St-Etienne-de-Tulmont’s wastewater treatment plant

The St-Etienne’s WTP treats the town’s wastewaters before discharging into the Tauge, an Aveyron’s affluent.

The plant’s presentation with some figures

 

General facts

Nominal capacity : 1900/2300 PE (a plant of 1900 PE extensible to 2300PE afterwards)
Opened in 2008
Contracting authority : Communauté de Communes des Terrasses et Vallée de l’Aveyron – CCTVA
Project engineer : Ginger Environnement Infrastructures – GEI
Constructor : Epur Nature  
Associated firms : Génie civil Causse & Brunet, granulats RUP, pompes ABS

Technical facts

Receiving water : La Tauge stream, affluent of the Aveyron river
Rejection norm : BOD < 25 mg/l ; CDO < 125 mg/l ; SS < 35 mg/l
Winter serie: VFCW1 (vertical flow constructed wetlands)+ VFCW2
Summer serie: VFCW1+ primary ponds+ VFCW2
Dimensions: 1.2 m²/PE (filtre 1) + 2.2 m²/PE (ponds - 5100 m²/2300PE) + 0.8 m²/PE (filtre 2)

Particularities:

• First constructed wetland plant > 1000 PE in the Tarn-et-Garonne department
• The primary pond is totally kept and integrated in the treatment steps
• motorized guillotine gate with a pneumatic command
• in case of the plant’s dysfunction the raw wastewaters aren’t discharged in the stream but are stored and pretreated on the ponds.

The integration of the primary ponds in the treatment steps (only during summer) improves the rejected water quality during the low water period therefore the most sensitive period for the receiving water.

Efficiency

Regular follow-up by the SATESE because the serie is new. The 24hours campaign done in the summer 2009 shows that the primary ponds’ insertion in the treatment steps improves the efficiency on phosphorus and especially on nitrogen contents.

• Gaëlle Aupiais, Purification follow-up of a couple pond-constructed wetland, 2008, a Centre universitaire d’Albi publication, with the SATESE 82
• André Paulus, Filters and ponds, à la carte wedding, Eaux Industries Nuisances-EIN, 2009
• André Paulus, Ponds-filters association, first results after experiences, Techniques, Sciences et Méthodes-TSM, 2009.

Economical facts

Only the treatment plant (except exterior network), from 1 to 1900 PE.
Implementation cost: 740 000 €HT or 389 €/PE
Planned running cost: 1900 PE x 10 €/PE = 19 000€/year
Real running cost (except extraction of sludges and renewal costs): 16000€/year

	2010
	Total	%	€/PE
Average cost	1200 EH
Usual maintenance	272 h x 20€/h = 5440 €	22	1.8
Filters maintenance	140 h x 20€/h = 2800 €	34	1.5
Green’s maintenance	220 h x 20€/h = 4400 €	28	2.3
Hydro cleaner	5 U x 142 = 710 €	3	0.4
Electricity	16 800 kWh x 0.08 = 1344 €	11	0.7
Drinking water	1155 m³ x 1.2 €/m³ = 1386 €	2	0.7
Total	16 070 €	100	8.4

 

Construction budget

Organisms	Studies and others	Works	General total	%
State	25 000 €	170 000 €	195 000 €	23 %
Water Agency	30 000 €	207 000 €	237 000 €	28 %
Department council	50 000 €	340 000 €	390 000 €	46 %
CCTVA	5 000 €	23 000 €	28 000 €	3 %
Total	110 000 €	740 000 €	850 000 €	100 %

Consult
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