This initiative is part of the renovation project sludge treatment, conveying and mixing, being carried out by SOGEA NORD OUEST TP, a major player in the water and wastewater sector, chosen in 2022 to modernize the Gally wastewater treatment plant in Villepreux designed to treat effluent from 45,000 Eqi (equivalent per inhabitant).

In 2002, when the Wastewater Treatment Plant (WWTP) was first built, Sodimate supplied a lime dosing system to feed a mixer, as well as a set of screws designed to transport the sludge to storage cells. However, the layout in two separate premises, located a considerable distance apart, gave rise to major operational complications. On one side, the entire lime dosing system; on the other, the centrifuges for the sludge dewatering process.

This configuration created significant difficulties, in particular the laborious transport of dewatered sludge via an underground network of pipes to the sludge storage area. The continuous flow of lime contrasted with the irregular arrival of the sludge, resulted in poor homogeneity of the treated sludge and clogging of the mixer.

For two decades, the teams at the wastewater treatment plant undertook various trials, from replacing the mixer to installing a mixer pump, without successfully resolving the problem. In 2020, faced with this persistent problem, SOGETI INGENIERIE, as engineering contractor, called on Sodimate, with its 40 years of experience, to design a sustainable solution for the sludge liming plant, while establishing an associated budget.

The solution was to install new centrifuges in a dedicated room close to the sludge area, thereby eliminating the problem of transferring sludge from one end of the plant to the other, as well as replacing the existing ageing equipment.

At the beginning of 2022, SOGEA NORD OUEST TP won the tender for this project, which was marked by challenges. They included integrating the dehydration and liming unit into the existing building with severe height constraints, and technically redefining the lime and sludge conveying line to improve its efficiency.

Following the execution studies, Sodimate supplied a new mechanical bin activator under the existing lime storage silo to prevent the formation of vaults in the silo, with a set of dosing and continuous conveying screws. This allowed the lime to feed its twin-shaft mixer with toothed paddles, which ensures a homogeneous mixture for good structure and hygienisation of the sludge.

In addition, a set of seven coreless sludge-conveying screws, up to 30 meters long, were supplied. These screw conveyors were designed to feed and distribute limed sludge into storage cells for evacuation during the agricultural spreading period, or into two containers in the case of unlimed sludge intended for composting. To complete the package, Sodimate was also selected for the emulsion-based polymer preparation station, equipped with a 1,000-litre capacity unit combined with a dilution panel, all instrumented by an integrated control cabinet.

Sodimate provided its expertise to SOGEA when the plant was commissioned in September 2023, and it has been operating continuously ever since.

SOGEA : “We particularly appreciated Sodimate’s involvement during the key design phase of the installation. We had to realise that the constraints of installing the system in the existing building left us with just 2 cm of height clearance on an overall structure around 8 m high. Discussions with the structural design office and SODIMATE were therefore fruitful, as the installation went smoothly and in accordance with the plans.

As for the operation of the plant, we have been satisfied with it since it was commissioned, which has gone without problem.”

This solution ensures optimum sludge quality before spreading or composting, while strictly complying with current environmental standards.

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