Innovative and scalable


Compresseur dans le local technique de la stationNègrepelisse’s WTP is one of the largest constructed wetland systems in France. It extends to 6000 PE the application range of a process previously limited to 1000 PE. Limited land influence: < 1.5 acres à 4000 PE, < 2 acres à 6000 PE, or 3 to 4 m²/PE including the circulations, embankment, abandons.

Conservation of existing ponds and their integration into the treatment process improves the outlet quality at minimal implementation and operating costs.

Operation of the valves, particularly switching between filters every 3 to 4 days, is entirely automatic.
The inlet of each filter is equipped with a pneumatic valve whose opening or closing occurs with the release of compressed air from the maintenance building.
The plant is operated by an automatic switch located in the maintenance building and externally controlled by remote transmission.

Annual reed cutting is conducted by CCTVA staff with the assistance of an external team specialising in river cleaning.


Extension station negrepelisseCurrent plant configuration is in fact the first stage of a plant conceived and designed for 6000 PE. Except for the filters, all the structural elements are sized and positioned for the final capacity, especially the pumping units, the flow meters, the sampling points, the circulations... Extension to 6000 PE will therefore be very simple and inexpensive: installation of two filters, of additional pumps and valves in the existing structure.

Extension work will be programmed based on the observed progressive decrease in water outlet quality as a result of the town’s population increase, i.e. probably exceeding 4000 PE connected to the sewer system. Construction of the plant in several successive stages is another major advantage of the constructed wetland system over its intensive treatment competitors rooted to their initial capacity.

roseaux filtre les MES
French constructed wetland’s history

The WTP was the biggest French constructed wetland plant when it was constructed.


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