Doosan Lentjes reaches important milestone in sewage sludge treatment project in Flanders

The first step in this phase is the installation of the electrostatic precipitator (ESP), which serves as the primary stage of flue gas cleaning by removing the majority of ash particles. In a separate installation, valuable phosphorus — listed by the EU as a critical raw material — can be recovered from the separated ash.

The flue gas cleaning system also includes a selective non-catalytic reduction (SNCR) unit to reduce nitrogen oxides (NOx). To meet strict emission limits and ensure a wastewater-free flue gas cleaning process, additional cleaning stages are installed downstream of the ESP. The semi-dry cleaning stage, consisting of a quench reactor, sorbent dosing system, and downstream fabric filter, removes heavy metals, dioxins and furans. The absorber (limestone scrubber) captures acid gases. Heat extracted from the flue gas via two heat exchangers is used to preheat the feed water required for the waste heat boiler.

The plant is designed to treat sewage sludge from the wastewater of approximately four million residents annually. Thanks to optimal heat and mass transfer conditions in the modern bubbling bed furnace, the facility achieves high combustion efficiency. This ensures energy self-sufficiency and enables the utilisation of waste heat for external steam applications. Excess steam is fed into a high-pressure turbine of a neighbouring industrial facility, where the energy is used for steel production. This efficient use of energy is expected to save around 28,000 tonnes of CO₂ emissions annually, making a significant contribution to reducing the ecological footprint.

The project was awarded by Aquafin, the Flemish public wastewater treatment company, to FOSTER — a consortium of the BESIX Group and Indaver NV — under a DBFMO contract (Design, Build, Finance, Maintain, Operate). Doosan Lentjes is responsible for the design, supply, installation, and commissioning of the process, mechanical, and electrical scope of the single-line bubbling bed system.

Doosan Lentjes, based in Ratingen, Germany, specialises in environmental technologies for efficient resource utilisation and provides customised solutions for thermal waste and sewage sludge treatment.