BESIX Environment and Socogetra modernise the Spiennes wastewater treatment plant

The Spiennes wastewater treatment plant plays a key role in treating municipal wastewater. In response to evolving environmental standards and the need to ensure long-term performance, the facility had to be refurbished and expanded, while guaranteeing service continuity throughout the works.

BESIX Environment and Socogetra will ensure the complete rehabilitation, technical upgrading and extension of the existing plant. Works are scheduled to begin on 1 June 2026. The plant will be designed to treat a load of around 8,000 population equivalents, with an average daily flow of 1,440 m³. The selected treatment process is based on mechanical pre-treatment, optimised primary settling with chemical precipitation, a Bardenpho-type activated sludge biological treatment, and tertiary filtration ensuring phosphorus removal. This configuration will make it possible to comply sustainably with strengthened discharge standards.

The project is designed to control capital and operating costs by reducing biological volumes, energy consumption and reagents. The modernisation will also make it possible to strengthen the plant’s capacity and operational reliability in a lasting way.

BESIX Environment and Socogetra rely on recognised expertise in the design, modernisation and expansion of municipal wastewater treatment plants across the Benelux. This is notably the case at the Trivières wastewater treatment plant, where BESIX Environment worked in partnership with Socogetra on a project to expand and modernise the existing facility. BESIX Environment brings its expertise in process engineering and environmental engineering for water treatment and overall technical integration, while Socogetra contributes with its civil engineering know-how.

The detailed design of the station will begin in autumn 2026, with the new structures being brought into service progressively. Full completion and industrial commissioning are scheduled for March 2028.