Scraper bridge at Bocholt sewage treatment plant removed for renovation

A 28 metre-long scraper bridge was removed today for extensive renovation work at the city of Bocholt's sewage treatment plant at Brömmelingstiege. The plant is now being thoroughly overhauled to ensure the long-term operational safety of secondary clarifier 3.

In a precise operation, a special crane lifted the scraper bridge consisting of two segments out of the 2850 cubic metre secondary clarifier 3 in Bocholt-Liedern. The plant, which has been in operation since the 1980s, is a central element of mechanical-biological wastewater treatment. During regular operation, the bridge rotates over the tank once an hour and uses a special scraper blade to push the settled activated sludge to the funnel-shaped centre of the tank. From there, the mass is pumped out and fed back into the cleaning cycle of the aeration tanks, while the clarified water flows over the edge into the outlet.

As the constructions from the 1980s were often more solid and durable than modern models, the treatment process offers technical advantages combined with a high level of stability.

"Through the targeted renovation of our existing scraper bridge, we are maintaining a technically high-quality and robust system, while at the same time keeping an eye on the costs for the citizens", explains Christian Schaffeldt, head of the Bocholt sewage treatment plant at the city's waste disposal and service company, "the estimated expenditure for the modernisation is also significantly lower than for a new purchase."

In addition to the actual bridge structure, the refurbishment project also includes the centre bearings, including the electrical supply via slip ring assemblies, as well as the scraper blade and the sheet metal covers in the entire outlet area. At the same time, the concrete surfaces will be professionally renewed in order to make the entire system fit for the coming years of operation and to secure the infrastructure in Bocholt-Liedern in the long term.