

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